Lack of adequate water flowing in the rivers, particularly in the summertime, is one of the primary constraints on maintaining the health of aquatic habitats and aquatic life. Daily streamflow measured by the U.S. Geological Survey at established stream gaging stations on the Sudbury River (in Framingham), Assabet River (in Maynard), and Concord River (in Lowell) is used to compute daily scores from May through September. The summer streamflow scores are calculated based on a comparison with statistics calculated from local comparable streams: once-in-ten-year low flows (7Q10), median August flows, the minimum level of water for fish to pass (R2Cross and Wetted Perimeter), and long-term flows at unaltered streams (Tennant method). These daily scores are averaged to compute seasonal and 5-year scores.