Enhancing adaptation to climate change through groundwater-based irrigation

Changing climate in Northern Ghana has led to erratic rainfall patterns which have affected agricultural practice over the years. This research interrogates various factors which affect the success of agriculture in the area, specifically the Nasia sub-basin, to suggest prudent water management strategies which will be required to adequately adapt to the impacts of climate change. The research evaluates the irrigation water requirements of the major staple crops in the area in the context of a changing climate, and the implications on available groundwater resources to support small-scale irrigation. The study then proceeds to use a robust geostatistical technique to estimate the spatial variations in the thickness and characteristics of the regolith in the Nasia sub-basin since the latter plays an important role in the hydrogeological characteristics and the groundwater resources potential of the rocks of the Neoproterozoic Voltaian Supergroup. The variography conducted on the regolith thicknesses in the area suggests a high level of spatial variability within short distances, consistent with the nature of the underlying geology. The models suggest that the older, sandstone formations in the north of the terrain are associated with thicker regolith compared to the finer grained, younger formations in the south. Locations of thick regolith are generally regarded as areas of high promise in terms of shallow groundwater-based irrigation. Based on local conditions which dictate the crop types cultivated during the major cropping season, this research has computed crop coefficients for four crops (i.e., millet, maize, groundnut, and rice). The analysis suggests that the crop water requirements for the various staple crops are sensitive to variations in climatic conditions and will respond to increasing temperatures and evapotranspiration rates as predicted by climate models over the sub-region. This research recommends further detailed hydrogeological research which builds on the predicted variations in regolith thickness and characteristics already identified here. This will facilitate a proper delineation of prolific groundwater-bearing units within shallow, easily accessible depths to support smallholder irrigation in the area.