Importance of Awash River is strongly linked to irrigation, industrial pollution and public health.rnBy far the greatest portion of Awash River was used for irrigation purpose. In addition to this,rnAwash River serves the surrounding communities as a source of drinking water, live stalkrnwatering and other. With regard to Lake Beseka, it is one of the natural Lake in Ethiopiarncharacterized by its brackish water and continuous level rise that expands out of the naturalrnsurface area which inundating main road and rail line connecting Ethiopian to Djibouti. Tornresolve the effect of the lake level rise, Ministry of Water Resources has been implemented arncontrolling mechanism though discharging controlled amount of water in to the Awash River.rnThis research paper initiated to study spatial and temporal vari ation of Awash River and LakernBeseka water together with the impact ofloading Lake Beseka water in to the Awash River.rnTo assess the current Awash River and Lake Beseka water quality, physicochemical laboratoryrnanalysis were undertaken on samples from ten representative locations (seven from the River andrnthree from Lake) for eight months. The result obtained revealed that the physicochemicalrnparameters were spatially and temporally varied in both water bodies.rnThe effect of Lake Beseka in the Awash River for most of all parameters, which were dominantrnin the Lake Beseka, showed a change between with and without Lake Beseka water at Metehararnsampling points and also there was a shift of water quality level in most down stream locationsrndue to the effect of Lake Beseka together with other natural phenomena. These shifts of somernparameters were resulted the Awash River water quality to exceed from the predicted value inrnthe proj ect document, and WHO and FAO guidelines. The output of this research was to amendrnprevious percentage of Lake Beseka discharge (2%) by considering monthly flow andrnconcentration of the Awash River and Lake Beseka water. Accordingly, for wet season and dryrnseason flow of the river, the alternative percentage of Lake Beseka discharge in to the AwashrnRiver can go up to 2.4% and 0.9 %, respectively. Further more, undeltaking of daily basis waterrnquality monitoring recommended and based on this to know the exact discharge percentage at therntime of monitoring on can calculate using the formula indicated in this paper.