Modeling climate and land use change impacts on water resources and soil erosion in the Dano catchment (Burkina Faso, West Africa)

Abstract

The study assesses the effect of climate and land use change on water resources and soil ero-sion in the Dano catchment, Burkina Faso. Field measurements and derived process under-standing are complemented by a physically based modeling approach that is also used to simu-late the impact of land use and climate change.<br /> Extensive hydro-meteorological (e. g. precipitation, discharge), pedological (e. g. texture, bulk density) and soil erosion measurements (e. g. suspended sediment load) are investigated to gain knowledge on governing hydrological and soil erosion processes. Data from erosion plot measurements suggest statistically significant differences of runoff and soil erosion between differently used plots.<br /> The data and the retrieved understanding are used to setup and drive the physically based spa-tially distributed hydrological and soil erosion model SHETRAN. Statistical performance measures (R², NSE, KGE) range between 0.66 and 0.8 for the calibration and validation of dis-charge. Achieved quality measures of suspended sediment load are lower than for hydrology but comparable to other SHETRAN studies. <br /> The impact of land use and land cover (LULC) change on water resources and soil erosion is studied by applying observed and modeled land use maps to the period 1990 – 2030. The past LULC change is studied using land use maps of the years 1990, 2000, 2007 and 2013. Based on these maps future LULC scenarios were developed for the years 2019, 2025 and 2030. Ob-served and modeled climate data cover the period 1990 – 2030. The observed past and modeled future LULC maps are used to feed SHETRAN. The isolated and combined influence of LULC and climate change is investigated. The land use investigation from 1990 to 2013 suggests a decrease of savanna at annual rates of 1.15% while cropland and settlement areas have increased. The simulations that assumed a constant climate and a changing LULC show in-creasing water yield (3.9% – 77.5%) and mainly increasing specific sediment yield (-1.4% – 115.78%). The simulations that assume constant LULC and climate as changing factor indicate increases in water yield of 24.5% to 46.7% and in sediment yield of 31.1% to 54.7%. The com-bined application of LULC and climate change signals a clear increase in water yield (20.3% – 73.4%) and specific sediment yield (24.7% to 90.1%). Actual evapotranspiration is estimated to change across all simulations by -6.8% to 3.35%.<br /> The predicted climate change signal is investigated in detail by comparing the future period 2021 – 2050 with the historical period 1971 – 2000. Representative concentration pathways (RCP) 4.5 and 8.5 of six datasets of the CORDEX framework were used to study the future change in tem-perature and precipitation. Most of the used climate models predict an increase of temperature between 0.9°C and 2.0°C. Large uncertainties among the climate models exist regarding the climate change signal of future precipitation. Some climate models predict an increase (5.9% – 36.5%) others a decreased (6.4% – 10.9%) or a mixed signal. The application of the historical and future climate data to SHETRAN shows that future changes in discharge and specific sedi-ment yield follow the predicted precipitation signal. Simulated future discharge change ranges from -43% to +207%. The future change in sediment yield is in the same order.