Effect of Large Dams on Groundwater Sources Down Stream of Dadinkowa and Balanga Dams, Gombe State Nigeria

Abstract

In Gombe State, Nigeria, two concrete dams were constructed in Balanga and Dadinkowa and completed in 1987 and 1988 respectively. Balanga dam with a capacity of 63 mcm, and Dadinkowa dam, 1,770 mcm, were to be both used for irrigation and provision of hydroelectric power supply. Since the completion of the two dams, they have not been commissioned for the intended use. The effects of these large dams on water table rise downstream of Dadinkowa and Balanga dams were determined using various groundwater potentials study methods. Ten wells from earlier sources of water before the construction of the dams down streams were selected and subjected to wells depth to water level measurement during the peaks of dry season (March and April) and rainy season (August and September). In Dadinkowa wells (W1-W10), water depth to ground level ranged from 1.39 - 4.12 m in the dry season, with a mean water depth range from 1.42 - 3.91m. In the peak of rainy season, water depth to ground level ranged from 2.45 - 5.96 m. In Balanga dam area, the water depth during dry season ranged from 2.15 - 2.87 m and a mean depth range from 2.16 - 2.81 m, in the rainy season, water depths ranged from 2.65 - 4.32 m and mean depths ranged from 2.96 - 4.85 m. During dry season, water depths in Dadinkowa wells entire site mean (E.S.M) was 2.46 m, and 4.28 m, in the rainy season. In Balanga, the E.S.M for dry season was 2.44 m and 3.80 m during rainy season. By comparison, the depth to water levels of the entire seasonal mean in Dadinkowa wells during dry season which is 2.46 m, to that of rainy season, 4.28 m, indicated that the level of water table increase due to rainfall influence was just by 1.82 m; while E.S.M for Balanga in the dry season (2.44 m) and rainy season (3.80 m) had rainfall infiltration influence by 1.36 m depth only. This means the hand dug wells maintenance of a steady depth to water level rise throughout the dry season comes from the replenishment of the ground.