Groundwater recharge with wastewater can occur either incidentally as in wastewater irrigation schemes or intentionally as in artificial recharge schemes. It can also occur indirectly as leakage from sewers and wastewater channels. The concern is that such recharge from whatever source may be leading to a build-up of potentially toxic trace organic compounds in the underlying aquifer. This pilot study, undertaken in association with the Botswana Department of Water Affairs, aims to assess the application of collector well systems for abstraction of groundwater from sand-rivers in NE Botswana. This area of Botswana, in common with other semi-arid areas underlain by crystalline basement rocks in southern Africa suffers a continual shortage of water.
Sand rivers are a main source of as yet unexploited good quality groundwater.
A comprehensive report describing methodologies developed and results obtained was prepared for the Department of Water Affairs. If denitrification in the unsaturated zone is a significant process, less nitrate than is in the current profile may reach the groundwater body. The occurrence and extent of denitrification beneath the rooting zone will be established in relation to geology and other controlling factors. Attention will be focused on the Chalk and Sherwood Sandstone aquifers. The project is investing in completion of an index to the 130,000 wells in the Wallingford archive and in a redesign of the hydrogeological databases.