A Tool to Assess Land Use Impacts on Surface Water Quality: Case Study from the Guapi-Macacu River Basin in Rio de Janeiro

Impacts of human activities, mainly land use and land cover (LULC) changes, on hydrology and water quality are manifold and need to be ascertained. In order to understand and assess such impacts, water quality monitoring programs are crucial for collecting the required data. Transforming data into information is an important step, and water quality indices (WQIs) can be a useful and concise method for aggregating several parameters and measurements into a single number to facilitate problem identification and decision-making. For this study, a monitoring program was designed and implemented to measure water quality in a rural river basin in Rio de Janeiro (Guapi-Macacu). Three sub-watersheds, together with other relevant sampling points, were selected to assess the influence of the most relevant LULC classes on water quality. The monitored parameters were used to calculate the Canadian water quality index (CCME-WQI). This index was able to capture the impacts of water quality impairments such as untreated sewage and agricultural activities. The index calculation and resultant map, used to depict the spatial distribution, aim at becoming tools for practitioners and decision-makers in the basin.