Evaluation of chloride mass balance and recharge in agricultural lands in Nigeria
Keywords:irrigation, groundwater, chloride mass, recharge, water management, salinity
Groundwater salinization studies and recharge estimation was carried out at the Irrigation Research Station, Kadawa, Nigeria. Groundwater samples from fifteen randomly selected piezometer locations were analyzed monthly for chloride using Mohr’s method for three years while recharge was estimated using the chloride mass balance (CMB) method. Groundwater chloride range from 22 - 91.4 mg/l, seasonal trend was identified with the hot dry season (April – June) having higher values than the wet season (July – October). Correlation analysis revealed chloride status that is not associated with one another in all soil types while salt build up was observed at the south western tip of the farmland indicating potential reduction of agricultural productivity. CMB revealed a mean annual recharge of 869 mm; the method was found to underestimate recharge because it does not account for lateral flow contribution, hence should be discouraged as a stand-alone methodology for recharge studies. Salt build-up was exacerbated by the collapse of the drainage system. Reconstruction of the drainage systems using tile drains should be executed to control the rising water level in the area; conjunctive use of groundwater and surface water is recommended to maximally utilise available water in order to ensure ecological sustainability and free some water for other uses.