Siltation in Rivers

2: A Minimum Monitoring Strategy for Two cSAC Rivers

Siltation in Rivers 2: A Minimum Monitoring Strategy for Two cSAC Rivers

Conserving Natura 2000 Rivers Conservation Techniques Series

David M Cooper, Pamela Naden, Barnaby Smith & Beate Gannon

CEH Wallingford

For more information on this document, contact: English Nature Northminster House Peterborough PE1 1UA Email: enquiries@english-nature.org.uk Tel: +44 (0) 1733 455100 Fax: +44 (0) 1733 455103 This document was produced with the support of the European Commission’s LIFE Nature Programme. It was published by Life in UK Rivers, a joint venture involving English Nature (EN), the Countryside Council for Wales (CCW), the Environment Agency (EA), the Scottish Environment Protection Agency (SEPA), Scottish Natural Heritage (SNH), and the Scotland and Northern Ireland Forum for Environmental Research (SNIFFER). © (Text only) EN, CCW, EA, SEPA, SNH & SNIFFER 2003 A full range of Life in UK Rivers publications can be ordered from: The Enquiry Service English Nature Northminster House Peterborough PE1 1UA Email: enquiries@english-nature.org.uk Tel: +44 (0) 1733 455100 Fax: +44 (0) 1733 455103l This document should be cited as: Cooper D, Naden P, Smith B & Gannon B (2003). Siltation in Rivers. 2: A Minimum Monitoring Strategy for Two cSAC Rivers. Conserving Natura 2000 Rivers Conservation Techniques Series. English Nature, Peterborough. Technical Editor: Lynn Parr Series Ecological Coordinator: Ann Skinner

Conserving Natura 2000 Rivers

This report on a strategy for monitoring siltation in two rivers has been produced as part of Life in UK Rivers – a project to develop methods for conserving the wildlife and habitats of rivers within the Natura 2000 network of protected European sites. The project’s focus has been the conservation of rivers identified as Special Areas of Conservation (SACs) and of relevant habitats and species listed in annexes I and II of the European Union Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC) (the Habitats Directive). One of the main products is a set of reports collating the best available information on the ecological requirements of each species and habitat, while a complementary series contains advice on and assessment techniques. Each report has been compiled by ecologists who are studying these species and habitats in the UK, and has been subject to peer review, including scrutiny by a Technical Advisory Group established by the project partners. In the case of the monitoring techniques, further refinement has been accomplished by field-testing and by workshops involving experts and conservation practitioners. Life in UK Rivers is very much a demonstration project and, although the reports have no official status in the implementation of the directive, they are intended as a helpful source of information for organisations trying to set conservation objectives and to monitor for ‘favourable conservation status’ for these habitats and species. They can also be used to help assess plans and projects affecting Natura 2000 sites, as required by Article 6.3 of the directive. As part of the project, conservation strategies have also been produced for seven different SAC rivers in the UK. In these, you can see how the statutory conservation and environment agencies have developed objectives for the conservation of the habitats and species, and drawn up action plans with their local partners for achieving favourable conservation status. For each of the 13 riverine species and for the Ranunculus habitat, the project has also published tables setting out what can be considered as ‘favourable condition’ for attributes such as water quality and nutrient levels, flow conditions, river channel and riparian habitat, substrate, access for migratory fish, and level of disturbance. ‘Favourable condition’ is taken to be the status of Annex I habitats and Annex II species on each Natura 2000 site to contribute adequately to ‘favourable conservation status’ across their range. Titles in the Conserving Natura 2000 Rivers ecology, monitoring and techniques series are listed inside the back cover of this report, and copies of these, together with other project publications, are available on the project website: www.riverlife.org.uk.

Executive summary This report is the second of two volumes. Part 1 reviewed the techniques available for monitoring suspended solids, siltation and sediment quality. The aim of this volume is to provide a minimum monitoring strategy to determine whether conservation objectives are being met in rivers which have been designated Special Areas of Conservation (SAC). The report considers only conservation objectives with respect to suspended solids and siltation, although some comment is made on phosphorus where this might relate to a need to monitor sediment quality. The possible implementation of the strategy is discussed for two candidate Special Areas of Conservation (cSAC) – the rivers Kerry and Eden. Key findings and recommendations are: 1. Conservation objectives have similarities with Environmental Quality Standards (EQS) as applied to,

for example, bathing waters and rivers, particularly in relation to the quality of receiving waters downstream of point discharges. Monitoring strategies adopted for these EQS are of direct relevance to monitoring for compliance with conservation objectives.

2. There is, however, an additional spatial component to conservation objectives which is lacking from many other forms of EQS, and new approaches to monitoring are needed to account for this.

3. It is recommended that by default a statistical approach should be taken to monitoring design, in common with other EQS compliance protocols. If representative or judgemental monitoring is used, it should be assessed with respect to a preferred statistical approach.

4. Careful consideration should be given to the selection and formulation of conservation objectives to ensure that compliance can be reasonably and unambiguously tested. An appendix is included that provides statistical details.

5. The River Kerry cSAC is a single short reach over which conditions are unlikely to vary significantly. However, little is known of present conditions. It is recommended that baseline data on both suspended solids and siltation be collected, with a modest programme of sampling at representative sites thereafter. It will also be necessary to develop a method for measuring siltation which is appropriate for freshwater pearl mussel habitats and which involves minimal disturbance. It should also be noted that mobility of coarse sediment in the River Kerry during natural flood events is also a threat to the pearl mussels.

6. The River Eden cSAC, while much larger, has a wealth of past data on water quality and to a lesser extent river substrate, although there is no siltation data. It is recommended that the present monitoring programme for suspended solids be continued, with more frequent manual sampling at a small number of sites which are close to non-compliance or have been identified as being of concern. It is also recommended that automatic samplers be installed at six sites within the cSAC where flow is currently gauged to provide monitoring during high flow events. The method for calculating an annual mean concentration from mixed manual and automatic sampling strategies is described. A new monitoring network for sampling river substrate is put forward for the collection of freeze cores for the assessment of siltation. Investigation of scour is also recommended at a subset of these sites. Some minor revision of these recommendations may be required once SAC units have been derived for the Eden but the principles involved will remain the same.

7. The two example rivers required quite different approaches to the development of a minimum monitoring strategy and this suggests that the provision of fixed guidelines is unwise. However, the principles involved in the development of the strategies are fully discussed and should be applicable to other SAC rivers.

8. The need for long term R&D to further our understanding of micro-habitat response to suspended solids loadings, and where relevant erosion, has been identified. This would also include an understanding of how the siltation of individual micro-habitats relates to more general assessments of siltation.

Contents 1. Introduction 1 2. Background 3 2.1 Existing river monitoring strategies 3 2.2 Statistical considerations in environmental monitoring network design 4 2.3 Monitoring design for conservation objectives on rivers 7 3. Application to the River Kerry 11 3.1 Conservation objectives 11 3.2 Description of the River Kerry and known pressures 12 3.3 Existing data on suspended solids and siltation 14 3.4 Monitoring strategy 15 3.4.1 Monitoring to establish a baseline 15 3.4.2 Investigative monitoring 18 3.4.3 Additional understanding 19 3.5 Summary 20 4. Application to the River Eden 23 4.1 Conservation objectives 23 4.2 Existing information and pressures 25 4.2.1 River habitat and geomorphological assessments 25 4.2.2 Suspended solids 26 4.2.3 Phosphorus 26 4.2.4 Bed substrate 27 4.2.5 Known adverse ecological influences 27 4.3 Monitoring strategy 28 4.3.1 Selection of sampling sites 28 4.3.2 Suspended solids concentrations 31 4.3.3 Siltation 32 4.4 Summary 34 5 Conclusions and recommendations 37 Acknowledgements 39 References 40 Appendix 1 43

1. Introduction This report is the second of two volumes. Part 1 (Naden et al. 2003) reviewed the techniques available for quantifying particulates in water columns and in substrates and provided recommendations for monitoring techniques. It also included essential background information and definitions relating to particle size, suspended solids, loads and siltation. In this volume, we develop a minimum sampling strategy for suspended solids and siltation for two of the cSAC rivers: the River Kerry and the River Eden. The purpose of monitoring SAC rivers is to determine whether conservation objectives are being complied with. These objectives are currently in draft form in the Favourable Condition Tables for individual species (see Part 1 Section 2.1 for a summary in relation to suspended solids and siltation parameters). These objectives relate to particular time frames and are intended to be met at all locations within the SAC. The monitoring programme must therefore have both a temporal and a spatial component. Since not all times and places can be sampled, it may be necessary to interpolate, by estimating from a sample, the compliance at unmeasured times and places. The interpolation component suggests that a statistically based monitoring programme be considered, rather than one based on convenience or judgement. Such a programme aids interpolation, and can provide uncertainty estimates of interpolated values from a limited sample. Conservation objectives for SAC rivers have been set in response to the requirements of the Habitats Directive (92/43/EEC). However, they also relate, in part, to the requirement for good ecological status laid down in the Water Framework Directive (2000/60/EC) and there may, in time, be synergies in the required monitoring strategies. At the present time, decisions as to the monitoring demands of the Water Framework Directive have yet to be made, particularly with respect to suspended sediment and siltation, although some discussion of monitoring principles can be pursued. The Water Framework Directive identifies three classes of monitoring: surveillance, investigative and operational. The purpose of surveillance monitoring is to provide an overview of conditions, spatially or temporally or both. Surveillance measurements will implicitly be used to interpolate information and a statistical design is likely to be desirable. Surveillance monitoring may be used to assess long-term changes in conditions, and provide information for use in designing other more focused monitoring programmes. Investigative monitoring is intended to provide information on the nature and extent of an identified problem. It is likely to evolve in space and time, as new information becomes available, and it is possible to focus more closely on the problem under investigation. In this case there may be no natural statistical population being sampled, and a statistical approach to monitoring may be meaningless. Operational monitoring may be viewed as surveillance monitoring of regions or periods identified as being “at risk”. It also refers to any monitoring which may be undertaken to determine changes in status following management interventions. The approach to monitoring design considered in this report might be appropriate for either surveillance or operational monitoring. Surveillance monitoring design for environmental variables is receiving increasing attention, motivated partly by legislative requirements, and also by a desire to estimate the effects of environmental management strategies. Statistical (or probability) designs for surveillance monitoring have been pursued particularly vigorously by the US Environmental Monitoring and Assessment Program (EMAP). In this, more rigorous survey methodologies have been introduced, with a commitment, for example, to probability sampling in all their monitoring programmes, rejecting convenience or judgemental sampling (Vos et al., 2000). In Europe, there has been less emphasis on this sort of rigour, partly because there is more expert knowledge of European rivers, a lower proportion of which are in wilderness or remotely populated areas about which little is known. Sampling in Europe often simply refines existing extensive knowledge. Particular water quality concerns on individual rivers are often well-known qualitatively, and all that is required is to quantify the problem with focused investigative monitoring. There is, for

example, no reference to statistical considerations in monitoring design in the Environment Agency proposals for developing a national environmental monitoring and assessment framework (Environment Agency, 1995). Nevertheless, statistically designed operational monitoring schemes are used in the UK and elsewhere in Europe to satisfy a number of legislative requirements, for example the EC Bathing Water (76/160/EEC) and Urban Waste Water Treatment (UWWT) (91/271/EEC) Directives. Statistically based protocols are used for consent monitoring for compliance, applied to point source discharges by the Environment Agency and SEPA. These are also applied to receiving waters at the point of complete mixing for compliance with Environmental Quality Standards (EQS). Designed monitoring schemes are also used in spatial classification schemes such as the UK River Habitat Survey (RHS) (Jeffers, 1998). Examples such as these can be used as a starting point for designing monitoring schemes for assessing whether conservation objectives are being met in rivers designated as SACs. Alternatively, any non-statistical scheme may be discussed with reference to the inferential limitations arising from the lack of a statistical design. Conservation objectives are similar to consents/EQS in that they include the concept of pass/fail for individual samples, with a requirement to make wider inferences from these measurements, particularly on a temporal scale. However, in common with river classification schemes, there is a spatial component to conservation objectives which is often lacking in consent/EQS compliance requirements. This report provides a general discussion of sampling strategies and monitoring protocols before going on to outline a generic process for selecting surveillance monitoring sites and their required temporal sampling. The suggested protocols are applied to the rivers Kerry and Eden to provide a minimum monitoring strategy for these rivers. Use of existing sampling protocols and sites within these catchments is discussed. Recommended techniques for monitoring (see Part 1 for details) are also included along with a discussion of costs and logistics where possible.

2. Background This section considers monitoring for conservation objectives in the broader context of existing approaches to environmental monitoring. Present UK monitoring programmes are discussed, including spatial sampling programmes which are thought relevant to compliance testing. Statistical approaches to monitoring are discussed, since these are believed likely to achieve increasing importance. Some of the statistical methodology underlying existing consent/EQS compliance requirements is discussed. The particular relevance of existing monitoring programmes and statistical monitoring strategies with respect to conservation objectives is then considered. 2.1 Existing river monitoring strategies Rivers in the UK are already monitored for a number of purposes. Routine water quality monitoring is carried out by the Environment Agency and Scottish Environment Protection Agency (SEPA) for a range of determinands. The monitoring network varies in density, but in lowland England includes most streams of order 3 and above. Data from these sites were originally intended to provide a record of water quality in major rivers and downstream of point sources at the point of complete mixing. Under the UK Water Resources Act 1991, the Environment Agency and SEPA are obliged to monitor the extent of pollution in controlled waters. The Environment Act 1995 prompted a review of the Environment Agency's and SEPA’s monitoring responsibilities. There were no statistical monitoring design considerations in setting up the present monitoring network, but it was established with the intention of giving good coverage of UK rivers, both spatially and temporally. An emphasis on monitoring downstream of (contaminated) point source discharges tends to bias measurements towards sites with poorer overall quality than would be indicated by a statistically designed monitoring programme. Typically, samples are collected monthly at routine monitoring sites, and, provided sampling is not biased, this is sufficient to give an indication of the most significant deviations from the usual conditions at the monitoring sites. In most cases it will not, however, provide a very precise estimate of the annual mean concentration. This is particularly true for water quality determinands that have a very skewed distribution, of which there are many, with suspended solids being probably the most extreme case. Although not designed for spatial interpolation, data from these monitoring sites are used to assign river reaches the chemical component of the General Quality Assessment (GQA) classification. This is done by linking river reaches to one or more monitoring sites, and assigning the quality of the whole reach on the basis of the water quality of the monitoring sites. Such a procedure tends to give estimates of water quality which are biased towards the poorer quality measured downstream of any point sources. Nevertheless, if the same monitoring sites are sampled repeatedly, probabilities of improvement at those sites may readily be computed and are likely to give a good indication of overall improvement in water quality in the river over time. Spatial interpolation and extrapolation for water quality often rests on the assumption that while water quality can change rapidly over time, spatial variation between major confluences or discharge points is not expected to be great. This is because the diffuse source contribution of water quality determinands will generally be small in relation to material already present in the river. This is particularly true of larger rivers, though less so for smaller tributaries. The role of in-stream processes in changing concentrations is also assumed to be small. In addition to monitoring river water quality, the Environment Agency and SEPA have a responsibility for monitoring point discharges to rivers. This is to ensure that discharge concentrations conform to the requirements of the UWWT Directive and other UK consent legislation. In the case of waste water, the directive itself specifies numbers of samples to be taken, and the number of individual failures allowable in a year before compliance is rejected. The monitoring design is concerned only with compliance over time at a single location. There are similar explicit monitoring criteria for compliance with the Bathing Waters Directive, although this also has a spatial component. The monitoring programmes in support of these two directives are statistically based.

While monitoring for consent and EQS compliance often does not have a spatial component, other monitoring schemes do. In addition to the Environment Agency and SEPA water quality monitoring programmes, there have been statistically-based monitoring programmes to provide data for classifying the river network according to a variety of criteria. Two examples are monitoring for the biological component of the GQA for rivers in England and Wales (Wright et al., 1997) and the RHS protocols for describing UK river habitat conditions (Raven et al., 1998). The outcome of such surveys is often a grading from good to bad with respect to some variable of interest. Some of these monitoring programmes are ongoing, and may provide information on the compliance with conservation objectives for specific catchments. At the UK scale, the RHS randomly selected three locations on rivers within each 10 km grid square (Jeffers, 1998). Other more locally based RHS applications have used a statistical sampling design based on random samples from a population of river reaches. 2.2 Statistical considerations in environmental monitoring network design Many environmental monitoring networks are not statistically designed but nevertheless provide useful information. Because of high correlations between locations, and qualitatively understood causal mechanisms, useful inferences may be made. For example, if there is a change in land use from permanent pasture to arable farming in a catchment, and there is a corresponding increase in mean annual suspended solids concentration, it might be reasonable to infer the change in land use as a cause. However, no probability measure can be assigned to the strength of the imputed causal hypothesis, and the farmers concerned might reasonably argue that some factor other than land use change was implicated. To demonstrate the validity of any inferences, we should ensure that data are collected using a statistically based monitoring scheme. Schreuder et al. (2001) emphasise the importance of understanding the constraints imposed by the sampling protocol on the interpretation of data. They point out that in the USA:

“…because of the threat of lawsuits coupled with an increased awareness of the need for statistically defensible survey methods among government, industry and environmental groups, use of probability samples is becoming mandatory.”

There are nevertheless major conceptual and logistical problems, as well as resource constraints, in implementing a statistical monitoring programme. The purpose of statistical monitoring design is to aid interpolation in space and time from sample data to statistics of the population sampled, which is assumed to be subject to statistical variability. The methodology used falls in the field of sampling theory, which finds wide application in all sorts of fields. Statistical monitoring design is appropriate in environmental sampling whenever it is possible to identify a population with statistical properties, whose individual members cannot all be measured. Having identified a population to be sampled, some rules are required, firstly to select which members of the population to sample, and secondly to estimate population values by extrapolation. This procedure will provide a probability distribution for population statistics, which may be used to assess the state of the environment, and may possibly be used as a basis for management. Typically in environmental monitoring we may want to decide whether certain criteria are being met, in a statistical sense. The key components of a statistically based monitoring scheme are:

• Identify question to be answered/hypothesis to be tested. • Identify a population to be sampled. • Identify the population statistics required to make decision. • Select a programme of random sampling to estimate the population statistics.

• Collect data. • Analyse data. • Make decision.

If a decision component is included, it may be that the population statistic need only be estimated with sufficient accuracy for a decision to be reached. This consideration enters into the selection of a sampling programme. In the context of river surveys, a number of possible populations may be of interest. These include the continuous discharge from a point source entering a river; the concentration of a determinand in the whole river network at any given time; or the composition of river substrate over the whole of the river network. Typical requirements are to determine, for decision purposes, whether a variable generally falls within a desired range, or whether there is any temporal change in its value. The monitoring design should ensure that sampling intensity in space and time is sufficient to provide population estimates within acceptable precision. It should also ensure that, by appropriate randomisation, the samples are taken in such a way as to eliminate biased inferences. If suitable designs are used and sufficient data collected, standard techniques can be used to estimate population statistics of interest, or carry out statistical tests. Appendix 1 describes t-tests for determining whether compliance values expressed as a mean and as a 0.90 quantile are being met. These include “benefit of the doubt” (BOTD) (i.e. 95% confidence of failure as used by the Environment Agency) and “fail-safe” (FS) (95% confidence of compliance, alternatives). Among water quality monitoring programmes in the UK, some of the most rigorous statistical analysis applies to discharge consents, leading to monitoring schemes with well defined probabilities of detection of non-compliance or compliance, and associated probabilities of incorrect classification. These properties are associated with each individual location, and refer to the distribution of concentrations over time. Ellis (1989) gives the statistical basis for the number of samples to be taken per year, and the overall compliance probabilities associated with differing numbers of point sample compliances. This comprehensive review of the statistical methodology behind many sampling programmes covers some of the background to EC and UK legislative requirements in this area. One of the commoner monitoring designs, discussed by Ellis (1989), which is provided here as an example, is that used in determining compliance of a point discharge with a consent. The design has no spatial component, but sufficient samples need to be taken to test compliance at that point over a period of time. A first requirement is that a target be set, namely the consent value. Owing to statistical variability, there is no expectation that the target will always be met, and consents include an allowance that the consent value be exceeded for a small proportion of the time. A monitoring programme is intended to determine whether that small proportion is being exceeded. Samples collected are classified as either passing or failing the compliance test, that is, they are either below or above the consent value. Several such samples are required to test compliance over a period, and Ellis suggests there are three basic requirements of the sampling programme. These are the selection of:

• A number of samples. • A statistic by which quality is characterised. • A pass/fail criterion to be applied to that statistic.

A consent may require that the 0.90 quantile for the concentration of some water quality determinand in a point discharge lies below a certain threshold. The population is the continuous discharge at that point. The 0.90 quantile is the population statistic to be estimated. Consent conditions may specify that at least 12 samples be collected during a year at equal time intervals. This is the random sampling programme with the selected sampling intensity. In this case the sampling design is systematic (equally spaced in

time). Each sample is designated a pass or a fail. These are the data that are collected. The number of passes is assumed to follow a binomial distribution with parameter 0.9. Data analysis is the calculation of the probability of obtaining the observed number of passes on the assumption that the 0.90 quantile takes the set value. The decision procedure is to assign the point discharge a pass or fail criterion on the basis of the number of individual passes or fails. This is based on the number of fails allowed before compliance is rejected. This number of values, for a given confidence level, is readily computed from the binomial distribution (see Appendix 1). Ellis gives tables showing the number of acceptable individual failures as a function of the number of samples collected, given a range of decision criteria. The natural spatial analogue of this consent monitoring programme is to use a quantile for the spatial distribution of samples, rather than the temporal distribution. This would imply an objective that, for example, the sample mean over a given period be less than a target value at over 90% of the catchment. Such an objective might allow some sites to fail consistently, while accepting that compliance was being achieved over the catchment as a whole. It is not clear whether this is a proposition which might be entertained. The imposition of absolute standards, with no acceptance of any compliance failure, is equivalent to the use of a Maximum Admissible Concentration (MAC) by the Drinking Water Directive. The implications of such a standard are discussed by Ellis (1989). Where there is a spatial network of monitoring sites, there are options for deciding which sites to visit on successive sampling visits. The simplest option is to revisit all on each occasion. One alternative is to resample some of the sites, but select a number of new sites, at random. More sophisticated schemes will base the selection of successive sampling sites on the outcomes of earlier samplings. This is clearly sensible where the location of a point source or localised diffuse source is being sought. The statistical analysis of such adaptive sampling schemes becomes complex, but this should be balanced against their convergence on problem areas. Statistical arguments are in this case of secondary concern. For a review of the issues see Fuller (1999). Texts on sampling and monitoring design in ecology and hydrology include Bartram & Ballance (1996), Green (1987), Gilbert (1987), with reviews in Patil & Rao (1994). The methodologies used are based on statistical theory, given for example by Cochran (1977). There are also a large number of practical guidelines on the design of monitoring networks (Platts et al, 1983; Macdonald et al., 1991). Barnett & O’Hagan (1997) in their report to the Royal Commission on Environmental Pollution give an overview of environmental monitoring. The authors emphasise the need for the compliance requirement to be defined in such a way that it can be tested, and probability statements made as to whether compliance has been achieved, using well-defined sampling protocols. They introduce the concept of a statistically verifiable ideal standard, comprising two parts: an ideal standard; and a standard for statistical verification of the ideal standard. This takes the form of a (probabilistic) level of assurance of compliance. 2.3 Monitoring design for conservation objectives in rivers SACs have been established in response to the Habitats Directive. This lays down procedures for identifying areas for conservation with respect to named species. The directive states:

“Member countries are required to establish conservation measures, and undertake surveillance of the conservation status…, with a report drawn up every six years… The directive encourages necessary research and scientific work…”

Under the Water Framework Directive, bodies of water forming habitat and species protection areas are to be monitored to determine compliance with conservation objectives. The directive states that:

“Bodies of water … shall be included within the operational monitoring programme … where, on the basis of the impact assessment and the surveillance monitoring, they are identified as being at risk of failing to meet their environmental objectives… Monitoring

shall be carried out to assess the magnitude and impact of all relevant significant pressures on these bodies and where necessary to assess changes in the status of such bodies resulting from the programmes of measures. Monitoring shall continue until the areas satisfy the water-related requirements of the legislation under which they are designated and meet their objectives…”.

In response to the Habitat Directive, draft Favourable Condition Tables (FTCs) have been drawn up for the Joint Nature Conservation Committee (JNCC), and are based on the ecological requirements of the species of European/Community interest listed in Annex 2 of the directive. These favourable conditions are used as the basis for conservation objectives. A typical conservation objective is that some physical habitat variable should remain within specified bounds, implicitly in some region of interest, and over a specified part of the year. Such objectives differ from most consents/EQS in being defined in both space and time. Nevertheless, like compliance with a consent/EQS, compliance with conservation objectives is essentially a form of classification. A site is either compliant or is not compliant on the occasion of sampling, depending on whether or not the measurement lies within the specified bounds. An alternative requirement is that there should be “no deterioration” in habitat. It is not possible to formally monitor such vague requirements, since it implies stability over some indeterminate length of time in the past. It is also difficult to define present behaviour, since this includes highly variable conditions. For example, extreme floods can be construed as part of the present-day characteristics of a catchment. It is very difficult to determine whether such behaviour is changing. Conservation objectives with respect to change can be reformulated along the lines: “There should be no deterioration in mean annual habitat attributes with respect to a five-year period 1995-1999”. This is testable, but the causes of any change in habitat would then need to be identified, and these might be simply long term climate variability. The FCTs recognise that conservation objectives do not need to be met at all locations and all times, and this limits the population (of rivers, periods) of interest and for which samples need be taken. Clearly, many objectives are unachievable, and do not need to be achieved, over significant lengths of river, which can readily be identified from inventories (exhaustive surveys). Monitoring is only required in areas which are not inherently unsuitable for the species of interest. For example, monitoring of substrate conditions for salmon spawning need not even consider reach lengths running over bedrock. Equally, the FCTs recognise that certain conservation objectives need not always be met outside the breeding season of some species. Where randomisation is used in spatial surveys, stratified sampling is often used. This may be accompanied by subsampling. Stratification is the division of a population into sub-populations. Sampling then focuses on each subpopulation, although, typically, combined statistics are computed from the sample data collected. Stratification is used to increase the accuracy of overall population estimates and to ensure that subdivisions of the population which are themselves of interest are adequately represented. To take an example, river reaches of interest may be defined, omitting those with no suitable habitat (though this omitted set may be regarded as a form of null stratum). The reaches are then stratified according to some census or inventory, such as land use, geology, gradient, stream order. A fixed number of reaches are selected at random from each stratum, with assigned probabilities within each stratum. This ensures control over the number of reaches selected from each stratum. Subsampling introduces flexibility into sampling. Under many definitions, a reach is a stretch of river between two major confluences. Such reaches may form primary units in a sampling scheme. Initial sampling is from

this population, which may be stratified. Each reach may be divided into subreaches of much shorter length, the secondary units. Subsampling is the random selection of a sample of these subreaches. Samples of river water, or river substrate, are collected from the randomly selected subreaches. Subsampling facilitates estimation of variability within primary units. In the context of stream sampling, one might expect measurements taken along a single reach to be more similar than measurements on different reaches. It may be important to distinguish and quantify these two different sources of variability. The temporal component of monitoring for conservation objectives depends on how those objectives are framed. If there is some specification of the length of time for which continuous exceedance is allowable, then the statistical distribution of exceedances needs to be estimated, implying that continuous measurement must be made. If conservation objectives are to be met at particular times of year, then continuous measurement may not be needed. It will be sufficient to sample at those times of year which are of interest, ensuring that the sampling regime accommodates any systematic temporal variation in the data. One refinement which may be useful is to stratify sampling according to conditions. In particular, high variability in concentrations of some determinands is expected during periods of high flow. To improve overall estimation, it may be desirable to stratify by flow, increasing the sampling frequency during periods of high flow. The analysis for this simple form of stratification is given in Appendix 1. Conservation objectives for a number of SAC species currently include specifications of suspended solids concentrations and substrate conditions. The monitoring design requirements for these two types of variable differ. In process terms suspended solids concentrations and substrate conditions are related. However, they are considered as independent criteria within the FCTs (Mainstone, pers. comm.). Suspended solids concentrations are already widely and routinely measured in the UK, typically at an interval of one month. Concentrations of suspended solids are related to flow, with large amounts of sediment being mobilised during high flow events. Figure 2.1 shows three typical examples of suspended solids time series derived from 15-minute turbidity data for three sites in the UK – an upland moorland site, an upland afforested site and a larger catchment which is part moorland and part agricultural with a small amount of urban development. Summary statistics are provided in Table 2.1. These illustrate the problems in defining simple routine monitoring strategies to provide reliable and consistent statistical measures. Conservation objectives are currently defined in terms of mean concentrations. First, it is assumed for the purposes of compliance that the mean concentration is an unweighted mean, although the mean concentration can be interpreted as the total load, or flux, over a period, divided by the total flow. This would give a mean concentration weighted by discharge, and is in general higher than the unweighted mean.

Figure 2.1. Examples of suspended solids time series derived from 15-minute turbidity data for three UK sites. Because suspended sediment concentrations are very high for very short periods, it is very difficult to estimate a mean concentration without very intensive sampling during high flow periods. Continuous monitoring of turbidity can be used but there are substantial problems in running the equipment and relating turbidity to suspended solids concentrations especially at the low levels of suspended solids required in the SAC rivers (see Part 1 Section 3). If a long data record of less frequent measurement is available, satisfactory estimates can be made on the assumption of stability over the period and an effective coverage of the flow regime. However, if annual means are required, monthly sampling is not adequate to estimate the mean. In addition, the standard statistical test (t-test) for compliance will be unreliable because of violation of distributional assumptions. More frequent sampling is essential, ideally by using an automatic sampler if the required frequency is higher than weekly but dependent on the logistics and practicalities of implementation.

Table 2.1 Example summary statistics for intensively monitored sites in the UK mean

flow m3s-1

mean SSC

mg l-1

st dev SSC

mg l-1

median SSC

mg l-1

75% SSC

mg l-1

90% SSC

mg l-1

max SSC

mg l-1

15 min 0.165 1.8 3.0 1.3 2.1 2.9 145.8 Cyff 1996 weekly 0.248 1.3 2.9 0.0 1.4 3.2 16.9

15 min 0.052 8.9 12.7 7.3 10.4 14.8 417.1 weekly + 3 hourly

0.073 4.8 20.3 0.0 4.3 8.5 288.6 Tanllwyth 1996

weekly 0.106 9.9 36.0 1.2 4.7 15.1 228.0 15 min 11.87 18.1 64.7 4.2 10.6 29.3 832.3 Swale at

Catterick 1995

weekly 17.36 29.5 116.3 2.1 3.3 9.8 638.4

An alternative is to express conservation objectives in terms of a median or some other quantile. Apart from the very highest quantiles these are likely to be more stable than the mean, and provide an estimate of the occurrence of particular concentrations. However, if the conservation species are particularly affected by infrequent, high concentration events, the mean or a combination of the median and a high quantile may be more appropriate. One feature of material in suspension or solution is that it is transmitted into rivers from sources that may be outside the SAC. If there are any monitoring sites outside the SAC area, data from these may be useful for any investigative monitoring if surveillance monitoring suggests cause for concern. However, sampling outside the SAC is not directly relevant to judging compliance with conservation objectives. Conservation objectives for river substrate specify maximum allowable percentages of fine sediment in the upper layers of gravels. The temporal variability of fine sediment content is much more limited than suspended solids but will vary through the year and in response to sediment transport events. Part 1, Section 4, detailed methods for monitoring siltation and discussed the relevance of different techniques. Freeze-coring was recommended as the standard technique for determining a reliable measure of percentage fine sediment in a coarser substrate but will not be an appropriate method for the pearl mussel habitats in the Kerry (see Section 3). Freeze coring provides a snapshot in time and should be carried out at a consistent time of year, for example, autumn, prior to spawning, to assess siltation. Freeze coring is both expensive and destructive (30 kg, approximately five cores, are required to give a reliable estimate of fine sediment content at a site). Annual monitoring for assessing fine sediment content is recommended except in areas where siltation is found to be a problem where a more investigative approach, possibly using baskets, will be required. It should be noted that it is not possible to test compliance against a maximum silt content and this should be reformulated, for example as a requirement that 90% of sites should have a fine sediment content less than 10%. 3. Application to the River Kerry The River Kerry is located in North-West Scotland, 3 km south of Gairloch. The catchment has an area of about 47 km2 and is predominantly upland with small pockets of farming in the lower reaches. The cSAC is restricted to the lower 3.4 km of river (Figure 3.1) and is designated for its outstanding

population of the freshwater pearl mussel (Margaritifera margaritifera), which includes the presence of juvenile mussels as well as abundant numbers of adults. This section reviews the conservation objectives for the Kerry, the pressures on the cSAC which have been identified and existing data. On the basis of this information, a minimum monitoring strategy is recommended for use on the Kerry. 3.1 Conservation objectives The conservation objectives for the site are currently being developed and might be quoted as:

• There should be no significant disturbance to the present population of freshwater pearl mussel. • The species should be capable of maintaining itself as a viable population. • The present distribution of freshwater pearl mussel within the Kerry river system, as defined by

the 1998 survey, should be maintained. • The present proportion of juvenile freshwater pearl mussel in the population should be

maintained or enhanced (to be defined by further survey). The conditions for how to maintain a viable population of pearl mussels are also being developed from the initial draft objectives given in Stuart (1998). With regard to in-stream and riparian habitat, these currently are

• There should be no deterioration in the current water quality in the River Kerry. • All target levels required to maintain favourable condition for the freshwater pearl mussel should

be met. • The flow regime in the river should be maintained. In particular the compensation flow in the

river should not be relaxed. Occasional moderate flushing flows in late spring should be obtained, to ensure a clean out of the sediments before the settlement of juvenile pearl mussels.

• Sudden changes between high and low flows due to hydro-generation should be avoided. • There should be no significant change to the quantity and distribution of the semi-natural

riverbed substrate or sediment composition. Particular care must be taken to maintain stability in the pearl-mussel--dense areas in the middle reaches of River Kerry.

• The extent of native bankside vegetation should be maintained or enhanced. There has already been an approximation to a census (Cosgrove, 1999) of freshwater pearl mussels in the River Kerry. This was undertaken between 14 and 23 September 1998, after a major flood in February that year. The census was based on an exhaustive survey of 50 m reaches along the complete length of the cSAC. Within each 50 m reach, a transect 1 m wide and 50 m long was searched so as to traverse the main areas of potentially suitable habitat as identified from previous surveys. Out of the 79 transects undertaken, Cosgrove recommends 12 easily identifiable “representative” transects for future monitoring which are stratified according to the abundance of pearl mussels (rare 1-50; scarce 51-100; common 500-999; abundant >1000 live mussels per transect). These have been identified in Figure 3.1. The population has also been studied by Hastie of Aberdeen University and this work has included preference curves (Hastie et al., 2000) and the impact of the 1998 flood (Hastie et al., 2001).

Figure 3.1. The River Kerry cSAC showing possible sampling locations. Approximate locations of Cosgrove’s (1999) reaches are shown in blue.

Inverkerry Fish Farm

Badachro Bridge

footbridge

HEP outlet

The conservation objectives concerned with suspended solids concentrations and bed substrate (see above) are expressed in terms of change from a baseline. However, there is no effective description of baseline conditions for the Kerry. The draft Favourable Condition Tables (FCTs) currently suggest that, for the freshwater pearl mussel, mean annual suspended solids concentrations should be less that 10 mg l-1 and that there should be less than 1% silt and fine sand (i.e. <0.2 mm) in the top 30 cm of substrates hosting juvenile and adult mussels. However, these target conditions are based on those for salmonids and are undergoing revision. A more appropriate depth may be the top 5–10 cm. Hastie et al. (2000) define preference curves for freshwater pearl mussels using substrate characteristics. Their work indicates that predominantly boulder substrate is preferred, while the pebble beds, dominant in the Kerry, are less preferred. It is suggested that the reason for this is the relative mobility of pebble beds in this high energy stream. Indeed, recently deposited pebbles and finer sediment were found on the banks of the Kerry during our visit in December 2001. Abrasion of the shells of pearl mussels throughout the Kerry also testifies to the intensity of sediment movement. The preference for boulder beds is not that the mussels live on the boulders but in the interstices between the boulders and on finer deposits in the lee of the boulders. In particular, clean sand is important for juvenile pearl mussels. It is important that there is sufficient flow through this fine substrate and that the interchange of interstitial and surface waters is not impeded by too great a content of fine sediment. However, this needs further clarification if quantified limits are to be set. Hastie et al. (2001) found no mussels in silty materials but concluded that this did not provide evidence that these areas are avoided, as patches of silty material are rare in the Kerry. 3.2 Description of the River Kerry and known pressures First, it should be pointed out that the River Kerry is highly modified, both in terms of the flow regime and fluvial geomorphology. We visited the Kerry on 4/5 December 2001. This was shortly after a heavy rainfall event and, consequently, much of the bed of the river was not visible. However, we were able to appreciate the pressures in the catchment and to see something of the habitat of the freshwater pearl mussels. Much of the catchment feeds into Loch Bad an Sgalaig which is managed as part of an HEP scheme by Scottish and Southern Energy. Figure 3.2 provides a schematic of the water management system and Plate 3.1a shows the overflow from the loch on 4 December 2001. The HEP scheme operates by balancing the amount of water in Loch Bad an Sgalaig and the lower storage reservoir. A minimum compensation flow of 0.45 m3 s-1 (85 million gallons per day) is maintained in the river below the HEP station. Flow has only fallen below this once in the last 20 years. At maximum generating capacity, the flow is 9.9 m3 s-1. Overtopping of the dam at Loch Bad an Sgalaig only occurs after sustained heavy rainfall.

Figure 3.2 . Schematic of the existing HEP scheme below Loch Bad an Sgalaig. The section of the river above the outlet from the HEP station, with its extremely steep forested slopes, may be a source of sediment (Plate 3.1b) but only during times when the loch is overflowing significantly. The catchment area around Loch Bad an Sgalaig is part of a large native woodland regeneration scheme. Agreement has been reached not to fertilise areas close to water courses as this might increase the nutrient content of the river. There is a proposal for a further woodland regeneration scheme along the lower reaches of the Kerry. Loch Bad an galaig not only regulates the flow regime in the River Kerry but will also trap any fine sediment from the upland area. It is understood that the gates and valves associated with the HEP scheme are tested annually but the effect of these tests in terms of flow, suspended solids concentrations and siltation is unknown. The cSAC begins just below the weir/fish heck below the outlet from the HEP

Plate 3.1a Dam at the outlet of Loch Bad an Sgalaig showing overflow on 4 Dec. 2001.

Loch Bad an Sgalaig

lower storage reservoir

HEP station

predominantly dry river bed River Kerry below HEP scheme

water transfers by pipeline

scheme, upstream of the footbridge at grid ref. NG 821723 (Plate 3.2a). Here the substrate is predominantly boulders and there is little finer material. Low densities of pearl mussels are found in the interstices of the boulders. The river has steep slopes and high velocities. The main area for pearl mussels begins around grid ref. NG 819727 (Plate 3.2b) where the bed slope is lower, there is a more varied substrate and there are areas of lower velocity, e.g. in marginal dead zones and under banks, which provide suitable habitat.

Plate 3.1b. Debris within the ‘dry’ channel above the HEP outlet; forestry bridge destroyed in February 1998 flood.

Plate 3.2a. Upper reaches of River Kerry cSAC; footbridge at grid ref. NG821723 above the only major tributary.

Plate 3.2b. Middle reach of River Kerry cSAC adjacent to fields used for agriculture. The large flood in February 1998 has been assigned a return period of 100 years (Hastie et al., 2001) on the basis of local memory. It is estimated to have destroyed about 10% of the freshwater pearl mussel population and moved gabion baskets put in by the Gairloch Anglers Association to enhance fishing. It also caused flooding of adjacent fields and massive disruption of communications. In response to this, flood berms have been built alongside the fields around grid ref. NG 819722 (Plate 3.3a). There is also concern about the road near to Badachro Bridge (grid ref. NG 827730) seen by the gabion reinforcing shown in Plate 3.3b. Hastie et al. (2001) describe the effect of the flood on substrate for a 250m stretch of the river near to its downstream limit. Evidence from visual estimates of dominant substrate type in over 430 1m2 quadrats suggests that the broad spatial patterns seen in different sediment types were preserved and that the most apparent effect was a reduction in the pebble beds, leaving a coarser, less mobile, substrate. There was also a small increase in the number of quadrats recorded as predominantly sand or gravel.

Plate 3.3a. Flood berm built to protect agricultural fields after major flood in 1998. In the middle reaches of the Kerry around Kerrysdale farm from Badachro Bridge to upstream of the lower gorge section, there is some farming activity with drainage of fields and strengthening of river banks. There is active sediment transport through this reach as seen by fresh pebble and finer deposits on the river banks. It is also in this area where potential sources of fine sediment are most apparent e.g. from fresh drainage ditches being dug for the field upstream of Badachro Bridge (Plate 3.4a) and eroding banks downstream of the bridge (Plate 3.4b). Whether this fine sediment poses a problem or whether it is simply carried out to sea is unknown, although anecdotal evidence is that, when pearl mussel surveys are carried out, there is some release of fines from the substrate. There is also some in-stream vegetation which may locally enhance the deposition of fine sediment.

Future possible threats to the River Kerry include a proposed second HEP scheme (http://www.highlandlightandpower.co.uk/our_latest_proposals.html). This will involve the building of a new turbine house at the southern end of Dubh Loch, which feeds into Loch Bad an Sgalaig. The scheme

Plate 3.3b. River Kerry at Badachro Bridge. Note gabions protecting main road to Gairloch.

Plate 3.4a. Potential sediment source – new drainage ditches in field above Badachro Bridge.

Plate 3.4b. Potential sediment source – bank erosion below Badachro Bridge.

also includes a second new turbine house at Slattadale, which will involve alterations to the flow regime on the Abhainn a’ Gharbh Choire, which also feeds into Loch Bad an Sgalaig. It is anticipated that this will increase the average daily flow in the Kerry by 23-4% and reduce the assurance of stable flows. A single access track to the southern end of Dubh Loch and buried pipelines to the proposed turbine houses will also be needed. The proposals include safeguards during construction such as the use of helicopters to ferry materials to the site and wooden pads across the ground for the movement of heavy machinery. Building activity generates fine sediment, although this should be retained within Dubh Loch and should not have an impact on the River Kerry itself. Other threats to the Kerry are increased flooding, in line with current experience in Scotland (Black, 1996; Mansell, 1997) and predicted climate change scenarios (Hulme and Jenkins, 1998). This will also lead to demands for road maintenance and associated river engineering.

3.3 Existing data on suspended solids and siltation Three samples of suspended solids concentrations are available from SEPA for the Badachro Bridge site on the River Kerry. These provide measures of 1.9 mg l-1 (23 Feb 1983), 2.4 mg l-1 (17 May 1984) and 4.2 mg l-1 (12 June 1985). Although these figures suggest that suspended solids concentrations in the Kerry are low, it is not known how representative these measurements are or under what flow conditions they were taken. There are no reliable flow data. Daily level data are available at the fish farm at the downstream limit of the Kerry but this simply records the level in the fish farm intake pool. It can provide information on when large flow events occurred but is not a reliable indicator of flow. Published level data from this site (Hastie et al., 2001) clearly show the effect of artificial influences. Scottish and Southern Energy do not record data on flows or levels, either in the river or at Loch Bad an Sgalaig. Sampling using hand grab samples undertaken by Hastie et al. (2000) gives a picture of the range of substrate characteristics across 454 1m2 quadrats taken from a 250m reach near to the downstream limit of the river. These data are reproduced in Table 3.1. Particle sizes are included as there are some slight differences in definition compared to the Udden-Wentworth scale quoted in Part I. The samples clearly

include areas with a silt and fine sand content of over 1% but how these relate to the micro-habitats of pearl mussels is not discussed. In addition, it is known that sampling using hand-grab methods tends to under-estimate fine sediment content as some of this is lost to the flow on sampling. There is one River Habitat Survey site on the Kerry at grid ref. NG 822722 just upstream of the footbridge in the upper part of the SAC. This 500 m reach reveals no silt or sand substrate (but see definitions in Part 1) and a mix of high and low energy flow patterns (high energy: 10% chute, 20% broken standing waves, 20% unbroken standing waves; low energy: 10% rippled, and 40% smooth). The site also has a very low fine sediment source index.

Table 3.1 Substrate characteristics for a 250m reach of the lower Kerry (after Hastie et al., 2000) Parameter mean % median % st dev % range % rock 11.1 0 24.7 0-100 boulder (>256mm) 14.3 5 18.8 0-90 cobble (>64mm) 22.5 20 17.5 0-80 pebble (>4mm) 37.8 40 24.7 0-95 gravel (>2mm) 7.6 5 7.7 0-60 coarse sand (>0.5mm) 3.6 0 5.3 0-45 fine sand (>0.25mm) 1.5 0 3.8 0-30 silt (>0.0625mm) 1.5 0 7.0 0-90 vegetation 18.5 5 25.3 0-100 From these minimal data, it is suggested that siltation is probably not a serious issue in the Kerry. However, there is no adequate baseline information from which to test the conservation objectives relating to suspended solids concentrations and substrate condition. Furthermore, given the long life cycle of the pearl mussel (100-130 years) and the difficulty of monitoring juvenile pearl mussels under 20-30 years old because of their size (growth rates are of the order of 1cm every 10 years), it is essential that physical habitat and environmental influences are monitored in order to foresee potential problems for the continued well-being of the existing population. 3.4 Monitoring strategy There are two essential aims required of a monitoring strategy on the River Kerry: (i) to establish a baseline from which to assess any future change and (ii) to investigate specific unknown issues or impacts. In addition to the monitoring, there are some areas where a better understanding of processes is required. These are outlined below. 3.4.1 Monitoring to establish a baseline Given the active population of freshwater pearl mussels, the minimal existing data and our observations of the river, it may be inferred that there is probably not a serious problem on the Kerry in terms of either suspended solids concentrations or siltation. Consequently, we would advocate minimum monitoring to establish a baseline. If this reveals a more serious concern, then we would propose more detailed monitoring. Fluvial audit and visual assessment While a brief description of the River Kerry was given in Section 3.2, it is recommended that a proper Fluvial audit be carried out on the river at a time of year when the substrate is visible. This will provide an assessment of sediment sources, areas of deposition and a geomorphological context for selecting sampling sites, interpreting quantitative data obtained from the baseline monitoring and assessing future pressures. It is recommended that the fluvial audit is updated every six years in order to point to any gross changes. It is also recommended that a continuous watching brief is kept on the number of flood

events (for example, by collating dates when the dam at Loch Bad a Sgalaig overflows) and any identified land or river management issues. The geomorphological assessment should also include a broad measure of the availability of suitable substrate throughout the Kerry, obtained by simple visual estimation methods. This should be undertaken at two distinct spatial scales. At the broad scale, it should detail the percentage cover of different sizes of sediment in each of the reaches identified by Cosgrove (1999). It should avoid the use of quadrats because of possible damage to the pearl mussels – photogrammetric methods may provide a suitable alternative. This measure can be used to identify any major change over time or following flood events. For example, although boulders are not likely to move far, even in an extreme event, they could be buried by other material. It is then suggested that a second measure is employed to indicate the availability of micro-habitats for pearl mussels – for example, a simple count of interstitial areas of a certain size, pockets of sand or gravel in the lee of boulders. The identification of the list of micro-habitat features should be undertaken in collaboration with pearl mussel surveyors. This second measure would be used to reveal less catastrophic changes in substrate availability due to changes in sediment regime. It is suggested that this measure could be focussed on the twelve "representative" transects identified for the monitoring of pearl mussels and be carried out at the same time as the pearl mussel surveys. Suspended solids concentration Given the low levels of suspended sediment already measured within the Kerry and the partially regulated flow regime, it is suggested that, from our experience in upland Wales (Section 2.3), weekly bottle samples may be adequate to establish the baseline mean suspended solids concentrations (Appendix 1). This may be most effectively carried out at this remote site using manual sampling by employing local independent and reliable assistance. It is suggested that sampling is carried out at a set time and day each week, unless the flow from the HEP outlet has either a diurnal or weekly rhythm. In this case, randomisation of the sampling times will have to be undertaken. It is essential that a range of flow conditions, including times of heavy rainfall and high flows are sampled. To ensure reliable data, a depth-integrated sample using a USDH-48 sampler is recommended. The bottle samples will need to be properly labelled with the site and time and date of sampling, kept in a refrigerator, and despatched, say at monthly intervals, to a UKAS accredited laboratory (e.g. SEPA) for filtering and weighing in accordance with standard procedures (see Part 1). Depending on these results, the frequency of sampling should be assessed and either increased, if weekly sampling is not sufficient to characterise the mean, or reduced, if the mean is well below the target level. If more frequent sampling is required, either because the data show a large standard deviation or because the criterion for suspended solids concentration is not met (e.g. under current FCTs, the mean is not below 10 mg l-1), we would expect that daily samples could also be collected manually. The use of an automatic sampler for more frequent samples on the Kerry might be considered but an automatic sampler may suffer from problems in winter either from freezing or battery failure and its maintenance would require more skilled assistance. As there is very good access to the river from the road, the sampler would also need some sort of housing to avoid any tampering with the equipment. A minimum monitoring strategy would sample at a single site and that at Badachro Bridge (grid ref. NG 827730) would seem to be suitable both in terms of access and its location in the centre of the main pearl mussel area. In addition, to collecting bottle samples, it is recommended that the river level at the time of sampling is also recorded. A stage board already exists at Badachro Bridge but this should be checked for stability and surveyed in to a local datum so that, in the event of the board being washed away, a replacement can be fixed so as to give identical readings. Monitoring stage will help to identify whether the samples have covered the range of flows and will be useful in interpreting differences in the data between years. If, after the first year of monitoring, suspended sediment levels are higher than expected, investigative work to look at the input and output of sediment from the cSAC would be advised. This would mean

adding additional sampling sites at the footbridge near the top of the cSAC at grid ref. NG821723 and near the fish farm at Inverkerry but above any tidal influence – for example, at grid ref. NG 814740. Stage boards should be installed at these sites. They should be properly sited so as to reflect the flow in the river. When installing a stage board, it is necessary to ensure that it is not going to be washed out by floods and to survey it into a fixed datum so that a new board can be re-installed to the same datum if it is washed out in an extreme event. If it is necessary to estimate sediment load, then quasi-continuous flow data will be required. A stable section is needed. The cheapest way of collecting flow data is using a pressure transducer, which measures water depth, connected to a data logger. To obtain a flow measurement, a rating curve will need to be established between the water depth and the flow. This will need the site to have a local control so that a given depth is always related to the same flow. It is thought that Badachro Bridge might fulfil this requirement, except for out of bank flows but further expert advice will be needed to confirm this. Measurements of flow at a range of depths will need to be carried out in the field using current meters in order to establish the rating curve. An alternative method is to use an ultrasonic flow gauge which obviates the need for a control section and rating curve, although the initial instrumentation is more expensive and more intrusive. Siltation As well as considering the gross availability of substrate, a baseline has to be established for the substrate condition in terms of siltation (the percentage of sediment less than 0.2 mm in the top 5-10 cm). Given the nature of the river and the designated species, it is recommended that this is monitored at the micro-habitat scale. It is also recommended that monitoring is carried out alongside the surveys of the pearl mussel population in order to ensure minimum disturbance. An initial survey is required and, if this does not reveal any potential problems, it should simply be repeated every year to assess temporal variability. If temporal variability is found to be low, frequency of sampling could be further reduced. The fluvial audit, visual assessment and watching brief (above) will provide a context for the interpretation of the results. The main problem is that suitable methods for sampling the substrate will have to be devised to ensure minimum disturbance on the pearl mussel population. This should be done in collaboration with those involved in the pearl mussel survey and conservation. The standard method of directly measuring siltation using freeze-cores is totally inappropriate in terms of scale. The coring equipment is not geared to small areas and, over a depth of 30 cm, 30 kg sediment must be removed from the river bed to provide an accurate measure. The hand grab method used by Hastie et al. (2000) is not suitable as this will lose fines and underestimate siltation. Possible techniques might employ some sort of adapted syringe that is strong enough to extract a small core of sediment or a modified small-scale freeze-coring device. Alternatively, some sort of disturbance technique might be used whereby a small cylinder is inserted into the substrate to the chosen depth, the sediment disturbed and the suspended mixture evacuated for subsequent laboratory analysis. These methods need to be tested for reliability and ease of use. This could initially be carried out in the laboratory to establish the number of replicates needed for an accurate assessment and in the field in similar substrate to those inhabited by pearl mussels. The method will then also need to be tested in collaboration with SNH and under licence to establish minimal disturbance to the pearl mussels. With regard to spatial sampling, it is suggested that the substrate sampling should closely follow the "representative" transects identified by Cosgrove (1999) for the population surveys and indeed be carried out alongside them to ensure minimal disturbance. As these transects have not been randomly selected, they cannot be reliably used to infer mussel densities along the river. Nevertheless, if change in the population, and any associated siltation, is the key concern, change at the specified transects, which are stratified according to mussel density, will be of interest in itself. If there were a decline in freshwater pearl mussels at these sites, this would be a matter for concern regardless of what was happening at

intermediate sites. It is suggested that 120 samples, randomly selected from the 12 transects (10 per transect) would be adequate to establish a baseline for siltation. Random sampling within transects will allow inferences to be made about the transect as a whole, although sample numbers are not high. In the event that the siltation requirements are not met, further investigative work may be required. If siltation requirements are met, then the sampling should simply be repeated every year. 3.4.2 Investigative monitoring In addition to the unknown baseline, there are a number of other unknown impacts on the sediment regime and substrate of the River Kerry that require investigation. Annual testing of gates and valves associated with HEP generation There is annual testing of the gates and valves associated with HEP generation. As there are supplies of fine sediment within the upper parts of the river and Loch Bad an Sgalaig acts as a sediment trap for fine sediment derived from the upper catchment, it is suggested that one of these events should at least be observed. If observations suggest that this is a significant event in fine sediment terms then monitoring, as outlined below, should be considered in order to quantify whether this does pose a potential problem. If necessary, this could then lead to recommendations regarding the time of year or ambient flow conditions under which this testing is undertaken. The minimum monitoring requirements for studying the impact of such an event is fine resolution sampling in time over the event at a series of points downstream. This may be done by installing a temporary set of automatic samplers or using manual bottle sampling at prescribed times. Given the possibility of high and turbid flows, it may be more reliable and safer to install automatic sampling for the events. It is suggested that three sample sites are chosen relating to the location of the pearl mussel habitat – the footbridge near the upstream end of the SAC at grid ref. NG 821723, Badachro Bridge (grid ref. NG 827730), and Inverkerry at the downstream end of the SAC but above any tidal influence (grid ref. NG 814740). During the event, it will also be useful to monitor stage using pressure transducers and dataloggers at each of the three sites. This will reveal changes in timing and attenuation of the flood wave as it passes downstream. The sampling should be geared to the temporal dynamics of the event, e.g. every 15 minutes, and continue until the end of the event or until background conditions are restored. If the event lasts six hours, then 72 samples will be generated for laboratory analysis. To assess whether the event caused any siltation, a subset of the baseline monitored points should be revisited and sampled. Future pressures A number of pressures relating to potential siltation in the Kerry have been identified, namely field drains, bank erosion, road protection and river engineering works, the additional Woodland Grant Scheme proposed for the lower reaches of the Kerry, and the proposed HEP scheme. Similar pressures elsewhere have been shown to have a marked impact on pearl mussel populations (Cosgrove & Hastie, 2001). If the baseline monitoring suggests that siltation is near the limit at a number of sites, then it may be necessary to develop sampling programmes to investigate the effect of these activities. 3.4.3 Additional understanding A number of research areas have also been identified where additional understanding should be gained. A key question is habitat stability. A stable substrate is necessary for the survival of the pearl mussel population. Once a pearl mussel loses its footing, this will not be regained and the mussel will die. It is estimated that 10% of the population was lost during the flood in February 1998 (Hastie et al., 2001) due to erosion. With the predicted increase in frequency of flood events in Scotland (Black, 1996; Mansell, 1997; Hulme and Jenkins, 1998), the stability of both the channel and individual micro-habitats is a major concern. For example, at the channel scale, the flood event in February 2002 was responsible for significant movement of coarse sediment and some channel change leaving pearl mussels stranded (Birkeland, pers.comm.). With regard to micro-habitat, the development of acoustic Doppler

velocimetry and three-dimensional fluid dynamics modelling has now reached the stage where the impact of high flows on small areas behind large boulders (e.g. Bouckaert and David, 1998) could be investigated in terms of both substrate stability and liability to siltation. This long-term R&D would seek to identify the magnitude of flows and sediment concentrations under which particular sediment patches in a given river reach would become unstable or incur siltation. A combination of laboratory flume work, field investigation and computer modelling would be required. It is recommended that methods of funding such work be explored. 3.5 Summary Table 3.2 summarises the monitoring strategy outlined above for the River Kerry in terms of equipment requirements, number of samples requiring analysis and logistics. Where relevant equipments costs and rough estimates of time have been included. As described above, there will also need to be an assessment of the data after the first year to ensure that this is an adequate monitoring strategy or if there is a case for concern in terms of the threshold levels of suspended solids concentrations and siltation. Table 3.2. Minimum monitoring strategy for the Kerry.

Activity Frequency Equipment No. samples for analysis

Logistics

Fluvial audit 6 yearly none none expert (3 days for survey and report)

Visual assessment 6 yearly digital camera none expert (15 days; collaboration with FWPM experts)

Routine monitoring of suspended solids

weekly USDH-48 (£250) stage board

52 per year local assistance SEPA labs

Method for assessing siltation

one-off unknown

none expert (and in collaboration with FWPM experts)

Routine monitoring of siltation

annually unknown 120 samples expert 5 days fieldwork plus lab analysis

Impact of gate and valve tests

at least one event if observations suggest necessary

3 autosamplers 3 pressure transducers and loggers

72 or 144 per event

expert 3 days fieldwork lab analysis data analysis

For suspended solids concentrations, weekly sampling has initially been suggested to provide an indication of baseline conditions. This was based on a comparison with an upland moorland catchment in central Wales. Should the mean and standard deviation of the data collected within the first year indicate that the sampling frequency is insufficient for adequately characterising the mean or assessing compliance then this should be increased to daily sampling. It will also be necessary to assess the coverage of the flow regime from the first year’s samples and adjust sampling times if necessary. Equally, if suspended solids concentrations are well below the target level, sampling frequency may be reduced for the continued assessment of compliance. The recommended continuous watching brief on the number of flood events and any identified land or river management issues should also be used to inform further monitoring needs. It is further

recommended that R&D work on siltation and stability of microhabitats be considered for future funding.

4. Application to the River Eden The River Eden (Figure 4.1) drains much of Cumbria between the Lake District and the Pennines, with a catchment area to the river mouth at Carlisle of 2300 km2.

Figure 4.1. The River Eden. Land use (Figure 4.2) is largely lowland livestock and mixed farming. There is also some upland sheep rearing, and one significant area of coniferous forest. The river is ecologically rich (Environment Agency, 1999), partly due to the influence of extensive outcrops of limestone within the catchment.

The cSAC, previously designated an SSSI, includes 410 km of the River Eden and 12 major tributaries. The main tributary excluded from the cSAC is the River Petteril. We visited the catchment in November 2001. This gave us a general impression of the catchment and some of the habitats but, as flows were high, we were unable to take a close look at the substrate. Plates 4.1 to 4.5 show some of the visited sites under these moderately high flow conditions.

Plate 4.1a. River Lowther salmon spawning habitat.

Plate 4.1b. Scandal Beck; diverse substrate with habitat for crayfish, salmon spawning and lamprey.

Plate 4.2a. River Eden at Kirkby Stephen.

Plate 4.2b. River Eden below Kirkby Stephen showing some evidence of bank erosion. Although not visible on the photograph, there was considerable fresh disturbance of the gravel substrate possibly during the high flows experienced on the previous day (21 November 2001).

Plate 4.3a. Crowdundle Beck. Some deposition of mostly sand material at confluence with field drain.

Plate 4.3b. Briggle Beck. Silt found within substrate; site below recently seeded field.

Plate 4.4a. River Eden at Lazonby.

Plate 4.4b. River Eden at Weatherall.

Plate 4.5a. River Irthing.

Plate 4.5b. Kingwater. Modified channel and evidence of silt on gravel bar.

Several species identified under the Habitats Directive are present in the river network covered by the cSAC, including three species of lamprey, bullhead, white-clawed crayfish, Atlantic salmon and Ranunculus communities. The cSAC stream network, and an indication of species richness, is shown in Figure 4.3. Significant stretches (926 km) of the Eden and its tributaries are designated salmon fisheries, and all complied with the imperative standards of the Freshwater Fisheries Directive (78/659/EEC) in 1998. Issues arising associated with water quality include potential pollution problems from major roads, and local problems associated with untreated or incompletely treated sewage effluent. This is particularly the case where most villages are not on mains sewerage. There is also concern over agricultural practices and intensive grazing which can lead to increased rates of soil erosion through runoff and increased erosion of river banks. Water quality in the river network is generally good, with around 85% classified as of good chemical quality in 1998 (Environment Agency, 1999), with a generally improving trend. This classification is based on dissolved oxygen, BOD and total ammonia, and tends to reflect the effectiveness of sewage treatment in the catchment. Biological quality is also generally good or very good, the classification being based on a comparison between measured biological scores and those expected in a river of equivalent size, type and location. While water quality is generally good, water quality objectives based on River Ecosystem Classification are in some cases even higher, so that much of the river network fails to comply with the water quality objectives set. 4.1 Conservation objectives The current conservation objectives for the River Eden are as follows: “To maintain, in favourable condition, the river habitat for:

floating formations of water crowfoot (Ranunculus) of plain and sub-montane rivers; populations of Atlantic Salmon (Salmo salar) and bullhead (Cottus gobio) populations of brook lamprey (Lampetra planeri), river lamprey (Lampetra fluviatilis) and sea lamprey (Petromyzon marinus) populations of white-clawed crayfish (Austropotamobius pallipes)

and the river and adjoining land as habitat for

populations of otters (Lutra lutra) to maintain the following features in favourable condition

residual alluvial woodland oligotrophic to mesotrophic standing waters of plains to subalpine level”

These objectives have been framed in terms of draft Favourable Conditions Tables drawn up for the JNCC. Although separate for each species, there is considerable overlap, and it is possible to identify an overall requirement for several criteria.

The draft favourable conditions identified for suspended solids, phosphorus and river substrate are given below. Although not strictly within the remit of this project, phosphorus has been included because of the interaction between fine sediment and the phosphorus concentrations in the overlying water. It was concluded in Part 1 Section 6 that an assessment of the potential for phosphorus uptake by and release from bed sediments using EPC0 determinations should be considered in areas where phosphorus is a concern. For this reason, it is included here.

• Suspended solids

Requirements vary according to species annual mean of <25 mg l-1 for bullhead, white-clawed crayfish and all three species of lamprey. Atlantic salmon requires <10 mg l-1 in spawning grounds from October to May, and an annual mean <25 mg l-1.

• Soluble reactive phosphorus Guideline concentrations have been suggested for the SRP concentration in streams:

0.02 mg l-1 – upland water courses 0.06 mg l-1 – mid-altitude water courses on hard substrates 0.06 mg l-1 – lowland, small and medium-sized watercourses on limestone and sandstone

• River substrate Channels should be dominated by clean gravels Maximum silt content:

Ranunculus beds: <20% in top 10 cm of mid-channel gravels Salmon and lamprey spawning areas: <10% in top 30% of spawning substrates Lamprey have other, rather complex, requirements for different stages in their life cycle. In particular, nursery habitat should be open-structure, silty and sandy, at least 2 cm in depth and overlain by less than 0.5m water.

Other favourable conditions concern water quantity and biological and River Ecosystem class. Only monitoring schemes for suspended solids, phosphorus and substrate are considered here, although it may be desirable to integrate monitoring with that required for testing compliance with other favourable conditions. 4.2 Existing information and pressures An environmental overview of the Eden catchment is provided by the Local Environment Agency Plan (LEAP) (Environment Agency, 1999). Stream water quality data in the catchment are obtained from an extensive array of Environment Agency monitoring sites (Figure 4.4) measuring a range of variables including suspended solids and soluble reactive phosphorus (but measured on unfiltered samples), usually monthly. There are also nine flow gauging sites on the Eden and its tributaries. Apart from national database information on soils, land use, agriculture, geology etc, there have been surveys of the river morphology, habitat and ecology. 4.2.1 River habitat and geomorphological assessments An RHS and geomorphological evaluation has been carried out on parts of the catchment (Parsons et al., 2001). The RHS covered the Eden between Appleby and its confluence with Scandal Beck, the Rivers Belah, Lowther and Eamont, Scandal Beck and Hilton Beck. All of these locations are known to be good ecological habitat for at least some of the SAC conservation species. Among the pressures on these catchments identified by the RHS was poaching of unfenced river banks in some tributary catchments. Some erosion of cliffs and bed scour was also noted. However, these concerns are not highlighted as issues in the LEAP, and the RHS survey concluded that extensive fine sediment infiltration into the river bed is not widespread. The RHS measure of habitat quality is closely related to diversity, and much of the region covered scores poorly when judged by this criterion. It has been suggested that the term “habitat quality” would be better expressed as “habitat diversity”. Many SAC species thrive in these low-habitat-quality streams and the major habitat quality pressures identified were poor bank vegetation structure and lack of trees.

The design for the RHS was statistically based, with all rivers being divided into 399 sections each of length 500 m. A full RHS was carried out on 227 randomly chosen sections. This sampling design is suitable for use in inferring statistically the river habitat along the complete length of river. The geomorphological assessment covered the same area as the RHS, with the exception of the River Eamont. It was conducted over all 500 m reaches of the selected rivers. It concluded that natural erosion was the most significant cause of erosion in all catchments, accounting for some 90% of erosion across the area studied.

In addition, a fluvial audit has been carried out for the River Caldew (Geodata, 2001). This provides a geomorphological context for the Caldew, including a study of historical changes and river management. It concludes that there is little evidence that catchment-wide issues, such as loss of bankside vegetation from grazing and poaching, have had any more than a local effect on the sediment system of the Caldew. The Environment Agency monitor suitable gravel beds in the river network annually to determine the location of salmon redds. These are present in most tributaries of the Eden, and along the main river as far downstream as Armathwaite. It is believed that the distribution of other conservation species has not been mapped in detail, although there is local knowledge of their abundance. 4.2.2 Suspended solids Suspended solids concentrations are routinely monitored at monthly intervals at the sites shown in Figure 4.4. These sites give a good spatial coverage of the catchment, although their location is not randomly determined. Note that the stream network shown in Figure 4.4 covers the whole catchment, including streams outside the cSAC. Comparison, by (Strahler) stream order, of the proportion of monitoring sites with the length of reach of each stream order in the catchment indicates first order streams are poorly represented by monitoring sites. First order streams are also poorly represented in the cSAC stream network, for which the existing monitoring sites give good coverage. What measurements there are for first order streams suggest that suspended solids concentrations are more variable spatially than in larger streams. This suggests a fine-scale patchwork of sources of suspended solids, or conditions for their mobilisation. A number of specific point and diffuse sources are also known to contribute significantly to the suspended solids load. Erosion has already been identified as a problem in several subcatchments of the Eden, and management options proposed (Parsons et al., 2001). Erosion has not been linked directly with the requirements of SAC species, but it is being reduced on the “precautionary principle”. Figure 4.5 shows mean suspended solids concentrations for the whole monitoring network in the Eden catchment. Figures 4.6a to 4.6d show the mean, standard deviation, median and 0.90 quantiles (or equivalently 90 percentiles) for those monitoring sites on cSAC rivers. These data are from 1993 to 2000, a period when records were available for most sites. Sites with fewer than 30 data points over the period are excluded. For sites where flow data are available, the suspended solids concentration data were found to provide good coverage of the flow regime up to the 95 percentile flow. The data are, therefore, sufficient to determine whether streams during that period were compliant with the suspended solids conservation objective of an annual mean concentration less than 10 mg l-1 or less than 25 mg l-1. Substantial numbers of samples showed suspended solids concentrations below detection (usually 3 mg l-1). In estimating the annual mean, the concentration for these samples has been set to one half of the detection limit value. Compliance test results are shown in Table 4.1. Results for both “fail safe” (95% confidence of being compliant) and “benefit of the doubt” (95% confidence of failure) tests are given. Some sites which fail these tests have shown clear recent improvement, and these sites may now have reached compliance. Inspection of past results, however, suggests that 10 of the 41 sites do not reach “fail safe” compliance with a 10 mg l-1 mean over the whole year. This is not surprising since 10 mg l-1 is not typically met in agricultural catchments under high flow conditions. Those sites which are “fail safe” compliant are less intensively farmed upland subcatchments. All sites are “benefit of the doubt” compliant although four sites have a mean concentration greater than 10 mg l-1.

WQ Monitoring Site EA Ref No Samples <detection Mean SD(mg/l)

RIVER IRTHING AT NEWBY EAST 88006332 102 27 11.77 24.6 fail FS pass BOTDBLENCARN BECK AT SKIRWIRTH ABBEY BRIDGE 88006291 105 13 11.22 12.92 fail FS pass BOTDRIVER IRTHING @ RULEHOLME BRIDGE 88006321 102 18 10.62 17.36 fail FS pass BOTDRIVER EDEN AT EDEN BRIDGE 88006382 105 24 10.61 21.68 fail FS pass BOTDKING WATER AT DOVECOTE BRIDGE 88006317 99 27 9.78 24.19 fail FS pass BOTDRIVER BELAH AT BELAH BRIDGE 88006196 105 37 9.61 23.47 fail FS pass BOTDLITTLE CALDEW AT CALDEWGATE 88006423 105 19 9.21 14.75 fail FS pass BOTDRIVER EDEN AT SHEEPMOUNT 88006427 94 21 7.78 13.78 fail FS pass BOTDRIVER EDEN AT ARMATHWAITE 88006301 99 31 7.66 17.9 fail FS pass BOTDRIVER LEITH U/S RIVER LYVENNET CLIBURN 88006202 96 25 7.59 12.89 pass FS pass BOTDRIVER EDEN AT LAZONBY 88006288 98 30 6.88 12.73 pass FS pass BOTDDACRE BECK AT A592 88006238 99 25 6.49 11.01 pass FS pass BOTDRIVER EDEN AT WARWICK BRIDGE 88006306 100 30 6.22 8.34 pass FS pass BOTDTROUT BECK AT KIRKBY THORE 88006197 100 29 5.99 7.6 pass FS pass BOTDRIVER EDEN AT WARCOP 88006173 95 33 5.97 16.76 pass FS pass BOTDRIVER GELT AT LOW GELTSIDE 88006329 101 44 5.82 25.36 fail FS pass BOTDRIVER EDEN AT BOLTON 88006186 95 26 5.73 6.7 pass FS pass BOTDRIVER EDEN AT APPLEBY 88006180 95 37 5.71 7.25 pass FS pass BOTDRIVER CALDEW AT HOLMEHEAD 88006421 76 24 5.55 7.46 pass FS pass BOTDRIVER LYVENNET UPSTREAM OF RIVER LEITH 88006212 101 40 5.54 10.94 pass FS pass BOTDRIVER IRTHING AT LANERCOST 88006313 104 36 5.49 7.89 pass FS pass BOTDHELM BECK AT LITTLE ORMSIDE 88006181 95 35 5.04 8.5 pass FS pass BOTDRIVER CALDEW AT SEBERGHAM 88006393 104 51 5 10.7 pass FS pass BOTDRIVER CALDEW AT THE GREEN DALSTON 88006418 78 31 4.86 5.55 pass FS pass BOTDKING WATER AT KINGBRIDGE FORD 88006318 101 42 4.75 6.93 pass FS pass BOTDRIVER IRTHING U/S B6318 88006331 98 46 4.61 6.57 pass FS pass BOTDHOFF (ASHBY) BECK AT COLBY HALL 88006190 98 37 4.27 7.62 pass FS pass BOTDCALD BECK DOWNSTREAM OF CALDBECK VILLAGE 88006392 103 54 4.09 9.39 pass FS pass BOTDRIVER LYVENNET AT MEABURN HALL 88006213 100 47 3.97 6.19 pass FS pass BOTDHILTON BECK AT ROMAN ROAD COUPLAND 88006185 95 44 3.79 6.72 pass FS pass BOTDSCANDAL BECK AT SOULBY 88006452 94 42 3.64 5.13 pass FS pass BOTDSCANDAL BECK AT A685 ROAD BRIDGE 88006163 96 48 3.56 4.75 pass FS pass BOTDRIVER EAMONT AT EXIT FROM ULLSWATER 88006262 98 47 3.43 4.65 pass FS pass BOTDRIVER EDEN UPSTREAM OF KIRBY STEPHEN 88006160 92 58 3.15 5.46 pass FS pass BOTDHOWE GRAIN AT SANDWICK 88006218 99 67 3.13 6.35 pass FS pass BOTDRIVER LOWTHER AT BAMPTON GRANGE 88006258 99 48 3.12 3.37 pass FS pass BOTDHAWESWATER BECK AT BOMBY BRIDGE 88006244 97 60 2.7 2.57 pass FS pass BOTDGOLDRILL BECK U/S ULLSWATER 88009739 77 64 2.17 2.18 pass FS pass BOTDSWINDALE BECK AT ROSGILL MOOR BRIDGE 88006241 96 70 2.13 1.5 pass FS pass BOTDRIVER CALDEW 50M D/S GRAINSGILL BECK 88006387 73 61 1.85 1.61 pass FS pass BOTDRIVER CALDEW AT MOSEDALE BRIDGE 88006388 101 82 1.81 1.32 pass FS pass BOTD

Test result?SS<10 mg/l

Table 4.1 River Eden Suspended solids concentration 1993-2000 compliance test

4.2.3 Phosphorus Phosphorus as “orthophosphate” (better described as soluble reactive phosphorus, or SRP, but determined by the Environment Agency on unfiltered samples) is routinely monitored at monthly intervals at the same sites as suspended solids. Mean values for the whole catchment are shown in Figure 4.7, and for the cSAC rivers, mean, standard deviation, median and 0.90 quantiles of phosphorus values are shown in Figures 4.8a to 4.8d. Total phosphorus, which includes particulate and dissolved unreactive phosphorus, is measured at only two sites on the Eden, Appleby and Bolton. Phosphorus is one contributory factor in eutrophication, which in rivers is generally associated with high SRP concentrations. These SRP monitoring sites provide good spatial coverage of the catchment, and Table 4.2 shows concentrations in the cSAC to have been generally “fail safe” compliant with the favourable conditions of 60 µg l-1. Many streams would fail “fail-safe” compliance at 20 µg l-1. However, the limit set is dependent on catchment type and only one small stretch of the River Eden is likely to have a target of <20 µg l-1, although some tributaries are likely to have a target of <40 µg l-1 (Robinson, pers.comm.). Tertiary treatment to remove phosphorus was introduced at Appleby STW in January 1998. The immediate impact of this in reducing SRP concentrations downstream is striking. In general, phosphorus has been a recent focus of attention and concentrations are almost uniformly falling. Usually this is due to improvements in sewage treatment. Given the generally compliant phosphorus concentrations, the extension to EPC0 determinations (see Part 1 Section 6) may be worth considering but only for a small number of tributaries and if ecological monitoring suggests that eutrophication is a problem. 4.2.4 Bed substrate The RHS and geomorphological evaluation identify sites with surface incidence of fine sediment (i.e. either a predominant component of the substrate or a discrete deposit). They do not provide an indication of “siltation” as such (see Part 1 Sections 2 and 5). River substrate composition is also visually assessed (in terms of percentage boulders, cobbles, pebbles, gravel, sand, silt and clay) at biological monitoring sites for GQA purposes. Estimates are made very rapidly using a somewhat different procedure to the RHS and tend to be biased towards sites with easy access. However, they do provide further indication of where substantial amounts of fine sediment occur on the surface of the river bed. These data are plotted in Figure 4.9, alongside the RHS data. It is clear from this that surface occurrence of fine sediment is relatively rare and localised within the catchment. There are no specific siltation data from either freeze-coring or other techniques available for the Eden.

WQ monitoring site EA Ref No Samples Mean SD(mg/l)

BLENCARN BECK AT SKIRWIRTH ABBEY BRIDGE 88006291 50 0.07 0.05 fail FS pass BOTD fail FS fail BOTDRIVER LEITH U/S RIVER LYVENNET CLIBURN 88006202 51 0.069 0.06 fail FS pass BOTD fail FS fail BOTDLITTLE CALDEW AT CALDEWGATE 88006423 55 0.055 0.039 fail FS pass BOTD fail FS fail BOTDRIVER CALDEW AT HOLMEHEAD 88006421 46 0.054 0.03 fail FS pass BOTD fail FS fail BOTDRIVER EDEN AT EDEN BRIDGE 88006382 55 0.053 0.022 pass FS pass BOTD fail FS fail BOTDRIVER EDEN AT SHEEPMOUNT 88006427 55 0.053 0.031 fail FS pass BOTD fail FS fail BOTDRIVER IRTHING @ RULEHOLME BRIDGE 88006321 53 0.052 0.037 fail FS pass BOTD fail FS fail BOTDRIVER EDEN AT LAZONBY 88006288 50 0.051 0.024 pass FS pass BOTD fail FS fail BOTDRIVER EDEN AT ARMATHWAITE 88006301 52 0.05 0.023 pass FS pass BOTD fail FS fail BOTDHELM BECK AT LITTLE ORMSIDE 88006181 50 0.048 0.074 fail FS pass BOTD fail FS fail BOTDRIVER EDEN AT WARWICK BRIDGE 88006306 53 0.046 0.017 pass FS pass BOTD fail FS fail BOTDRIVER IRTHING AT NEWBY EAST 88006332 53 0.043 0.032 pass FS pass BOTD fail FS fail BOTDDACRE BECK AT A592 88006238 53 0.041 0.034 pass FS pass BOTD fail FS fail BOTDRIVER EDEN AT BOLTON 88006186 52 0.036 0.038 pass FS pass BOTD fail FS fail BOTDRIVER CALDEW AT THE GREEN DALSTON 88006418 46 0.036 0.027 pass FS pass BOTD fail FS fail BOTDHAWESWATER BECK AT BOMBY BRIDGE 88006244 51 0.033 0.024 pass FS pass BOTD fail FS fail BOTDTROUT BECK AT KIRKBY THORE 88006197 52 0.032 0.014 pass FS pass BOTD fail FS fail BOTDRIVER LYVENNET UPSTREAM OF RIVER LEITH 88006212 54 0.023 0.026 pass FS pass BOTD fail FS pass BOTDRIVER EDEN AT WARCOP 88006173 51 0.021 0.009 pass FS pass BOTD fail FS pass BOTDHILTON BECK AT ROMAN ROAD COUPLAND 88006185 51 0.021 0.081 pass FS pass BOTD fail FS pass BOTDCALD BECK DOWNSTREAM OF CALDBECK VILLAGE 88006392 53 0.02 0.037 pass FS pass BOTD fail FS pass BOTDRIVER CALDEW AT SEBERGHAM 88006393 53 0.02 0.008 pass FS pass BOTD fail FS pass BOTDRIVER EDEN AT APPLEBY 88006180 51 0.019 0.015 pass FS pass BOTD fail FS pass BOTDHOFF (ASHBY) BECK AT COLBY HALL 88006190 50 0.019 0.02 pass FS pass BOTD fail FS pass BOTDSCANDAL BECK AT A685 ROAD BRIDGE 88006163 50 0.016 0.015 pass FS pass BOTD fail FS pass BOTDRIVER LYVENNET AT MEABURN HALL 88006213 50 0.016 0.013 pass FS pass BOTD pass FS pass BOTDRIVER IRTHING AT LANERCOST 88006313 53 0.016 0.012 pass FS pass BOTD pass FS pass BOTDKING WATER AT DOVECOTE BRIDGE 88006317 51 0.016 0.015 pass FS pass BOTD fail FS pass BOTDRIVER GELT AT LOW GELTSIDE 88006329 53 0.016 0.014 pass FS pass BOTD pass FS pass BOTDKING WATER AT KINGBRIDGE FORD 88006318 52 0.013 0.016 pass FS pass BOTD pass FS pass BOTDSCANDAL BECK AT SOULBY 88006452 50 0.011 0.007 pass FS pass BOTD pass FS pass BOTDRIVER IRTHING U/S B6318 88006331 52 0.009 0.017 pass FS pass BOTD pass FS pass BOTDRIVER BELAH AT BELAH BRIDGE 88006196 51 0.007 0.003 pass FS pass BOTD pass FS pass BOTDRIVER EDEN UPSTREAM OF KIRBY STEPHEN 88006160 49 0.005 0.005 pass FS pass BOTD pass FS pass BOTDRIVER EAMONT AT EXIT FROM ULLSWATER 88006262 53 0.005 0.007 pass FS pass BOTD pass FS pass BOTDRIVER LOWTHER AT BAMPTON GRANGE 88006258 51 0.004 0.003 pass FS pass BOTD pass FS pass BOTDHOWE GRAIN AT SANDWICK 88006218 50 0.003 0.003 pass FS pass BOTD pass FS pass BOTDRIVER CALDEW 50M D/S GRAINSGILL BECK 88006387 42 0.003 0.005 pass FS pass BOTD pass FS pass BOTDGOLDRILL BECK U/S ULLSWATER 88009739 52 0.003 0.003 pass FS pass BOTD pass FS pass BOTDSWINDALE BECK AT ROSGILL MOOR BRIDGE 88006241 52 0.002 0.003 pass FS pass BOTD pass FS pass BOTDRIVER CALDEW AT MOSEDALE BRIDGE 88006388 51 0.002 0.001 pass FS pass BOTD pass FS pass BOTD

?SRP<.06 mg/lTest result

?SRP<.02 mg/l

Table 4.2 River Eden SRP (orthophosphate) concentration 1997-2000 compliance test

4.2.5 Potentially adverse ecological influences Some potential areas of concern, which may be the focus for future monitoring, have been identified by English Nature (Maggie Robinson, pers. comm.): River Leith This receives drainage from the M6 and A6 roads, as well as localised pollution from point source inputs. Scandal Beck This is generally considered a near pristine river, though possible overgrazing has been identified. Crowdundle Beck Localised pollution from point source inputs. River Lowther The Lowther is considered to have the best spring salmon run and also has abundant Ranunculus communities. Localised pollution from point source inputs. River Belah The River Belah has significant erosion and a very mobile stream bed but no identified habitat problems. Hilton Beck Purchase of land in this catchment by the MOD should reduce overgrazing and local afforestation may increase. Briggle Beck Localised pollution problems from agricultural units. Rivers Irthing and Gelt Both rivers have good salmon runs. The Irthing is considered the most natural tributary of the Eden, including remnants of old floodplain woodland. River Kingwater The tributaries of the River Kingwater drain an area of plantation coniferous woodland, where there may be production of fine sediment by forest operations In general, Ranunculus communities appear to be healthy but there is a concern over siltation with regard to a range of species. However, there is little hard evidence to support this due to lack of monitoring. The source of this fine sediment is thought to be largely due to natural erosion processes exacerbated by over-grazing and cattle poaching. There is also a concern over recent changes in land use, following on from the Foot and Mouth outbreak, with the introduction of maize cultivation at the expense of grazing, as far south as Appleby. 4.3 Monitoring strategy A monitoring strategy is required for both suspended solids concentrations and siltation. For suspended solids concentrations, this should build on the existing monitoring network. For siltation, there is no baseline data available and a suitable sampling strategy needs to be devised. In consultation with English Nature, the focus of the siltation monitoring should not be individual habitats but a more general measure. Thus, it has been assumed that a strategy can be designed around individual river reaches. The relationship of such measurements to specific habitats and sediment dynamics needs further research.

4.3.1 Selection of monitoring sites Since the Eden cSAC is so large, it is currently being divided by English Nature into subregions or SAC units, each identified as having distinct landscape and conservation needs. It is likely that compliance with conservation objectives will have to be demonstrated for each subregion. However, as the subregions have not yet been defined, the strategy for site selection outlined here has been produced for the complete cSAC. The general principles used will apply to smaller units if subdivision of the cSAC dictates that more sampling is required. The region to be considered for monitoring is the cSAC stream network. Note that this network forms only a subset of the rivers and streams in the catchment which appear as blue lines on the 1:50,000 Ordnance Survey map. Of the streams present as blue lines, the River Petteril, for example, is absent from the cSAC stream network, as are most of the blue-line first- and second-order tributaries. The cSAC stream network is available in digital form as a sequence of nodes on a 50 m Digital Terrain Model (DTM) grid. This digital network can readily be analysed using GIS software, and can form the basis for any quantitative analysis of the network, including aspects of monitoring site selection and definition. The monitoring strategy used to assess compliance with conservation objectives on the cSAC stream network should take appropriate account of the extensive present understanding of the water quality and ecology of the river. The existing Environment Agency monitoring programme provides a near-inventory of water quality near the confluence of major tributaries. On the Eden and its tributaries, these are generally streams of order 3 (defined using “blue lines” the 1:50,000 Ordnance survey map). The Environment Agency monitoring programme provides only slightly less coverage of streams of order 2, and for higher order streams there is generally more than one existing monitoring site. A reach structure defined by the Environment Agency linked to these sites gives complete coverage of streams of order 2 and above. Biological monitoring sites on these reaches are used for biological GQA and include a visual assessment of substrate. Historical water quality data from those monitoring sites on the cSAC stream network are suitable for assessing past compliance with conservation objectives. However, existing river substrate data are not. The assessments made have been visual and descriptive. They do not provide the quantitative depth-profile information needed to determine compliance. A new programme of monitoring river substrate is therefore required and there may be some merit in sampling at a subset of the existing GQA biological monitoring sites. This has the advantage of falling within the existing monitoring framework, and allows some rough comparison with previous visual assessments. The disadvantage is that the GQA and cSAC stream networks are not coincident and GQA sites cannot strictly be used for unbiased spatial interpolation within the cSAC. In view of this, the option of using a new monitoring programme for assessing river substrate for conservation objectives should be considered. This would have the advantage of using the cSAC stream network directly, and the sampling programme could be linked to stream order, and provide statistical estimates of spatial variability. The disadvantage is that it is unrelated to existing monitoring protocols. If new monitoring sites for river substrate were to be selected, it would be desirable for the purpose of spatial interpolation to have a statistically designed array of sites. There is an extensive body of theory used routinely by those undertaking sample surveys. Methods such as stratified and random sampling are well-known and readily applied to populations of individuals. To apply these techniques to a stream network, some preliminary problems of population definition need to be overcome. Because a stream network is spatially continuous, unlike a population of individuals, and because there is direct causal linkage between upstream and downstream points, the definition of a suitable statistical framework requires some thought. We must identify a suitable population to be sampled, and a means of selecting samples from this population. It is natural to consider the network as a population of reaches. We can readily divide the digital stream network into such a population, following some agreed procedure. However, because some reaches are causally linked, while others are not, they cannot be viewed as a

population of equivalent independent units. To facilitate inference, it is proposed that the reaches be defined and grouped in such a way that those within each group, or sub-population, are hydrologically independent and have similar upstream drainage area. The first level of sampling is from the enumerated reaches in these subpopulations. Constructing the subpopulations of reaches is based on Strahler stream order. Working downstream through the network, first-order streams are clearly all hydrologically independent. The same water cannot flow through two different first-order streams. These first-order streams form the first sub-population for sampling. Further downstream, Strahler ordering splits second and higher order reaches at any confluence with a lower order stream. However, if we define any contiguous reaches of the same order as a single reach, then all resulting reaches of the same order are also hydrologically independent. This procedure, which can readily be implemented by GIS software, creates sequentially a separate subpopulation of independent reaches for each stream order. The subpopulations superficially resemble a form of stratification, but the causal links between some reaches in separate subpopulations make this interpretation open to investigation. Once the subpopulations of reaches have been defined, standard procedures can be used to select reaches for sampling within each subpopulation, and to identify within-reach precise sampling locations. Simple random sampling may be appropriate, or some form of stratification. Statistical inference from sampled data, including uncertainty estimation for unsampled reaches, is straightforward when carried out separately for each subpopulation. The Eden cSAC stream network has been divided into sub-populations of reaches as defined, using the ArcInfo GIS package. This generates a total of 47 reaches. Of these 35 are independent in the sense described (Table 4.3). Table 4.3 Strahler stream order of reaches in the Eden cSAC Stream order (Strahler)/subpopulation

Number of reaches (Strahler)

Number of reaches (independent)

1 24 24 2 15 8 3 4 2 4 4 1 The cSAC stream network mapped by stream order is shown in Figure 4.10. Clearly, as there is only one independent fourth order stream in the Eden cSAC, there is no information on variability between fourth order streams. We can of course estimate variability within the reach by subsampling. There is also very little which can be done statistically with the two third order streams. It is recommended that the monitoring strategy be able to identify both within- and between- (independent) reach variability for each sub-population, where possible. This would require the selection of several sampling sites within some reaches. Knowledge of between-reach variability will enable prediction, with quantified uncertainty, of properties of unmonitored independent reaches. It may also be a requirement that certain streams of particular interest be sampled with probability 1. This classification of the cSAC stream network can be used as a basis for any new sampling. Any further stratification, for example by SAC unit, should be considered within this framework.

4.3.2 Suspended solids concentrations The recommended technique for suspended solids concentrations (see Part 1 Section 3) is bottle sampling as this provides a reliable direct measure of suspended solids concentrations at the time of sampling. Surrogate measures are generally fraught for the low levels of suspended sediment required in the SAC rivers. Both manual and automatic sampling may be employed depending on the required frequency of measurement. For manual sampling, use of a USDH-48 sampler for depth-integrated sampling is also recommended rather than the bucket methods currently in use by the Environment Agency. Automatic sampling is most cost-effectively employed to collect high frequency data over flow events and so triggering by stage is desirable. Although this requires additional outlay in terms of equipment (i.e. pressure transducer and data logger), there will be considerable saving in the number of samples requiring analysis. One disadvantage of the existing Environment Agency monitoring programme for suspended solids concentrations is that the infrequency of sampling leads to poor estimation of suspended solids concentrations at high flows. Satisfactory estimates of the mean have been obtained from historical data because of the length of the data record, and the lack of any major changes. However, precise estimates of means for individual years cannot be obtained from such infrequent sampling (see Appendix 1). In addition, the t-test for compliance is severely compromised for such small samples and the test is unreliable for data as skewed as suspended solids concentrations. To overcome this, it is recommended that weekly samples be collected at selected monitoring sites where historical evidence suggests stream water may be close to non-compliance or where there are known concerns (see Section 4.2.5). Sites might include the Leith upstream of the Lyvennet (88006202), the Irthing at Newby East (88006332) and a new site on Briggle Beck at grid ref. NY 576346. It is also recommended that automatic samplers triggered by stage be installed at the flow-gauging sites on the Irthing at Greenholme, the Caldew at Holm Hill, the Eamont at Udford, the Lowther at Eamont Bridge and the Eden at both Temple Sowerby and Warwick Bridge. This will enable high-precision estimates of mean suspended solids concentrations to be calculated, and these will also be available for load estimation if necessary. Data from automatic samplers and routine monitoring data effectively comprise samples from two different strata, and may be analysed as described in Appendix 1. Details of equipment costs are included in Part 1 and summarised in Section 4.4 below. For the smaller streams within the Eden, it may be that the sites proposed for monitoring under the CHASM programme could provide useful data. Those within the cSAC area are located on Scandal Beck and Helm Beck. At these sites, it is proposed to install flow gauging and suspended sediment monitoring, using both turbidity measurements and automatic water samplers. 4.3.3 Siltation The requirement for river substrate is that the maximum percentage fines (<0.83 mm) in the top 30 cm should not exceed 10%. As noted above, a general measure of substrate quality is required, rather than focussing on particular habitats. The recommended standard method for measuring the fine sediment content of a substrate is freeze-coring (Part 1, Section 4). This is relatively expensive, time-consuming and destructive. To provide a representative measure for a single site, approximately 30kg of material need to be removed. This usually involves taking five cores. Considering both costs and conservation issues, the number of sampling sites should, therefore, be kept to a minimum. Sampling will need to be carried out during low flows and at a consistent time of year, for example, late summer. Within the framework of stratification and subsampling discussed, it is suggested that, of the second order reaches, those of the Lowther, Eamont above Penrith, Eden in the vicinity of Appleby and the Caldew be sampled. This ensures that each of the major rivers with second order reaches is sampled. Because these reaches are not selected at random but with certainty, they strictly form separate strata and inferences cannot formally be extended to the remaining four second order reaches. Additional sampling should be carried out to estimate within-reach variability as little is known about this. It is

suggested that a total of three sites be selected on the Lowther and three on the Caldew, both of which have long reaches of stream order 2. There are too many first-order streams for all to be sampled. However, from a consideration of the perceived pressures within the catchment, some need to be sampled with probability 1. These would appear to include Scandal Beck, River Belah, Crowdundle Beck, Briggle Beck, and the River Irthing, although there may be some other grouping of interest once SAC units are identified. A further six sampling sites should be selected from the remaining 19 first-order streams. It is assumed that these can be used to characterise the silt content of all first-order streams. If the characteristics of first-order streams are highly variable, then stratification by stream type/SAC unit would be advised and additional sampling may be required. Each reach sampled is a different length, and one option is to sample the six first-order reaches with probability proportional to length. There may be some merit in this, but reach lengths are all the same order of magnitude, so this refinement is not considered for the present. In addition, sites should be selected on the third-order reaches of the Rivers Eamont and Eden. The main Eden is the only fourth-order stream and this should be sampled at three sites to give some indication of within-reach variability. This may need careful consideration because of the size of the river. Generally, freeze-coring can only be accomplished if the flow depth is less than 30-40cm and the maximum velocity is less than 0.5m s-1. If these sites can be sampled, this gives a total of 24 sampling sites (see Table 4.4). Sampling sites, that is 50 m sub-reaches within reaches, should be identified by simple random sampling, on the assumption that suitable river gravels are located within most 50 m reaches. If they are not, the nearest convenient location, bearing in mind access, permission and availability of suitable substrate, may be selected. The precise location of these sampling sites should be noted for revisiting. Table 4.4 Number of sampling sites for river substrate on the Eden cSAC Stream order

Reaches Sampling sites

1 24 11 2 8 8 3 2 2 4 1 3 The data obtained from such a sampling exercise needs to be interpreted with respect to both the temporal sequence of sediment transporting events and the micro-habitats of concern. Part 1 Section 4 detailed the information obtainable from different methods of measurement. It was pointed out that freeze-coring gives a single spot sample in time. If salmonid redds were being sampled then freeze-coring after hatching would provide an assessment of the amount of siltation over the current year during the spawning season as the gravel is cleaned by the salmonids in creating their redds. However, for general bar areas, the silt content will depend on the history of sediment movement. Fine sediment may be deposited either at the time of gravel displacement or infiltrate subsequently (Part 1 Section 2). It is therefore useful to know when sediment movement occurred and the installation of scour chains (Part 1 Section 4.1) at a small number of these sites is additionally recommended to provide some indication of temporal variability. These should be monitored after each flood event to gain an understanding of the sediment regime and enable the freeze-core data to be put in context. Freeze-coring itself should be undertaken annually in order to estimate temporal variability in silt content. In addition, it is recommended that a fluvial audit, like that for the Caldew (Geodata, 2001), is undertaken throughout the cSAC region, with a briefer update every six years in line with the reporting cycle required by the Habitat Directive. This will provide a qualitative understanding of the fluvial geomorphology and the sediment regime. It is preferred to the geomorphological addition to the RHS (see Part 1 Section 5) but can build on the data already collected (Parsons et al., 2001). In particular,

interpretation of these data in terms of the rates of bank erosion, their relationship to the timing and transport capacity of flow events and the existing suspended solids loads of the Eden, and their significance within the catchment should be addressed. Further research issues may be to quantify the contribution of fine sediment from field drains (Chapman, et al., 2001) and to assess travel distances of sediment i.e. where and when it is deposited relative to the passage of the flood wave in individual events (Smith et al., in press). In the event that siltation measurements reveal a problem, more detailed monitoring might also be required. Baskets will show siltation over the year and can effectively be deployed in salmon redds (see Part 1 Section 4). The issue of relating general levels of siltation to species-specific habitats, and indeed to ambient levels of suspended sediment concentrations, should not be overlooked. This is a current gap in our understanding of sediment behaviour and its relation to physical habitat in rivers. It requires a combination of measurement and modelling skills which have currently been developed to the point where bridging this gap is now feasible. It is recommended that funding routes for this vital long-term R&D are explored. 4.4 Summary On the Eden, given the large amount of existing knowledge, the focus has been on recommending a strategy for surveillance monitoring for compliance with the draft favourable conditions. Thorough discussion of the number of sampling sites and the rationale for their selection has already been presented. Table 4.5 summarises the recommended minimum monitoring strategy in terms of equipment requirements, number of samples for analysis and logistics. In the case of the automatic samplers located at existing flow gauging stations, it has been assumed that a power supply and housing will already be available. Table 4.5. Minimum monitoring strategy for the Eden. Activity Frequency Equipment No. samples

for analysis Logistics

Fluvial Audit 6-yearly none none expert Suspended solids: weekly sampling

weekly USDH-48 (£250)

52 per year for 3 sites

Environment Agency

Suspended solids: automatic sampling

visits after triggered events

6 automatic samplers with pressure transducers and data loggers

24 per event per site

Environment Agency or expert

Freeze-coring annually to define temporal variability

none 5 cores at each of 24 sites

expert with own freeze-core equipment; approx. 30 days fieldwork and 10 days laboratory work

Scour survey after flood events

scour chains (5 per site; 10 sites randomly selected)

none expert

It is recommended that monthly sampling is continued at the other Environment Agency water quality sampling sites within the cSAC and that there is liaison with University of Newcastle over the CHASM monitoring sites.

As there are currently no siltation data available for the Eden, the recommended sampling strategy should be assessed after the first year's data collection. If this reveals that siltation is a potential problem within the Eden, then more intensive and targeted sampling should be considered. For example, baskets could be used to examine the annual rate of accumulation of fine sediment in the gravel substrates. It is also recommended that longer term R&D to determine the relationship between general siltation and that in particular habitats be explored. This may also be designed to indicate the levels of suspended solids concentrations which would be detrimental to particular habitats under the existing range of flow conditions.

5. Conclusions and recommendations In recommending a monitoring strategy, a balance has to be struck between desirable statistical properties and the practicality of particular field sampling programmes. This has been taken account of in the recommendations for the Kerry and the Eden. The experience of these two quite different cSACs suggests it would be imprudent to set out fixed guidelines for monitoring. However, it is recommended that the default approach to monitoring design should be statistical, and any deviations from this should be justified. Nevertheless, rigorous adherence to statistical design is unlikely to be desirable in most cases. Stratification based on stream order and possibly other criteria, coupled with subsampling of major reaches is likely to be a widely applicable approach whenever a new spatial monitoring programme is required. While the need for statistically based temporal monitoring has been appreciated for some years (and is incorporated in some legislation), statistical aspects of spatial monitoring of rivers have not been fully explored. The recommended strategy appears practical and intuitively appealing, as well as having a sound statistical underpinning. Conclusions may be summarised as follows: General • Conservation objectives should ideally be phrased in such a way as to be testable. Requirements

such as “no-change” are difficult to assess unless reference is made to a specific period in the past. A maximum level is unsuitable for compliance testing.

• In defining conservation objectives there should be some assurance that they truly summarise

favourable conditions for species present. A mean suspended solids concentration is difficult to estimate with precision, and may not be representative of species requirements. It is notable that some objectives are expressed in terms of means and others in terms of percentiles. The median would provide a better measure of average suspended sediment concentrations while a high percentile (e.g. 90 or 95%) would provide a measure of extreme concentrations. The specification of the summary statistic has implications for the required frequency of sampling.

• By default, monitoring design should be statistically based, since this allows for unbiased estimation of

population statistics from much smaller samples. However, non-statistical monitoring using representative or judgemental sampling may be sufficient when estimation of population values is less important, or when any possible bias arising from non-random sampling is unlikely to be large. However, whenever a non-randomised design is used, there is a possibility of bias in inference.

• It is currently unclear what overlap there is with the monitoring required under the Water

Framework Directive, particularly with regard to suspended solids and siltation.

For the River Kerry • Conservation objectives are expressed as “no change”. This should be rephrased to “no change on

baseline conditions measured in 2002” or other testable consent objective as in the case for the pearl mussel population.

• Since the Kerry cSAC is a single reach, representative sampling of suspended solids and river

substrate is sufficient. Nevertheless the inferential limitations of this need to be recognised. • Existing data are inadequate to provide any estimate of the mean suspended solids concentration.

Weekly sampling is recommended to provide baseline values, although after the first year of sampling, the required sampling frequency should be re-assessed.

• A fluvial audit and visual assessment of substrate is recommended to provide a context for assessing

siltation. • A suitable monitoring technique, for minimal disturbance, will need to be developed for assessing

siltation in pearl mussel microhabitats. Once this has been achieved, annual sampling of randomly selected sites within the representative transects identified by Cosgrove (1999) is recommended.

• Coarse sediment movement and associated channel change during natural flood events is also of

considerable impact on the pearl mussels and their habitat. For the River Eden • Existing water quality monitoring sites give good coverage of the cSAC. Although the spatial

component of the design is not statistical, interpolation between sites is unlikely to be far wrong. The evidence is that most sites are compliant with conservation objectives for suspended solids if a “benefit of the doubt” (95% confidence of failure as used by the Environment Agency) test is carried out, with some 25% failing a “fail safe” (95% confidence of compliance) test. Most sites appear to be compliant with the phosphorus objectives under the appropriate test, depending on whether the catchment is upland or lowland.

• To determine compliance for suspended solids it is essential to increase the sampling frequency from

monthly to weekly at sampling points where compliance with the suspended solids conservation objectives is marginal or there is cause for concern. Elsewhere, monthly sampling is inadequate to give a satisfactory estimate of the annual mean suspended solids concentration, but if historical data suggest the site is compliant, then monthly sampling will suffice until there is evidence that the site has become marginal.

• A continuation of monthly sampling at existing sites is sufficient for phosphorus. If any site becomes

marginal, an increase in sampling frequency should be considered. In addition, for reaches with high phosphorus and where ecological monitoring suggests that eutrophication may be a problem for the species of interest, determinations of EPC0 on bed sediments is recommended to assess the potential for uptake and release of phosphorus. However, this would only be required when investigating problem sites or assessing management plans.

• Automatic sampling equipment triggered by stage should be installed at six flow gauging sites in the

Eden catchment to provide precise estimates of mean suspended solids concentrations, and ensure results are consistent with those obtained using less-frequent monitoring. The data collected may

also be used for load estimation and the assessment of load control measured in relation to siltation problems.

• There are no available data on siltation suitable for assessing compliance with conservation

objectives. Since sampling is expensive and invasive, it is recommended that the number of sample sites be restricted to 24. It is also recommended that a stratified sampling scheme with subsampling of main reaches be used to identify sample sites for monitoring river substrate using freeze-coring techniques.

In addition to the specific recommendations for a minimum sampling strategy on the two rivers of interest, it has been pointed out that there is a gap in scientific understanding of micro-habitat response to suspended solids loadings. The monitoring for siltation on the Eden has been designed in terms of general levels of siltation within gravel bars. However, what this means for any specific micro-habitat within the reach is unknown. In the case of the Kerry, as there is only one species of concern, sampling of the specific micro-habitat has been recommended and it has been pointed out that erosion of this micro-habitat, as well as the movement of coarse sediment during flood events, is also of concern. Detailed velocity measurements and reach-scale modelling has now advanced to the point where long-term research and development could be recommended to address this gap in scientific understanding. Results could be expressed in terms of what flow and suspended solids conditions would cause problems of siltation within the different microhabitats within a reach. This could then be related to both a general measure of siltation and the likely conditions of flow and suspended solids concentrations experienced to provide a better indication of threshold levels. This would also need to be set in the context of the catchment as a whole (the sources of sediment and the distance travelled in individual events prior to deposition). Where relevant, this work could also be extended to the issue of erosion and to the role of surface-groundwater interactions. It is recommended that possible funding routes for such work are explored. Acknowledgements This document was produced with the support of the European Commission’s LIFE Nature Programme. We would like to thank Maggie Robinson and Liz Locke of English Nature and Kjersti Birkeland of SNH for sharing their knowledge of the Eden and Kerry catchments. We would also like to thank Liz and Kjersti for showing us around in the field.

References Barnett, V. and O’Hagan, A. (1997). Setting Environmental Standards. Chapman & Hall, London. Bartram, J. and Balance, R. (1996). Water quality monitoring. E&F Spon. Black, A.R. (1996). Major flooding and increased flood frequency in Scotland since 1988. Physical and

Chemical Earth, 5, 463-468. Bouckaert, F.W. and Davis, J. (1998). Microflow regimes and the distribution of macroinvertebrates

around stream boulders. Freshwater Biology, 40, 77-86. Chapman, A.S., Foster, I.D.L., Lees, J.A., Hodgkinson, R.A. and Jackson, R.H. (2001). Particulate

phosphorus transport by sub-surface drainage from agricultural land in the UK. Environmental significance at the catchment and national scale. Science of the Total Environment, 266, 95-102.

Cochran, W.G. (1977). Sampling techniques. John Wiley & Sons, New York. Cosgrove, P.J. (1999). Survey of the River Kerry for the presence of freshwater pearl mussels. Report to SNH,

Edinburgh. 15pp. Cosgrove, P.J. and Hastie, L.C. (2001). Conservation of threatened freshwater pearl mussel populations:

river management, mussel translocation and conflict resolution. Biological Conservation, 99, 183-190.

Ellis, J.C. (1989). Handbook on the design and interpretation of monitoring programmes. Water Research

Centre, Marlow, UK. English Nature (2001). River Eden: Conservation objectives for the European interest features on the SSSI.

English Nature, Peterborough. Environment Agency (1995). Viewpoints on the environment: developing a national environmental monitoring

and assessment framework. Environment Agency, Bristol. Environment Agency (1999). Eden, Esk & Solway: Local Environment Agency Plan. Environment Agency,

94pp. Fuller, W.A. (1999). Environmental surveys over time. J. Agric. Biol. Environ. Stat., 4, 4, 331-345. Gilbert, R.O. (1987). Statistical methods for environmental pollution monitoring. Van Nostrand Reinhold,

New York. Green, R.H. (1979). Sampling design and statistical methods for environmental biologists. John Wiley & Sons,

New York. Hastie, L.C., Boon, P.J. and Young, M.R. (2000). Physical microhabitat requirements of freshwater pearl

mussels, Margaritifera margaritifera (L.). Hydrolbiologia, 429, 59-71. Hastie, L.C., Boon, P.J., Young, M.R. and Way, S. (2001) The effects of a major flood on an endangered

freshwater mussel population. Biological Conservation, 98, 107-115. Hulme, M. and Jenkins, G.J. (1998) Climate change scenarios for the UK: scientific report. UKCIP Technical

Report No. 1, Climatic Research Unit, Norwich. 80pp.

Jeffers, J.N.R. (1998). The statistical basis of sampling strategies for rivers: an example using River Habitat

Survey. Aquatic conserv: Mar. Freshw. Ecosyst., 8, 447-454. Kelly, M.G. and 21 others (1998). Recommendations for the routine sampling of diatoms for water

quality assessments in Europe. J. Appl. Phycol., 10, 215-224. Macdonald, L.H., Smart, A.W. and Wissmar, R.C. (1991). Monitoring guidelines to evaluate effects of forestry

activities on stream waters in the Pacific Northwest and Alaska. US EPA 910/0-91-001. Mansell, M.G. (1997). The effect of climate change on rainfall trends and flooding risk in the West of

Scotland. Nordic Hydrology, 28, 37-50. NRA (1994). Water Quality Objectives: Procedures used by the National Rivers Authority for the purpose of the

Surface Waters (River Ecosystem)(Classification) Regulations 1994. National Rivers Authority, Bristol, UK.

Parsons, H., Walker, J., Scarlet, P. and Hornby, D. (2001) River Eden RHS and geomorphology evaluation.

Environment Agency, 133pp. Patil, G.P. and Rao, C.R. (1994). Environmental Statistics. Handbook of Statistics 12. North Holand. Platts, W.S., Megahan, W.F. and Minshall, G.W. (1983). Methods for evaluating stream, riparian and biotic

conditions. USDA Forest Service General Technical Report INT-138. Raven, P.J., Boon, P.J., Dawson, F.H. and Ferguson, A.J.D. (1998). Towards an integrated approach to

classifying and evaluating rivers in the UK. Aquatic conserv: Mar. Freshw. Ecosyst., 8, 383-393. Särndal, C-E., Swennson, B. and Wretman, J.H. (1992). Model-assisted survey sampling. Springer-Verlag,

Berlin. Schreuder, H.T , Gregoire, T.G and Weyer, J.P. (2001). For what applications can probability and non-

probability sampling be used? Environ. Monit. Assess., 66, 281-291. Smith, B.P.G., Naden, P.S., Leeks, G.J.L. and Wass, P.D. (in press). The influence of storm events on fine

sediment transport, erosion and deposition within the River Swale, Yorkshire, UK. Science of the Total Environment.

Stuart, E. (1998). River Kerry Site of Special Scientific Interest and possible Special Area of Conservation. Site

Management Statement 1998/99-2003/04. Scottish Natural Heritage, Edinburgh. Vos, P., Meelis, E. and Ter Keurs, W.J. (2000). A framework for the design of ecological monitoring

programs as a tool for environmental and nature management. Environ. Monit. Assess., 61, 317-344.

Wright, J.F., Moss, D., Clarke, R.T. and Furse, M.T. (1997) Biological assessment of river quality using the

new version of RIVPACS (RIVPACS III). In: Freshwater quality: Defining the indefinable. P.J. Boon and D.L. Howell (eds.) SNH, Edinburgh.

Appendix 1 One- and two-sided tests Consents and Environmental Quality Standards (EQS) are sometimes expressed as a requirement that a mean concentration lie below a given value. The sample mean has a distribution, and we require to test whether the sample data indicate compliance. There is a choice of appropriate tests, depending on the way hypotheses are framed. We may take as the null hypothesis that the mean is the set value. The alternative may be either:

• The mean is greater than the consent/EQS value: rejection of the null hypothesis implies failure of compliance.

• The mean is less than the consent/EQS value: rejection of the null hypothesis implies achievement of compliance.

A different confidence interval and test strategy will be adopted in each case. Under the first hypothesis, compliance will be accepted if the test statistic lies below an upper confidence limit. In the second, compliance will be accepted if the test statistic falls below a lower confidence limit. The commoner alternative hypothesis, used by the Environment Agency, is the first, giving a “benefit of the doubt” (BOTD), or 95% confidence of failure, test. The alternative is a “fail-safe” (FS), or 95% confidence of compliance, test. In the binomial test, the null hypothesis is that a quantile, typically 0.90, is the consent value. The BOTD alternative hypothesis is that the 0.90 quantile is above the consent value. This translates to an alternative hypothesis that the probability of achieving the consent is less than 0.9. A one-sided test of this alternative is that, if the number of samples achieving consent is above some fixed number representing a lower confidence limit, the null hypothesis, and therefore compliance, is accepted. Under the second FS alternative, if the number achieving consent is above an upper confidence limit, the null hypothesis is rejected, and achievement of compliance is accepted. The second test is more stringent than the first. If there are very few samples, then under either test there will be no reason to reject the null hypothesis. The FS alternative will never be entertained, and compliance will not be achieved. The default condition of the river is non-compliance. Under the BOTD alternative, the default condition is compliance. Sometimes the mean of a distribution needs to be estimated to a given precision, and in this case the number of samples required is of interest. This of course depends on the standard deviation of the sample. Figure A1 shows the number of samples needed for a range of precisions and standard deviations. It is clear that for apparently modest precision requirements the number of samples can quickly become very large. Use of percentiles In setting consents it is common to require that the 0.90 quantile for the concentration of a determinand being discharged to a river be less than some specified value. Suppose this value is, for example, 5 mg l-1. This means that the proportion of all values less than 5 mg l-1 should be at least 0.95. Compliance testing uses only a limited number of measurements. Assume that n statistically independent random measurements of concentration are made over a period. If 5 mg l-1 truly is the 0.90 quantile, then the number of values, r, below 5mg l-1, has a binomial distribution:

0.9 0.1r n rnr

− ×

(1)

For a given n this probability can be computed for any r , and a one-sided hypothesis test readily derived. The null hypothesis is that the probability of a value being less than 5 mg l-1 is equal to 0.90. The

BOTD alternative hypothesis is that this probability is less than 0.90. Note that the alternative hypothesis corresponds to the 0.90 percentile being greater than 5 mg l-1. Under the one-sided hypothesis test, the probability of obtaining r values or fewer below 5 mg l-1 is computed using equation (1). If this probability is less than a pre-assigned level, say 0.05, the null hypothesis is accepted and the site is classified as compliant. Under the FS alternative, if the probability of r values or more is less than the assigned level, then the null hypothesis is rejected, and the site is judged compliant. Note that in this case compliance with the consent may not be achievable with a small number of samples. t-test In the one sided t-test, BOTD compliance with a requirement that the mean concentration AC be below 5 mg l-1 is accepted if the following condition is met:

10.95; 1 5C

A nC t mg ln

σ −−− < (2)

FS compliance is accepted if the following condition is met:

10.95; 1 5C

A nC t mg ln

σ −−+ < (3)

In equations (2) and (3), C is the mean of a sample of n values 1 2( , ,..., )nx x x and Cσ is the sample standard deviation:

( )2

1

1

n

i Ai

C

C C

nσ =

−=

−

∑ (4)

The term 0.95; 1nt − is the 0.95 quantile of the t distribution with 1n − degrees of freedom, giving a 0.05 significance level in a one-sided test. Other quantiles may be used to define the significance level. This test rests on the assumption that the iC are Normally distributed, but is quite robust to violations.

Typically the larger n, the more sensitive is the test, and n may be selected to raise the value of AC which is accepted as below 5 mg l-1.

Combined analysis of two sampling regimes Much of the uncertainty in estimating the mean annual concentration comes from poor coverage of high flow conditions. To reduce this uncertainty, a stratified sampling procedure may be adopted such that if discharge is greater than some threshold value, suspended sediment concentrations are measured more frequently. This might be achieved, for example, through the use of an automatic sampler. In this case, the annual mean concentration may be split into two components:

1 2

1 2

( ) ( )t t

A

t t

c t dt c t dtC

dt dt

+

=+

∫ ∫

∫ ∫ (5)

Here 1t and 2t denote the periods over which stage is above and below the threshold respectively and ( )c t is the instantaneous concentration at time t . Equation (5) may be written:

1 21 2

1 2

A AA

t C t CC

t t+

=+

(6)

Now replace

1AC and

2AC by sample values, using only data for which discharge is above and below the

threshold respectively, giving:

1 2

1 2

1 21 2

1 2

A AA A A

t C t CC RC R C

t t+

= = ++

% (7)

The variance of AC% is

1 2 1 2

2 21 2 1 2var( ) var( ) 2 ( , )A A A AR C R C R R Cov C C+ + (7)

ignoring any possible covariance between Rs and Cs. If the covariance term in equation (7) can also be ignored, then:

( )

( ) ( )1 21 2

2 22 2

1 21 22

1 11 1 2 21 2

1var( )1 1

n ni A i A

Ai i

C C C Ct tCn n n nt t = =

− − = + − −+ ∑ ∑% (8)

As expected, the variance depends on the number of samples taken when discharge is below and when it is above the threshold. By selecting an appropriate threshold and sampling frequencies, the variance of

AC% can be controlled. This is a special case of the analysis of a stratified sample.