Assessment of Groundwater for Irrigation Purpose in Ife North Local Government area, Southwestern Nigeria

Abstract

The analysis of water quality characteristics provides valuable information useful in water resources management. This study assessed the quality of water samples from Ife North Local Government Area, Southwestern Nigeria, with a view to establishing their suitability for irrigation purpose. A total of 52 water samples were collected and analyzed during the dry season for the major cations (sodium, calcium, magnesium and potassium), anions (chloride, sulphate and bicarbonate), and physico-chemical parameters (temperature, pH, total dissolved salts and electrical conductivity). Based on these analyses, irrigation quality parameters such as sodium adsorption ratio (SAR), percentage of sodium (Na%), magnesium hazard (MH), permeability index (PI), residual sodium carbonate (RSC) and Kelly’s ratio (KR) were computed. The electrical conductivity of the water samples varied from 78.00 to 1041.00 µS/cm with a mean value of 443.83 µS/cm and the total dissolved solids varied from 0.10 to 1.17 mg/l with an average value 0.44 mg/l. The salinity hazard result shows no degree of restriction on the use of the water for irrigation. Sodium concentration in the samples varied from 2.40 to 31.80 mg/l with an average value of 14.13 mg/l, indicating no degree of restriction for sensitive crops on the use of the water for irrigation. Based on the US salinity diagram, the water samples are predominantly of the C2-S1 class representing 57.69% of the total number of samples followed by C1-S1 and C3S1 classes at 28.85% and 13.46% of the samples, respectively; hence all the samples are suitable for irrigation. The Na% varied from 4.94% to 50.44% with a mean value of 25.42%, indicating no degree of restriction on the use of the water for irrigation. The obtained Cl^- ion concentration varied from 0.2 meq/l to 4.43 meq/l with a mean value of 1.74 meq/l representing slight to moderate degree of restriction on the use of this water in irrigation. The MH values range from 0.04% to 61.70% (with a mean value of 21.69%); only one sample has a value above the acceptable limit of 50%. Using the PI, 24 water samples fell under Class 1 and the remaining 28 samples fell under Class 2; therefore, the water samples are suitable for irrigation. The calculated RSC values varied from -1.37 to 0.21meq/l with a mean value of -0.52 meq/l, thus making the water suitable for irrigation purpose. The KR values for the study area are all less than 1, except one value, and therefore the water in the study area is suitable for irrigation purpose. In general, the water samples in the study area are suitable for irrigation purpose.

Keywords: salinity hazard, Kelly’s ratio, basement complex, irrigation farming, alkaline soil, Ipetumodu