Impacts of Climate Change on Water Resources in Malawi

Surface temperatures in Africa have increased by at least 0.5°C over the past century, and the continent is projected to warm faster than the rest of the globe in the 21st century. Climate change has also affected the hydrological cycle, altering precipitation variabilities, soil moisture, and surface runoff. The African continent is considered one of the most vulnerable regions to climate change due to its extensive reliance on rainfed agriculture and low adaptive capacity. Malawi, a landlocked country in southeastern Africa, is highly dependent on rainfed subsistence farming, with more than 90% of the population relying on this practice. The country's food security is also a major concern, with 60% of the population being food insecure. Climate change is projected to intensify the water cycle in the future, increasing the uncertainty in crop water availability. The soil moisture component is vital for agricultural production, and its impacts on water resources need to be assessed to design and implement proper adaptation measures. A comprehensive study was conducted to assess the impacts of climate change on water resource components in Malawi. The study used downscaled general circulation model (GCM) outputs to drive the soil and water assessment tool (SWAT) model. The SWAT model is a widely used watershed and river basin-scale model that simulates the impact of management practices on water, sediment, and agrochemical yields in ungauged watersheds. The model is physically based and spatially distributed, running on a daily time step and capable of continuous simulation over long periods of time. The study area consisted of nine watersheds in Malawi, with a total area of approximately 118,500 km2. The watersheds were divided into northern and southern regions, with the northern region being more prone to floods and the southern region being more prone to droughts. The SWAT model was used to simulate the impacts of climate change on potential and actual evapotranspiration, surface runoff, water yield, and soil moisture by the mid-21st century. The results of the study showed a significant impact of climate change on water resources in Malawi. At the country level, the results showed a -5.4% to 24.6% change in annual rainfall, a -5.0% to 3.1% change in annual evapotranspiration, and a -7.5% to over 50% change in annual surface runoff and water yield. At the watershed level, the results showed an increase in annual rainfall and evapotranspiration in the north and a gradual decline towards the south. The subbasin-level analysis showed a large probability of increase in the annual precipitation, surface runoff, water yield, and soil moisture, especially in the north. The study's findings are expected to help stakeholders and watershed managers make informed decisions and formulate targeted adaptation strategies to minimize the negative impacts of climate change in Malawi. The results of this study can also be used to assess the impacts of climate change on water resources in other African countries, providing valuable information for policymakers and water managers.