Nonpoint source pollution during dry and wet weather flows in an urbanized watershed

This research evaluates the quality of urban runoff, from various nonpoint sources during dry weather flows (DWF) and wet weather flows (WWF) in the Las Vegas Valley. Standard constituents in urban runoff were measured to assess the quality of urban runoff, to identify the possible sources of DWF (groundwater flows, excessive irrigation and car washing) and to determine the quality of runoff from residential areas and parking lots during WWF. DWF samples were collected from storm channels on a weekly and monthly basis. WWF samples were collected when the precipitation was at least 1mm. DWF water quality results indicated that monitoring stations were possibly influenced by flows from groundwater and over irrigation including construction activities and erosion. Car washing was a significant source of nutrients and total Fe. WWF indicate higher levels of Ortho-P, TP-P, COD, total Fe, and NH3-N in the residential area and the parking lot.