From forest to urban: Assessing the impact of land cover on water quality

Land use changes driven by population growth and economic development lead to water pollution, making clean water access a strategic global issue. Water quality is not only compromised by factors such as land use, seasonality, and human activities, but it is also vulnerable to climate conditions. This study explored the influence of land cover in sub-catchment and riparian areas on surface water quality, considering temporal, seasonal, and climatic variations. Ten sampling points were selected in a Brazilian populous watershed. Water quality data and semi-automatic land cover classifications were collected, providing a combined remote sensing and statistical analysis. The results indicated that increased urban development in the watershed negatively impacts water quality. Anthropogenic areas have a strong negative correlation with water quality in both sub-catchment and riparian area, with urbanized (ρ = -0.69 and ρ = -0.60; p-value <0.001) and exposed soil (ρ = -0.45 and ρ = -0.42; p-value <0.001) areas having the greatest effect. Forest cover in riparian areas is crucial for minimizing pollutant transfer to water bodies (ρ = 0.41), even in dry or rainy periods (ρ = 0.45 and ρ = 0.37, respectively). The Redundancy Analysis (RDA) indicates that urban areas negatively affect water quality with key contaminants such as organic matter, solids and Escherichia coli. This study emphasizes the challenges posed to water quality by urbanization and the importance of adaptive analysis beyond seasonal patterns, underscoring the need for effective policies and targeted conservation strategies for safeguarding water resources and ecosystem health.