Modeling runoff and sediment yield with current and future climatic conditions in Andit Tid watershed central highland of Ethiopia
Ayele, Desalegn Woldemariam
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Understanding the impacts of climate change on runoff and sediment yield enables us to invest in long-term land management strategies that will benefit both land and water users. The purposes of this study were to model runoff and sediment yield under current and projected climatic scenarios and to identify the spatiotemporal distribution of runoff and sediment yield in the Andit Tid watershed of Ethiopia. Estimation and spatial distribution of runoff and sediment yield were done using SWAT and Arc GIS 10.5 software. Geospatial data including land use map, digital elevation model, soil map, and climate data of rainfall, and minimum and maximum temperature were used. SWAT-CUP with the SUFI-2 algorithm was used to assess the sensitivity, calibration, and validation of the model. The relationship between climate variables and runoff and sediment yield was examined using correlation and regression analysis. The future runoff and sediment yield of the study watershed have been modeled using the wettest scenarios (CCCma (CRCM4)) and the driest scenarios (MPI (RCA4)) climate models. The current rate of runoff and sediment yield were estimated to be 17.9 t ha-1 yr-1 and 0.0374 m3/sec, respectively. The R2 was found to be 0.83 and 0.72 for runoff calibration and validation and 0.62 and 0.72 for sediment yield calibration and validation, respectively. The relationship between rainfall and runoff and rainfall and sediment yield were found to be significant with (r=0.88) and (r=0.86), respectively. while it was determined that there was no significant relationship between temperature and runoff or sediment yield. According to the wettest scenario, the projected runoff and sediment yield was equivalent to the current rate, they were 0.0322 m3/sec and 16.3 t ha-1, respectively. In the driest scenario, the projected runoff and sediment yield were lower than the current rate, they were 0.0147 m3/sec and 4 t ha-1, respectively. In both current and future climate conditions, northern and central regions were contributing the majority of runoff, while the northeastern, eastern, and western regions were contributing the higher sediment yield in the watershed. The majority of these watershed hotspot areas were located in cultivated land with active gullies and a slope of greater than 20%. The watershed community and decision-makers are advised to use the spatial distribution map during the planning and implementation of management solutions in the seriously affected areas.