With an area of some 115,523 km2, the Awash basin mainly comprises the north-western and south-easternrnhighlands and the rift valley. The basin is endowed with abundant surface water and groundwater resources thatrnrequire proper management if they are to be wisely utilized in a sustainable manner. With the Awash river as thernmajor resource, the Awash valley is the most developed part in Ethiopia in terms of irrigated agriculture.rnThe Awash river water balance has been computed with recent level of irrigation development for a period of fivernyears. The results show that the Awash river is generally influent with transmission loss of some 2.1 BCM andrn6.8 BCM for the reaches Koka-Metahara and Metahara-Tendaho respectively during the given period. Thesernvalues include potential indirect recharge as well as loss due to over-bank flooding and subsequent evaporation.rnOne such place where considerable loss (about 500 MCM/yr from evapotranspiration) occurs is Gedebassarnswamp, situated in the middle part of the Metahara - Tendaho reach.rnInfluent conditions may be valid as groundwater tables are relatively deeper than the Awash river in the valleyrnand highly permeable river bed sub-reaches exist (alluvial sediments and fractured/faulted volcanic rocks).rnNevertheless, there are intermediate reaches where the Awash may also be effluent. These include the vicinitiesrnof major irrigation schemes and the sub-reach immediately downstream of Koka reservoir where groundwaterrntable is shallow.rnThe Awash river receives considerable surface runoff inflow (about 2.7 BCM/yr) in the middle and lower valleys,rnmainly from the western sub-catchments. About 60% of this amount is acquired upstream of Gedebassa swamprnand the rest 40% downstream. In the upper valley, the Awash river receives inflow of some 420 MCM/yr, which isrnless than one-fifth of what is received in the reach between Metahara and Tendaho. And yet, from the overallrnirrigation abstractions (currently less than 1 BCM/yr), more than 60% take place in the upper valley.rnWith computed overall irrigation efficiency of less than 45%, the Amibara Irrigation Schemes (AIS) in the middlernvalley have been studied at semi-detailed level. Groundwater hydrograph analysis based on peizometersâ€™ datarnhas shown that surface irrigation in Amibara is responsible for rising groundwater tables with average rates of 0.3rnto over 1 m/yr in the 70s up to 90s. Further investigations on possible Awash river-groundwater as well as canalrnwater-groundwater interactions in Amibara have been made possible by conducting groundwater flow analysis.rnThe prepared depth to groundwater map portrays that average groundwater levels are within 3m (shallow depth)rnin one-third of AIS.rnAs evidenced from analysis results of bulk water and surface soil samples collected as part of this study, thernAwash river is regarded as suitable for irrigation with moderate salinity and low sodicity; the groundwater inrnAmibara is generally saline (85% of AIS above 5 mS/cm); and about 20% of AIS soils are saline and 3% salinesodic.rnThe groundwater levels have currently reached close to surface, due to recharge from irrigation, that evaporationrnhas now become one of the major outputs other than groundwater outflow. The relatively higher evaporation raternin Amibara favours upward movement of salts from the saline, shallow groundwater during the fallow period. Inrnaddition, the shallow groundwater has further hindered effective leaching of soluble salts below the root zone,rnnecessitating measures of groundwater level control by sub-surface drainage installation or other means.