Abstract:
Soil erosion is a major environmental challenge in Ethiopia, particularly in the Upper
Blue Nile Basin, where it contributes to severe land degradation and sediment-related
problems. Climate change worsens these problems. However, the links among soil
erosion, climate projections from the Coupled Model Intercomparison Project Phase 6
(CMIP6), and mitigation efforts remain poorly understood. This study aimed to assess
climate change impacts on soil erosion and sediment yield and to evaluate the
effectiveness of best management practices (BMPs) for future climate in the Beressa
watershed using the Soil and Water Assessment Tool (SWAT). This study is among
the first in the Upper Blue Nile Basin to integrate CMIP6 climate projections with
SWAT for evaluating future BMP performance. Both observed and bias-corrected
future climate data were used. The MRI-ESM2-0 and BCC-CSM2-MR model were
selected based on their superior performance in reproducing observed temperature and
precipitation patterns in the study region, respectively. Simulations covered the
baseline period (1995–2023), near-term period (2030–2059), and far-term period
(2060–2089), under SSP2-4.5 and SSP5-8.5 scenarios. The SWAT model
demonstrated satisfactory performance in simulating observed streamflow and
sediment yield during calibration and validation. Climate projections indicated
increasing temperature and precipitation, leading to higher soil erosion and sediment
yield, with shifts in erosion hotspot areas. Sediment yield is projected to increase under
both SSP2-4.5 (32% near-term, 27.9% far-term) and SSP5-8.5 (19.2% near-term,
45.4% far-term) compared to the baseline. BMP evaluation showed sediment-yield
reductions by terracing (48.36–50.64%), conservation agriculture (29.70–32.76%),
contour farming (19.65–20.40%), and combined use (58.20–59.86%). Variations
among sub-watersheds highlighted the influence of local watershed characteristics on
erosion response to climate change and on the effectiveness of BMPs. These findings
enhance understanding of climate-driven erosion processes and support the
development of adaptive conservation strategies
