Influence of Land Use and Land Cover Change on Water Quality in Lake Tana Basin, Upper Blue Nile, Northwest Ethiopia

Abstract

Lake Tana Basin, located in northwest Ethiopia, is an important ecological and hydrological system supporting diverse plant and animal life. It is the source of the Blue Nile River, an essential water resource offering multiple services to millions of people in Ethiopia, Sudan, and Egypt. However, due to changes in land use and land cover (LULC), the basin is at risk of Water quality deterioration. The study adopted a mixed-methods research design that comprised of a cross-sectional survey, ecological survey and finally desktop research that involved literature search, to investigate Land Use/Land Cover (LULC) changes and their impact on water quality parameters such as Turbidity and Chlorophyll a.  Landsat 5 thematic mapper (TM) and Landsat 8 operational land imager (OLI) were used to generate temporal LULC change for 20 years (2004 – 2024). At the same period, the surface reflectance products of MODIS Terra (MOD09A1) and measured selected water quality parameters were used to develop equations for predicting time series water quality. The equations were developed, validated and adopted to predict Turbidity and Chlorophyll a respectively.  The relationship of LULC change and the dynamics of Turbidity and Chlorophyll a concentration were analyzed by ANOVA, which indicated that the increase in Turbidity was highly influenced by the rise in Agricultural land and least influenced by the increase of Bare-land at a P-value of 0.00892 and 0.655 respectively. Similarly, the surge in chlorophyll a concentration was highly influenced by the increase in the Built-up area and least affected by the increase in Bare-land at a P-value of 0.0049 and 0.918 respectively.  The study recommends implementing sustainable LU and water management strategies to mitigate the negative impacts of LC changes, such as deforestation, increased agricultural land, and urban expansion, leading to heightened water turbidity and chlorophyll a concentration in Lake Tana over.