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Item COMPARISON OF SWAT AND WEPP FOR MODELING ANNUAL RUNOFF AND SEDIMENT YIELD AND QUANTIFCATION OF NUTRENT LOSS IN AGEWU MARIYAM WATERSHED, NORTHERN ETHIOPIA(Hawassa University, 2022-10-22) YALELET ABIE WORKUUnevenly heavy rainstorms during the rainy season create runoff and soil erosion which affects soil fertility and production, especially in northern Ethiopia. In this study soil and water assessment tool (SWAT) and geographic water erosion prediction project (GeoWEPP) were applied to compare estimation of annual runoff and sediment yield and quantification of nutrient loss in Agewu-Maryam watersheds eastern Amhara, region, Ethiopia. To run both models, need spatial and temporal data distribution is required as an input. The soil textures and other selected soil properties were determined in the field and the laboratory and a soil map were derived from the digital soil map of the world. A land-use map was prepared based on manually digitizing from Google earth image. A Digital Elevation Model of the watershed was used for delineating the watershed and preparing a slope map. ArcGIS 10.4 was used for both models for basic interface for further analysis. During each runoff event, runoff samples were collected and the sediment concentrations were analyzed in the laboratory. The simulation result of long-term (24-year) average means annual runoff and sediment yield from WEPP and SWAT models were estimated. The results were performed well as indicated by R 2 0.86 and 0.91 and with NSE 0.54 and 0.71 for monthly runoff were satisfactory for SWAT and WEPP models compared with observed value respectively The estimated average mean annual runoff and sediment yield at the outlet of the watershed was 65.54mm and 146.14mm and 43t/ha/yr and 41.7t/ha/yr respectively for WEPP and SWAT models. The t statics result shows that there is no statistically significant difference with p-value (0.97 for runoff and 0.98 for sediment) between the two models' simulation results. Some of the Sub watershed were identified and prioritized as more susceptible to soil erosion and give more attention first to this area for reducing runoff and soil erosion. The total nutrients loss within the suspended sediment were 33.74kg/ha/yr N,6.79kg/ha/yr P, 642.5 OM kg/ha/yr, and 1.52 K for the watershed. Hence SWAT and WEPP models were well suited for the estimation of annual runoff and sediment yield. The sediment yield simulated from both models was high which was alarming and far beyond the soil loss tolerable rate. Therefore, the result of the model could be used as a decision-making toolItem ASSESSING THE EFFECT OF LAND USE LAND COVER CHANGE ON STREAM FLOW AND SEDIMENT YIELD: THE CASE OF ROBIGUMERO WATERSHED, UPPER BLUE NILE BASIN, ETHIOPIA(Hawassa University, 2024-07-26) KASAHUN TADESSE MARELand use and land cover change significantly affected global water yield and sediment yield. The population within the Robigumero watershed experiences periodic increases that are attributable to changes in land use and land cover patterns occurring over both a spatial and temporal scale. Therefore, this study mainly focused on assessing LULC change and analyzing its impact on stream flow and sediment yield in the Robigumero watershed. For this study, spatial and hydro-meteorological data were used as model input. ERDAS Image 2015 was used to assess land cover classification and accuracy. SWAT model was used to simulate stream flow and sediment yield in monthly time steps. The model predicted stream flow with R2 values of 0.89 and 0.77, NSE values of 0.87 and 0.76, and PBIAS values of -2.3 and -5.1 during calibration and validation periods, respectively. Similarly, the model predicted sediment yield with R2 values of 0.80 and 0.75, NSE values of 0.80 and 0.74, and PBIAS values of -7.1 and 0..9 during the calibration and validation periods, respectively. During the study period from 1994 to 2021, the Robigumero watershed experienced substantial LULC change, with agricultural land and built-up area increasing by 18.6% and 160.8%, respectively, while forest, grassland, and shrubland cover decreased by 12.7%, 10.4%, and 40%, respectively. The calibrated model predicted results showed that on the watershed outlet point, mean annual stream flow increased by 4.64 m3 /s, and mean monthly stream flow increased by 0.86 m3 /s during the wet season and decreased by 0.14 m3 /s during the dry season from 1994 to 2021. Similarly, annual sediment yield increased by 5.5 t ha- 1 .yr-1 , with seasonal yields increasing by 4.84 t ha-1 .yr-1 during the wet season and 0.49 t ha- 1 .yr-1 during the dry season. Spatially, nine subbasins (43.3%) of the catchment revealed sediment yield-critical areas; from these, 24.02 t ha-1 yr-1 of sediment was generated. Implementing terracing, filter strips, and contouring in the critical subbasins demonstrated sediment yield reductions of 71.1%, 46.3%, and 51.9%, respectively. The findings of this study indicate that annual and wet season stream flow and sediment yield increased, while dry season stream flow was reduced. The change in stream flow and sediment yield is a direct result of the significant change in land use and land cover in the watershed. This suggests soil and water resource development in the catchment needs urgent regulation by the LULC and should be given priority to sediment reduction measuresItem ESTIMATION OF RUNOFF AND SEDIMENT YIELD USING SWAT MODEL: THE CASE OF KATAR WATERSHED, RIFT VALLEYLAKE BASIN OF ETHIOPIA(Hawassa University, 2019-07-27) Dulo HusenEstimating of runoff and sediment yield at watershed level is important for better understanding of hydrologic processes and identifying appropriate measures to combat erosion. In this study, Soil and Water Assessment Tool (SWAT) was used to calibrate and validate a hydrologic component on Katar river discharges at Habura gauging station and predict the stream flow of Katar watershed. The objective of the study was estimating the runoff and sediment yield for the Katar watershed using SWAT model. Sensitivity analysis, model calibration and validation were also performed to assess the model performance. From the result of Global sensitivity analysis, twelve(12) highly sensitive parameters were identified, and coefficient of determination (R2 ), Nash-Sutcliffe (ENS) and percent bias (PBIAS) were used as objective function to evaluate model calibration and validation on the monthly basis, and it could simulate runoff to a good level of accuracy. The results obtained were satisfactory for the gauging station (R2 = 0.80, ENS = 0.6 and PBIAS=0) for calibration and (R2 = 0.6, ENS = 0.55 and PBIAS=1.2) validation period. The simulated runoff and sediment yield of Katar watershed was quantified and also the utmost erodible part of the watershed was identified and prioritized. Among all sub-watersheds, nine (9) sub watersheds were more vulnerable to soil loss and potentially prone to erosion risk, which was out of range of tolerable soil loss rate (18 tha-1 yr-1 ). Large area of watershed covered by Haplic Luvisols(high clay content) and agriculture is the dominant activities in area. The simulated mean of sediment yield and runoff loss from watershed for 26 years were 11 tha-1 yr-1 and 12.3 m 3 s -1 respectively. The result of the study could help stakeholders to plan and implement appropriate watershed management strategies based prioritizations of severity of erosion. In conclusion, the SWAT model could be effectively used to predict runoff and sediment yield and result of the study could help different stakeholders to plan and implement appropriate interventions strategies in the Katar watershed.