Assessment of the effects of land use/cover changes on surface water quality and treatment costs in river Malaba Catchment, eastern Uganda

Abstract

Changing land use and cover (LULC) is a major contributor to water quality degradation in various regions of the world. Unfortunately, there are not enough data on how LULC change affects water quality and prices in different catchments. Therefore, the research has covered gaps left by previous research by looking at three different aspects of the River Malaba catchment: first, the extent to which land use and cover have changed, second, the impact that land use has had on water quality, and finally, the impact that water quality has had on treatment costs. Sentinal-2 images of 2015 and 2021 were downloaded and analyzed using GIS. Water samples were picked at different land use/ cover types along the river and analyzed for physical-chemical as well as bacteriological parameters, statistical tools such as ANOVA at 95% confidence interval were done to understand land use/cover influence on water quality. Costs of water treatment influenced by water quality were analyzed retrospectively using data from the National Water and Sewerage Corporation and ANOVA at a 95% confidence interval. Results indicated LULC patterns shifted radically between 2015 and 2021, with most conversions to farming. The farmlands (15.3%) and built-up (1.0%) increased over time as woodlands (-2.8), grasslands (-13.2), and wetlands (-0.2) shrunk during the study period. Land use/cover significantly affected COD (P=0.023), Electrical Conductivity (P=0.004), and Nitrate levels (P=0.004), COD was observed highest in farmland and least in woodlands, and EC and Nitrates were highest in wetlands and also least in woodlands. Seasons also showed significance across all water quality parameters except for Feacal Coliforms (P=0.233) Total Phosphates (P=0.943) and Total Iron (P=0.147). Water quality parameters significantly affected the costs of Aluminium Sulphate, high-test hypochlorite, and polymer. Costs of water treatment were high downstream than the upstream, also in the rainy season than in the dry season. These findings suggest that River Malaba basin has been subjected to LULC changes as a result of human activities, which has repercussions on the quality of water, hence increasing the cost of water treatment. This has repercussions for the livelihoods and well-being of humans, for instance by increasing the likelihood of disease and limiting the use of water to provide material items such as food. Therefore, interventions should be implemented to conserve these catchment regions. In addition, because this study was conducted over a short period of time and with limited monitoring of water quality and trends in water treatment costs, future studies should be clear in examining LULC developments over time and how they relate to water quality and treatment costs.