An introduction to groundwater in South Africa

An introduction to groundwater in South Africa

South Africa is a relatively dry country.  Its average rainfall of ~497 mm/a compares unfavourably with the world average of ~860mm/a.  Twenty one percent of the country receives less than 200mm/a, qualifying it to be classed as desert. However the names of many towns reflect the dependence of the early settlers on groundwater and its importance in the establishment and spread of settlements.  Names such as De Aar (the vein, an underground water source), Springs, the Fountains at Pretoria and the many towns ending with “”fontein”” testify to the importance of groundwater and its importance in the development of South Africa.

 Drill rig at Beaufort West

Coupled with a low average rainfall and skewed distribution (less than 150mm in the arid north-west to greater than 2000mm in the south-west and east coast areas), the geology of the country largely precludes the development of regional scale highly productive aquifers. More than 90% of the country is underlain by indurated sedimentary and crystalline basement rocks with little or no primary porosity. Highly permeable zones can be developed in fracture zones but it follows from the limited porosity and low rainfall over much of the country that long-term sustainable borehole yields are mostly low.

Despite this somewhat gloomy prologue, groundwater plays a very important role in water supply to domestic, industrial, agricultural and mining users. Below find an attempt to summarize groundwater use in South  Africa and also to describe  its availability. This summary draws heavily on the work of others and the author gratefully acknowledges the valuable work of previous researchers who have made this review possible.

   

Previous work

 

A few of the main sources and main works on the subject of groundwater use and availability are listed below. These are, in chronological order:

 

 Vegter, JR (1995), An Explanation of a set of National Groundwater Maps. 

This was the first attempt of a synoptic and visual representation of South Africa’s groundwater resources.  It consists of an explanation booklet and a set of seven maps on two A0 sheets. These depict borehole prospects, saturated indices, mean annual recharge, groundwater component of river flow, depth to groundwater level, groundwater quality and hydrochemical types. The main maps basically represent a statistical analysis of information stored in the National Groundwater Data Base.

 

Baron, Seward and Seymour (1998). The Groundwater Harvest Potential Map of the Republic of South Africa

This work covers the Harvest Potential  Map published by the Department of Water Affairs and Forestry in 1996 and the subsequent report explaining the methodology followed.

 

DWAF (2001). Water Situation Assessment Model.  Groundwater Resources of South Africa (Haupt, C)

This work represents a modification and update of the Harvest Potential Map to develop an overview of the groundwater resources of South Africa at a quaternary catchment level.

 

DWAF (1995-2003). Groundwater Resource Assessment Phase 1

Production of a set of 21 hydrogeological maps covering the country at a scale of 1:500 000, with accompanying explanatory booklets.

 

DWAF (2003-2005).  Groundwater Resource Assessment Phase 2

There are five projects active under this portfolio:

• Project 1 : Methodology for Groundwater Quantification

• Project 2 : Groundwater Planning Potential Map

• Project 3 : Groundwater Recharge and Groundwater/Surface Water Interaction

• Project 4 : Classification of Aquifers

• Project 5 : Water Use.

 

HOW MUCH GROUNDWATER IS USED?

The first detailed breakdown of groundwater use per sector is that contained in Management of the Water Resources of the Republic of South Africa, (DWAF 1986).  This is shown in Table 1 below.

Table 1.  Use of groundwater in South Africa (1980)

Urban

70

Rural domestic

120

Stock watering

100

Irrigation

1400

Mining and quarries (total pumped from mines, quarries and boreholes = 405 million m3/a)

100

TOTAL

1790 Mm3/a

 

A more up to date comparison of groundwater use estimates is provided by Hughes et al (2004) and is shown in Table 2, which gives a summary of sectoral and total groundwater use derived from the available data and using an updated groundwater use estimation method.

Table 2.  Use of groundwater in South Africa (2004)

Sectoral

Groundwater Use  (Mm3/a)

Urban

Domestic / Municipal

Rural

Domestic / RDP

Irrigation

Stock watering

Mining

Industry

Other

Total

(Mm3/a)

Seward & Baron (2001)

131

106

 

 

 

1968

   

Haupt (2000)

 

 

 

 

 

 

 

2000*

NWRS (WSAM)

 

 

 

 

 

 

 

1100

CSIR (2004)

153

141

1137

111

156

65

5

1771

* excludes mines and industry

 

Groundwater currently contributes about 13 % of the total water use in South Africa. 

 

 

 

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