Assessment of well design and sustainability in hard-rock formations in northern Ghana

Some of the main problems in well construction are associated with installation of casing, especially in the overburden. A total of 1,485 lined and open wells, drilled in the hard rocks of the Precambrian basement complex and Palaeozoic sedimentary (Voltaian) formations in northern Ghana were studied. Of these, 500 were directly monitored. It was observed that the surfaces within the production zones of open wells had weathered, leading to silting and reductions in depth and yield, posing physical water-quality challenges. Also, the average life span of the open wells is about 15 years. The fully lined wells, on the other hand, perform very well with time, lasting for over 40 years on average, with a more sustainable physical water quality over their life span. The comparative cost of constructing an open well was found to be about 26% less than that of a lined well due to less construction material requirements. Although open wells may be relatively cheaper than lined wells to construct in hard rocks, the life span is shorter and should not be encouraged for groundwater exploitation especially in community or rural water supply schemes.