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STAS Governance of Groundwater Resources in Transboundary Aquifers (GGRETA) Project – Phase 1

Documentation: A read-only folder structure of all reports, data, and models related to the STAS can be accessed from here: Read more

Stampriet Transboundary Aquifer System (STAS) Projects

Documentation: A read-only folder structure of all reports, data, and models related to the STAS can be accessed from here: Read more

Support to Phase 3 of the ORASECOM Basin-wide Integrated Water Resources Management (IWRM) – Plan: Overview

Overview The main objectives of this consultancy were to undertake scenario analyses, economic, water requirement projection and ecological support studies Read more

Water Resources Quality Joint Basin Surveys (JBSs)

The second 5-yearly comprehensive Joint Basin Survey (JBS2) of the quality of the water resources of the Orange-Senqu River Basin was undertaken Read more

  • WIS > Geology and Soils > STAS Governance of Groundwater Resources in Transboundary Aquifers (GGRETA) Project – Phase 1

STAS Governance of Groundwater Resources in Transboundary Aquifers (GGRETA) Project – Phase 1


A read-only folder structure of all reports, data, and models related to the STAS can be accessed from here:

Project approach and main activities

The assessment of the Stampriet Transboundary Aquifer System (STAS) was undertaken based on a multi-disciplinary methodology developed by the UNESCO International Hydrological Programme (UNESCO-IHP) and the International Groundwater Resources Centre (IGRAC) that includes the collection and processing of national data (hydrogeological, socio-economic and environmental, gender, legal and institutional), and the harmonization of data across all three countries to enable a joint assessment of the transboundary resource.

Activities were done within the framework of the Governance of Groundwater Resources in
11 Transboundary Aquifers (GGRETA) project, executed by UNESCO-IHP, in close cooperation with IGRAC, and funded by the Swiss Development Corporation (SDC). The assessment has been carried out by a team familiar to the area and composed of professionals of Botswana, Namibia and South Africa. Apart from collecting and studying relevant literature for assessment and diagnostics, the team has spent much attention on compiling basic data and to GIS mapping. In total, more than 40 thematic maps were prepared and have been uploaded to the Information Management System (IMS) developed by the project (

Location, delineation and type of aquifer

The STAS covers a large arid region stretching from Central Namibia into Western Botswana and South
Africa’s Northern Cape Province (See Figure 1). It contains two confined sandstone aquifers, overlain by unconfined Kalahari aquifer units. The delineation of the STAS area follows the outer boundary of the Ecca Group of geological formations within the catchments of the Auob and Nossob Rivers. The STAS is a very large transboundary aquifer system, receiving insignificant recharge, in a dry region without permanent surface water.

Figure 1: Extent of the Stampriet Transboundary Aquifer System

General features of the Stampriet Transboundary Aquifer System (STAS) area

The STAS area is 86 647 km2 in extent and has a generally flat topography, gently sloping from NW to SE, between 1450 and 900 m above mean sea level. It has a hot and dry climate, with an annual mean temperature of 19-22 °C and mean rainfall ranging from 140 mm/yr in the SW to 300 mm/yr along the northern and north-eastern segment of the STAS area. During the period May through September there is hardly any rainfall. The Namibian sector of the area covers approximately two-thirds of the area and is almost completely in use as agricultural land. The Botswana sector occupies 19% and includes from North to South three distinct land use zones: agricultural land (mainly in Ghanzi district), wildlife management area and national park. The South African sector (8%) is entirely used as a national park. The area is sparsely populated with an estimated population of nearly 50 000 of which more than 90% which is in Namibia. Major settlements are Aranos and Koes, but their population is less than 5000; all other settlements have less than 2000 inhabitants. Commercial industrial and mining activities are absent.

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Water and water use in the area

Given the climatic and other geographic features, there are no permanent rivers in the STAS area. Apart from the ephemeral Auob and Nossob Rivers that provide some water during the rainy season, there are surface water pans scattered over the area that collect and store water for livestock watering during rainy season; these reserves can last a few months after the rains. The only permanent and dependable water resource in the area is groundwater. Groundwater is withdrawn from the Kalahari, Auob and Nossob aquifers, by means of dug wells and boreholes. It is estimated that at least 20 million cubic meters per year is abstracted; 66% of this volume comes from Kalahari aquifers, 33% from the Auob Aquifer and 1% from the Nossob aquifer. The breakdown of overall water use is as follows: 47% for irrigation, 37.5% for stock watering, 16% for domestic use, and 0.5% for tourism. In general, the urban centers and villages receive water from governmental and parastatal water supply corporations. Private landowners usually have their own wells.

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The Stampriet Transboundary Aquifer System (STAS)

Conceptually, the physical processes taking place in this system of two confined aquifers are reasonably understood in Namibia and not much in both Botswana and South Africa, but quantification is still limited –in spite of many efforts made over a long period of time. Apart from diffuse recharge by downward seepage from the Kalahari aquifers, there are a few recharge zones in the western part of the STAS area where sinkholes facilitate concentrated recharge during rare wet years. The mean annual
recharge rate for these confined aquifer units is likely to be significantly less than that of the Kalahari aquifers, for which rates of around 1 mm/year, averaged over the area, have been estimated. The general direction of groundwater flow is from NW to SE. In the SE quadrant of the area, groundwater is presumed to seep upward from the confined aquifers and discharges into the Kalahari formations, from where it evaporates. Groundwater salinity in this zone – known under the name Salt Block – therefore is rather high.

Main groundwater management challenges in the area

Lack of monitoring data (climate, groundwater abstraction, water levels, water quality) seriously hampers a systematic diagnostic analysis. Nevertheless, the findings and combined experiences of the assessment team have revealed a number of challenges.

Groundwater quantity stress has not been observed. Lack of monitoring may be an explanation, but the exceptionally low intensity of groundwater withdrawal certainly plays a major role. If for some reasons (population growth, economic development, water transfer, etc…) the demand for water in the region would increase significantly, then very soon the groundwater resources may run short of meeting these demands. Therefore it is very important to initiate effective control of groundwater quantity, e.g. by some initial practical steps such as solving the problem of water spillage by leaking boreholes in the Auob aquifer and preventing future problems by improved regulation of drilling.

Groundwater quality has its natural variations. Most notable are generally poor conditions in or near the Salt Block zone. Pollution, however, may also lead to groundwater quality degradation elsewhere in the area. The confined transboundary aquifers have very low vulnerability to pollution, but they will experience higher withdrawal pressures if overlying Kalahari aquifers become polluted. The shallower
and usually phreatic Kalahari aquifers are vulnerable to pollution; in particular in the Namibian sector the pollution risk is often medium to high due to irrigated agriculture (using fertilizers and pesticides) and environmentally unfriendly sanitation and waste disposal practices. Partly from the groundwater management point of view and partly for health reasons, there is scope for enhancing water supplies and even more for improving sanitation in the entire area.

Improving groundwater governance

Given the fragility of the aquifer system and the fact that groundwater is the only permanent source of water in this huge area, it is evident that the STAS should be governed and managed wisely. A large part of the provisions and interventions to be considered are of a local nature, but transboundary cooperation will be very useful by sharing information, exchanging experience and by harmonizing interventions across the international boundaries. At the level of the assessment, the three countries have already proven to be willing and capable to cooperate effectively.

Botswana, Namibia and South Africa all possess individually the main elements of a domestic legal framework that provides essential controls on groundwater use and pollution. However, 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.

Botswana, Namibia and South Africa could benefit from further collaboration to develop jointly 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 arrangement among the three STAS countries that pays attention to the needs of the STAS. Consequently, the need for a multicountry co-operation mechanism has been identified.

The over-arching objective of a multi-country cooperation mechanism for STAS (MCCM) is to transition from GGRETA project-driven cooperation in the study and characterization of STAS to institutionalized cooperation among the STAS countries, beyond the life of the project. In the short-tem, the specific objective of the MCCM is to continue the joint study of STAS, also by generating a steady flow of agreed additional/fresh data and information feeding the Information Management System (IMS) for STAS, generated by the GGRETA project. In the long-term, as cooperation takes hold and matures, the MCCM’s institutionalized cooperation objective may expand from data collection and exchange to joint strategizing and advising STAS countries on management issues of the STAS groundwater resources.

Two potential models for the establishment of a MCCM for the STAS have been identified. One builds upon national government capacities and institutions in the three STAS countries, and seeks to synergize them towards a common purpose, i.e., the cooperative husbanding of the STAS and its resources. The other model taps into the regional existing institution whose mandate comes closest to the STAS, i.e., ORASECOM, and nests in it dedicated attention to the STAS.

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