Groundwater quality evaluation for irrigation, Modjo River catchment, a wash basin, Central Ethiopia

Irrigated agriculture is dependent on an adequate water supply of usable quality. Water containing impurities, which are injurious to plant growth, are not satisfactory for irrigation. Water quality for agricultural purposes is determined on the basis of the effects of the water on the quality and yield of the crops, as well as the effects on drainage efficiency and characteristic changes in the soil [16]. This study aims to assess the quality of groundwater in Modjo river catchment for irrigation. Hence, the groundwater samples were collected from well and borehole situated at different site within the catchment to analyze for necessary parameters. Consequently, in-situ measurements such as; EC, pH and TDS were carried out in the field inventory using portable ( pH) meters, whereas major ions are analyzed in Sinana Agricultural Research Center Soil laboratory. The chemical analysis of the samples shows that Na-Ca-HCO3 water type in the recharge area, intermediate water type Ca-Mg-Na HCO3 in northern and central part of the area and Ca-Mg-HCO3 water type towards the east of the subbasin. Most of the water in the study area is clustered as Calcium-Sodium-Magnesium-Bicarbonate type, which is characterized by a high concentration of HCO3 and Ca. Generally water quality analysis shows that as the concentrations in the water sample is below the maximum allowable limits for irrigation (i.e.EC<2000 µS/cm and SAR<9) and therefore the groundwater could be used safely for irrigation.