Assessment of the groundwater potential of the Middel Kop/Appleby aquifer, Stella District, Northwest Region

[摘要] English: The importance of groundwater is strongly reflected in the new South African waterpolicy and legislation. All water resources, including groundwater, are now seen as anindivisible asset, with the National Government as its custodian to ensure that theresources are protected, developed and managed properly.Groundwater is the sole source of potable water for the town of Stella in the Lower VaalWater Management Area of the Northwest Province, but the existing well-field is barelyable to supply the present demand. Previous attempts to supply the town with water fromgroundwater resources have failed, because of the low potential of the aquifers and thepoor quality of the groundwater. The proposed resettlement of 2 000 people therefore hasto be postponed until sufficient additional water resources can be found for the town.One possible source, not included in previous groundwater explorations of the area, is thegranitic aquifer on the farm Middel Kop situated approximately 5 km south-east of Stella.Farmers have used this aquifer extensively since 1990 to irrigate 171 ha of agriculturalland. It was consequently decided to investigate this aquifer as a possible additionalsource of water for Stella. However, farmers have already noticed a continuous decline inthe water levels over the years. This meant that the focus of the investigation had to bechanged from merely an exploration exercise to an evaluation of the aquifer and thedevelopment of a suitable management scheme for the aquifer, as described in this thesis.There are not enough data available to perform a detailed assessment of the aquifer at themoment, a deficiency that should be addressed in future investigations and managementof the aquifer. The existing data, however, indicate that the aquifer may be able to sustaina yield of approximately 4 227 m3 d-I in the near future. This volume of water will be ableto supply in the needs of the present population and the additional 2 000 resettled people,while allowing 73% of the current irrigated area approximately 8 000 m3 ha-I annually forirrigation. The latter figure can only be achieved if the farmers are allowed to produce onecrop per year instead of the two, which is in some cases the practice. This reduction in thewater allocated for irrigation may seem harsh, but the decline in the water levels over thelast couple of years clearly indicate that the farmers cannot continue with the presentpractices for much longer.The groundwater quality of the Middel Kop aquifer can be rated as marginal for humanconsumption. This applies in particular to the relatively high concentrations of fluorideand nitrate in the water, which could affect the health of the population adversely if useduntreated for long periods. The conclusion reached in the thesis is that the Middel Kop aquifer can only be used as asource of water for Stella on condition that a detailed monitoring scheme is introducedfrom the beginning and used to develop a suitable management scheme for the aquifer.This approach will ensure that any impacts on the resource can be properly evaluated andthat the quality and quantity of the water can be preserved for future generations.

[发布机构] University of the Free State