Assessment of Shallow Groundwater Quality for Irrigation Purposes in Basement Complex Terrain of Southwestern Nigeria

Abstract

This research attempts the investigation of shallow groundwater quality for suitability in agriculture (irrigation) and other uses. Samples were investigated for sodium adsorption ratio, magnesium hazard, Kelley’s ratio, residual sodium bicarbonate, and alkalinity hazard and permeability index. The methodology involves sampling of hand dug wells <30m for laboratory analyses. ICP-MS was used in determining the major metals present in the water samples while titrimetric method was employed for anions determinations. Physico-chemical results revealed a midly acidic pH of mean value 6.3, TDS of 329mg/l, E.C of 427uS/cm, Ca of 25mg/l, Mg of 8.5mg/l, and Na of 42.5mg/l. Calculated indices such as MAR, RSBC, PI indicate that majority of the water are suitable for irrigation. Kelley’s ratio shows that 31% of the water samples are above permissible limit of good irrigation waters while 69% fall within. Calculated SAR and EC classify 69% of the samples into medium salinity to low sodium hazard (C2S1), 25% within low salinity and low sodium hazard (C1S1) and 3% each within the high salinity and low hazard (C3S1) and medium salinity and medium hazard (C2S2) respectively. The groundwater qualities satisfy the condition for use in industry and livestock farming.