Impact of climate and land use/ land cover change on the surface area of Lake Wamala.

Abstract

Water resources especially lakes are vital ecosystems that sustain all aspects of life. However, lake systems worldwide are extremely fragile, and many are shrinking due to changing climate and anthropogenic activities. Impacts of climate and land use changes on relatively larger lakes have been well documented but smaller lakes have been given less attention. This study objectively sought to determine trends in the lake surface area, rainfall, temperature, and the different Land use classes of Lake Wamala. The study determined the impact of climate and land use/ land cover change on the surface area of Lake Wamala. This was achieved using Landsat TM, ETM+, OLI images, rainfall, and temperature datasets for the period 1990-2020. The modified Normalised Difference Water Index (MNDWI) method was employed to detect fluctuations in the Lake surface-water area. Supervised classification was used to compute land use/cover changes. Trends in surface area, climate, and land use change were determined using the Mann-Kendall test statistic and Sen’s slope estimator. Results reveal that the lake has recorded a statistically significant increasing trend (Kendall’s Tau, τ = 0.607, p-value = 0.0008) in its surface area for the period 1990-2020. However, there was a 55.6% decrease in total lake surface area between 1990 and 1995. The trend analysis revealed a statistically significant (p-value = 0.001) increasing (Kendall’s tau = 0.456) trend in annual maximum temperatures and a statistically significant (p-value = 0.045) decreasing (Kendall’s tau = -0.256) trend in annual rainfall. Built-up areas, agricultural land, and open water increased by 317.9%, 8.38%, and 6.7% respectively while wetlands and forests decreased by 19.8% and 58.9%. The variations in lake surface area are greatly contributed by the changes in land use resulting in increased runoff and sediment yield into the lake causing the increase in lake surface area. Therefore, this study provided reliable information to researchers, scholars, and policymakers on how climate and land use change have influenced the trends in the surface area. This information will act as a basis for monitoring and management of Lake Wamala.