Modeling The Impacts Of Climate And Land Use Land Cover Change On Streamflow And Sediment Yield, And Developing Best Management Practices In The Upper Awash Sub-Basin, Ethiopia

Abstract

Climate Change And Land Cover Change, As Well As Its Consequences On Water Resources, Have Been Hot Topics In Recent Years. Understanding The Impact Of Climate Change And Land Use/Land Cover (Lulc) Has Become A Top Priority For Awash Basin Water Management And Resources Utilization.In This Study, Swat Is Used To Assess The Impacts Of Climate And Land Use Land Cover Changes On Streamflow And Sediment Yield, And The Development Of Best Management Practices(Bmps) In The Upper Awash Sub-Basin (Uasb), Ethiopia. Cordex-Africa Ramo22t (Ec-Earth) Data Outputs For Uasb Were Chosen Under The Representative Concentration Pathways (Rcp4.5) Scenario To Make Mid-Term Rainfall And Temperature Projections (2041-2070). The Lulc Change Analyses For Three Periods (1990, 2005, And 2020) Were Performed Using Erdas Imagine 2015With A Maximum Likelihood Classifier. Based On The Result Obtained (1990-2020), Significantly Increasing Rates Were Observed In Urban/Settlement (3.5%), And Agriculture (17.8%) And A Decreasing Rate Were Observed In Forest (3.1%), Grassland (9.7%), And Shrubland (8,6%). The Simulation Was Done By Dividing The Watershed Into 27 Sub Watersheds And By Assigning A Hydrological Response Unit Based On Multiple Hru Definition. The Model Performance In Simulating Streamflow And Sediment Yield Was Evaluated Through Sensitivity Analysis, Calibration, And Validation Processes. The Results Of The Model Calibration (2002-2006) And Validation (2007-2010) Showed Reliable Estimates Of Monthly Streamflow And Sediment Yield With R2 = 0.83 &0.85, Ens= 0.78 &0.81 And Pbias=11.35 &14.1 During The Calibration Period And R2=0.77 &0.8, Ens=0.73 &0.78 And Pbias=8.9 & 12.5 During The Validation Period Respectively. Streamflow Increased By 4.8% Under Lulc Change And Decreased By 1.26% Under The Impacts Of Climate Change. The Change In Sediment Was 12.64% Under Lulc Change And 3.28% Under The Climate Change Effect. The Lulc Change Had A Greater Contribution To Changes In Sediment Yield Than Climate Change. Both Streamflow And Sediment Yield Increased Under Combined Impacts, With 4.6% For Streamflow And 15.54% For Sediment Yield. During 1989???2019, The Combined Impacts Of Climate And Lulc Played A More Important Role In Alterations Of Streamflow And Sediment Than Individual Impacts. Simulation Of Sediment Yield Established Nine Sub-Basins That Yielded Higher Sediments. They Were Sub-Basin ,9,12, 13, 14, 18, 20, 21, 22, And 27. Hence, Three Bmps Namely Filter Strips, Terracing And Reforestation Were Developed For Critical Sub-Watersheds To Reduce The Sediment Yield And Filter Strip 5 M Wide Is The Most Effective For Reducing Sediment Yield In Upper Awash Sub-Basin. The Findings Of This Study, In Particular, Will Provide Valuable Information For Planning And Designing Sustainable Water Management Approaches That Reduce The Impact Of Droughts, Floods, And Sedimentation In Upper Awash Sub-Basin.