FROM PERENNIAL TO NON-PERENNIAL RIVER SYSTEM: INVESTIGATING THE KEY DRIVERS OF HYDROLOGICAL FLOWS IN LRB MALAWI

Abstract

Changes in climate coupled with human activities persist to be the main drivers of hydrological response in many parts of the world. Therefore, this study investigated the key drivers in the LRB (LRB) in central Malawi. The study used the Mann Kendall Trend Test to study trends in the historical hydroclimate regime, and the Water and Snow Balance Model (WASMOD) to model flow regime changes under 10 climate and land-use change scenarios. Unsupervised image classification was used for land cover change analysis. The study also used the Double Mass Curve (DMC) to investigate the impact of climate change and human intervention on water availability. The results on climate trends revealed that there is an insignificant increase in temperature, coupled with an insignificant decrease in rainfall in the catchment. The performance of WASMOD was acceptable with a Nash Sutcliffe Coefficient (NSE) of 0.70 and coefficient determination (R 2) of 0.93 during calibration and NSE of 0.66 and R2 of 0.94 during validation. The synthetic scenarios used to perturb runoff and evapotranspiration showed that during the rainy season (Nov-March), scenarios 1 (∆T=+2, ∆P= -20%) and 2 (∆T=+2, ∆P= -10%) had a decrease in runoff consequently affecting water availability. Climate remains the main driver altering hydrological events and there is no major construction of dams in the catchment. However, human activities such as deforestation and poor agriculture practices exacerbate the climate impact on rainfall availability consequently affecting water availability in the catchment. The study, therefore, recommends the management of the catchment area through vegetative cover and forest conservation