Assessment of Land Use Change Impact on Sediment Yield Using SWAT and Partial Least Squares Regression Model

Abstract

AbstractA holistic understanding of the impact of land use/land cover (LC) changes on the sedimentations is important for efficient decisions on sustainable watershed management practices. Integrated application of hydrologic modeling and partial least squares regression (PLSR) model was applied to quantify the impact of anthropogenic activities on sediment yield in the Upper Awash basin. The soil and water assessment tool (SWAT) model performed well for simulation of monthly sediment yield at four main gauged subbasins. More than 55% of the total annual sediment yield occurs in the main rainfall season (JJA) peaking in July and August. Larger areas of the basin are experiencing beyond the tolerable limit of soil loss, with more than 39% area of the basin generates >20 t/ha/year. The effect of land cover change on sediment yield is highly pronounced at the subbasins scale than the whole basin scale. Moreover, the watershed area which is under higher soil loss severity increases with the change in land cover. The PLSR correlation matrix, variable importance for the projection (VIP), and the standardized PLSR coefficient exhibited that sediment yield is highly attributed to the change in cropland and pasture land. Pasture and cropland demonstrated the higher VIP values of more than 1.0. Thus, the variables were considered more critical for the prediction of sediment yield. While shrubland and water body were relatively less important factors affecting sediment yield, which resulted in a lower VIP value of less than 0.5. It also exhibited that encroachment of cropland and urban area at the expense of forest and grassland significantly triggered sediment yield. Hence, future land use plans should consider appropriate vegetative measures and reforestation of the upland areas to reduce sedimentation. PLSR model is a useful statistical tool for assessment of the relative impacts multiple land management practices on sediment yield.KeywordsSediment yieldLand cover changeSWAT modelPLSR modelUpper Awash basin