Evaluating long-term impacts of land use/land cover changes on pollution loads at a catchment scale

The objective of this study was to investigate the long-term effects of anthropogenic LULC change on NPS pollution loads in a highly human-dominated catchment, in central Ethiopia. In the study, hydrologic modeling was used to estimate the NPS parameters from multispectral Landsat images, multivariate statistical techniques were then used to extract major LULC types that explain the variances of pollution loads between 1981 and 2020. The results demonstrated that there were human-induced LULC changes, as the built-up area and agricultural landscapes are rising (186.4 and 5.8%, respectively), and shrub and forest lands are decreasing (67.1 and 41%, respectively). As a result of these changes, the concentrations of nitrate (NO3), total P, total N, organic N, and organic P loads were increased by 69.41, 19.83, 18.45, 18.88, and 24.05%, respectively. Reductions in natural vegetation, as well as agriculture intensification, are the major contributors to the NPS pollutant losses to surface water sources. The result also revealed that pollution nutrients are strongly related to deforestation and agricultural land expansion. Proper adaptation strategies should be implemented to minimize the negative impact of LULC changes in the area.