Analyzing the impacts of watershed management interventions and scenarios on soil erosion reduction using InVEST model in Yezat watershed, North West Ethiopia

Abstract

ABSTRACT Land degradation is a serious problem for Ethiopia's productive capacity for land resources. To reverse these environmental dynamics, slow down soil degradation, and raise smallholder farmers’ agricultural yields, watershed management interventions have been implemented in Ethiopia since the 1980s. Thus, this study was aimed at assessing the effects of watershed management interventions on soil erosion reduction by using the InVEST model in the Yezat watershed, north-west Ethiopia. The modified ecosystem services valuation model (InVEST) was employed to evaluate soil loss reduction in response to watershed management interventions. Different watershed management intervention scenarios (baseline scenarios, afforestation scenarios, soil/stone bund scenarios, and integrated scenarios) were also applied to evaluate the effectiveness of watershed management interventions on soil loss reduction. The result of the study indicated that a high amount of mean annual soil loss (111 tons ha− 1 year−1) was observed in 2000 in the study area due to the expansion of cultivated land and built-up area at the expense of forest, shrubland, and grassland. However, the mean annual soil loss decreased from 111 tons per year in 2000 to 79 tons per year in 2021 in the study area due to different watershed management interventions. Additionally, at the baseline scenario, the estimated mean annual soil loss of the watershed was 111 tons ha-1 yr-1. Conversely, it was reduced to 49.3 ton ha-1 yr-1 in the reforestation scenario, 16.49 ton ha-1 yr-1 in the soil bund scenario, and 8.26 ton ha-1 yr-1 in the integrated scenario. The watershed covered by the very severe soil erosion severity class was reduced in all watershed management intervention scenarios. Among others, the highest soil erosion reduction was observed in the integrated (bio-physical) scenarios of watershed management interventions. Therefore, watershed management interventions and scenarios were the best mechanisms for soil loss reduction.