Characterization of Urban Runoff from Grange Hall Creek at Northglenn, Adams County, Colorado

摘要

Quality and quantity of urban runoff in upper Grange Hall Creek basin was studied during 1978-79. For selected storms a median of 54.5 percent of rainfall resulted in runoff in the urbanized upper subbasin and 24 percent in the entire basin; runoff volumes increased almost linearly with rainfall. Peak flows from thunderstorms also increased with rainfall but responses were two-phase linear. No simple relationships were observed between rainfall and runoff. In dry-weather flow, specific-conductance values in the creek ranged from 500 to 3,930 micromhos per centimeter and in the unnamed southern tributary ranged from 430 to 2,500. Specific conductances tended to be greater in winter and less in summer. Storm runoff decreased specific conductance, except during snowmelt runoff when streets were sanded with up to 7-percent salt. Lead, manganese, cadmium, chromium, and copper concentrations exceeded Colorado water-quality standards. During storm runoff, major ion concentrations usually decreased with increased flow.