A THESIS PROPOSAL SUBMITTED TO THE FACULTY OF HYDRAULIC AND WATER RESOURCE ENGINEERING ARBA MINCH INSTITUTE OF WATER TECHNOLOGY SCHOOL OF POST-GRADUATE STUDIES ARBA MINCH UNIVERSITY

Abstract

Many river catchments, including those in the upper Jemma sub-basin, lack continuous streamflow monitoring, and existing hydrologic models for ungauged catchments are data-intensive, requiring calibration and uncertainty analysis. The study evaluates the regionalization of SWAT (Soil and Water Assessment Tool) model parameters for use in ungauged catchments of the upper Jemma sub basin targeted on Ajima ungauged catchment. The SWAT model is calibrated and validated using monthly streamflow data from five selected nearby gauged catchments over the period 1996-2002 and 2003-2009 respectively using SWAT-CUP (SIFU-2). Model performance is satisfactory, with a coefficient of determination (R²) ranging from 0.61 to 0.90 and Nash-Sutcliffe Efficiency (NSE) from 0.62 to 0.93 for both calibration and validations. Parameters like CN2, GW_DELAY, ESCO and GW_REVAP are identified the most influential model parameter for streamflow prediction in the study area. Selected regionalization methods are tested by applying a leave-one-out cross-validation technique on the four gauged catchments, treating each as pseudo-ungauged catchment. All regionalization methods performed reasonably well (R² > 0.6) in estimating streamflow for ungauged catchments. However, spatial proximity outperformed the other methods, providing the most accurate streamflow estimates. The stream flow of the ungauged Ajima catchment is estimated to 44.55 million cubic meters (MMC).base flow is a key water balance components which influence the stream flow. The estimated stream flow and other water balance components used for different water application in the catchment.