Civil and Environmental Research www.iiste.org ISSN 2224-5790 (Paper) ISSN 2225-0514 (Online) Vol.9, No.8, 2017 55 Assessment of Groundwater for Irrigation Purpose in Ife North Local Government area, Southwestern Nigeria Kamar Taiwo Oladepo * Abeeb Abiola Jimoh Julius Olatunji Jeje Obafemi Awolowo University, Ile-Ife 20005, Nigeria * E-mail of the corresponding author: koladepo1@yahoo.com 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 1. Introduction Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and vegetation of disturbed soils in dry areas and during periods of inadequate rainfall (Snyder & Melo-Abreu 2005). Irrigation water is supplied to supplement the water available from rainfall and the contribution to soil moisture from groundwater; and in many areas of the world the amount and timing of rainfall are not adequate to meet the moisture requirements of crops, hence, the need to supplement with irrigation (Osunbitan et al. 2005). The Ife region is underlain by crystalline basement complex rocks, which cover about 50% of the total land areas of Nigeria (Hubbard 1968). Rocks found in these areas are pre-Cambrian in age and lie within the zone of Pan African reaction (Rahaman 1975). The climate of southwestern Nigeria is characterized by two distint seasons: wet and dry seasons. The wet season lasts from April to October while the dry season lasts from November till March (Hayward & Oguntoyinbo 1987). According to Oke & Aladejana (2012), in order to alleviate the challenges of food insecurity in Nigeria, irrigation farming must be given serious attention. In a study conducted by Osunbitan et al. (2005), it was concluded that the groundwater supply could meet the water requirements demand on a small-scale irrigation project in the areas underlain by the basement complex with Ile-Ife as a case example. The suitability of groundwater from Ife North Local Government Area for drinking purpose has been studied by Oluyemi et al. (2011) and Jeje & Oladepo (2014). However, the area has large expanse of agricultural brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by International Institute for Science, Technology and Education (IISTE): E-Journals