INMACOM Hydrocensus
SADC-GMI supported a hydrocensus in the Incomati and Maputo Basins. The total project area of the combined Maputo and Incomati Basins is 77,000 km2, with both catchments covering parts of South Africa, Eswatini, and Mozambique. The most significant part of the basins is underlain by the Precambrian Basement, characterized by generally low potential for groundwater development and discontinuous, low-yielding aquifers, primarily associated with deep weathering and fracturing zones. Along the border of Mozambique, South Africa, and Eswatini are the Lebombo volcanics of the Karoo Supergroup. These formations are marked by low primary permeability but have moderate productivity within major faults and along lithological contacts. The unconsolidated intergranular aquifers along the coast of Mozambique generally have a high potential for groundwater development and are the most productive. The scope of the assignment included collecting information on groundwater resources and existing boreholes in the INMACOM area.
An analysis was performed on the selected borehole sites from the SADC GMI (2010) country databases within the hydrocensus sample quadrants. The 846 borehole chosen sites from the country databases represent 1221 borehole records: 705 in the Incomati Basin and 516 in the Maputo Basin. No active monitoring of operational boreholes was observed in any of the 3 INMACOM countries, neither by public institutions nor private owners. None of the 26 motorized boreholes visited during the hydrocensus survey was fitted with a functional water meter or dipper line. Furthermore, none of the 52 active DWS-IUCMA monitoring boreholes are used for groundwater abstraction. As a result, DWS-IUCMA is not conducting abstraction monitoring, and little is known about the status of the aquifers and the volumes of groundwater withdrawn through pumping. Where monitoring practices are in place, only water levels, EC/TDS, and a few other hydrochemical parameters are routinely monitored; most macro and trace constituents are not measured.
Field parameters measured include EC, TDS, pH, and Temperature, and qualitative parameters (colour, odour, taste, and general appearance). In the Incomati Basin, most upper and middle catchment area parameters are within standard limits, with a few exceptions. Samples from the lower catchment area exhibit higher mineralization, alkalinity, and hardness levels, as well as elevated concentrations of specific other parameters, with several exceeding standard limits. Whilst in the Maputo Basin, generally marked by relatively good water quality and lower mineralization, with most parameters within acceptable limits, but with a few exceptions.
