| Land use land cover(LULC)changes on soil erosion,hydrology,ecosystem functions and services is essential not only to identify challenges and targeting interventions but also for watershed management planning measures.The purpose of this study was intended to comprehend the impacts of LULC changes on soil erosion,sediment yield,hydrology and ecosystem services in the Muger sub-basin of the Upper Blue Nile basin during the 1986-2020 periods.A combination of remotely sensing,field interview,observations,and modelling analysis to examine the dynamic and identify the driving forces of land cover change(LCC)from 1986-2020.Information from focus group discussions and the variable ranking method were used to explain the drivers of the observed changes.The land use classification techniques multi-temporal satellite images(1986,2003 and 2020)were classified using supervised and unsupervised methods;the integration of Revised Universal Soil Loss Equation(RUSLE)model and geographic information system(GIS)for estimating the rate of soil erosion and sedimentation;the Soil and Water Assessment Tool(SWAT)for hydrological modeling;the modified ecosystem services valuation model for exploring the changes in ecosystem services were employed.The different layer of the spatiotemporal changes on the land cover(LC)were the basis for assessing the changes in soil erosion,sediment yield,hydrology and ecosystem services.The study results showed a decline in forest cover from 11.80%in 1986 to 5.90%in 2020,which indicates a loss of 49.90%of the forest cover that existed in 1986.Bare land declined from 1.15%in 1986to 0.57%in 2020.Similarly,grazing land declined from 1.52%in 1986 to 0.41%in 2020.Wetland also declined from 1.93%in 1986 to 0.31%in 2020.Conversely,during the same period,the proportions of cultivated land,built-up areas,shrubland,and water bodies have risen from 68.86%to 70.44%,from 0.03%to 1.53%,from 14.39%to 20.27%,and from 0.34%to 0.56%,respectively.Population growth and poor agricultural practices were identified as the main causes of LCC in the sub-basin.The LULC changes have also increase the average soil erosion rate from 53.2 ton/ha/year in 1986and increased to 63.6,and 64 ton/ha/year in 2003,2020,respectively.The mean sediment yields of the study area is estimated to 7.8 ton/ha/year in 1986,and later increased to 10,and 10.2 ton/ha/year in 2003,and 2020,respectively.Results revealed that the steep slope areas with crop land experience considerable soil loss,with mean soil loss increasing over all study period.During the study period(1986-2020),changes in the cultivation land,forest land,and settlement areas were the major land cover changes(LCCs)that had an effect on hydrological parameters in the Muger catchment.The findings revealed that between 1986 and 2003,the significant factors for the increment in surface runoff and the reduction in the groundwater component were the increment of cultivation land and the decline in forest and shrubland.Additionally,it was identified that the settlement was the primary factor contributing to increases in evapotranspiration(ET),surface runoff generation,and water yield.Water resources would be negatively impacted by increased surface runoff and declined base flow,particularly with regard to sedimentation and erosion in the Upper Blue Nile River basin(UBNRB).The LCCs that occurred between 1986 and 2020 reduced the average annual,wet season,and dry season stream flow.However,between 2003 and 2020,surface runoff and water yield decreased by3.71%and 0.064%,respectively,as a result of the effect of land changes on hydrological response.The LCCs occurred between 1986-2020 periods the findings revealed that there is a decline in total ESV(Ecosystem Services Value)from US$492.77 x 10~6 in 1986 to US$400.65 x 10~6 for the year 2020.The ESV lost between 1986 and 2020 period was about US$92.11 x 10~6.Results show that except food production and biological control,the contributions of other ecosystems services decreased in the study area.Among the major contributors of ESVs,food production,water regulation,erosion control,climate regulation,nutrient cycling,waste treatment and water supply representing a total of 89%,88%,86%in1986,2003 and 2020,respectively.Soil erosion and sediment transport under environmental pressure significantly contributed for the loss of ecosystem services(ES)in the sub-basin.The major shift from vegetation to non-vegetation cover in the sub basin is a direct cause of the alteration in soil erosion,sediment yield,hydrological components,and ecosystem services.These suggest an urgent need to regulate the LCCs in order to preserve the hydrological balance,stop the anticipated increase in soil erosion and sediment yield,and to reduce the expected loss of ecosystem services. |
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