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TRANSNET S24G FOR THE MORELETASPRUIT GABIONS CONSTRUCTION PROJECT

Aquatic Assessment

SEF Reference No. 505013

Prepared for:

Gibb Engineering & Science 14 Eglin Road, Sunninghill 2191

P O Box 2700 Rivonia 2128 Fax: +27 11 807 5670 Web: www.gibb.co.za

Prepared by:

November 2012

Strategic Environmental Focus (Pty) Ltd P.O. Box 74785 Lynnwood Ridge

0040 Tel. No.: (012) 349-1307 Fax. No.: (012) 349-1229 e-mail: [email protected]

Transnet S24G for the Moreletaspruit Gabions Construction Project: Aquatic Impact Assessment 505013

Strategic Environmental Focus (Pty) Ltd i

Declaration of Independence

I, BYRON GRANT , in my capacity as a specialist consultant, hereby declare that I -

� Act as an independent consultant;

� Do not have any financial interest in the undertaking of the activity, other than remuneration for the work performed in terms of the National Environmental Management Act, 1998 (Act 107 of 1998);

� Have and will not have vested interest in the proposed activity proceeding;

� Have no, and will not engage in, conflicting interests in the undertaking of the activity;

� Undertake to disclose, to the competent authority, any material information that has or may have the potential to influence the decision of the competent authority or the objectivity of any report, plan or document required in terms of the National Environmental Management Act, 1998 (Act 107 of 1998);

� Will provide the competent authority with access to all information at my disposal regarding the application, whether such information is favourable to the applicant or not;

� As a registered member of the South African Council for Natural Scientific Professions, will undertake my profession in accordance with the Code of Conduct of the Council, as well as any other societies to which I am a member;

� Based on information provided to me by the project proponent and in addition to information obtained during the course of this study, have presented the results and conclusion within the associated document to the best of my professional ability;

� Reserve the right to modify aspects pertaining to the present investigation should additional information become available through on-going research and/or further work in this field; and

� Undertake to have my work peer reviewed on a regular basis by a competent specialist in the field of study for which I am registered.

________________________

Byron Grant Pr. Sci. Nat. Project Manager / Senior Natural Scientist

SACNASP Reg. No. 400275/08

________04/12/2012__________

Date


Strategic Environmental Focus (Pty) Ltd ii

EXECUTIVE SUMMARY Strategic Environmental Focus (Pty) Ltd, as independent environmental practitioners and ecological specialists, was appointed by Gibb Engineering & Science to undertake an aquatic impact assessment in terms of Environmental Impact Assessment requirements as part of the Transnet S24G for the Moreletaspruit Gabions Construction Project. This report presents the results obtained following a field survey of the area in question. The field survey was conducted on the 9th November 2012. Based on data obtained during the assessment of the aquatic ecosystem associated with the study area, it was determined that the biota present were representative of a largely to seriously impaired system. However, this was determined to be primarily as a result of the urbanised nature of the catchment which has significantly altered the characteristics of the associated watercourses, and not due to the presence of the gabions. Additional examination of the gabion structures revealed that several structural failures were evident at Site 1, and were deemed to be a combination of poor design as well as installation, the exact details of which are provided within. As such, while the gabions currently have a limited impact on the aquatic biota present, the gabions in their current configuration are likely to have an impact on the biota in the future. It is therefore recommended that a re-design of the structures be undertaken taking into consideration the hydrology of the catchment given the urbanised nature, an exercise which should include a wetland specialist with significant experience in wetland rehabilitation planning and implementation. It may further be necessary to install additional erosion-prevention measures at key locations within the catchment so as to prevent future erosion of constructed gabion features at the sites required for the protection of the fuel line given the high energy nature of the system under study. Finally, although the height of the constructed gabion structures will obstruct the movement of fish species from downstream reaches into the upper part of the catchment, the necessity for including structures such as fish ladders is not considered important in the present situation when considering the fish species present and hydrological nature of the watercourses within the study area.


Strategic Environmental Focus (Pty) Ltd iii

TABLE OF CONTENTS EXECUTIVE SUMMARY ................................................................................................................ II TABLE OF CONTENTS ................................. ............................................................................... III LIST OF FIGURES ........................................................................................................................ IV LIST OF TABLES .................................... ...................................................................................... IV 1. INTRODUCTION ..................................................................................................................... 1

1.1 PROJECT DESCRIPTION ...................................................................................................... 1 1.2 TERMS OF REFERENCE ....................................................................................................... 1 1.3 ASSUMPTIONS AND LIMITATIONS .......................................................................................... 1

2. DESCRIPTION OF THE ENVIRONMENT ............................................................................... 2 2.1 LOCATION .......................................................................................................................... 2 2.2 BIOPHYSICAL DESCRIPTION ................................................................................................. 2

2.2.1 Climate .......................................................................................................................... 2 2.2.2 Geology ......................................................................................................................... 2 2.2.3 Associated Water Courses ............................................................................................ 2

2.3 BIOREGIONAL CONTEXT ...................................................................................................... 3 2.4 NATIONAL FRESHWATER ECOSYSTEM PRIORITY AREAS STATUS ........................................... 3 2.5 SELECTION OF SAMPLING SITES .......................................................................................... 3

3. RESULTS ................................................................................................................................ 6 3.1 GENERAL OBSERVATIONS ........................................................................................................ 6 3.2 IN SITU WATER QUALITY PARAMETERS ..................................................................................... 9 3.3 INVERTEBRATE HABITAT ASSESSMENT SYSTEM ...................................................................... 10 3.4 AQUATIC MACROINVERTEBRATES ........................................................................................... 11

3.4.1 Present Ecological State ............................................................................................... 11 3.5 ICHTHYOFAUNA ..................................................................................................................... 12

3.5.1 Species of Conservation Importance ........................................................................... 14 3.5.2 Present Ecological State ............................................................................................... 14

4. IMPACT ASSESSMENT AND MITIGATION .................. ....................................................... 15 4.1 ASSESSMENT CRITERIA .................................................................................................... 15 4.2 IMPACT ASSESSMENT ....................................................................................................... 15

4.2.1 Aquatic Habitat Alteration ............................................................................................ 16 4.2.2 Erosion of Downstream Watercourse .......................................................................... 16 4.2.3 Pollution of Watercourse ............................................................................................. 17 4.2.4 Loss of Connectivity .................................................................................................... 17

4.3 MITIGATION MEASURES .................................................................................................... 18 5. CONCLUSION AND RECOMMENDATION ..................... ...................................................... 19

5.1 MONITORING PROGRAMME................................................................................................ 19 REFERENCES ............................................................................................................................. 20 APPENDICES .............................................................................................................................. 22


Strategic Environmental Focus (Pty) Ltd iv

LIST OF FIGURES Figure 1: Location of study area ...................................................................................................... 5

Figure 2: Extent of reno mattress apron on downstream portion of gabion structure. Length of downstream reno mattress determined to be approximately two meters. .......................... 7

Figure 3: Path for circumvention / outflanking of gabion structure during periods of high flows (indicated by arrow) due to obtuse angle, as evident by debris deposited on gabion structure during a previous high-flow event ....................................................................... 7

Figure 4: Loss of structural integrity of the reno mattress apron (indicated by arrows) .................... 8

Figure 5: Upstream deposition of sediment at Site 2 ....................................................................... 8

Figure 6: Barbus cf. anoplus (Chubbyhead Barb) sampled within the study area during November 2012 ................................................................................................................................ 13

Figure 7: Pseudocrenilabrus philander (Southern Mouthbrooder) sampled within the study area during November 2012 .................................................................................................... 14

Figure 8: Relationship between drivers and fish metric groups...................................................... 28

LIST OF TABLES Table 1: Summary of relevant ecological attributes ......................................................................... 4

Table 2: Description of aquatic sampling sites ................................................................................ 4

Table 3: In situ water quality variables obtained during the field survey .......................................... 9

Table 4: Adapted IHAS values obtained within the study area during November 2012 ................. 10

Table 5: Summary of SASS5 Data obtained during November 2012 ............................................ 11

Table 6: Present Ecological Class of sites surveyed during November 2012 as determined following application of the MIRAI index (Thirion, 2008) .................................................. 12

Table 7: List of fish species likely to be present within the general study area under natural conditions ........................................................................................................................ 13

Table 9: Present Ecological State of fish assemblage within the Moreleta River tributary assessed based on the FRAI model ................................................................................................ 15

Table 9: Primary impacts relating to the associated aquatic ecosystem arising from construction of gabion structures at identified locations ........................................................................... 15

Table 10: Allocation protocol for the determination of the Present Ecological State for aquatic macroinvertebrates following application of the MIRAI .................................................... 27

Table 11: Main steps and procedures in calculating the Fish Response Assessment Index .......... 29

Table 12: Allocation protocol for the determination of the Present Ecological State/Ecological Category for fish following application of the FRAI .......................................................... 30

Transnet S24G: Aquatic Impact Assessment 505013

Strategic Environmental Focus (Pty) Ltd 1

1. INTRODUCTION

Biodiversity within inland water ecosystems in southern Africa is both highly diverse and of great regional importance to livelihoods and economies. Current estimates suggest the overall magnitude of described freshwater animal species is 126,000, half of which are represented by the very species-rich class of Insecta. Some 45% (13–14,000 species) of known species of fish inhabit freshwater, representing almost 25% of the world’s known vertebrates. While terrestrial and marine ecosystems have a larger percentage of known species, the relative richness of freshwater ecosystems is higher as these species are restricted to living in a habitat which only covers an estimated 0.8% of the world’s surface area (Darwall et al., 2009).

1.1 Project Description

Strategic Environmental Focus (Pty) Ltd, as independent environmental practitioners and ecological specialists, was appointed by Gibb Engineering & Science to undertake an aquatic impact assessment in terms of Environmental Impact Assessment requirements as part of the Transnet S24G for the Moreletaspruit Gabions Construction Project. This report presents the results obtained following a field survey of the area in question. The field survey was conducted on the 9th November 2012.

1.2 Terms of Reference

The terms of reference for the current study were as follows:

• Outline the study approach and identify assumptions and sources of information

• Describe the affected environment and determine the status quo

• Identify current and future sources of risk associated with the proposed project during construction, operation and decommissioning

• Indicate exactly how much of a particular resource or community (human or biological) will be affected, how intensely, and for what duration

• Perform a sensitivity or vulnerability analysis

• Assess and evaluate potential impacts on the area of influence according to the prescribed parameters and characteristics, including magnitude, spatial scale, timing, duration, reversibility/irreversibility, probability, significance and acceptability

• Propose and explain mitigation measures for unavoidable impacts, and enhancement measures, according to the prescribed format, giving detailed prescriptions for their implementation and methods to assess their likely success

• Provide a monitoring programme for mitigation measures and project implementation activities, explaining what should be monitored, when, how, how often and by whom.

1.3 Assumptions and Limitations

Ecological studies should ideally be conducted during various times of the year so as to account for seasonal variation in aquatic assemblages due to migration, breeding cycles, etc. Given the time constraints generally associated with the Environmental Impact Assessment process, such long-term studies are not deemed feasible.



2. Description of the Environment

2.1 Location

The study site located adjacent to Garsfontein Road (M30) and south of Solomon Mahlangu Road (M10; previously Hans Strijdom Road), Pretoria. More specifically, the study area encompasses the Moreleta River within Erf 492 of Moreleta Park Ext. 3 and where the river forms the boundary of Erf 3823 of Garsfontein Ext. 15 and Erf 925 Pretorius Park Ext. 1.

2.2 Biophysical Description

2.2.1 Climate

The study area is located with the Western Bankenveld ecoregion and experiences early to mid-summer rainfall, receiving a mean annual precipitation of 500mm to 700m. Mean annual temperatures within the study area range from 14°C to 18°C, with mean daily maximum temperatures in February ranging from 24°C to 28°C, and mean daily minimum temperatures in July ranging from 0°C to 3°C (Kleynhans et al., 2007).

2.2.2 Geology

Geology underlying the study area is represented by the Timeball Hill Formation of the Pretoria Group (Transvaal Supergroup; Vaalian Era). The Timeball Hill Formation consists primarily of quartzite sandwiched between shale and siltstone.

2.2.3 Associated Water Courses

The study area is located within Quaternary Catchment A23A in the Crocodile (West) and Marico water management area. The Crocodile (West) and Marico water management area borders on Botswana to the north-west, with its main rivers, the Crocodile River and the Marico River, giving rise to the Limpopo River at their confluence. The economic activities within this management area are dominated by the urban and industrial complexes of northern Johannesburg and Pretoria and platinum mining north-east of Rustenburg. This is the second-most populous water management area in the country and has the largest proportionate contribution to the national economy (DWAF, 2004).

The watercourses associated with the study area include tributaries of the Moreleta River, which confluences with the Hartbeesspruit before confluencing with the larger Pienaars River some distance downstream of the study area. According to Nel et al. (2004), the heterogeneity signature of the Moreleta River was determined to be Bushveld Basin 1, and is regarded as having a conservation status of Critically Endangered, with the Present Ecological State (PES) being regarded as moderately modified (PES Category C). In addition, the slope category of the Moreleta River in close proximity to the study area was determined to be Upper Foothills.



2.3 Bioregional Context

The present study area is located within the Southern Temperate Highveld freshwater ecoregion, which is delimited by the South African interior plateaux sub-region of the Highveld aquatic ecoregion, of which the main habitat type (in terms of watercourse) is Savannah-Dry Forest Rivers. Aquatic biotas within this bioregion have mixed tropical and temperate affinities, sharing species between the Limpopo and Zambezi systems. The Southern Temperate Highveld freshwater ecoregion is considered to be bio-regionally outstanding and its conservation status Endangered. The ecoregion is defined by the temperate upland rivers and seasonal pans. (Nel et al., 2004; Darwall et al., 2009).

2.4 National Freshwater Ecosystem Priority Areas Status

The National Freshwater Ecosystem Priority Areas project is a project currently underway, and represents a multi-partner project between the Council for Scientific and Industrial Research (CSIR), South African National Biodiversity Institute (SANBI), Water Research Commission (WRC), Department of Water Affairs (DWA), Department of Environmental Affairs (DEA), Worldwide Fund for Nature (WWF), South African Institute of Aquatic Biodiversity (SAIAB) and South African National Parks (SANParks). More specifically, the NFEPA project aims to:

• Identify Freshwater Ecosystem Priority Areas (hereafter referred to as ‘FEPAs’) to meet national biodiversity goals for freshwater ecosystems; and

• Develop a basis for enabling effective implementation of measures to protect FEPAs, including free-flowing rivers.

The first aim uses systematic biodiversity planning to identify priorities for conserving South Africa’s freshwater biodiversity, within the context of equitable social and economic development. The second aim comprises a national and sub-national component. The national component aims to align DWA and DEA policy mechanisms and tools for managing and conserving freshwater ecosystems. The sub-national component aims to use three case study areas to demonstrate how NFEPA products should be implemented to influence land and water resource decision making processes at a sub-national level. The project further aims to maximize synergies and alignment with other national level initiatives such as the National Biodiversity Assessment (NBA) and the Cross-Sector Policy Objectives for Inland Water Conservation. Based on current outputs of the NFEPA project, no Freshwater Ecosystem Priority Areas are associated with the study area. A summary of the relevant attributes associated with the study area is presented in Table 1. A locality map is also given in Figure 1.

2.5 Selection of Sampling Sites

Sampling sites were selected so as to characterise the present state of the aquatic ecosystem associated with the installed gabion structures, as well as provide a comparative basis by which future impacts can be evaluated. Co-ordinates of the selected sampling sites were determined using a Garmin GPS global positioning device and are presented below in Table 2 and graphically in Figure 1. Photographs of the selected sampling sites are provided in Appendix 1.



Table 1: Summary of relevant ecological attributes

Map Reference 2528CD

Political Region Gauteng Province

Level 1 Ecoregion 7. Western Bankenveld

Level 2 Ecoregion 7.06

Freshwater Ecoregion Southern Temperate Highveld

Geomorphic Province Southern Bankenveld

Geology Timber Hill Formation

Vegetation Type Marikana Thornveld

Water Management Area Crocodile (West) and Marico

Secondary Catchment A2

Quaternary Catchment A23A

Associated Watercourses Tributary of the Moreleta

Heterogeneity Signature Bushveld Basin 1

Slope Category Upper Foothills

NFEPA Status None

Table 2: Description of aquatic sampling sites

Site name Co-ordinates Site description

Site 1 S: 25° 48' 28.98"

E: 28° 18' 07.05"

Site located on a tributary of the Moreleta River east of Garsfontein Road (M30) marginally upstream of the confluence with the Moreleta River

Site 2 S: 25° 48’ 38.50”

E: 28° 18’ 03.20”

Site located on a small tributary of the Moreleta River west of Garsfontein Road (M30) and adjacent to the Eastside Community Church



Figure 1: Location of study area



3. RESULTS

3.1 General Observations

Site 1 was located within a channelled valley-bottom wetland and within a highly urbanised catchment, and was noted to support alien flora. Further, the watercourse was characterised by an incised channel that supported marginal vegetation and a largely sand/mud substrate. In several locations, cobbles were present within the channel, likely owing to erosion processes as a result of runoff from the urban areas.

Gabion structures constructed within the channel at Site 1 were observed to extend across the width of the channel at an angle, with the upstream portion showing clear evidence of sediment deposition. However, several concerns were noted upon review of the structural diagrams provided (Sharman Consulting Engineers, 2011) and the gabion construction installed. These included:

• The downstream extent of the reno mattress did not appear to extend to the degree represented in the structural diagrams provided, appearing to extend only two meters as opposed to four meters as designed (Figure 2);

• The double crest gabion design that was proposed by Sharman Consulting Engineers (2011) does not appear to have been implemented during construction;

• The angle at which the gabion structure was placed relative to the direction of water flow has resulted in the river circumventing/outflanking the crest structure of the gabion during times of high flow in favour of the downstream-most edge of the structure on the northern bank of the watercourse (Figure 3);

• The reno mattress apron that was constructed on the downstream side of the gabion structure was observed to have failed structurally, with several gabion baskets noted to have opened (Figure 4), a result of a design flaw that did not take into account the hydrological nature of the catchment and excluded suitable dissipating features on the downstream portion of the structure; and

• No features (such as still basins, stepped gabions, etc.) were included in the design of the gabion structures that would have accounted for the hydraulic jump that would be present on the downstream portion of the structure.

As such, the design and installation of the gabion structure at Site 1 was not considered to be suitable for long-term persistence.



Figure 2: Extent of reno mattress apron on downstre am portion of gabion structure. Length of

downstream reno mattress determined to be approxima tely two meters.

Figure 3: Path for circumvention / outflanking of g abion structure during periods of high flows

(indicated by arrow) due to obtuse angle, as eviden t by debris deposited on gabion structure during

a previous high-flow event



Figure 4: Loss of structural integrity of the reno mattress apron (indicated by arrows)

Site 2 was located within a channelled valley-bottom wetland system, with significant canalisation and channel scouring of the watercourse downstream of the gabion structure present as a result of increased catchment runoff and subsequent loss of attenuation functionality. In general, the construction of the gabion structure appears stable for the time being with no noticeable structural failures as yet, with deposition of sediment upstream of the structure clearly evident (Figure 5). Such deposition has resulted in the prevention of further head-cut erosion extending in an upstream direction, provides for the re-establishment of lateral wetting of the wetland and allows for the possible establishment of marginal vegetation in the future.

Figure 5: Upstream deposition of sediment at Site 2



3.2 In Situ Water Quality Parameters

The assessment of water quality variables is important for the interpretation of results obtained during biological investigations, as aquatic organisms are influenced by the environment in which they live. Table 3 provides in situ water quality variables obtained during the November field survey.

Table 3: In situ water quality variables obtained during the field s urvey

Site Name Temp.

(°C) pH

Electrical conductivity

(mS/m)

Dissolved oxygen

(mg/ℓ) (% sat)

Site 1 18.00 7.81 21.80 7.92 83.20

Site 2 19.00 7.64 22.10 7.89 86.40

* Electrical Conductivity

In general, the chemistry of a watercourse reflects the underlying geology and the activities present within the catchment which the watercourse drains. In this regard, urbanised catchments are characterised by impervious surfaces which result in a highly variable flow regime that is strongly dependant on rainfall and that result in canalisation of watercourses, with a concomitant decreased in the natural water storage capacity of the catchment. As a result of runoff from an urbanised catchment, several pollutants are expected to occur within the study area, including a reduction in the concentration of dissolved oxygen (owing to increased organic enrichment; not present during the present study) and increases in nutrient input, heavy metals and hydrocarbons from runoff from roads (Dallas and Day, 2004).

Unfortunately, there is very little information available with regards to the salinity tolerances of freshwater organisms in South Africa, although some research is being done by various tertiary institutions in this regard. However, available research does indicate changes in the distribution patterns of individual species or communities can be attributed to changes in salinities. Nevertheless, a number of generalisations can be made based on current research results, including (Dallas and Day, 2004):

• It is often the rate of change rather that the final salinity that is most critical;

• Juvenile stages are often more sensitive to increased salinity concentrations; • Salinity may act as an antagonist or a synergist in relation to a variety of toxicants; and

• The responses of freshwater organisms to alterations in salinity are likely to be related to the evolutionary origins on the taxon of which they are part.

Nevertheless, in situ water quality variables obtained during the current assessment did not present a significant limiting factor to the occurrence of aquatic biota.



3.3 Invertebrate Habitat Assessment System

The Invertebrate Habitat Assessment System (IHAS, Version 2.2), developed by McMillan (1998), has routinely been used in conjunction with the South African Scoring System (SASS) as a measure for the variability in the amount and quantity of aquatic macroinvertebrate biotopes available for sampling. However, according to a recent study conducted within the Mpumalanga and Western Cape regions, the IHAS method does not produce reliable scores with regard to the suitability of habitat at sampling sites for aquatic macroinvertebrates (Ollis et al., 2006). Furthermore, the performance of the IHAS seems to vary between geomorphologic zones and between biotope groups (Ollis et al., 2006). Therefore, more testing of the IHAS method is required before any final conclusion can be made regarding the accuracy of the index. An adaptation of the IHAS method was, however, retained for the purposes of this assessment, as the basic data remains of value and is suitable for the comparison of sampling effort across the various sites based on available invertebrate habitat. Results are thus presented relative to an “ideal” diversity of aquatic macroinvertebrate sampling habitat, and need to be interpreted with caution taking into consideration the nature of the surveyed watercourse. Results obtained during the November 2012 field survey are presented in Table 4.

Table 4: Adapted IHAS values obtained within the st udy area during November 2012

Site Name Adapted IHAS Value Description

Site 1 74.54 Good

Site 2 56.36 Adequate/Fair

Values obtained within the Moreleta River tributaries assessed following application of the adapted IHAS approach indicated that sampling habitat diversity ranged from adequate/fair at Site 2 on the western side of Garsfontein Road, to good on the eastern side of Garsfontein Road at Site 1 (Table 4). Site 1 provided several riffle habitats that presented cobbles as a substrate. However, such cobbles and riffle habitat are likely to the result of erosion processes within the catchment, and are not considered to be natural given the position of the watercourse in the larger catchment. Nonetheless, obstructions within the river channel did provide several diversities of hydraulic habitats not present at Site 2, and allowed for the establishment of more diverse aquatic biota relative to Site 2. It should be noted that Site 2 was located within a smaller tributary of the Moreleta River relative to Site 1, with limited aquatic habitat diversity, particularly downstream of the established gabion where significant erosion of the channel was observed in association with bed scouring (Section 3.1), a clear indication of increased surface runoff from the surrounding catchment. Further, contact of marginal vegetation with water was limited due to limited erosion processes occurring upstream of the gabion structure, with the presence of shale within the channel providing some hydraulic diversity.



3.4 Aquatic Macroinvertebrates

Due to the differential sensitivities of aquatic macroinvertebrates, the composition of the aquatic macroinvertebrates can provide an indication of changes in water quality and other conditions within a river. The use of the South African Scoring System (SASS) has undergone numerous advances, culminating in the Version 5 presently being utilised in river health studies.

SASS5 data obtained during the field survey is summarised below in Table 5. A total of 21 taxa were sampled during the field survey, with the number of taxa identified at each site ranging from 11 to 19 at Site 2 and Site 1, respectively. In addition, a number of taxa regarded as moderately sensitive to water quality were sampled, including Dixidae (Meniscus Midge), Aeshnidae (Hawker and Emperor Dragonflies) and Hydaenidae (Minute Moss Beetles). Furthermore, SASS5 scores obtained within the watercourses during November 2012 were observed to range from 48 at Site 2, to 98 at Site 1, while ASPT (Average Score Per Taxon) values were observed to range from 4.36 at Site 2 to 5.16 at Site 1 (Table 5).

Table 5: Summary of SASS5 Data obtained during Nove mber 2012

Site Name SASS5 Score Number of Taxa ASPT*

Site 1 98 19 5.16

Site 2 48 11 4.36

* Average Score Per Taxon

It is well documented that alterations of natural flow regimes together with changes in water chemistry result in the development of aquatic macroinvertebrate assemblages that are tolerant of intermittent period so of severe environmental stress. For example Walsh (2000; cited in Dallas and Day, 2004) determined that biotic communities of streams showed increased degradation with increased urbanisation, suggesting the degradation was a result of increased efficiency of pollutant delivery to receiving watercourses. As such, the assemblage of aquatic macroinvertebrates determined to be associated with the tributaries of the Moreleta River under study was regarded as being related to catchment practices, and not necessarily as a result of the construction of the gabion structures.

3.4.1 Present Ecological State

SASS5 data obtained during the present assessment was used in the Macroinvertebrate Response Assessment Index (MIRAI; Thirion, 2008) in order to determine the Present Ecological Sate according to the most applicable method (Table 6). Chutter (1998) developed the SASS protocol as an indicator of water quality. It has since become clear that SASS gives an indication of more than mere water quality, but rather a general indication of the present state of the invertebrate community. Because SASS was developed for application in the broad synoptic assessment required for the River Health Programme (RHP), it does not have a particularly strong cause-effect basis. The aim of the MIRAI, on the other hand, is to provide a habitat-based cause-



and-effect foundation to interpret the deviation of the aquatic invertebrate community (assemblage) from the reference condition (Thirion, 2008). This does not preclude the calculation of SASS scores should they be required. However, the recent tendency is to use the MIRAI even for River Health Programme purposes, and it is now the preferred approach.

Table 6: Present Ecological Class of sites surveyed during November 2012 as determined following

application of the MIRAI index (Thirion, 2008)

Site MIRAI % PES Category Description

Site 1 54.45 D Largely Impaired

Site 2 39.48 D/E Largely to Seriously Impaired

Based on results obtained following the application of the MIRAI approach, it was determined that the aquatic macroinvertebrate assemblages within the tributaries of the Moreleta River investigated represented largely to seriously impaired ecological states, with an extensive loss of ecosystem functions having occurred. This was attributed primarily to the urbanised nature of the catchment, which has resulted in a change of macroinvertebrate assemblages through modification to system hydrology, habitat and chemistry.

3.5 Ichthyofauna

According to Kleynhans et al. (2008), there may be approximately 13 species of fish associated with the catchment. However, as the study area is likely to have represented a wetland system in the upper reaches of a catchment with little aquatic habitat diversity under natural conditions, it is likely that the diversity of fish species associated directly with the present study area is limited to a maximum of approximately nine species, several of which will have a low probability of occurrence (Table 7). During the course of the investigations, only two species, represented by three individuals, were sampled within the study area. These included Barbus cf. anoplus (Chubbyhead Barb) and Pseudocrenilabrus philander (Southern Mouthbrooder). A short account of each species collected during the survey is presented below. Of the species likely to occur, all species were considered to be potadromous (i.e. migrates in freshwater to complete lifecycle), with several species suspected of having migration ranges of over 50km and being considered key migratory species, although habitat availability would limit the occurrence of these species within the area. Those species that were confirmed to occur within the study area are only suspected of having migration ranges of less than 10km, and having a limited dispersal range. Further, several species of the fish likely to occur within the study area under natural conditions are considered to be moderately tolerant of water quality impairment, with the remainder being regarded as tolerant.



Table 7: List of fish species likely to be present within the general study area under natural

conditions

Scientific Name Common Name Endemic Status

Red List Category

Barbus cf. anoplus Chubbyhead Barb Endemic LC

Barbus paludinosus Straightfin Barb LC

Barbus trimaculatus Threespot Barb LC

Barbus unitaeniatus Longbeard Barb Endemic LC

Labeobarbus marequensis Lowveld Largescale Yellowfish Endemic LC

Mesobola brevianalis River Sardine Endemic LC

Oreochromis mossambicus Mozambique Tilapia Endemic NT

Pseudocrenilabrus philander Southern Mouthbrooder LC

Tilapia sparrmanii Banded Tilapia LC

Barbus cf. anoplus (Chubbyhead Barb; Figure 6) prefers cool waters, occurring in a wide variety of habitats from small streams to large rivers and lakes (Skelton, 2001). This fish species breeds during summer when rivers are swollen after rain. It reaches sexually maturity in one year, and feeds on insects, zooplankton, seeds, green algae and diatoms (Skelton, 2001). Velocity-depth flow preferences include fast-shallow, fast-deep and slow-deep classes, and the preferred cover being substrate and the water column (Kleynhans, 2003). Currently, this fish species is considered to be a species complex, with further genetic studies likely to yield several different species.

Figure 6: Barbus cf. anoplus (Chubbyhead Barb) sampled within the study area dur ing November

2012

Pseudocrenilabrus philander (Southern Mouthbrooder; Figure 7) is considered to be tolerant of a wide variety of environmental conditions, and has a preference for marginal vegetation and undercut river banks in slow, shallow watercourses. This small fish species feeds on insects, shrimps and occasionally small fish, with males of the species also exhibiting strong territorial behaviour particularly during times of breeding. Furthermore, P. philander is occasionally used as an aquarium species, as well as, in behavioural and evolutionary research (Skelton, 2001).



Figure 7: Pseudocrenilabrus philander (Southern Mouthbrooder) sampled within the study a rea

during November 2012

3.5.1 Species of Conservation Importance

It was noted that a number of species that are considered to be endemic to the southern African region were likely to be associated with the study area (Table 7), although only one such species was sampled within the study area, namely Barbus cf. anoplus (Chubbyhead Barb). It was further noted that that only one species of a conservation concern was likely to occur within the study area, namely Oreochromis moassambicus (Mozambique Tilapia; listed as Near Threatened). However, the probability of this species occurring within the study area was considered to be low given the likely natural attributes of the site. This species is widely dispersed beyond this range to inland regions and to the south west and west coastal rivers including the lower Orange and rivers of Namibia where it occurs in all but fast-flowing waters, and thriving in standing waters. Oreochromis moassambicus has until recently not been considered of conservation importance in the southern Africa region. However, Oreochromis niloticus (Nile Tilapia) is invading its natural range in the Zambezi and Limpopo river systems, with hybridisation occurring in the Limpopo system and pure strains of O. mossambicus are likely to become extirpated in those systems through competition and hybridisation.

3.5.2 Present Ecological State

Assessment of the Present Ecological State of the fish assemblage of the Moreleta River tributary during November 2012 was conducted by means of the Fish Response Assessment Index (FRAI; Kleynhans, 2008). The procedure followed to determine the fish Present Ecological State, or Ecological Category, in accordance with the FRAI methodology is an integration of ecological requirements of fish species in an assemblage and their derived or observed responses to modified habitat conditions. In the case of the present assessment, the observed response was determined by means of fish sampling as well as a consideration of species requirements and driver changes (Kleynhans, 2008). Table 9 provides a summary of the Present Ecological State class and description for the present state of the fish assemblage of the Moreleta River tributary assessed.



Table 8: Present Ecological State of fish assemblag e within the Moreleta River tributary assessed

based on the FRAI model

Watercourse FRAI % PES

Class Description

Moreleta River Tributary 46.50 D Largely impaired

Based on the FRAI model, the Present Ecological State of the fish assemblage within the tributary of the Moreleta River was considered to be largely impaired. Further interrogation of the model indicated that flow modification within the catchment was the likely primary driver of the determined state, with migration obstructions and velocity-depth modifications further likely to be contributing factors.

4. IMPACT ASSESSMENT AND MITIGATION

Any development in a natural system will impact on the surrounding environment, usually in a negative way. The purpose of this phase of the project was therefore to identify and assess the significance of the impacts that have arisen or are likely to arise in the future as a result of the installed gabion structures and provides a short description of the mitigation required so as to limit impacts of the on the natural environment.

4.1 Assessment Criteria

Impact assessment criteria utilised during the course of the present study was based on the methodology as supplied by Gibb Engineering and Science.

4.2 Impact Assessment

Possible significant impacts associated with the constructed gabion structures are provided in Table 9.

Table 9: Primary impacts relating to the associated aquatic ecosystem arising from construction of

gabion structures at identified locations

Possible impact Source of impact

Aquatic habitat alteration • Impedance of flow by gabions and poor

design

Erosion of downstream watercourse • Design of gabion structures

Pollution of watercourse • Erosion of structural collapse of fuel pipeline

Loss of connectivity • Design of gabion structures



4.2.1 Aquatic Habitat Alteration

Impact Nature Intensity Extent Duration Probability Confidence

Impact 1: Aquatic habitat alteration

Positive &

Negative Medium Local Long term Definite High

With Mitigation Positive Low Local Long term Probable High

Impact Consequence Probability Significance Confidence

Impact 1: Aquatic habitat alteration

Medium Definite High High

With Mitigation Low Probable Low High

Description of Impact

The placement of gabion structures within the channel of the watercourse has resulted in the improvement of aquatic habitat upstream of the structures, and the movement of the watercourse to pre-urbanised conditions. However, poor design and construction through a seeming lack of understanding of the infrastructure requirements given the present hydrological state of the upstream catchment as well as poor construction has led to several design flaws and structural failures of the presently installed gabion structures, which is highly likely to lead to localised downstream aquatic ecosystem degradation through the enhancement of erosion.

4.2.2 Erosion of Downstream Watercourse


Impact 2: Erosion of downstream watercourse

Negative Medium Local Long term Definite High

With Mitigation Positive Low Local Long term Improbable High


Impact 2: Erosion of downstream watercourse

Medium Definite High High

With Mitigation Low Improbable Low High


Erosion within the watercourse is seen to be primarily the result of increased catchment runoff. However, the constructed gabions can contribute the this erosion process by changing or



transferring energy, particularly where it is channelled through a narrow opening, thus concentrating the flow and having little positive application in terms of the downstream environment.

4.2.3 Pollution of Watercourse


Impact 3: Pollution of watercourse

Negative High Regional Long term Definite High

With Mitigation Neutral Medium Regional Long term Improbable High


Impact 3: Pollution of watercourse

High Definite High High

With Mitigation High Improbable High High


The present design of the gabion structures allows for structure failure of the gabion structures themselves, and possible erosion of the foundations of the structures. Should such erosion occur, this may result in the gabion structure collapsing onto the fuel line which it was designed to protect, thereby possibly causing a rupturing of the line and subsequent pollution of the downstream aquatic environment.

4.2.4 Loss of Connectivity


Impact 4: Loss of connectivity

Negative Low Local Long term Definite High

With Mitigation Neutral Low Local Long term Definite High


Impact 4: Loss of connectivity

Low Definite Low High

With Mitigation Low Definite Low High


The design of the gabion structures has resulted in a vertical drop of between 0.8m at Site 2 and 1.3m at Site 1 from the upstream to downstream portions of the watercourse. Based on current knowledge of fish migrations in South Africa and the ability of different fish species to negotiate impeding structures, the design is likely to result in a complete loss of upstream movement of fish within the area. However, the significance of this was determined to be low, as the study area was likely to support only a limited diversity of fish fauna given the inherent characteristics of the



watercourse under natural conditions, and the range covered of the species while migrating. Further, the incised nature of the watercourse and hydrology under present day conditions is likely to have limited the success of any upstream movement that may occur given the species confirmed to be present.

4.3 Mitigation Measures

Based on the results obtained during the present study, the following mitigation measures are deemed to be most relevant:

� The exercise of combating any eroded system must, of necessity, be a holistic one, covering not only the degradation in the eroded area, but possible causative factors in the catchment area upstream. The solution to a given problem in a wetland system should therefore only be decided following a thorough investigation of both the entire wetland (including its soils) and it catchment (Russell, 2009). In this regard, it is strongly recommended that a detailed investigation into the hydrology of the catchment be conducted taking careful consideration into the present state of urbanisation within the catchment and likely future increases so as to inform the design of structure that will be resilient to the high surface water runoff generated as a result;

� The erosion of the gully banks associated with the hydraulic jump that forms downstream of the toe of the step or chute is one of the most frequent causes of failure of these structures (Russell, 2009). The design of such structures must therefore provide protection against this erosion and must ensure that the jump remains in the protected reach and does not extend downstream. In this regard, it is strongly recommended that a wetland rehabilitation specialist with proven success be consulted in order to advise on the most appropriate structural design to be utilized. Such a design may include end sills, cut-off sills, stilling basins, stepped gabions, etc. Cognisance should also be given to the width of the structure as well as the angle at which it is placed relative to the flow of water. Ideally, structures should be designed to be placed perpendicular to the flow of water so as to prevent outflanking of the structure and the creation of erosion features on the lateral edges of the structures which would otherwise cause instability; and

� Further, although the present structures have resulted in the fragmentation of longitudinal connectivity though the prevention of the upstream movement of fish species, the impact associated with this fragmentation is not deemed to be significant due to the incised nature of the wetland and the fact that none of the species confirmed to be present are regarded as key migratory species. It is therefore not considered necessary for fish ladders to be installed within the structures, and focus should instead be placed on effective rehabilitation of the wetland.



5. CONCLUSION AND RECOMMENDATION Based on data obtained during the assessment of the aquatic ecosystem associated with the study area, it was determined that the biota present were representative of a largely to seriously impaired system. However, this was determined to be primarily as a result of the urbanised nature of the catchment which has significantly altered the characteristics of the associated watercourses, and not due to the presence of the gabions. Additional examination of the gabion structures revealed that several structural failures were evident at Site 1, and were deemed to be a combination of poor design as well as installation, the exact details of which are provided within. As such, while the gabions currently have a limited impact on the aquatic biota present, the gabions in their current configuration are likely to have an impact on the biota in the future. It is therefore recommended that a re-design of the structures be undertaken taking into consideration the hydrology of the catchment given the urbanised nature, an exercise which should include a wetland specialist with significant experience in wetland rehabilitation planning and implementation. It may further be necessary to install additional erosion-prevention measures at key locations within the catchment so as to prevent future erosion of constructed gabion features at the sites required for the protection of the fuel line given the high energy nature of the system under study. Finally, although the height of the constructed gabion structures will obstruct the movement of fish species from downstream reaches into the upper part of the catchment, the necessity for including features such as fish ladders is not considered important in the present situation when considering the fish species present and hydrological nature of the watercourses within the study area.

5.1 Monitoring Programme

The purpose of a monitoring program is to directly measure, assess and report on the status and trends of the associated environment. Due to the nature of the activity as well as the fact that impacts on the receiving aquatic environment are largely based on the success of the measures implemented, it is recommended that the development of an aquatic biomonitoring programme be abandoned in favour of the development of a detailed wetland rehabilitation monitoring programme that seeks to ensure the future success of the activity. During the development of the wetland rehabilitation plan or programme, the level at which monitoring should be conducted following the design and installation of suitable structures must be identified and appropriate monitoring techniques and frequencies stipulated.



REFERENCES Chutter, F.M. (1998). Research on the Rapid Biological Assessment of water quality impacts in

streams and rivers. Report to the Water Research Commission, Pretoria. WRC Report No. 422/1/98.

Dallas, H.F. (1997). A preliminary investigation of aspects of SASS (South African Scoring System) for the rapid bioassessment of water quality in rivers, with particular reference to the incorporation of SASS in the national biomonitoring programme. Southern African Journal of Aquatic Sciences 23: 79-94.

Davies, B. & Day, J.A. (1998). Vanishing Waters. University of Cape Town Press.

Dallas, H.F. & Day, J.A. (2004). The effect of water quality variables on aquatic ecosystems: A review. Water Research Commission, Report number TT224/04.

Darwall, W.R.T., Smith, K.G., Tweddle, D. & Skelton, P. (eds) (2009). The Status and Distribution of Freshwater Biodiversity in Southern Africa. Gland, Switzerland: IUCN and Grahamstown, South Africa: SAIAB. Vii+120pp.

Department of Water Affairs & Forestry (2004). National Water Resource Strategy: First Edition. Department of Water Affairs and Forestry, Pretoria.

Dickens, C.W.S. & Graham, P.M. (2002). South African Scoring System (SASS) Version 5 Rapid Bioassessment Method for rivers. African Journal of Aquatic Science 27: 1-10.

Gerber, A. & Gabriel, M.J.M. (2002). Aquatic Invertebrates of Southern African Rivers Field Guide. Institute for Water Quality Studies, Department of Water Affairs and Forestry. 150pp.

Kleynhans, C.J. (1999). The development of a fish index to assess the biological integrity of Southern African rivers. Water SA 25(3): 265-278.

Kleynhans, C.J. (2003). National Aquatic Ecosystem Biomonitoring Programme: Report on a National Workshop on the use of Fish in Aquatic System Health Assessment. NAEBP Report Series No. 16. Resource Quality Services, Department of Water Affairs and Forestry, Pretoria, South Africa.

Kleynhans, C.J. (2008). River Ecoclassification: Manual for Ecostatus Determination (Version 2). Module D: Volume 1 – Fish Response Assessment Index (FRAI). WRC Report No. TT 330/08. Water Research Commision, Pretoria.

Kleynhans, CJ, Thirion, C, Moolman, J and Gaulana, L (2007). A Level II River Ecoregion classification System for South Africa, Lesotho and Swaziland. Report No. N/0000/00/REQ0104. Resource Quality Services, Department of Water Affairs and Forestry, Pretoria, South Africa.



Kleynhans, C.J., Louw, M.D. & Moolman, J. (2008). River Ecoclassification: Manual for Ecostatus Determination (Version 2). Module D: Volume 2 – Reference Frequency of Occurrence of Fish Species in South Africa. WRC Report No. TT 331/08. Water Research Commision, Pretoria.

McMillan, P.H. (1998). An Integrated Habitat Assessment System (IHAS v2), for the Rapid Biological Assessment of Rivers and Streams. A CSIR research project, number ENV-P-I98132 for the Water Resources Management Programme, CSIR. ii+44pp.

McMillan, P.H. (2006). Personal communication.

Nel, J., Maree, G., Roux, D., Moolman, J., Kleynhans, N., Silberbauer, M. & Driver, A. (2004). South African National Spatial Biodiversity Assessment 2004: Technical Report. Volume 2: River Component. CSIR Report Number ENV-S-I-2004-063.

Ollis, D.J., Boucher, C., Dallas, H. & Esler, K.J. (2006). Preliminary testing of the Integrated Habitat Assessment System (IHAS) for aquatic macroinvertebrates. African Journal of Aquatic Science 31(1): 1-14.

Russell, W. (2009). WET-RehabMethods: National Guidelines and methods for wetland rehabilitation. Wetland Management Series. WRC Report No. TT341/09. Water Research Commission, Pretoria.

Sharman Consulting Engineers (2011). Plan, elevations and cross sections for the protection of a Transnet pipeline – Drawing Number DBN-11-201-101. Project: Proposed river traing structures to stabalise embankment and protect Transnet pipelines at MP 775.5 at Moroletta Spruit, Pretoria, Gauteng Province, South Africa.

Skelton, P.H. (2001). The Complete Guide to Freshwater Fishes of Southern Africa. Struik Publishers (Pty) Ltd., Halfway House.

Thirion, C.A., Mocke, A. & Woest, R. (1995). Biological monitoring of streams and rivers using SASS4. A Users Manual. Internal Report No. N 000/00REQ/1195. Institute for Water Quality Studies. Department of Water Affairs and Forestry. 46.

Thirion, C.A. (2008). River Ecoclassification: Manual for Ecostatus Determination (Version 2). Module E: Volume 1 – Macroinvertebrate Response Assessment Index (MIRAI). WRC Report No. TT 332/08. Water Research Commision, Pretoria.



APPENDICES

Appendix 1: Photographs of sampling sites

Appendix 2: Methodology

Appendix 3: Aquatic Macroinvertebrate Assemblages



APPENDIX 1: PHOTOGRAPHS OF SAMPLING SITES

Site 1

Site 2



APPENDIX 2: METHODOLOGY

In situ water quality

During the various field surveys, in situ water quality variables were measured at each site using a ExTech EC500 combination meter for measurement of temperature, pH, electrical conductivity, and Total Dissolved Solids, as well as a ExTech DO600 Portable Dissolved Oxygen Meter.

Invertebrate Habitat Assessment System (IHAS), Vers ion 2.2

Assessment of the habitat available for aquatic macroinvertebrate colonization and the habitats sampled during rapid biomonitoring practices are vital in the correct interpretation of results obtained following biological assessments. Previous methods of determining habitat were not specific to rapid biomonitoring assessments, and were far too variable in their approach to achieve consistency amongst users.

The Invertebrate Habitat Assessment System (IHAS) was developed by McMillan (1998), and has routinely been used in conjunction with the South African Scoring System (SASS) as a measure of the variability in the amount and quantity of aquatic macroinvertebrate biotopes available for sampling. The habitat scoring system is based on 100 points (or percentage), and is split into two sections, namely the sampling habitat (comprising 55% of the total score) and the general stream characteristics (comprising 45% of the total score). Summation of the scores obtained for the two sections will provide an overall habitat percentage, which can be categorised according to the following values (McMillan, 2006):

IHAS Score (%) Description

>75 Excellent

65-74 Good

55-64 Adequate / Fair

<55 Poor

It has, however, become clear that the IHAS requires field validation and testing, and results obtained should be interpreted with care. Nevertheless, the IHAS does still provide a convenient and rapid method to record details about aquatic macroinvertebrate biotopes sampled during SASS application. For the purpose of the present biomonitoring activities, an adaptation of the IHAS method was used that takes into consideration the sampling habitat only, and did not include the general stream characteristics portion of the IHAS approach.



South African Scoring System, Version 5 (SASS5)

Rapid biomonitoring protocols have become important tools in the investigation of water quality. Where routine chemical analysis provides a snap-shot of the water quality present at the precise time of sample collection, biomonitoring protocols have the advantage of being able to assess the cumulative effect of water quality on biological systems over a longer time period.

There is a general consensus that benthic macroinvertebrates are amongst the most sensitive components of the aquatic ecosystem. Furthermore, aquatic macroinvertebrates are largely non-mobile and are thus representative of local site conditions, allowing for the spatial analysis of disturbances which might be present. However, A major limitation regarding the use of aquatic macroinvertebrates in bioassessments is their heterogeneous distribution and patchiness that results in both spatial and temporal variability in macroinvertebrate assemblages (Dallas and Day, 2004).

The South African Scoring System, Version 5 (SASS5) is essentially a biological index which determines the health of a river based on the aquatic macroinvertebrates present, whereby each taxon is allocated a score based on its perceived sensitivity/tolerance to environmental perturbations (Dallas, 1997). This method of aquatic ecosystem assessment forms the backbone of the River Health Project. The SASS5 method relies on the sampling of aquatic macroinvertebrates from the various habitats present at the selected site with the aid of a net (300mmm x 300mm, 1000 micron mesh size) using standard sampling times and areas. Habitats sampled during SASS5 application include:

• Stones (both in-current and out-of-current);

• Vegetation (both aquatic and marginal); and

• Gravel, sand and mud.

Once collection is complete, aquatic macroinvertebrates are identified to family level (Thirion et al, 1995; Davies & Day, 1998; Dickens & Graham, 2002; Gerber & Gabriel, 2002). Data interpretation is based on two calculated values, namely the total SASS score and the Average Score Per Taxon, which is the SASS score divided by the total number of taxa identified. The SASS index has been proven to be an effective and efficient means by which to assess water quality impairment and general river health (Dallas, 1997; Chutter, 1998).

During the present study, the MIRAI (Macro Invertebrate Response Assessment Index) was used to determine the present ecological state of aquatic macroinvertebrates within the study area. This was done by integrating the ecological requirements of the aquatic macroinvertebrate taxa in a community or assemblage and their response to modified habitat change (Thirion, 2008). Also taken into account during the assessment of the PES was the presence and abundance of the aquatic macroinvertebrates relative to a derived expected list likely to be present under natural, unimpacted conditions.



The four metric groups utilised during the application of the MIRAI were then combined within the model to derive the PES Class of the site in terms of aquatic macroinvertebrates. The allocation protocol is presented in Table 10.

Chutter (1998) developed the SASS protocol as an indicator of water quality. It has since become clear that SASS gives an indication of more than mere water quality, but rather a general indication of the present state of the invertebrate community. Because SASS was developed for application in the broad synoptic assessment required for the River Health Programme (RHP), it does not have a particularly strong cause-effect basis. The aim of the MIRAI, on the other hand, is to provide a habitat-based cause-and-effect foundation to interpret the deviation of the aquatic invertebrate community (assemblage) from the reference condition (Thirion, 2008). This does not preclude the calculation of SASS scores should they be required. However, the recent tendency is to use the MIRAI even for River Health Programme purposes, and it is now the preferred approach (Thirion, 2008).

The present ecological state was determined for each individual sampling site during the present survey.



Table 10: Allocation protocol for the determination of the Present Ecological State for aquatic

macroinvertebrates following application of the MIR AI

MIRAI Percentage

Category Description

>89 A Excellent Unimpaired; community structures and functions comparable to the best situation to be expected. Optimum community structure for stream size and habitat quality.

80-89 B Very Good – Minimally impaired; largely natural with few modifications. A small change in community structure may have taken place but ecosystem functions are essentially unchanged.

60-79 C

Good – Moderately impaired; community structure and function less than the reference condition. Community composition lower than expected due to loss of some sensitive forms. Basic ecosystem functions are still predominantly unchanged.

40-59 D Fair – Largely impaired; fewer families present then expected, due to loss of most intolerant forms. An extensive loss of basic ecosystem function has occurred.

20-39 E Poor – Seriously impaired; few aquatic families present, due to loss of most intolerant forms. An extensive loss of basic ecosystem function has occurred.

<20 F Very poor – Critically impaired; few aquatic families present. If high densities of organisms, then dominated by a few taxa. Only tolerant organisms present.

Fish Response Assessment Index

Fish were collected by means of electro-narcosis, whereby an anode and a cathode are immersed in the water to temporarily stun fish in the near vicinity. Thereafter, the fish are easily scooped out by means of a hand net. A photographic record of fish collected was taken. All fish were identified in the field and released back into the river where possible.

Assessment of the Present Ecological State of the fish assemblage of the watercourses downstream of the present study was conducted by means of the Fish Response Assessment Index (FRAI; Kleynhans, 2008). The procedure followed to determine the fish Present Ecological State, or Ecological Category, is an integration of ecological requirements of fish species in an assemblage and their derived or observed responses to modified habitat conditions. In the case of the present assessment, the observed response was determined by means of fish sampling as well as a consideration of species requirements and driver changes



(Kleynhans, 2008). The expected fish species assemblage within the study area was derived from Kleyhans et al. (2008) and aquatic habitat sampled.

It should be emphasised that although the FRAI uses essentially the same information as the Fish Assemblage Integrity Index (FAII), it does not follow the same procedure. The FAII was developed for application in the broad synoptic assessment required for the River Health Programme, and subsequently does not offer a particularly strong cause-and-effect basis. The purpose of the FRAI, on the other hand, is to provide a habitat-based cause-and-effect underpinning to interpret the deviation of the fish assemblage from the perceived reference condition (Kleynhans, 2008).

The FRAI is based on the assessment of metrics within metric groups. These metrics are assessed in terms of:

• Habitat changes that are observed or derived;

• The impact of such habitat changes on species with particular preferences and tolerances; and

• The relationship between the drivers used in the FRAI and the various fish response metric groups are indicated in Figure 8. Table 11 provides the steps and procedures required for the calculation of the FRAI.

Figure 8: Relationship between drivers and fish met ric groups



Table 11: Main steps and procedures in calculating the Fish Response Assessment Index

Interpretation of the FRAI score follows a descriptive procedure in which the FRAI score is classified into a particular Present Ecological State Class or Ecological Category based on the integrity classes of Kleynhans (1999). Each class gives a description of generally expected conditions for a specific range of FRAI scores (Table 12).



Table 12: Allocation protocol for the determination of the Present Ecological State/Ecological

Category for fish following application of the FRAI

FRAI Percentage

Category Description

90-100 A Unmodified and natural. Community structures and functions comparable to the best situation to be expected. Optimum community structure for stream size and habitat quality.

80-89 B Largely natural with few modifications. A small change in community structure may have taken place but ecosystem functions are essentially unchanged.

60-79 C

Moderately modified. Community structure and function less than the reference condition. Community composition lower than expected due to loss of some sensitive forms. Basic ecosystem functions are still predominantly unchanged.

40-59 D Largely modified. Fewer species present then expected due to loss of most intolerant forms. An extensive loss of basic ecosystem function has occurred.

20-39 E Seriously modified. Few species present due to loss of most intolerant forms. An extensive loss of basic ecosystem function has occurred.

0-19 F Critically modified. Few species present. Only tolerant species present, if any.



APPENDIX 3: AQUATIC MACROINVERTEBRATE ASSEMBLAGES

Abundances: 1 = 1 individual A = 2 – 10 individuals B = 11 – 100 individuals C = 101 – 1000 individuals D = >1000 individuals

Taxon Perceived Reference

Abundance Site 1 Site 2

Baetidae >2spp B B

Dytiscidae/Noteridae A 1

Gomphidae A

Hydrophilidae A

Naucoridae A

Pleidae A

Tabanidae 1

Ancylidae A A

Caenidae B A A

Coenagrionidae B B A

Libellulidae A

Tipulidae 1

Baetidae 2spp B

Leptoceridae A

Gyrinidae A A A

Ceratopogonidae A 1

Hydropsychidae 1sp A A A

Simuliidae A B B

Atyidae A

Chlorolestidae (Synlestidae) 1

Dixidae A A

Ecnomidae A

Gerridae A

Hydracarina A

Hydrometridae

Lestidae A

Veliidae/Mesoveliidae A 1

Aeshnidae A A

Athericidae 1

Elmidae A

Hydraenidae A A



Belostomatidae B

A

Corixidae B A

Culicidae 1

Ephydridae 1

Lymnaeidae A

Nepidae A

Notonectidae A

Physidae

Planorbinae A A

Sphaeridae A

Hirudinea A

Oligochaeta A A 1

Chironomidae A B B

Potamonautidae A A A

Muscidae A

Turbellaria A

A

SASS5 Score 98 48

No. of taxa 19 11

Average Score Per Taxon 5.16 4.36

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