ASSESSING THE IMPACT OF CLIMATE CHANGE AND LAND USE LAND COVER CHANGE ON SOIL EROSION IN SHEFFE WATERSHED, WESTERN PART OF LAKE ABAYA

Abstract

Soil erosion is accelerated by human activities and it poses serious environmental and economic risk through worldwide. Climate and land use land cover change can influence susceptibility to erosion and consequently land degradation. This study was undertaken to study climate and LULC change impact on soil erosion potential in the Sheffe watershed through assessing the impact of climate change on the R factor, the effect of LULC change on C and P factor and the impact of these factors on soil losses in the study area by using RUSLE model. CORDEX RCM from the period of (2041-2070) under medium emission scenarios of RCP4.5 and RCP8.5 were used for future climate projection. The land use land cover change analyses were performed using ERDAS Imagine 2016. Land use land cover changes for three different years of 1986, 2000 and 2020 land use scenarios were generated. During the study period most parts of the Forest land and shrub land were changed to cultivated land and grass land. An increase of cultivated land by 15.25% and grass land by 2.02% over 36 years period (1986 – 2020) resulted an increase of Annual Soil Loss by +110328.1 (t yr-1) and +5729.808(t yr-1) respectively. The projected (2041–2070) R factor based on CORDEX datasets under RCP 4.5 and RCP 8.5 model showed both increase trends over the catchment. Due to the increase in rainfall, the value of average rainfall erosivity factor changed from 528.7 MJ mm ha−1h−1 year −1 in base line period to 544.2 MJ mm ha−1h−1year−1in RCP 4.5 and 558.03 MJ mm ha−1h−1year−1 in RCP 8.5 future period scenarios. The rainfall erosivity showed an increasing trend by 2.9%, under the RCP 4.5 and 5.5%, under the RCP 8.5 scenario due to this the projected soil erosion result showed that under the RCP 4.5 scenario, the average annual soil loss increased by 0.4 tons ha−1year−1 (1.2%), in the period of 2041-2070s, as compared with the base period (1986-2020). Likewise, under the RCP 8.5 scenario, the average annual soil loss increased by 0.9 t ha−1year−1 (4.0%), during the period of 2041 2070 compared with the base period. The average annual soil loss rate estimated for the entire watershed was 22.7 tons ha−1year−1 in RCP 4.5 scenario and 23.2 in RCP 8.5 scenario. In fact, the results suggest that the amount of mean annual precipitation in the catchment is predicted to have an increasing trend, causing a higher R factor corresponding to high Soil erosion.