Geophysical Ivestigations of a Rural Water Point Installation Program in Nampula Rapale District, Nampula Province, Mozambique - A Minor Field Study
- O. 2016. Enkel, E. Sjöstrand
Access to clean water for drinking and sanitation is a human right. Today water scarcity is a large problem and inequality in access to safe water is a striking truth. In Mozambique, the US foreign aid agency Millennium Challenge Corporation introduced the Rural Water Point Installation Program to increase access to safe water and sanitation – a step towards reducing poverty. 600 water points – including a drilled well, hand pump and washing basin were installed in the provinces Nampula and Cabo Delgado. Unfortunately, a high failure rate was seen and 25% of the wells in Nampula had insufficient yields for communal use. To investigate the reasons for the failures, geophysical borehole logging was carried out at ten sites in Nampula during September 2015. Resistivity and natural gamma radiation of the subsurface in the borehole vicinities was measured to gain knowledge regarding hydrogeology, capacity and characteristics of the investigated wells. Logging resistivity was compared to ERT resistivity-depth models with data from previous investigations on the same boreholes, in order to verify the reliability of using ERT-investigations for borehole siting in the Nampula area. The geophysical borehole logging confirmed the ERT-resistivity findings, implying that ERTmeasurements should be carried out before drilling. By doing this less boreholes with insufficient yields would be drilled – saving time and money. The geophysical borehole logging gave more detailed information regarding the subsurface, and it is suggested to use borehole logging to determine placement of screens in order to get a well with as high efficiency as possible.