Land use/land cover change impact on streamflow using Arc-SWAT model, in case of Fetam watershed, Abbay Basin, Ethiopia

Changes in Land Use Land Cover (LULC) are currently one of the greatest pressing issues facing the watershed, its hydrological properties of soil, and water management in catchment areas. One of the most important elements impacting streamflow in watersheds is LULC change. The main objective of this study was to evaluate the effect and future predication of LULC change on streamflow of the Fetam watershed by using Cellular Automata (CA)-Markov in IDRISI software. To analyze the impact of land use/cover change on streamflow, the Soil and Water Assessment Tool (SWAT) calibration and validation model was used. LULC map was developed by using Cellular Automata (CA)-Markov in IDRISI software, and the coverage of LULCs was including parameters of cropland, vegetation, grassland, Built-up area/Urban and water body. The findings of this study showed that the major challenges of land use/cove changes were rapid population increase, farming, and industrial activity. During the study period (2000-2020), most portions of the water body, vegetation, and grassland were changed into cropland and constructed by building. Cropland and construction areas increased by 15% and 46.95%, respectively, whereas water bodies, vegetation, and grassland decreased by 62.7%, 70.02%, and 38.1%, respectively. According to the forecasted results for the period of 2030-2040, cropland and built-up areas are increased, while vegetation, grassland, and water bodies were decreased. The SWAT model's calibration and validation performance was evaluated using the streamflow of the most sensitive parameters. For the years 2000-2004, and 2005-2012, the models were calibrated and validated, and the results showed good agreement between observed and simulated streamflow, with NSE and R-2 values of 0.88 and 0.72 and 0.9 and 0.85, respectively. The results of this study indicated that the seasonal streamflow was decreased from 2000 to 2010 and 2010-2020 years during the dry and rainy seasons. In general, the impacts of land use/cover change on streamflow are significant considerations for planning and implementing water resource projects. In order to address the risks, effective land-use planning and climate-resilient water management strategies will be improved.