SOIL LOSS RISK ASSESSMENT UNDER CLIMATE CHANGE AND MANAGEMENT PRACTICES: A CASE OF NERI WATERSHED, OMO-GIBE BASIN, SOUTHWESTERN ETHIOPIA

Abstract

Soil erosion is one of the biggest global environmental problems resulting in both on-site and off site effects. Climate change is expected to affect soil erosion based on a variety of factors, including a direct impact on soil loss by increasing precipitation amounts and erosive power. Neri watershed was chosen for this study. The objective of study is to assess soil loss risk under climate change and anticipated management practices. Revised Universal Soil Loss Equation model was applied by integrating bio physical and remote sensing data. Model parameters were computed from available data. Three Representative concentration Pathway scenarios (RCP2.6, RCP4.5 and RCP8.5) and management practices considered for estimation of annual soil loss rates. The resultant annual soil loss map under baseline condition shows the mean and total of 9.955t/ha/yr- 1 and 0.46m t/yr respectively. Estimates suggest that out of the total (46546 ha), about 32.7% % of the total area exceeded the tolerable limit and 67.3%% of the total area were below tolerable rate. The future soil loss rates are higher than the baseline period if no management actions are taken. Under no- management action scenario, the predicted the incremental rate of soil loss from (21.95%) for RCP8.5 (2051-2080) followed by 4.57% RCP4.5 (2021-2050) to insignificant decline (-0.75%) for RCP2.6 (2021-2050) compared to baseline period whereas, the other two predicted reduction. Moreover, inclusion of comprehensive management may result much higher reduction in soil loss over baseline and future condition of no action. The maximum reduction by 41.2% of its soil loss due to climate change is predicted RCP8.5 (2051-2080). The resultant soil loss map of baseline period was used in prioritization of intervention areas based on soil loss tolerance. Among eleven (11) sub-watersheds, eight and ten administrative kebeles out of nineteen are above the tolerable limit. However, watershed as planning unit, taking the proportion of soil loss to area, seven sub watersheds were identified as areas of intervention. To ensure sustainable resource use, management practice like contour cropping system complimented with terraces in agricultural fields and with giving special attention through strong policy measures to climate change, erosion minimization in non-agricultural land use classes were needed. Finaly, the study indicates a need for further study to understand the land suitability that consider the climate change