Relationship between land use and water quality in a tropical urban catchment of the Congo Basin: A case study of N'Djili River catchment

This study focuses on N'Djili River catchment, a vital water source in Kinshasa which undergoes anthropogenic pressure and land use changes. The lower course of the river is particularly affected by uncontrolled urbanization, informal settlements, improper waste management practices, and vegetation degradation. The aim of this study is to determine the relationship between land use and river water quality in this catchment. Water samples were collected for physico-chemical and bacteriological analysis from 10 sampling sites along the river course. Land use categories were determined using Sentinel-2 land cover imageries and buffer scaling techniques. A redundancy analysis (RDA) was conducted to determine the relationship between land use categories and water quality variables. The laboratory analysis revealed physical, chemical, and biological pollution of the river waters. The RDA results showed that 70% of water quality parameters were explained by the studied land use categories. The urbanized area was the most significant explanatory variable at all buffer scales, negatively impacting water quality parameters. Conversely, trees and range lands had a positive impact on water quality. The study concludes that further research is needed to assess the extent of water pollution and develop integrated management strategies for minimizing pollution in this catchment.