Assessment of Surface and Ground Irrigation Water Quality for Small Scale Irrigation in East Shoa Zone of Oromia, Ethiopia

Abstract

Irrigation with poor quality waters may bring undesirable elements to soil in excessive quantities affecting its fertility. The seasonal variation in surface and ground water quality of different district in East Shoa zone has been evaluated for two years from 2013/14 to 2014/15 for assessing the suitability of water for irrigation purpose. In the present study water samples were collected from River, Lake and ground water and analyzed for ten parameters of physical and chemical properties. The analyzed water quality parameters show seasonal variation and high concentration in dry season compared to wet season due to dilution effects. Electrical conductivity, pH, ionic composition, sodium adsorption ratio (SAR) & total dissolved solids (TDS) were calculated using the standard equations. Analysis showed a wide range of electrical conductivities that varied from 332-2627.5 µS/cm and salinity ranged between 197.9-1681.6mg/L. The SAR in the study area lies between 1.42 and 22.09 in most irrigation water sources. Considering SAR as important parameter of suitability for irrigation, most of the results are under usual range compared to the irrigation water standards, except for some samples collected from underground. The mean pH values of almost all water sources were between 7.58 and 8.19 which can be categorized as normal range for irrigation purpose. The results concluded that water quality at some of the locations is above permissible limit for irrigation and needs proper monitoring to preserve and maintain its quality for agricultural purpose. Since water quality alone would not sufficient enough to evaluate potential salinity hazard of irrigation water, consideration should be given to crop, soil, climate, agronomic and irrigation management practices. Therefore the present study only serves as baseline survey for future research needs.