ASSESSMENT OF GROUNDWATER POTENTIAL AND QUALITY FOR IRRIGATION IN WOTER WATERSHED, WABESHEBELLE RIVER BASIN, ETHIOPIA

Abstract

Groundwater is a valuable and significant natural resource throughout the world, and it is the most crucial for a country's growth and development. However, due to the nature of groundwater, assessing the potential of groundwater and quality for irrigation is still questionable. Therefore, this study tries to assess groundwater potential and quality for irrigation purposes in Woter Watershed, Wabeshebele River Basin, Ethiopia. The study used GIS and remote sensing techniques. Various input maps were prepared and weighted. finally, all layers were overlayed and groundwater potential zones were delineated. The result of the groundwater potential assessment shows that 13.07% (33.39 km2) of the study area was classified as very good; 33.94% (86.69 km2 ) of the area as Good; 33.47% (85.5 km2 ) as moderate; 19.14% (48.89 km2 ) as Poor, and the rest 0.38% (0.98 km2 ) as Very Poor potentials for groundwater exploitation. Moreover, the western and northern portion of the study area falls on a very good groundwater potential zone. Water quality indices, namely sodium adsorption ratio, percent sodium (%Na), residual sodium carbonate (RSC or RA), Kelly’s ratio, permeability index, chloroalkaline indices (CAI1 and CAI2), potential salinity (PS), magnesium hazard, total dissolved solids and total hardness, have been calculated for separate bore wells. The Classification of groundwater (r1 and r2) indices show that groundwater of the study area is Na+ –SO4 2− and deep meteoric percolation type. Majority of the wells are fall under moderate to unsuitable category of water for irrigation purposes. 11% magnesium hazard,78% Potential salinity and 89% Corrosivity ratio of the sample were found not suitable for irrigation. It is possible to conclude that a large proportion of the areal groundwater was found to have inadequate potential, but suitable quality so effective utilization with proper management techniques should be used to use it for irrigation.