Impact of drought on wastewater contaminants in an urban water supply.

The concentrations of selected wastewater contaminants, including conductivity, nitrate, and pharmaceuticals and endocrine disrupting compounds (EDCs), were monitored from 2003 to 2007 in Lake Mead, the raw (untreated) drinking water for southern Nevada. Monitoring was also conducted in two inflows to Lake Mead: the Colorado River and the wastewater-dominated Las Vegas Wash. There was a statistically significant increase in source water conductivity, nitrate, and pharmaceutical and EDC concentrations over this time period, concomitant with a statistically significant decline in the volume of Lake Mead. There was no statistically significant increase in conductivity and nitrate in the Colorado River or the Las Vegas Wash over this period, nor was there an increase in flow of the Las Vegas Wash or Colorado River. Thus, the deterioration of source drinking water quality is due to the decrease in the volume of Lake Mead which has been attributed to drought. This phenomenon may also be a harbinger of how water quality may be adversely affected by climate change as patterns of surface water flow shift and treated wastewater becomes a larger fraction of surface water flow in some areas.