Water resource development planning is usually referred as thernprocess to define how to utilize the available water resource tornmeet the desired objectives. In order to compensate for thernscarcity of data for the available water resource, regionalizationrnis found to be one of the best methods of transferringrninformation from the gauged station to ungaged sites.rnThe purpose of this paper is to develop regionalized FlowrnDuration Curve for Abbay Basin. Based on similarity ofrnstandardized rainfall patterns eight regions were identified andrnFlow Duration Curves of each region are developed.rnFor the development of reliable flow duration curve, daily flowrndistribution from the mean monthly stream flow is derived. FlowrnDuration Curve based on the estimated daily flow is developedrnand an equation for each region is determined.rnThe regional equations were developed using regressionrnanalysis. These equations relate discharges of 70 and 80rnpercent of exceedance for ungauged watershed in the basin, orrnfor short record length stations and catchment characteristics.rnEstimation of low flow for ungaged sites (below 50% ofrnexeedance) can be obtained using regional regression methodrnand subsequently Flow Duration Curve for each regions.rnFor the evaluation of hydropower potential sites requiresrnknowledge of the time availability of flow at a certain point in arnriver as described in Flow Duration Curve. It is also useful inrnother hydrologic investigations where knowing the average time availability of flow is required, such as for irrigation projects andrnothers.