ESTIMATION OF WATER BALANCE IN THE NORTHERN REGION OF GHANA

Abstract

A study was carried out to understand the reasons why there is low groundwater potential in the Northern Region of Ghana. This was done by determining the mean annual recharge using three independent methods. These are the: (i) use of hydrological parameters like precipitation and evapotranspiration (ii) use of the recession curve where baseflow was separated as recharge and (iii) use of Cl concentration in rainfall and groundwater for only the Tamale area. Among the three methods, (i) produced the least recharge values of 1.4% (Pwalugu-Nawuni catchment) and 4.1% (Lawra-Bui catchment) of the annual rainfall. This was considered to be the minimum recharge and was similar to that obtained by the Cl (4.5%) and may not be enough to replenish the groundwater. The amount of storage was also calculatedfor some parts of the Black and White Volta and the Kulpawn rivers. The change in storage ranged from 4 in the Kulpawn to about 13 mm in the Black Volta rivers. The high storage in the Black Volta partly explains the .'1ighgroundwater availability in the south of the region. The low storage coupled with low mean annual recharge also partly explains the law groundwater potential in the Voltaian sediments. Another critical factor to explain the low recharge was high runoff. This was attributed to availability of impermeable strata within the Voltaian sediments that prevent sufficient infiltration to take place.