Mapping water quality parameters using Landsat 8 multispectral imagery, case study of Rwandan water bodies

Water plays significant role in an aquatic ecosystem, and it displays its own biotic and abiotic characteristics that indicate the status of the ecosystem. Thus, it is crucial to assess and monitor the quality of water to ensure that it remains functional. Field-based methods are used to assess and quantify key water quality indicators such as temperature, nitrogen, phosphorus, and turbidity levels. However, such methods are labour intensive, expensive, and therefore not ideal to monitor broad scale spatial and temporal variations of biotic and abiotic characteristics of water. On the other hand, remote sensing can offer information on surface water quality parameters that are not readily available when using field surveys, making it possible to continuously monitor, and quantify specific water quality parameters. The main aim of this study was to determine the spatial distribution of temperature, nitrogen, phosphorus, and turbidity in several Rwandan water bodies. Images from Landsat 8 acquired in August and November were processed according to individual band, band rationing as well as band combination. Maps were produced according to the correlation between the field based measured water parameters and the reflectance values of the Landsat 8 image. Results showed that Rwandan water bodies are more turbid and eutrophied; and warmer in the wet season compared to the dry season. These results can help Rwandan water resource management to create a geographically located database for future water surface in different water bodies.