Viability of marginal yield boreholes in selected geological formations in Ghana

The Community Water and Sanitation Agency (CWSA) has adopted standards for borehole provision in rural communities in Ghana. One of such standards is declaring as marginal or unsuccessful, borehole with yield less than 0.81m3/hr. This has resulted in most marginal yield boreholes in fractured zone aquifers either being abandoned for insufficient water, or are possibly ear marked for hydro fracturing to enhance their viability. The study reviewed the use of marginal yield boreholes (0.30-0.78m3/hr) in order to specify criteria for their sustainable use. Out of 3,025 boreholes drilled between 1995 & 2005 in the Voltaian, Granite and Birimian, 438 were marginal yield boreholes which were viably used, each serving a population ranging from 90 to 400. The results have shown that the viability of these boreholes depend on aquifer characteristics such as the Specific Capacity, Transmissivity and Recovery rate and the population using the marginal yield borehole. The paper specified the required ranges of the aquifer parameters and community sizes for viable use of such boreholes.