Abstract

Watershed hydrology is primarily affected by Land Use/Land Cover (LULC) and climate change (CC). This study assessed the hydrological response of the Mulunguzi River Basin (MRB) to the impact of LULC and climate change between 1990 and 2020. Hydro-climate trends were analyzed using the Mann-Kendall method. The hydrological responses of the Mulunguzi watershed to various LULC and CC scenarios were quantified using the SWAT model. Based on the hydro climatic analysis, it was found that the mean monthly and annual temperatures were consistently increasing by 0.004°C per month and 0.041°C per year. In addition, an increasing trend of 5.8mm per year was observed in rainfall. However, these trends were not statistically significant at a 95% confidence level. The decade of 2010-2020 experienced the highest amount of rainfall, totaling 9,529 mm, compared to the previous two decades of 1990-1999 and 2000-2009. According to the evaluation criteria, the SWAT model performance was satisfactory during calibration and validation, with respective Nash-Sutcliffe efficiency (NSE) of 0.59, coefficient of determination (R2) of 0.62, and RSR of 0.64. NSE of 0.83, R2 of 0.84, and observations standard deviation ratio(RSR) of 0.41. The SWAT results show that a reduction in the forested area of 24.04 % between 1990 and 2020 caused a 119.9% increase in surface runoff and a 17.8% decrease in base flow. With changes in rainfall and temperature, CC alone increased surface runoff, baseflow, evapotranspiration, and water yield by 152.2%, 33.6%, 19.1%, and 51.1 %, respectively. The combined impacts increased surface runoff and water yield by 303.8% and 71.2%, respectively. The study found that the combination of LULC alteration and CC led to more significant effects than that of either LULC or CC alone. These findings will provide valuable insights for effectively managing water resources, safeguarding the catchment area, and implementing climate change adaptation measures. This is critical because the water supply in Zomba City relies on the Mulunguzi catchment.

More details

School	: School of Natural and Applied Sciences
Issued Date	: 2024

Download full document