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 Forestry
Private bag X313
Pretoria 0001
Tel:012 336 7500
www.dwaf.gov.za
Water Research Commission
Private Bag X03,
Gezina, 0031
Tel: 012-330-0340
www.wrc.org.za
IUCN
P O Box 11536, Hatfield, Pretoria, 0028
Tel: 021-342-8309
Water Research
Commission
Project leader:
Project manager:
Main Author:
Technical specialist:
Illustrations & review
Graphics:
Photographs:
Maps:
Afrikaans translation:
Layout:
Anthea Stephens, IUCN.
Lutske Newton, IUCN Assoc.
Christine Colvin, CSIR
Dave Bredenkamp, WREM
Lisa Cavé, CSIR
Pannie Engelbrecht, CSIR
Anthea Stephens, IUCN
Claus Mischker, MCA Planners; Simon Hughes, CSIR
Pannie Engelbrecht, CSIR
Magdel van der Merwe
This report should be cited as: WRC, 2003. Understanding Groundwater: A
stakeholders guide to the North West dolomite aquifer.
Understanding Groundwater in the Dolomites
Contents
1.
INTRODUCTION ...................................................... 2
1.1
1.2
1.3
The WRC project ........................................................... 2
The purpose of this booklet ............................................ 2
Key concepts for water management .............................. 2
2. GROUNDWATER...................................................... 4
2.1
2.2
2.3
What is groundwater? .................................................... 4
Types of aquifers ........................................................... 4
The importance of aquifers............................................. 5
3. THE GROUNDWATER CYCLE ................................... 6
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
From the beginning of life on earth… .............................. 6
The dolomites as aquifers .............................................. 8
Recharge of aquifers ...................................................... 8
Recharge to the dolomites .............................................10
Flow and storage in aquifers..........................................10
Aquifer compartments in the dolomites ..........................10
Groundwater abstraction ...............................................11
Groundwater abstraction from the dolomites ..................12
Groundwater discharge to the environment ....................14
Springs and outflow from the dolomites .........................15
Are the dolomite aquifers in danger?..............................17
Management of the dolomites in transition .....................19
4.5
What do we need to know to make decisions? ............... 24
5. FUTURE MANAGEMENT OF THE NW DOLOMITE
AQUIFERS ............................................................. 25
5.1
5.2
5.3
Getting the right information ........................................ 25
How much is sustainable? ............................................. 25
The role of WUAs ......................................................... 28
6. FURTHER SOURCES OF INFORMATION.................. 29
6.1
6.2
6.3
Groundwater - websites ............................................... 29
Groundwater – Books and Reports ................................ 29
Water Management - websites ...................................... 30
7. GLOSSARY ............................................................ 31
8. ABBREVIATIONS ................................................... 35
4. GROUNDWATER MANAGEMENT IN RSA ................ 21
4.1
4.2
4.3
4.4
Principles of water management in RSA .........................21
Who does what to manage groundwater ........................22
The role of Water User Associations ...............................22
Groundwater management in RSA .................................23
September 2003
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Understanding Groundwater in the Dolomites
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
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Understanding Groundwater in the Dolomites
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;
September 2003

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.
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Understanding Groundwater in the Dolomites
Figure 1: Groundwater forms the base of the water cycle: Illustration of key terms.
September 2003
page 3
Understanding Groundwater in the Dolomites
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.
3 cm
20 m
Pores in
unconsolidated
sedimentary
deposits
Caverns in
dolomite
a
b
1m
1m
Rubble zone
and cooling
fractures in
extrusive
igneous rocks
Fractures in
intrusive
igneous rocks
c
d
Figure 2: Different types of aquifers
September 2003
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
page 4
Understanding Groundwater in the Dolomites
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
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.
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.
September 2003
page 5
Understanding Groundwater in the Dolomites
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.
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
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.
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.
SEQUENCE
FORMATION
Figure 3.1
THICKNESS
(m)
EC C A
PR ET OR IA
DWYKA
TIMEBALL
HILL
ROOIHOOGTE
ECCLES
C HU NIE SP OO R T
TR AN SV A AL
Carbonaceous shale, coal
LYTTELTON
MONTE
CHRISTO
O AK TRE E
BLACK REEF
QUARTZITE
September 2003
LITHOLOGY AND MEMBER
Mudstone
Figure 3: The geology of the
dolomites
PR OT ER OZ OI C
GROUP
Sandstone
K AR OO
PE R M O C AR B O NIF ER OU S
System/
Erathem
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.
Diamictite
Shale
Diamictite
Klapperkop Quartzite Mb wacke
and ferruginous quartzite
Graphitic and silty shale
Quartzite
Shale
Bevets Conglomerate Member
Breccia
270 - 660
10 - 150
Chert-rich dolomite with large
and small stromatolites
380
Dark chert-free dolomite with large
elongated stromatolitic mounds
150
Light coloured recrystallised dolomite
with abundant chert; stromatolitic;
basal part oolitic
700
Dolomite, becoming darker upwards
Chocolate-coloured weathering
200
Shale
Quartzite
Arkosic grit
Lithostratigraphical sequence of the dolomite.
25 - 30
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Understanding Groundwater in the Dolomites
Figure 4:
Compartment
s of the
dolomite
aquifer
September 2003
page 7
Understanding Groundwater in the Dolomites
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 (CaCO 3), 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.
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.
Figure 5: Wondergat sink hole in karst terrain: the land
surface has collapsed revealing groundwater below.
(Photograph A.Stephens, IUCN).
September 2003
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.
page 8
Understanding Groundwater in the Dolomites
Figure 6:
Pristine
dolomite
aquifer
with very
low level of
use.
September 2003
page 9
Understanding Groundwater in the Dolomites
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.
September 2003
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.
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Understanding Groundwater in the Dolomites
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 8: Cone of depression around a pumped borehole.
Figure 7: Poster showing ‘Playground Pumps’
September 2003
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.
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Understanding Groundwater in the Dolomites
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.
Use of Dolomitic Groundwater (2002)
4%
industry
3%
mining
17%
domestic
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.
76% agriculture
1
2
3
4
Figure 9: Use of Dolomitic Groundwater (Source:
Bigen,2002)
September 2003
page 12
Understanding Groundwater in the Dolomites
Figure 10: Map
showing land-use
(Source: National
Land Cover
Database)
September 2003
page 13
Understanding Groundwater in the Dolomites
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.
September 2003
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.
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Understanding Groundwater in the Dolomites
large quantities of water from the Grootfontein unit, causing this spring to
stop flowing in the dry season.
Deep tap
root
Groundwater
fed wetland
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 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
September 2003
Figure 13: Groundwater fed spring at XXX Anthea? with
associated riparian vegetation.
page 15
Understanding Groundwater in the Dolomites
Figure 14:
Map of
springs,
rivers and
wetlands.
September 2003
page 16
Understanding Groundwater in the Dolomites
Simulated vs Actual flow
10
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.
September 2003
8
7
6
6
5
4
4
2
3
2
0
1
-2
1999
1995
1992
1989
1986
1983
1980
1976
1973
1970
1967
1964
1961
1957
1954
1951
1948
1945
1942
1938
1935
0
1932
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).
8
1929
Aquifers are vulnerable to contamination, drought, subsidence (collapse of
the ground surface) and over-exploitation. These threats are illustrated in
figure 16.
Flow of spring mil cub
m/mth
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.
10
9
Time
Actual flow
MA simulated flow
Wondergat level
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.
page 17
Wondergat level (m on
gauge)
3.11 Are the dolomite aquifers in danger?
Understanding Groundwater in the Dolomites
Figure 16:
Unsustainabl
e use of
groundwater
in the
dolomites.
September 2003
page 18
Understanding Groundwater in the Dolomites
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.
Bicarbonate mg/l
300
50
45
40
35
30
25
20
15
10
5
0
250
200
150
1995
1994
1993
1992
1991
1989
1988
1987
1986
1985
1984
1983
100
Chloride mg/l
Water Quality - Renos terftn
Ye ars
HCO3 alk
chloride
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,
September 2003
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.
page 19
Understanding Groundwater in the Dolomites
Figure 18:
Major
compartments
and Water
Management
Area boundaries.
September 2003
page 20
Understanding Groundwater in the Dolomites
4. GROUNDWATER MANAGEMENT IN
RSA

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;
4.1

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;
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.
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 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;
September 2003
page 21
Understanding Groundwater in the Dolomites



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.
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:
Figure 19: Water should be used to redress past inequities,
ensuring some, for all, forever.
September 2003
‘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, cooperative associations of individual water users who wish to undertake
water-related activities for their mutual benefit. A water user association
page 22
Understanding Groundwater in the Dolomites
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
September 2003
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).
page 23
Understanding Groundwater in the Dolomites
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 sourcedirected 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
September 2003
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?
page 24
Understanding Groundwater in the Dolomites
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.
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 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
September 2003
page 25
Understanding Groundwater in the Dolomites
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.
Pivot irrigation
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.
Groundwater fed wetland
Diamond digging from alluvial
gravel overlying the dolomite
Brick-making
Figure 20: Different uses of groundwater from the North
West Dolomites
September 2003
page 26
Understanding Groundwater in the Dolomites
National office
DWAF
International Stakeholders
Regional offices
Grootfontein
Crocodile west-Marico
Grootpan
DOLOMITE AQUIFER
MANAGEMENT COMMITTEE*
WUAs
Lichtenburg/Itsoseng
CMAs
Middle Vaal
Lower Vaal
Zeerust
Ventersdorp
Technical Committee
Sub-committee
Sub-committee
Sub-committee
Figure 21: Proposed Institutional Framework for Groundwater Management in Dolomitic Terrains
September 2003
page 27
Understanding Groundwater in the Dolomites
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:





Figure 22: Pollution occurs underground as well as on the
surface.
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
September 2003
page 28
Understanding Groundwater in the Dolomites
*Colvin C 1999. Handbook of Groundwater Quality Protection for Farmers.
Report No. TT 116/99, Water Research Commission. (Available in
English/Afrikaans)
6. FURTHER SOURCES OF
INFORMATION
6.1
Groundwater - websites
Check
info
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 orders@wrc.org.za
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:
tensions and opportunities. UN DESA & ISET.
September 2003
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.
Resources,
page 29
Understanding Groundwater in the Dolomites
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.
September 2003
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/
page 30
Understanding Groundwater in the Dolomites
7. GLOSSARY
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
Acidic Water with a low pH ( <7).
Catchment Management Agency A statutory body established by the
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.
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).
Aquiclude An impermeable geological unit that cannot transmit water at
all. (Very few natural geological materials are considered aquicludes.
The typically cone-shaped area around a well
where the groundwater level is lowered by pumping.
Cone of depression
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.
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;
Borehole
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.
Confined aquifer
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 unnatural levels.
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.
Diabase An altered (weathered) or metamorphosed dolerite in which the
Carbonate Material containing CO3, as found in limestone (CaCO3) or
Discharge Water which leaves the aquifer to become surface water, soil
dolomite (MgCaCO3).
September 2003
original texture can no longer be seen.
water, seawater or atmospheric water vapour.
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Understanding Groundwater in the Dolomites
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.
The scientific study of the origin, history, structure and
composition of the earth.
Geology
Groundwater Water in the subsurface, which is beneath the water table,
Dissolution (In this case - ) Breaking up of the rock strata by dissolving
and dispersing by flowing groundwater.
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.
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.
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.
The difference in hydraulic head between two
measuring points within an aquifer.
Hydraulic gradient
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.
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
Folded Rocks may be folded and crumpled by slow movements of the
earth.
The scientific study of water that occurs in rocks,
specifically aquifers.
Hydrology The study of the water of the earth and its atmosphere.
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
Hydraulic head The height of water in a borehole (in this case) which is
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.
The scientific study of water that occurs in rocks,
specifically aquifers.
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Understanding Groundwater in the Dolomites
Perched water Unconfined groundwater held above the water table by
Recharge Water that adds to groundwater stored in an aquifer, e.g. – the
a layer of impermeable rock or sediment.
small proportion of rainfall that seeps through the ground surface and flows
through the unsaturated soil until it reaches the water table.
Percolate The downward flow of water through the pores or spaces of
unsaturated rock or soil.
Recharge areas Areas of land that allow groundwater to be replenished
through infiltration or seepage from precipitation or surface runoff.
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).
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.
pH A measure of the acidity or alkalinity of the solution (concentration of
hydrogen ions)
Rock strata A layer of a particular rock type or geological unit.
Pollution
Salinity The concentration of dissolved salts in water. The most desirable
drinking water contains 500 ppm or less of dissolved minerals.
Porosity The degree to which the total volume of soil or rock comprises of
spaces or cavities through which water or air can move.
Sampling Obtaining a small amount of, in this case, groundwater, for
Potable water Water, which is safe for human consumption
measurement of analysis to indicate the characteristics of the larger
groundwater store.
Potentiometric or piezometric surface An imaginary surface formed
Saturated zone - The subsurface zone below the water table where all
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.)
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.
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).
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Sink holes An opening in the ground surface which has collapsed as a
result of groundwater dissolving the rock.
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Understanding Groundwater in the Dolomites
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.
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.
Where the matrix of the aquifer is formed from uncemented materials such as sand, gravel pebbles or mixtures of these.
Unconsolidated
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.
The loss of water vapour from plants through pores
(stomata) in the leaves.
Transpiration
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
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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.
Co-operative associations of water users
which undertake water related activities for the mutual benefit of their
Water User Associations
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Understanding Groundwater in the Dolomites
members. They may manage local infrastructure, supply water and
implement the management decisions of their members.
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.
Wetland
Zone of aeration (a.k.a. unsaturated zone) Zone under the ground
surface in which the spaces contain air and sometimes water.
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8.
ABBREVIATIONS
CMA
CSIR
IUCN
MAP
NWA
RDM
RQOs
WMA
WRC
WSA
WUAs
Catchment Management Agency
Council for Scientific and Industrial Research
World Conservation Union
Mean Annual Precipitation
National Water Act
Resource Directed Measures
Resource Quality Objectives
Water Management Area
Water Research Commission
Water Services Act
Water User Associations
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