The study area of this research is Kobo Valley catchment, situated south of Raya Valleyrnin Northern part of Ethiopia. The low lying inter mountain valley part of the area isrnknown by its high groundwater potential and semiarid climate. Currently, it isrnunderground water source exploitation and investigation mainly for irrigation because ofrnscarce surface water and low annual rainfall. In the study area 17 single well constantrnpumping test and recovery test data were collected besides 14 of 17 wells have the steprndrawdown test data. In this research where conducted to re- analyze the transmissivityrnvalue estimated for design. Having checked the data quality for all 17 wells in the Kobornwell field transmissivity was estimated using Theis and Cooper-Jacob method for therntime drawdown data collected and the residual drawdown analysis time residualrndrawdown data. For each well three transmissivity value were estimated the geometricrnmean value estimated ranges from a minimum of 26m2/day to2790m2/day. For thernsame wells the range of transmissivity value used in the design of the kobo irrigationrnscheme was 55.2m2/day to 3145m2/day. Among the 17 wells 11 wells were found tornunder estimate transmissivity obtain in this research 4- 82% but one are found tornoverestimate the transmissivity with 8-178%.given the fact that both this research andrnthe design document uses the same well test data, such huge variation in the estimationrncould only because by data interpretation techniques. Appropriate data correction shallrnbe made test for any well analysis for hydraulic parameter estimations. In well datarnobtained for single well test such correction is even more vital. For the well with underrnestimated transmissivity values the well yield could have been larger conversely for overrnestimated transmissivity values will not supply the estimated yield.rnKey words: -kobo pressurize irrigation project, pumping test, single well test,rnstep drawdown test