A Stakeholders’ Guide to the North West Dolomite Aquiferfred.csir.co.za/project/groundwater/documents/WUA... · This booklet is concerned with the dolomite aquifers of the North

UNDERSTANDING GROUNDWATER

A Stakeholders’ Guide

to the North West Dolomite Aquifer

Understanding Groundwater:

A stakeholders guide to the North West Dolomite Aquifer

WRC Project 1324 – Institutional Arrangements for Groundwater Management in Dolomitic Terrains.

September 2003

CSIR Report Number 2003-128

Contact details:

Department of Water Affairs and ForestryPrivate bag X313

Pretoria 0001Tel:012 336 7500www.dwaf.gov.za

Water Research CommissionPrivate Bag X03,

Gezina, 0031Tel: 012-330-0340

www.wrc.org.za

IUCNP O Box 11536, Hatfield, Pretoria, 0028

Tel: 021-342-8309

Project leader: Anthea Stephens, IUCN. Project manager: Lutske Newton, IUCN Assoc. Main Author: Christine Colvin, CSIR Technical specialist: Dave Bredenkamp, WREM Illustrations & review Lisa Cavé, CSIR Graphics: Pannie Engelbrecht, CSIR Photographs: Anthea Stephens, IUCN Maps: Claus Mischker, MCA Planners; Simon Hughes, CSIR Afrikaans translation: Pannie Engelbrecht, CSIR Layout: Magdel van der Merwe This report should be cited as: WRC, 2003. Understanding Groundwater: A stakeholders guide to the North West dolomite aquifer.

Water Research Commission

Understanding Groundwater in the Dolomites

September 2003 page i

Contents 1. INTRODUCTION ...........................................................2

1.1 The WRC project...........................................................2 1.2 The purpose of this booklet............................................2 1.3 Key concepts for water management ..............................2

2. GROUNDWATER ...........................................................4 2.1 What is groundwater? ...................................................4 2.2 Types of aquifers ..........................................................4 2.3 The importance of aquifers ............................................5

3. THE GROUNDWATER CYCLE ......................................6 3.1 From the beginning of life on earth… ..............................6 3.2 The dolomites as aquifers ..............................................8 3.3 Recharge of aquifers .....................................................8 3.4 Recharge to the dolomites ........................................... 10 3.5 Flow and storage in aquifers ........................................ 10 3.6 Aquifer compartments in the dolomites ......................... 10 3.7 Groundwater abstraction.............................................. 11 3.8 Groundwater abstraction from the dolomites ................. 12 3.9 Groundwater discharge to the environment ................... 14 3.10 Springs and outflow from the dolomites ........................ 15 3.11 Are the dolomite aquifers in danger?............................. 17 3.12 Management of the dolomites in transition .................... 19

4. GROUNDWATER MANAGEMENT IN RSA.................21 4.1 Principles of water management in RSA ........................ 21 4.2 Who does what to manage groundwater ....................... 22 4.3 The role of Water User Associations.............................. 22 4.4 Groundwater management in RSA ................................ 23

4.5 What do we need to know to make decisions?............... 24

5. FUTURE MANAGEMENT OF THE NW DOLOMITE AQUIFERS .................................................................... 25

5.1 Getting the right information........................................ 25 5.2 How much is sustainable?............................................ 25 5.3 The role of WUAs........................................................ 28

6. FURTHER SOURCES OF INFORMATION .................. 29 6.1 Groundwater - websites............................................... 29 6.2 Groundwater – Books and Reports ............................... 29 6.3 Water Management - websites..................................... 30

7. GLOSSARY ................................................................... 31

8. ABBREVIATIONS......................................................... 35


September 2003 page i

Figures Figure 1: Groundwater forms the base of the water cycle: Illustration of key terms. ......................................................................................................................3 Figure 2: Different types of aquifers .................................................................................................................................................................................................4 Figure 3: The geology of the dolomites ............................................................................................................................................................................................6 Figure 4: Compartments of the dolomite aquifer ..............................................................................................................................................................................7 Figure 5: Wondergat sink hole in karst terrain: the land surface has collapsed revealing groundwater below. (Photograph A.Stephens, IUCN). .......................8 Figure 6: Pristine dolomite aquifer with very low level of use...........................................................................................................................................................9 Figure 7: Poster showing ‘Playground Pumps’................................................................................................................................................................................11 Figure 8: Cone of depression around a pumped borehole.............................................................................................................................................................11 Figure 9: Use of Dolomitic Groundwater (Source: Bigen,2002) .....................................................................................................................................................12 Figure 10: Map showing land-use (Source: National Land Cover Database)...............................................................................................................................13 Figure 11: Aquifer Dependent Ecosystems in the catchment .........................................................................................................................................................14 Figure 12: Groundwater feeding plants and a wetland from a shallow sandy aquifer. ..................................................................................................................15 Figure 13: Groundwater fed spring at XXX Anthea? with associated riparian vegetation. ............................................................................................................15 Figure 14: Map of springs, rivers and wetlands..............................................................................................................................................................................16 Figure 15: Water levels recorded at Wondergat with responses in the flow of springs. ................................................................................................................17 Figure 16: Unsustainable use of groundwater in the dolomites. ....................................................................................................................................................18 Figure 17: Pollution at Rhenosterfontein indicated by high chloride values in 1983......................................................................................................................19 Figure 18: Major compartments and Water Management Area boundaries. .................................................................................................................................20 Figure 19: Water should be used to redress past inequities, ensuring some, for all, forever. ......................................................................................................22 Figure 20: Different uses of groundwater from the North West Dolomites ....................................................................................................................................26 Figure 21: Proposed Institutional Framework for Groundwater Management in Dolomitic Terrains ..............................................................................................27 Figure 22: Pollution occurs underground as well as on the surface...............................................................................................................................................28


September 2003 page 2

1. INTRODUCTION 1.1 The WRC project This booklet is produced by the Water Research Commission as part of a project lead by IUCN on Institutional Arrangements for Groundwater Management in Dolomitic Terrains (WRC Project 1324). The aim of the project is to develop institutional arrangements for groundwater management in Water Management Areas (WMAs), using the dolomitic terrain of North West Province as the pilot area. The dolomitic aquifer crosses three WMAs. Sustainable and equitable management of the aquifer needs to take into account the geohydrology of the area, the ecological role of groundwater and the social and institutional dynamics of the area. This booklet and accompanying posters have been produced to provide useful information on groundwater to the wide variety of stakeholders who are likely to make up the Water User Associations in the area. It is necessary for stakeholders to understand some of the important basics about groundwater and aquifers so that they can make decisions about using groundwater sustainably. 1.2 The purpose of this booklet This booklet is written for people who use groundwater from the dolomite aquifers of North West Province, South Africa. It is aimed particularly at Water User Associations, as the new institutions of local water management in South Africa. This booklet will: Help people who use groundwater understand more about its value

and occurrence;

Outline how groundwater management should take place in South Africa;

Illustrate some of the consequences of water users’ actions and decisions.

This booklet introduces some of the key concepts underpinning water management in South Africa. Chapter 2 introduces the reader to groundwater and the importance of aquifers. More detail on how groundwater occurs and behaves is given in chapter 3, with particular focus on the dolomite aquifers of the North West. The current context and history of groundwater management in South Africa is summarised in chapter 4 and a discussion of important elements for future management of the dolomites is given in Chapter 5. The reader is introduced to technical, scientific and management terminology in this booklet and the Glossary at the end provides definitions of important terms. Further sources of information from books, reports and the Internet are listed in chapter 6. 1.3 Key concepts for water management Management of water resources should:

• Be lawful; • Meet the basic needs of people and the environment; • Use resources sustainably; • Enable the maximum benefit to be gained from the use of water; • Minimise the negative effects of water use; • Be able to adapt to natural variability and uncertainty.

The key principles underpinning water resource management in South African water law are sustainability and equity. This is captured in the motto for the Department of Water Affairs and Forestry as Some, For All, Forever: some water should be used, fairly, by all people for the benefit of the nation in a sustainable way.



Figure 1: Groundwater forms the base of the water cycle: Illustration of key terms.



Worldwide, water resources are being managed in an increasingly integrated way. This means that each part of water management – for example, licensing and use, monitoring, protection, economic aspects, environmental aspects, surface water management and groundwater management – should consider the whole cycle of water management and not be carried out in isolation. We recognise that we cannot continue to take water out of the natural environment without understanding what sustains our supplies. We also recognise that our use of water may affect our neighbours, on near-by farms, adjacent catchments or neighbouring countries, and we need to consider their needs if we are to avoid conflict over water. Groundwater management is part of Integrated Water Resource Management (IWRM) and has its own special rewards and problems. Groundwater, found in aquifers, is often a reliable source of good quality water that is widely available to rural users. However, because we can’t see the water in aquifers we need to develop a good understanding of how groundwater behaves. We need to make decisions informed by observations of groundwater.

Figure 2: Different types of aquifers

2. GROUNDWATER 2.1 What is groundwater? Most of the usable water that occurs on earth (i.e. liquid, freshwater) occurs underground. Water occurs underground in unsaturated rocks and soil as soil moisture. Most water that is used by crops and other plants is soil moisture from the unsaturated zone (or zone of aeration). Water also saturates soil and rock strata underground so that all the spaces in between grains of sand or pieces of rock are full of water. Rocks which have well connected spaces in them allow the water to flow through them. This is called permeability, and rocks with good permeability which allow flow make aquifers. When we discuss groundwater in this booklet we mean water that is found in aquifers – in other words, water which occurs underground in saturated rocks which allow enough flow to supply a well or borehole. Figure 1, on the previous page, shows how aquifers are part of the water cycle and illustrates some terms used to describe different parts of the water cycle. 2.2 Types of aquifers Aquifers are formed by rock strata and different types of aquifers are found in different types of rocks. The different rock formations are cemented, folded, fractured and dissolved in ways which differ depending on the materials they contain. This means that they store and allow the flow of groundwater in different ways. For example, a sandy alluvial aquifer contains water in the spaces between the sand grains as shown in Figure 2 (a). These spaces may make up about 20% of the volume of the strata (porosity) and have an average permeability of 1m/ day. This means that one drop of water would take one day to travel 1m through the spaces in the rock. Alluvial aquifers are

Pores in unconsolidated sedimentary deposits

Caverns in dolomite

Fractures in intrusive igneous rocks

Rubble zone and cooling fractures in extrusive igneous rocks

1 m 1 m

3 cm 20 m

a b

c d



generally quite long and narrow and only up to 30 m deep, therefore they do not store vast quantities of water. The water quality is usually good where they contain mainly quartz sand grains, because there are few salts to dissolve into the water. This booklet is concerned with the dolomite aquifers of the North West Province. These are carbonate aquifers, which includes limestone and dolomite. Carbonate aquifers have fissures and caverns as shown in Figure 2b, and these relatively large spaces allow relatively fast flow of groundwater. Some rocks have relatively high porosity (volume of space) but poor connections between the spaces (permeability). An example of this is clay which may have a porosity of 30% but a very low permeability of only 1m/ year. These rocks are called aquicludes, where they have very low permeability, or aquitards, where they have almost no permeability. 2.3 The importance of aquifers It is estimated that over 90% of the usable water in most catchments is found in aquifers. Groundwater therefore represents a critically important water resource world-wide. This huge store of water has usually taken many years to accumulate and some aquifers contain groundwater that fell as rain thousands of years ago. Aquifers act as natural reservoirs of water, storing large volumes for long periods of time. This means that the availability of groundwater is not dependent on this year’s rains, or even last year’s rains. Aquifers are therefore very important sources of water during drought years. However if an aquifer is over-exploited it could take many years to recover. Aquifers not only act as natural reservoirs, storing water in pore spaces, cracks and fissures, but they are natural distribution networks as permeable rock types allow water to flow over long distances.

Deep reservoirs of groundwater are protected from pollution at surface by the filtering effect of soil and rock. Generally, the risk of groundwater contamination is lower than surface water contamination and this means that groundwater in many areas is cheaper to use domestically because it doesn’t need to be treated. However, groundwater pollution can take longer to clear up. Section 3.11 discusses what makes some aquifers more vulnerable to pollution than others. In summary, aquifers represent strategically important sources of water because: Groundwater is less vulnerable to drought than surface water; Groundwater is better protected from pollution than surface water; Groundwater is more widely distributed than surface water.



3. THE GROUNDWATER CYCLE Groundwater and aquifers are an important part of the total hydrological system, or water cycle. The study of groundwater is called hydrogeology or geohydrology and it links the study of rocks (geology) with water (hydrology). 3.1 From the beginning of life on earth… Geologists believe that the dolomites of North West province were deposited in a shallow sea that covered the Transvaal some 2.5 billion years ago. These dolomites are some of the oldest carbonate rocks in the world.

This 2 km thick sequence of carbonates took 100 million years to accumulate. The dolomites cover an area of about 3 750 km2 as shown in the map in Figure 4. The layers of rock strata which comprise this group are shown in the diagram below. The dolomite layers contain some chert-rich layers (silica oxide rich) and chert-poor layers, limestone and sedimentary layers with rock fragments and fine grained shale. The different compositions of the different rock layers affects their characteristics and the way that they behave as aquifers. The chert-rich layers of dolomite, the Monte Christo and Eccles formations, form the best aquifers in the sequence with high permeabilities of up to XX Dave? m/day.

Figure 3: The geology of the dolomites

System/Erathem

SEQUENCE GROUP FORMATION LITHOLOGY AND MEMBER THICKNESS(m)

DWYKA

TIMEBALLHILL

ROOIHOOGTE

ECCLES

LYTTELTON

MONTECHRISTO

OAKTREE

BLACK REEFQUARTZITE

Sandstone

MudstoneCarbonaceous shale, coal

Diamictite

ShaleDiamictiteKlapperkop Quartzite Mb wackeand ferruginous quartziteGraphitic and silty shaleQuartziteShaleBevets Conglomerate MemberBreccia

Chert-rich dolomite with largeand small stromatolites

Dark chert-free dolomite with largeelongated stromatolitic moundsLight coloured recrystallised dolomitewith abundant chert; stromatolitic;basal part ooliticDolomite, becoming darker upwardsChocolate-coloured weatheringShaleQuartziteArkosic grit

25 - 30

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700

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270 - 660

PER

MO

-C

AR

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NIF

ERO

US

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TER

OZO

IC

TRA

NSV

AA

L

CH

UN

IESP

OO

RT

PRET

OR

IA

KA

RO

O

ECC

A



Figure 4: Compartments of the dolomite aquifer



3.2 The dolomites as aquifers The dolomite aquifers are widespread, highly productive aquifers containing good quality water that supplies significant agricultural and domestic water needs, as well as the environment, in the North West. Dolomites are calcium- magnesium carbonate rocks (Ca Mg (CO3 ) 2). They are similar to limestone, which is calcium carbonate (CaCO3), and both are rocks that are may be dissolved by rainwater over long periods of time. Dolomites and limestones form karst landscapes, such as that seen in the North West Province. These landscapes often appear dry but most of the water flow is below ground and sink holes and springs are common features.

Figure 5: Wondergat sink hole in karst terrain: the land surface has collapsed revealing groundwater below. (Photograph A.Stephens, IUCN).

Dolomites form very good aquifers because over long periods of time they are dissolved by rain and groundwater. Rain water becomes slightly acidic as it filters through soil. This enables recharging water to dissolve the carbonate more easily. Fissures (caves or gaps in the rock) are dissolved out of the rock by flowing groundwater. Figure 6 shows how fissures and cavities occur in the dolomites in a cross-section of the aquifer. These cavities give dolomites a very high permeability, which allows groundwater to flow rapidly through them. They can also store significant quantities of water. It is estimated that about 5000 million m3 are stored in the dolomite aquifers. This is twice the volume stored in the Vaal dam. 3.3 Recharge of aquifers Whilst aquifers store great quantities of water, they may not receive large volumes of water each year. If we want to use groundwater sustainably we need to understand how much water is available on average each year. If we take out more than is naturally replenished, or recharged, each year, groundwater levels will fall and eventually the aquifer may be depleted. Recharge is the amount of water that is added to the aquifer each year. This water generally comes from rainfall and represents the relatively small proportion of rainfall that percolates or trickles down through unsaturated soil and rock to the water table. Recharge may also come from rivers, other aquifers or artificial sources such as irrigated water or water leaking from pipes. The amount of recharge may be given as a percentage of mean annual precipitation (MAP) (e.g. 5% of MAP), a depth (e.g. 30 mm for an area) or a volume for an aquifer. If the total volume of water that flows out of an aquifer (e.g. from springs) plus that which is pumped out per annum, is greater than the average amount that recharges the aquifer per year, water levels will start to fall. In other words, there should be a balance between what comes in and what goes out to maintain water levels.



Figure 6: Pristine dolomite

aquifer with very low level

of use.



The actual amount of recharge may vary considerably each year and usually recharge is not a fixed percentage of rainfall. However, for management purposes it is usually sufficient to consider the annual average because the relatively large volumes of groundwater stored in an aquifer buffer the effects of variable rainfall. 3.4 Recharge to the dolomites Several scientific studies have been carried out to find out how much rainwater seeps through the soil to recharge the dolomite aquifer. These studies help us to understand, on average, how much water goes into the aquifer each year and therefore how much may be abstracted sustainably. Studies estimate that between 130 and 190 million m3/annum are recharged to the main aquifer compartments each year. 3.5 Flow and storage in aquifers We all know that water flows down hill, and this happens underground too. In aquifers, water flows down ‘hill’ or down-gradient from areas of high water levels to low water levels through permeable rocks. The more permeable the rocks, the faster the water can flow. Some aquifers store groundwater under pressure. These aquifers have a low-permeability or confining layer on top of them, and they are called confined aquifers. The water pressure or head in a confined aquifer may be higher than the ground level, resulting in free-flowing artesian boreholes and springs. In other confined aquifers, the water level in a borehole will rise higher than the depth of the top of the aquifer, but not reach the surface. Groundwater is therefore stored in the spaces in an aquifer and under pressure as a result of the compressibility of the water and the aquifer. The rocks themselves may compress and even collapse when groundwater is removed.

Rainwater is very fresh water with few dissolved salts. As water trickles through soil and flows slowly through aquifers, it dissolves some of the more soluble material it passes. The chemistry of groundwater varies depending on the type of aquifer material and the age of the water. Some aquifers have naturally poor quality water but the dolomites have good quality water containing dissolved calcium, magnesium and bicarbonate. Water levels vary through-out the year at any one place depending on how much water is entering and leaving the aquifer. After recharge, e.g. rainfall, the water table rises. As groundwater leaves the aquifer, e.g. through pumping, the water table slowly falls, 3.6 Aquifer compartments in the dolomites The dolomite aquifer has been naturally divided into compartments by volcanic rocks (diabase). These rocks intrude upwards through the dolomite sequence in long sheets, known as dykes. Dykes are less permeable than dolomite and act as barriers to flow, rather like a dam wall. This is shown in figure 6 where a spring forms at a dyke which is blocking groundwater flow, pushing the water table up to the ground surface. The map in Figure 4 shows 37 compartments that have been identified in the dolomites. These can be grouped, for management purposes into 5 main units– Ventersdorp (or Schoonspruit), Groot Pan, Itsoseng/ Lichtenburg, extended Grootfontein and Zeerust. The boundaries between the compartments are based on the naturally occurring dykes. In most instances the dykes act as leaky barriers, and allow limited flow through. They are usually between 10m and 30m wide.



3.7 Groundwater abstraction People have used springs and taken water from aquifers since ancient times. Historical methods included building brick-lined wells and horizontal tunnels (adits or qanats) into mountain-sides. The wind pump is a feature of the South African landscape that signals groundwater abstraction. Today diesel mono-pumps, solar powered pumps and less conventional ‘Playground’ pumps (shown below) are used to bring groundwater to the surface.

Figure 7: Poster showing ‘Playground Pumps’

Figure 8: Cone of depression around a pumped borehole. Most groundwater abstracted is used in agriculture – an estimated 80% in South Africa. Pumping groundwater from a well or borehole lowers the water table in the vicinity of the abstraction, forming a cone of depression as shown in Figure 8. There may be several meters difference in the water level of a pumped well and a non-pumped well close by. Measurements of the water level in the aquifer, which represent the background or rest water



level, should be taken from a borehole that has not been pumped for at least one day, or from an un-pumped borehole. 3.8 Groundwater abstraction from the dolomites The dolomite aquifer is one of the most productive aquifers in South Africa. Every year an estimated 187 million m3 are pumped out of the aquifer, about XX% of the average abstraction from the Vaal Dam. This can be averaged to about 50 000m3/km2 over the entire area of the aquifer, however, abstraction is heavier [and unsustainable] in some areas and negligible in others. Figure 10 shows land-use in the dolomite area and this gives an indication of the use of groundwater. As shown in Figure 9, approximately 76% of groundwater from the dolomites is used for agriculture, 17% for domestic use and 3 % by the mining sector. The towns of Mafikeng, Zeerust and Welbedacht are dependent on groundwater for more than XX% of their water supply.

Figure 9: Use of Dolomitic Groundwater (Source: Bigen,2002)

Use of Dolomitic Groundwater (2002)

76%

17%

3%

4%

1 2 3 4

agriculture

industry

domestic

mining



Figure 10: Map showing land-use

(Source: National Land Cover Database)



3.9 Groundwater discharge to the environment Some groundwater remains as ‘fossil water’ trapped in aquifers which do not link back to the water cycle. However, most groundwater moves to another part of the water cycle as it is discharged to surface water, the atmosphere or to the sea. Where groundwater feeds the environment, plants and animals are often adapted to make use of it. These may be plants at an oasis in an otherwise dry landscape, or, for example, reed beds on a salty estuary which need fresh water supplied by an aquifer. Plants and animals are linked in ecosystems. Ecosystems which exist where groundwater discharges are often dependent on aquifer supplies and may be changed if that water is no longer available. Some species may die-off. This reduces biodiversity and upsets the balance of the ecosystem. The animals and plants that have evolved in groundwater-fed areas are often very intolerant to changes in water supply or pollution of the water. Because aquifers store large amounts of water, they can provide a more steady supply of water. Other ecosystems which rely on only rain or river water are adapted to tolerate greater variations in water supply. Figure 11 shows some of the habitats which may receive groundwater. Sometimes groundwater feeds into surface water and sometimes rivers and lakes ‘leak’ to aquifers below. Where a river runs over very low permeability rocks it may be isolated from underlying aquifers. Similarly wetlands may receive groundwater or be fed by surface water drainage and exist perched above the water table. Figure 1 shows a perched wetland which is not connected to the underlying aquifer. Often the direction of flow between a river and an aquifer changes with the seasons and varies along the length of the river, resulting in a complicated exchange of water between surface and underground systems.

Figure 11: Aquifer Dependent Ecosystems in the catchment Plants may transpire groundwater directly to the atmosphere where the water table reaches the base of the rooting zone. This is known as ‘cryptic discharge’ as we cannot see the water leaving the aquifer. Most plants can only root to a few meters depth, but some trees have tap roots that can extend over 50m deep and reach deeper aquifers. This has been seen in the Kalahari desert with deep rooted Acacias. Figure 12 shows plants rooting to a relatively deep water table that creates a wetland in a topographic low.

1 Springs2 Seeps, wetlands3 Baseflow4 In-aquifer ecosystems5 Riparian zone6 River bed7 Plant tap water table8 Estuarine9 Coastal zone



Figure 12: Groundwater feeding plants and a wetland from a shallow sandy aquifer. 3.10 Springs and outflow from the dolomites Springs are a feature of the dolomite landscape. They were a critical water supply for early civilizations. Figure 14 shows the location of some of the springs on the dolomites. Many of these springs are located where the permeable aquifer comes into contact with less permeable dykes and surrounding rock, forcing groundwater to discharge at the surface. Outflow happens as discrete springs, to wetlands, such as the Malmani wetland, or forms the headwaters of rivers, such as the Groot Marico. The spring with the largest outflow on the Dolomites is Molopo Spring [in which dolomitic unit?] which has an average flow of 190 l/second, or 6 million m3/annum. This spring, and pumping at the Grootfontein Spring, supplies the town of Mafikeng with most of its water. Farmers also pump

large quantities of water from the Grootfontein unit, causing this spring to stop flowing in the dry season. The Molopo eye, on the other hand, is still in a pristine condition in terms of its flow and the wetland it supports. The natural environment has evolved to make use of natural supplies of groundwater to the surface. Communities of fish and riparian vegetation that live in the rivers and wetlands formed in groundwater discharge areas, are dependent on supplies from the aquifer. Many rare species which occur only in this area are associated with groundwater fed springs and eyes in the North West. These include the short fin barb (Barbus paludinosus) and the large mouth bass (Sperudocrenilabrus philander). They rely on the water balance of the aquifer providing a consistent flow of good quality groundwater.

Figure 13: Groundwater fed spring at XXX Anthea? with associated riparian vegetation.

C oarse aeolian sand

S aturated zone

R ainfa ll, groundwater flow

W ater tab le

Deep tap root

Groundwater fed wetland



Figure 14: Map of springs, rivers and wetlands.



3.11 Are the dolomite aquifers in danger? The dolomites are a hugely important water resource in a semi-arid area of the country with few alternative sources for supply. This importance has been appreciated by water managers who have monitored the aquifer’s behaviour and status. Aquifers are vulnerable to contamination, drought, subsidence (collapse of the ground surface) and over-exploitation. These threats are illustrated in figure 16. Water levels in boreholes and sinkholes, and rates of outflow from springs, tell us whether groundwater resources are being over-exploited and used beyond sustainable limits. The water level of a borehole is like the heart beat of the aquifer – but this is a heart that typically beats only once a year, with a peak during recharge from the summer rains (see Figure 15). Dave I would prefer to have a graph of rainfall and levels vs time. Do you have this data? Figure 15 shows how recharge of the aquifer causes a rapid rise in water levels. This high level then recedes gradually until the next recharge event. The rate of recession, or falling, of the water table levels off as it falls because groundwater flows away and discharges more slowly. The high recharged water levels shows the hydraulic head, or pressure, which forces groundwater flow more quickly. When groundwater is being over-exploited or the climate becomes drier, the levels of the peaks and the troughs become gradually lower. The pressure of the heart beat drops. Most of the water level monitoring of the dolomite aquifer shows us that levels are sustained. However, in the area around Grootfontein water levels are falling at XX and XXX (Dave?) showing that the aquifer is in danger of being depleted.

Figure 15: Water levels recorded at Wondergat with responses in the flow of springs. Even if there are sufficient volumes of water in the aquifer, they may be polluted making them dangerous to use for drinking water or for livestock. The dolomite aquifer is relatively vulnerable to contamination because in most areas the material overlying the aquifer will allow contaminants to wash through to the water table. This is because the soil is permeable and the water table is close to the surface. Therefore pollutants at the surface, such as fertilizers and leaks from pit latrines, can percolate quickly to the water table and enter the aquifer. Examples of pollution from sanitation and farming are shown in figure 16.

Simulated vs Actual flow

0

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of s

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/mth

-2

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Won

derg

at le

vel (

m o

n ga

uge)

Actual flow MA simulated flow Wondergat level



Figure 16: Unsustainable

use of groundwater in the dolomites.



Figure 17: Pollution at Rhenosterfontein indicated by high chloride values in 1983. The dolomite aquifers do not appear to have suffered widespread pollution. On the whole, water quality has remained fairly good over the last few decades of measurement. However, the graph above shows evidence of a pollution incident at Renosterfontein. Examples like this have been noted over the years. Figure 17 shows high chloride levels (pink squares) between 1983 and 1985. These chloride levels indicate a pollution incident. Once the pollution has stopped, the high levels eventually return to normal, but this may take many years. In the case of Renosterfontein, chloride levels took nearly 10 years to return to their natural levels after the pollution. Dolomite aquifers are in danger of subsidence when water levels are lowered and the land surface above them collapses. This may happen above particularly permeable areas with well developed fissures and caverns. Once subsidence occurs it is irreversible and results in a loss of aquifer storage as well as the destruction of property. Subsidence and the formation of sinkholes are natural features of the karst landscape, however,

more collapses are likely to occur in dolomitic areas which have suffered a drop in the water table. Subsidence is known to have occurred in mining areas, such as XXXX, where the aquifer has been dewatered to allow mining. 3.12 Management of the dolomites in transition Section 1.3 of this booklet outlined some of the key concepts on which water management is based. These include sustainability, equity and integrating groundwater and surface water to make the best use of both resources. These principles of water management have been recognised in South Africa within the last decade. Previously water management was guided by different values and groundwater was viewed as a separate resource. Currently the management of the dolomites is changing, as with all water management in South Africa. The National Water Act (NWA) and the Water Services Act (WSA) changed the legal duties for water management in the late 1990s. Previously, management of the dolomites was overseen by the Bo-Molopo and Schoonspruit Subterranean Groundwater Control Areas. These areas are shown in Figure 18. Catchment management agencies (CMAs) will manage water resources in South Africa at a regional level in the future. A CMA will be responsible for ensuring the sustainable use of water resources in their water management area (WMA). The dolomites of the North West occur in three Water Management Areas: the Crocodile West- Marico WMA; the Middle Vaal WMA and the Lower Vaal WMA. These WMAs fall under the current responsibilities of Gauteng, North West, Free State and Northern Cape DWAF regional offices, respectively.

Water Quality - Renosterftn

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Figure 18: Major compartments and

Water Management Area boundaries.



4. GROUNDWATER MANAGEMENT IN RSA

4.1 Principles of water management in RSA The principles of water management in South Africa are aligned with our constitution and laid out in two important laws – the Water Services Act (1997) and the National Water Act (1998). The Water Services Act essentially outlines how we should manage the delivery of water to users (water in pipes) and the National Water Act, how we should manage water in the environment (water in rivers, wetlands and aquifers). The ultimate aim of water resource management is to achieve the sustainable use of water for the benefit of all users. Some, for all, forever. The principles for water management in South Africa are summarized in the preambles to each of our water laws. These are summarized below:

• Water is a scarce and unevenly distributed national resource which occurs in many different forms, all of which are interdependent and part of the water cycle;

• Water is a natural resource that belongs to all people, however, the

discriminatory laws and practices of the past have prevented equal access to water, and use of water resources;

• The National Government should ensure the equitable allocation of

water for beneficial use, including the redistribution of water;

• The government should take account of international water matters;

• The protection of the quality of water resources is necessary to

ensure sustainability of the nation's water resources in the interests of all water users;

• The management of water resources should integrate all aspects of

water resources and, where appropriate, should be delegated to a regional or catchment level so as to enable everyone to participate;

• Every person has the right of access to basic water supply and

basic sanitation necessary to ensure sufficient water and an environment not harmful to health or well-being;

• Water supply services and sanitation services should be provided in

a manner which is efficient, equitable and sustainable;

• Different government departments should work co-operatively to supply water and sanitation;

• All spheres of Government must strive to provide water supply

services and sanitation services sufficient for subsistence and sustainable economic activity;

South Africans’ right to Water Chapter 2, section 3 of the Water Services Act states that: (1) Everyone has a right of access to basic water supply and basic sanitation. (2) Every water services institution must take reasonable measures to realise these rights. (3) Every water services authority must, in its water services development plan, provide for measures to realise these rights.



• The provision of water supply services and sanitation services, although an activity distinct from the overall management of water resources, must be undertaken in a manner consistent with the broader goals of water resource management;

• Water supply services and sanitation services are often provided in

monopolistic or near monopolistic circumstances and that the interests of consumers and the broader goals of public policy must be promoted; and

• The National Government is the custodian of the nation's water

resources.

Figure 19: Water should be used to redress past inequities, ensuring some, for all, forever.

4.2 Who does what to manage groundwater The management of groundwater is currently in transition. Currently most management is carried out by DWAF and users. Within the next ten years, responsibilities for management will be devolved along the following lines: National DWAF – Will be the national custodian and ensure continuity of protection and use between the water management areas. They will ensure that our international obligations are met and the Reserve is maintained. The Catchment Management Agency (CMA) – will ensure that aquifers within its area are protected within sustainable limits for the best use. Water User Associations (WUAs) – will ensure that the needs of their members are met in a fair way, whilst not compromising the sustainable limits of their groundwater resources. Water Service Providers (WSP) – will efficiently delivery water to users to meet their basic needs and support beneficial use. Individual users – will ensure that they use groundwater efficiently within either the General Authorisations for their area or their license conditions. 4.3 The role of Water User Associations In South Africa the role and structure of Water User Associations is defined under the National Water Act: ‘Although WUAs are water management institutions their primary purpose, unlike catchment management agencies, is not water management. They operate at a restricted localized level, and are in effect voluntary, co-operative associations of individual water users who wish to undertake water-related activities for their mutual benefit. A water user association



may exercise management powers and duties only if and to the extent that these have been assigned or delegated to it by the CMA.’ WUAs may develop differently in different areas, depending on what they set out to achieve. Their aims will vary depending on the resources they have, including the capacity of their members to carry out different water management responsibilities. It is expected that they may manage local water infrastructure, monitor water use and take part in broader IWRM decision making in their regions. They may even supply water to a range of consumers. WUAs may be formed around a single sector or user group, such as mining or farmers. But many are expected to represent the range of users within a geographical area, and this would include groups such as emerging farmers who were not previously involved in water management. 4.4 Groundwater management in RSA Groundwater management has a history of neglect in South Africa. Despite recent developments in policy, and the importance of groundwater as a strategically important resource on which many rural communities depend, water management in South Africa remains largely determined by surface water systems. Aquifers do not always coincide with the catchment management areas demarcated for the delegation of water resources management. This is shown in figure 18 where aquifers cross boundaries between catchments, Water Management Areas and countries. Historically, the management of groundwater in South Africa was a complicated affair, as under the 1956 Water Act groundwater could be classified as: Subterranean water: includes, ‘water naturally occurring underground or

obtained from underground in an area declared as a subterranean Government water control area’. Subterranean water is not defined as either public or private water in the Act but is a

category of water distinct from underground water with different allocation rules.

Public’ Surplus water: Surface water (streams) qualified as public water and was further categorized as either normal flow or surplus water. Because underground water cannot qualify as normal flow since this must visibly flow, it qualifies as surplus water, which is any public water other than normal flow.

‘Deemed’ Private water is water that is pumped from underground (e.g. borehole water). Provided this water is not derived from a public stream, the Act deems this water to be private water. The sole rights to use and enjoy private water vest in the owner of the land on or under which it is found.

Under the new National Water Act, groundwater has the same status as surface water, and may not be privately owned. Individuals, such as farmers, may be given the right to use water for a limited period of time under conditions of agreed sustainability. They do not own the water under their property but may have a right to use it. The sustainable use of groundwater can be achieved by protecting aquifers using four legal measures, which will be used for all water resources. These are summarized below: The CMA and DWAF, in consultation with stakeholders, need to develop a vision for water resources in an area. This vision will describe what the available water should be used for, how much impact is acceptable, how the ecosystems linked to rivers and aquifers should be managed and what aspects of the resource should be protected and monitored. All significant water resources in an area need to be identified, quantified and classified according to how much impact is acceptable. Resource quality objectives (RQOs) describe aspects of the resource to be protected and the Reserve describes how much water needs to be set aside for basic human needs and aquatic ecosystems. Together this set of measures is referred to as the resource directed measures (RDM).



The CMA may allocate water resources to different users. They may grant a licence to use a certain amount of water from a particular resource for a particular use, and this will usually require monitoring of the resource and impacts of abstraction. Certain low-volume uses of water may be generally allowed and do not require a licence, eg for basic domestic use or livestock watering. These are called the general authorisations and Schedule 1 uses. The general authorisations are usually for a limited volume of annual abstraction per hectare. For example for the XX catchment the general authorisation is XXX(Dave do you have these figures or can you give me quart catchment numbers?) We need to control the pollution of groundwater. This is done using source-directed controls to prevent and minimise, at source, the impact of development on groundwater. This should be initiated by DWAF and the CMA and implemented by the people who control the potentially impacting activities, eg, farmers, mining companies, or industry. If pollution or degredation has already occurred we need to clean up. This is called remediation. Polluted water may be remediated where practicable to ensure at least fitness for agreed uses. Whoever has polluted aquifers is responsible for cleaning them up, but if this is not possible, the CMA should do it. Although groundwater now enjoys the same legal status and protection as surface water, we should not forget that it is in fact a part of the total resource with unique characteristics. The special qualities of groundwater – its wide distribution, drought resilience and often good quality – mean that it is a valuable and strategic resource. Ideally, we should use groundwater in a way which derives the maximum benefits for the catchment stakeholders. 4.5 What do we need to know to make decisions? Decision making for integrated water resource management (IWRM) often requires complicated trade-offs between different stakeholders and is based on incomplete information. We never know exactly how much rain

has fallen, even less how much has recharged our aquifers and we can make only a best guess at how much rain is going to fall. We need to make decisions that result in optimal use of the resource, while protecting the environment and contributing to economic development. Often, because we can only make estimates about the amount of water available or the likely impacts of using it, we need to examine the risk of decisions. When the potential negative consequences of the decision are severe, we tend to spend more time and money getting all the necessary information together and will proceed cautiously. When we think the costs, either economic, social or environmental, are low and the gains expected are high we may take more of a ‘risk’ and start using the resource more heavily. Decision making in South African IWRM should be:

- transparent, with a clear record of how the decision was made; - defensible, with an explanation of why the decision was made

based on the values of stakeholders and scientifically valid information;

- participative, with stakeholders influencing the process; and - accountable, with a clear understanding of who made the

decision and how the consequences of the decision will be managed.

We therefore need to know:

- How much water is available? We need to understand the level of confidence we have in these estimates and how much the available water varies between seasons and years.

- What are the likely impacts of using water from different resources at certain places and times of the year?

The impacts will depend on the state of the aquifer and on the ability of those using and managing the resource to adapt to changing conditions and levels of understanding.

- What are the likely benefits of using water in different ways or allocating water to the environment?



5. FUTURE MANAGEMENT OF THE NW DOLOMITE AQUIFERS

5.1 Getting the right information We need to have the right information to base decisions on if we are to manage water resources sustainably. Any management strategy should include plans which enable decisions to be made and based on measured facts rather than beliefs. Information that is essential to know in areas of groundwater use includes: Rainfall (to determine recharge and sustainable aquifer yield), which aquifers connected to surface water, wetlands or other aquifers, groundwater levels (to confirm recharge), water quality, the health of ecosystems that depend on groundwater discharge (e.g.

wetlands), how much is being used, by whom, what are the known negative impacts of abstraction?

Most of this information is based on monitoring and field measurements which need to be reliably stored in an information system and presented usefully to decision makers and stakeholders. Monitoring should be carried out by users and the CMA. The quality and the accuracy of the information needs to be understood. This information will be used to develop and improve aquifer models which can help predict future impacts as conditions change. However, the results should always be treated with caution as they are only estimates of possible outcomes which are based on our best current understanding and many assumptions. The quality of information that is required, and the intensity of monitoring, should be linked to the risk being managed. For example, if water abstraction is licensed next to an important wetland, regular water level

monitoring should take place from several boreholes between the wetland and the production borehole. Information that will help future decisions on the allocation of water include: How efficiently is the water being used, what benefits are derived from using the water, how does the water use improve the standard of living for people in the area, are the impacts acceptable, is the Reserve being met, are International Obligations being met? 5.2 How much is sustainable? Can deal with concept of sustainability and equity (NB) upfront in ch 5. Sustainable use of resources is typically viewed as - the use of resources to meet the needs of present generations which does not compromise the ability of future generations to meet their needs. Sustainable use of water has been defined as “the use of water that supports the ability of human society to endure and flourish into the indefinite future without undermining the integrity of the hydrological cycle or the ecological systems that depend on it.” South African water law accepts that water use should be sustainable. However, any use of water is likely to have some negative impact, and the law also says that we should protect water resources for their use. In other words, we should not leave all water resources untouched. This means that we have to decide which impacts are acceptable and which are neither sustainable nor acceptable to most stakeholders. Deciding how much water we can sustainably use often requires us to decide how much risk are we prepared to take in terms of negative impacts. Most decisions about using water will require a trade-off of costs and benefits.



The cross-sections in figures 6 and 16 show two different scenarios for the under-development and over-development of the same dolomitic aquifer. The under-used aquifer has only slightly lowered water levels at a single pump. Springs are flowing, groundwater feeds rivers and trees and the aquifer is essentially full. These near natural conditions are almost pristine, but the aquifer is not supporting development. The over exploited aquifer has experienced land subsidence where boreholes are over-pumping and are too close to each other. Springs and rivers have dried up and vegetation has disappeared. Pollution from sanitation is evident and the aquifer is channelling this pollution towards a river. Contamination from fertilizers has also occurred. The aquifer here is supporting heavy use at a high ecological cost. This use is unsustainable because not only is it destroying wetlands and rivers, but it is destroying the aquifer itself by subsidence and contamination. This aquifer will not be able to support the next generation to the same extent it has supported the current users.

Figure 20: Different uses of groundwater from the North West Dolomites

Diamond digging from alluvial gravel overlying the dolomite

Pivot irrigation

Groundwater fed wetland

Brick-making



Figure 21: Proposed Institutional Framework for Groundwater Management in Dolomitic Terrains

DOLOMITE AQUIFER MANAGEMENT COMMITTEE*

International Stakeholders DWAF National office

Regional offices

CMAs

Crocodile west-Marico

Middle Vaal

Lower Vaal

Grootpan WUAs

Lichtenburg/Itsoseng

Grootfontein

Zeerust

Ventersdorp

Technical Committee

Sub-committeeSub-committeeSub-committee



5.3 The role of WUAs Luts, need new/updated info here based on ph 2… Luts: Yes, I’ll supply new text here. The dolomite aquifer should be managed as a single water resource. However, the option of establishing one WUA for all users of dolomitic groundwater was rejected owing to the vast area of the dolomite, the numerous stakeholders and complexity of management issues. Five WUAs have been defined according to internal boundaries of compartments within the aquifer1, and are in different stages of establishment. The proposed WUAs are (see Figure 9): Lichtenburg-Itsoseng Grootfontein Grootpan Ventersdorp Zeerust

Although WUAs should represent all water users using a resource, commercial farmers, who have had to register their water use in terms of the NWA, are driving the establishment of WUAs in the dolomites. WUAs can play a key role in terms of: Educating their members about best practices to protect groundwater

and use it efficiently; Providing a forum to discuss local water management issues; Representing their members at higher levels of management; Monitoring groundwater use; etc

Figure 24 shows how WUAs could fit into the overall management framework of the dolomites

1

Figure 22: Pollution occurs underground as well as on the surface.



6. FURTHER SOURCES OF INFORMATION

6.1 Groundwater - websites http://www.iah.org http://www.gwd.co.za http://www.wrc.org.za http://www.groundwater.com/index.html http://www.bgs.ac.uk/hydrogeology/droughta.htm http://csir.co.za/environmentek/water/ http://www.epa.gov/grtlakes/seahome/groundwater/src/ground.htm http://gwpc.site.net/ http://home.att.net/~intlh2olaw/groundwa.htm 6.2 Groundwater – Books and Reports * Water Research Commission reports may be obtained free of charge from the WRC on 012 333 00340 or [email protected] Bredenkamp DB (1999). Development of a hydrodynamic model of the Grootfontein and surrounding dolomitic compartments with the view to improved groundwater management and more effective control of abstractions. Report by Water Resources Evaluation and Management, Pretoria. Bredenkamp DB, Botha LJ and Venter D (1991). The flow of dolomitic springs in relation to groundwater levels and rainfall. Techn. Rep. GH 3757, Department of Water Affairs and Forestry, December 1991. Burke, J.J., Moench, M.H. 2001. Groundwater and Society: Resources, tensions and opportunities. UN DESA & ISET.

*Colvin C 1999. Handbook of Groundwater Quality Protection for Farmers. Report No. TT 116/99, Water Research Commission. (Available in English/Afrikaans) Driscoll, F.G., 1986. Groundwater and wells. Second edition. Published by Johnson Filtration Systems Inc., St Paul, Minnesota. DWAF, 2000. Policy and Strategy for Groundwater Quality Management in South Africa. Number W1.0, First Edition. Department of Water Affairs and Forestry, Pretoria. *Moat, C., van den Voorden, C., Wilson, I. 2003. Making Water Work for Villages. Water Research Commission. Report number TT 216/03. *Pegram, G., Mazibuko, G. 2003. Evaluation of the role of Water User Associations in Water Management in South Africa. Water Research Commission. Report number TT204/03 SADC Water Sector Coordination Unit, 2000, Minimum Common Standards and Guidelines for Groundwater Development in the SADC Region, Report No. 2 (Draft), Maseru. Shah, T., Molden, D., Sakthivadel, R., Seckler, D. The Global Groundwater Situation: Overview of Opportunities and Challenges. International Water Management Institute 2000. *Stephens, A. Institutional Arrangements For Groundwater Management In Dolomitic Terrains: Phase 1: Situation Analysis Synthesis Report. Draft Report to Water Research Commission. *Vegter, J.R., 1995. An explanation of a set of national groundwater maps. Report TT 74/95. Water Research Commission, Pretoria.

Check info



Viljoen, M.J., Reimold, W.U. 1999. An Introduction to South Africa’s Geological and Mining Heritage. Mintek & Geological Society of South Africa. Weaver, J.M.C. 1992. Groundwater sampling. Report No. TT 54/92, Water Research Commission, Pretoria. Xu, Y., Colvin, C., van Tonder, G.J., le Maitre, D., Zhang, J., Braune, E., and Pietersen, K., 2003, Towards Determination of the Resource Directed Measures: Groundwater Component, Water Research Commission Report. DWAF Hydrogeological map series – available from DWAF head office.

6.3 Water Management - websites http://www-dwaf.pwv.gov.za/idwaf/ www.dwaf.gov.za/iwmi/ http://www.cgiar.org/iwmi/ http://www.polity.org.za/govdocs/legislation/1998/nwa.doc http://www.sadcwscu.org.ls/ http://www.ccwr.ac.za http://www.thewaterpage.com http://www.nwl.ac.uk/gwf/ http://www.unesco.org/water/



7. GLOSSARY

Acidic Water with a low pH ( <7).

Alluvial Recent sediments, formed by rivers, e.g. the sediments laid down in the river beds, flood plains, lakes, fans at the foot of mountain slopes, and estuaries.

Aquiclude An impermeable geological unit that cannot transmit water at all. (Very few natural geological materials are considered aquicludes.

Aquifer A geological formation which has structures or textures that hold water or permit appreciable water movement through them. Appreciable water is usually taken to be enough water to supply a well.

Aquitard A rock with relatively low permeability which may contain water but cannot transmit enough to supply a well.

Borehole Includes a well, excavation or any artificially constructed or improved underground cavity which can be used for the purpose of - (a) intercepting, collecting or storing water in or removing water from an aquifer; (b) observing and collecting data and information on water in an aquifer; or (c) recharging an aquifer;

Artesian aquifer An aquifer in which the water is held under pressure and will rise above the ground surface if intercepted by a borehole, i.e. it is free-flowing.

Carbonate Material containing CO3, as found in limestone (CaCO3) or dolomite (MgCaCO3).

Catchment The area from which any rainfall will drain into the watercourse or watercourses or part of a watercourse, through surface flow to a common point or common points.

Catchment Management Agency A statutory body established by the Minister of DWAF responsible for the management of water resources within a defined water management area.

Chert A sedimentary rock composed of very fine grained silica (SiO2).

Cone of depression The typically cone-shaped area around a well where the groundwater level is lowered by pumping.

Confined aquifer An aquifer that is located between two low permeability layers, where the water is under pressure and the water level is above the upper boundary of the aquifer. The water level in a well tapping a confined aquifer usually rises above the level of the aquifer. If the water rises above ground level, the aquifer is called artesian.

Contact zone The join or interface between different geological units. Where the different rocks have different permeabilities, springs may form.

Contamination The addition of potentially harmful substances to, in this case, groundwater, or an increase in naturally occurring substances to un-natural levels.

Diabase An altered (weathered) or metamorphosed dolerite in which the original texture can no longer be seen.

Discharge Water which leaves the aquifer to become surface water, soil water, seawater or atmospheric water vapour.



Discharge area The area or zone where ground water emerges from the aquifer naturally or artificially. Natural outflow may be into a stream, lake, spring, wetland, etc. Artificial outflow may occur via pumping wells.

Dissolution (In this case - ) Breaking up of the rock strata by dissolving and dispersing by flowing groundwater.

Dolerite A fine grained intrusive igneous (volcanic) rock usually occurring as dykes or sills with the same minerals as a basalt.

Dolomitic terrain Land underlain by dolomite rocks whose features are determined by the characteristics of those rocks.

Down gradient Direction toward lesser hydraulic head.

Dyke A tabular (sheet like) intrusion of (igneous) molten rock that cuts through the surrounding rock strata.

Equitable Reasonable and fair.

Eye A small area where the groundwater is visible from surface or occurs at surface.

Folded Rocks may be folded and crumpled by slow movements of the earth.

Fracture Breaks in rocks such as joints, due to intense folding or faulting.

Fracture connectivity A measure of how well the individual fractures or fracture systems, are connected to each other and thus of the potential permeability.

Geohydrology The scientific study of water that occurs in rocks, specifically aquifers.

Geology The scientific study of the origin, history, structure and composition of the earth.

Groundwater Water in the subsurface, which is beneath the water table, and thus present within the saturated zone of aquifers. In contrast, to water present in the unsaturated or vadose zone which is referred to as soil moisture.

Groundwater management Organised control of activities which may affect aquifers. Typically this would include controlling pollution and the amount of groundwater abstracted from boreholes. Monitoring and geohydrological assessments are necessary if the management is scientifically based.

Hydraulic gradient The difference in hydraulic head between two measuring points within an aquifer.

Hydraulic head The height of water in a borehole (in this case) which is determined by the pressure head and elevation head. Flow will occurs from regions of higher values to regions of lower values through permeable or semi-permeable material.

Hydrogeology The scientific study of water that occurs in rocks, specifically aquifers.

Hydrology The study of the water of the earth and its atmosphere.

Institutional arrangements Anthea?



Karst An area of limestone, dolomite or other highly soluble rock, in which the landscape is mainly formed as a result of dissolution and subsurface drainage in the aquifer.

Perched water Unconfined groundwater held above the water table by a layer of impermeable rock or sediment.

Percolate The downward flow of water through the pores or spaces of unsaturated rock or soil.

Permeability (In this case) The capacity of rock or soil to transmit water. The permeability results from the spaces in a rock and the degree to which they are connected to each other. In some aquifers the spaces were formed when the rock was deposited (primary aquifers), in other rocks the spaces were dissolved (e.g. dolomites) or cracked (e.g. faulted sandstone) into the rock after it was formed (secondary aquifers).

pH A measure of the acidity or alkalinity of the solution (concentration of hydrogen ions)

Pollution

Porosity The degree to which the total volume of soil or rock comprises of spaces or cavities through which water or air can move.

Potable water Water, which is safe for human consumption

Potentiometric or piezometric surface An imaginary surface formed by measuring the level to which water will rise in wells of a particular aquifer. For an unconfined aquifer the potentiometric surface is the water table; for a confined aquifer it is the static level of water in the wells. (Also known as the piezometric surface.)

Primary aquifer Aquifers in which the water moves through the spaces that were formed at the same time as the geological formation was formed, for instance intergranular porosity in sand (e.g. alluvial deposits).

Recharge Water that adds to groundwater stored in an aquifer, e.g. – the small proportion of rainfall that seeps through the ground surface and flows through the unsaturated soil until it reaches the water table.

Recharge areas Areas of land that allow groundwater to be replenished through infiltration or seepage from precipitation or surface runoff.

Reserve The quantity and quality of water required – (a) to satisfy basic human needs by securing a basic water supply, as prescribed under the Water Services Act, 1997 (Act No. 108 of 1997), and (b) to protect aquatic ecosystems in order to secure ecologically sustainable development and use of the relevant water resource.

Rock strata A layer of a particular rock type or geological unit.

Salinity The concentration of dissolved salts in water. The most desirable drinking water contains 500 ppm or less of dissolved minerals.

Sampling Obtaining a small amount of, in this case, groundwater, for measurement of analysis to indicate the characteristics of the larger groundwater store.

Saturated zone - The subsurface zone below the water table where all spaces are filled with water. Aquifers are located in this zone.

Secondary aquifer (a.k.a. as fractured-rock aquifer) - Aquifers in which the water moves through spaces that were formed after the geological formation was formed, such as fractures in hard rock.



Sink holes An opening in the ground surface which has collapsed as a result of groundwater dissolving the rock.

Soil moisture water held in the pores (gaps between the particles) in the soil and in the soil itself.

Spring A place, usually a distinct point or small area, where groundwater emerges.

Stakeholders People who are affected or interested in the management of the resource, in this case aquifers.

Storativity Capacity of the aquifer to store water in its pores, voids, fissures and fractures. It is given as the volume of water released from storage per unit surface area of the aquifer per unit decline in the hydraulic head (typically m3/m2/m, i.e. dimensionless).

Strata Layers of rock (singular stratum).

Stromatolite A laminated mounded structure, formed over a long period of time by micro-organisms trapping sediment.

Subsidence The collapse of the ground surface.

Surface water Bodies of water, snow, or ice on the surface of the earth (such as lakes, streams, ponds, wetlands, etc.).

Sustainability The use of resources and the environment by people to meet their present needs in a way which will not compromise the ability of future generations to meet their needs.

Transpiration The loss of water vapour from plants through pores (stomata) in the leaves.

Unconfined aquifer (a.k.a. water table aquifer) - An aquifer which is not restricted by any confining layer above it. Its upper boundary is the water table, which is free to rise and fall. The water level in a well tapping an unconfined aquifer is at atmospheric pressure and does not rise above the level of the water table within the aquifer. An unconfined aquifer is often near to the earth's surface and not protected by low permeability layers, causing it to be easily recharged as well as contaminated.

Unconsolidated Where the matrix of the aquifer is formed from un-cemented materials such as sand, gravel pebbles or mixtures of these.

Unsaturated zone (a.k.a. zone of aeration) An area, usually between the land surface and the water table, where the openings or pores in the soil contain both air and water.

Up gradient Direction toward greater hydraulic head than point of origin, or point of interest.

Vulnerability (of groundwater) The degree to which groundwater may be impacted and provide fewer benefits to people and the environment.

Water level (groundwater) The level at which groundwater rests in an aquifer, borehole or point of discharge.

Water Management Areas an area established as a management unit in the national water resource strategy within which a catchment management agency will conduct the protection, use, development, conservation, management and control of water resources

Water table The top of an unconfined aquifer where water pressure is equal to atmospheric pressure. The water table depth fluctuates with climate conditions on the land surface above and is usually gently curved and follows a subdued version of the land surface topography.



Water User Associations Co-operative associations of water users which undertake water related activities for the mutual benefit of their members. They may manage local infrastructure, supply water and implement the management decisions of their members.

Wetland Land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil.

Zone of aeration (a.k.a. unsaturated zone) Zone under the ground surface in which the spaces contain air and sometimes water.

8. ABBREVIATIONS

CMA Catchment Management Agency

CSIR Council for Scientific and Industrial Research

IUCN World Conservation Union

MAP Mean Annual Precipitation

NWA National Water Act

RDM Resource Directed Measures

RQOs Resource Quality Objectives

WMA Water Management Area

WRC Water Research Commission

WSA Water Services Act

WUAs Water User Associations

Documents

A Stakeholders’ Guide to the North West Dolomite Aquiferfred.csir.co.za/project/groundwater/documents/WUA... · This booklet is concerned with the dolomite aquifers of the North