Earth observation data from NASA’s MODIS instruments are helping to improve the accuracy and decision-making effectiveness of a widely used tool for water-quality management. SPAtially Referenced Regressions On Watershed Attributes (SPARROW) is a primary water-quality tool used by the USGS to document contaminant input sources, monitor rates of contaminant flux in streams, and determine the factors affecting contaminant transport. Current models are formulated to represent long-term average conditions. MODIS metrics like an EVI and Gross Primary Production (GPP) enhance the temporal frequency of SPARROW models from long-term to seasonal evaluations and improve our understanding of the temporal dynamics of contaminant sources and transport, thereby enhancing the USGS’s ability to produce improved water-quality assessments throughout the Nation.