Impact of land-use/land-cover dynamics on water quality in the Upper Lilongwe River basin, Malawi

摘要

Abstract The United Nations 2018 World Water Development report projected that by 2050, nearly 6 billion globe population is likely to face acute water scarcity. In Africa, about 65% of the population has no access to clean water. In Malawi, increased water pollution instigated by environmental degradation and land-use/land-cover dynamics (LULCD) is one of the major causes of clean water scarcity. The situation is worse, especially in the Malawi capital city Lilongwe. This study used 1989, 1994, 2014, and 2019 Landsat images to dissect the link between water quality variation and LULCD in the Upper Lilongwe River catchment. The water quality data were obtained from Water Quality and Environmental Management Division, Lilongwe Water Board. The LULCD results showed a decrease in forest land (46.6%), water body (25%), and grass/shrubs/bare land (11.5%). The built-up area increased by 130% while cultivated land by 35.2%. The study showed an increase in turbidity, nitrate, phosphate, sulfate, biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), electric conductivity (EC), faecal coliform, and total dissolved solids (TDS). Dissolved oxygen (DO) and pH on the other hand decreased. The LULCD (cultivated and built-up areas) correlated positively with major nutrient loading, EC, faecal coliform, TDS, BOD, COD, and TSS. The DO and pH negatively correlated with cultivated and built-up classes implying that LULCD to some extent contributed to the water pollution in the river. Therefore, proper land-use planning and catchment management are required to improve the status of water quality in the river.