The geology, hydrology, hydro geology and hydrochemistry of the Borkena catchment which isrnlocated on the western edge of the Afar rift was studied based on conventional geologic andrnhyd rogeological mapping, river discharge measurements, water sample analysis and assessmentrnand interpretation of hydrometeorological data. The main objective of this work is tornunderstand the different lithologic unit and to characterize and group them intornhydrostratigraphic unit and map them, to analyze the water balance and to study the waterrnquality.rnFour hydrostratigraphic units were recognized and mapped. These are: colluvial and riverrnchannel deposits, alluvial deposits, scoraceous and basaltic lava flow and fractured massivernbasalt, welded tuff and rhyolite. Generally the volcanic rocks lie with in the recharge zonernwhile the Quaternaiy sediments lie in the discharge zone. Accordingly the hydrostratigraphicrnunit located on the Quaternary sediments are characterized by many springs and hand dug wellrnwhere as low or rare in the volcanic regions.rnFrom storage, utilization and abstraction point of view, the colluvial and river channel depositsrnare the most promising units than other units as a result most of the springs, hand dug wellsrnand boreholes are located in this hydrostratigraphic units.rnGenerally seven rock units and three set of faults are identified and mapped at the scale ofrnI :50,000. Among the rock units, scoraceous and basaltic lava flow and alluvial deposits coverrnmore than 70 percent of the catchment. From hydrochemical analysis, measurement of TDS, EC and other variables, the water bodiesrnare characterized by low total dissolved solids (TDS) and low electrical conductivity (EC)rnvalues as a result they are classified as fresh water and their utilization for vanous purposesrnscarcely bring danger.