The assessment of the Stampriet Transboundary Aquifer System (STAS) is based on a multi-disciplinary approach including the collection and processing of national hydrogeological, socio-economic and environmental, gender, and legal and institutional data, and the harmonization of data across all three countries to enable a joint assessment of the transboundary resource.
The STAS stretches from Central Namibia into Western Botswana and South Africa’s Northern Cape Province, and lies within the Orange River Basin. The STAS covers a total area of 86 647km², for which 73% of the area is in Namibia, 19% in Botswana, and 8% in South Africa. The STAS area is lightly populated with population concentrated in small rural settlements. The population of these settlements is estimated to be over 45,000. Major settlements are Aranos, Koes and Stampriet in Namibia, Ncojane and Kule in Botswana. The total population of the area is difficult to estimate because it includes an itinerant population that move into and out of the area.
The STAS is made up of two deep confined artesian transboundary aquifers in the Karoo sediments (Auob and Nossob aquifers), overlain by an unconfined aquifer system in the Kalahari sediments (Kalahari aquifers). The STAS is located in an arid area with an annual mean temperature varying between 19 and 22°C. Temperature in summer can reach 50°C. Average rainfall in the STAS area is of 150 to 310 mm/yr. Recharge to the Kalahari aquifer during years with average rainfall is estimated at 0.5% of rainfall. Recharge to the Auob and Nossob aquifers in normal rainfall years is negligible but considerable recharge occurs during extreme rainfall events. The general groundwater flow in the STAS is from northwest to southeast. Groundwater quality generally decreases towards south-western Botswana and the north-western Cape in South Africa for all the three aquifers.
Groundwater is the major source of water in the STAS, to provide portable water to the people, livestock and for irrigation. There is neither industry nor mining activities taking place in the STAS area. Over 20 million m³/year are abstracted in the STAS most of which occurs in Namibia (over 95%).The largest consumer of water is irrigation (~46%) followed by stock watering (~38%) and domestic use (~16%).
Groundwater pollution threat is localized around settlements, notably around bores and wells. The main sources of this groundwater pollution are pit latrines, wastewater facilities, and waste dumps. High levels of nitrate in the Kalahari aquifers are found in some places in Namibia, where the majority of water abstraction occurs and are attributed to anthropogenic activities such as irrigation and stock watering at boreholes. It is only the near surface Kalahari aquifers that are currently threatened by pollution
While the STAS is not threatened by over abstraction or pollution at current levels of development, this might change if population, irrigation or mining activities substantially increase.
Namibia, Botswana and South Africa all possess the main elements of a legal framework that provides essential controls on groundwater use and pollution. The implementation and enforcement of groundwater quantity and quality regulations raise more challenges. The STAS includes large areas where water abstraction and pollution is not subject to regular inspection and controls.
Current policy issues include; data gaps, lack of scientific capacity and modern analytical tools including GIS, shortfalls in bore construction, monitoring and maintenance, lack of protection of bores and recharge areas, and pollution from pit latrines, wastewater ponds and waste dumps around settlements.
Botswana, Namibia and South Africa could benefit from further collaboration to develop policy legal and institutional responses to current and future development of the STAS. The three countries already collaborate through regional bodies notably the Orange-Senqu River Commission (ORASECOM) and the Southern African Development Community (SADC), but there is no legal instrument that is specific to the management of the STAS transboundary aquifers.