Modelling potential areas of groundwater development for agriculture in northern Ghana using GIS/RS

Groundwater development potential in northern Ghana (108-671 km(2)) has been assessed by combining spatial layers for five critical factors-recharge rate, regolith thickness, transmissivity, borehole success rate and static water level-through a multi-criteria analysis approach to rank development potential from the viewpoint of groundwater availability and accessibility at a resolution of 1 km(2). The results indicate a high potential for development in the study area, as about 70% of the area was found to have high to moderate groundwater availability, while 83% has high to medium groundwater accessibility. Comparing the two main hydrogeological environments, the Precambrian Basement rocks (PCB) area was found to generally have a higher groundwater development potential than the Voltaian Sedimentary rocks (VSB). More detailed investigation revealed that the VSB can produce a small proportion of exceptionally high-yielding boreholes that can support large-scale irrigation. A test of the reliability of results showed that generally, the majority of high- and low-yielding boreholes fall in areas predicted by the model as having high and low groundwater availability, respectively.