Hydrological processes and water resources management in a dryland environment III: Groundwater recharge and recession in a shallow weathered aquifer

In crystalline basement regions of Africa, shallow weathered aquifers provi de vital water resources for rural communities. To quantify evidence of the behaviour of these shallow aquifers, groundwater levels were observed at a network of 65 boreholes within the Romwe Catchment in southern Zimbabwe. S oil moisture was monitored at selected sites. Groundwater hydrographs showed considerable spatial and temporal variation. Where the soil profile was freely draining, groundwater levels typically r esponded within a few days of major rainstorms and large annual fluctuation s in the water table of up to 7 m were recorded. In areas where a thick cla y layer exists, annual fluctuations were smaller and groundwater levels ros e more gradually in response to rainfall. In cultivated areas, vertical dra inage was an important recharge mechanism. Groundwater hydrographs typicall y have an exponential recession and, by the end of the dry season in the ye ars studied, levels were close to the base of the weathered aquifer. Variat ions in hydrograph response between years illustrate the importance of rain fall amount, intensity and distribution on groundwater recharge.