The Gidabo River Catchment area is found within southern Main Ethiopian rift, North-east ofrnLake Abaya; or more specifically lies in Sidama and Gedio Zones of Southern region and BorenarnZone of Oromia region. The Catchment area coverage and the perimeter of the Gidabo Riverrnare 3342.37 square kilometers and 305.25 kilometers respectively. Assessment of groundwaterrnresource potential of the catchment is studied based on conventional hydrogeologicalrntechniques, by gathering and interpreting geological, hydrometeorological, hydrogeological andrnhydrochemical data.rnThe Gidabo River Catchment area is dominantly covered by pyroclastic fall (flow) deposits andrnTrap-Series basalts with Trachytic compositions; alluvial and lacustrine deposits also coverrnconsiderable area of the Catchment.rnUsing analysis of the available meteorological data, potential evapotranspiration (PET) wasrncalculated by two methods; (i.e. Thornthwaite (1948) and Penman). PET values obtained byrnThornthwaite method for Highland, Escarpment and rift floor are estimated to be 689.85mmrn786.8mm and 1307mm respectively. Modified Penman approach is used only for calculatingrnPET of the rift floor and gave the value of 1301mm. Actual Evapotranspiration (AET) wasrncalculated using Turc and Soil water balance method. The AET values obtained by Turc methodrnfor Highland, Escarpment and Rift floor is 665mm, 950mm, 1456mm respectively. AET valuesrnobtained by soil-water balance method for the Highland, the Escarpment and the Rift floor arernestimated to be 688.9mm, 803.9mm, 1063.6mm respectively. Conventional water balancernmethod has been used to compute the total groundwater recharge of the basin and rechargernvalue of 353mm/year is obtained.rnGround water potential of the Gidabo Rive Catchment is seen to be under the control ofrnfractures (faults) and weathering. Higher hydraulic conductivity zones are mapped at or nearrnfractured regions and their values are decreasing away from the fractures (faults).rnGraphical presentation (i.e. Piper (1944)) is used in order to facilitate the interpretation andrnanalyses of the chemical data. The piper plot shows that most boreholes and spring waterrnsamples are Ca-Mg-HCO3 type in the discharge area and Na-HCO3 type towards the rechargernareas.rnThe surface and shallow groundwater systems are characterized by high iron concentrations.rnThe source is believed to be the red soils that cover the study area. According to Kedir Yasinrn(2002), the concentration of iron in the water is greater in the wet season than the dry seasonrndue to leaching effect.rnHigh concentration of fluoride within the study area is noticed in the western part (dischargernarea) in geothermal borehole and hot springs