Geochemical studies of groundwater systems of semiarid Yola area, northeast, Nigeria

Geochemical studies of Yola area of Northeast Nigeria were studied during a dry season period (November 2008). This was to determine the process controlling the water chemistry and to assess the quality of water. Theresults show that, based on ionic ratios, precipitation and water-rock interaction (silicate weathering) are the main controlling factors contributing to solute concentration in these areas. The main water types in the area include Mg2+- HCO3 - and Na+-Cl- are the dominant ion types for the shallow groundwater, Mg2+-Cl-, Mg2+-HCO3 - and Na+-HCO3- for the deep groundwater and Na+-Cl- for the surface water bodies.Equilibrium specification calculations revealed that the water samples are largely undersaturated with respect to calcite and dolomite in the water samples. Groundwater samples from the shallow groundwater indicate pH values (6.10 to 7.08) and Eh values (mean 0.72 volt) whereas those of the deep groundwater revealed pH range (6.60 to 7.80) and Eh values (mean 0.75 volt). They are slightly acidic to neutral, largely soft, clean waters with fairly low to moderate concentration of dissolved solids that fall within the international acceptable limits for drinking, domestic and irrigation purposes. However some samples indicate iron and nitrate values that are above the recommended limits and should be treated before use. Employing Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Magnesium Adsorption Ratio (MAR), Permeability Index (PI), Kellys Ratio (KR), and Residual Sodium Bicarbonate (RSBC) as criteria, the waters appear suitable for irrigation purposes

Hydro-geophysical investigation of Bauchi and environs NE of Nigeria

Seven Schlumberger vertical electrical soundings (VES) and Fifteen Seismic refraction profiles carried out around Bauchi and its environ have been interpreted. The resistivity data were first interpreted using conventional partial curve matching technique in order to obtain the initial model parameters. The model parameters obtained were used as input into an optimizing computer program. The results obtained from VES 6 and 7 displays the presence of three-layer earth model. The first layer consists of loose topsoil materials, the second is weathered and/or fractured basement, while third layer is the bedrock. However VES1-5 display four-layer earth model, whereby the thickness of the weathered and/or fractured basement is over 19 m, except VES2 where the thickness is 8.7 m. The results obtained from the fifteen seismic refraction profiles indicate also a three-layer model. The first layer represents the topsoil with an average velocity of 146 m/s and a mean thickness of 3.1 m. The second layer has an average velocity of 1809 m/s and a mean thickness of 13.6 m. This represents the weathered/fractured basement. The third layer has a mean velocity of 4496 m/s, and represents fresh basement. From the Hydrogeological studies of borehole data, a mean depth to water table of 4.12 m, a mean hydraulic conductivity of 0.91 m/day and an average transmissivity of 19.88 m2/day, were recorded. Finally the geochemical analysis for hand-dug wells indicates a mean value of Chlorite and hardness of 186 and 381 mg/l respectively. The results from this study will no doubt serve as background information for groundwater prospecting and subsequent exploitation. Keywords: geology, hydrogeology, resistivity and seismic refraction data interpretation of Bauchi and environsGlobal Journal of Geological Sciences Vol. 3(2) 2005: 143-15