CLIMATE CHANGE IMPACTS ON THE HYDROLOGICAL PROCESSES OF DENSU RIVER BASIN (DRB) USING THE SWAT MODEL

ABSTRACT

The impact of climate change is now posing a greater threat on the hydrological cycle leading to drought and water stress in small basins. Matters of climate change have now become a primary concern to most nations due to the implication on society and humanity. The study used 17 ensemble climate model from the Coupled Model Intercompersion Project Phase 5 (CMIP5) to estimate the future climatic condition for the 2050s (2035 to 2065) under Representative Concentration Pathways (RCP) 4.5 and 8.5. The Soil and Water Assessment Tool (Arc SWAT) model was used in assessing the effect of the generated climate change on the hydrological processes (rainfall, water yield, soil water storage and evapotranspiration) in the Densu River Basin (DRB). After calibration and validation of the SWAT model, there was a strong correlation between the simulated and the observed stream discharge with a coefficient of determination (R2) of 0.84 for the calibration and 0.77 (validation). The CMIP5 estimated an annual mean increase of 2.7 oC and 1.3 oC for maximum and minimum temperature respectively and 20.1 mm in rainfall by 2050s. Simulation from ArcSWAT predicted an increase of 60% in actual evapotranspiration and 80 mm increase in soil water storage and a sharp decline of 23 mm in water yield by 2050s. The condition predicted in the future gives an indication that dry condition will occur at the DRB since increase in temperature and soil water aid increased evapotranspiration causing an acute decline in water yield which contribute to stream flow at the basin.