Withdrawals of large volumes of water from streams in the basin for agricultural and urban use result in less water to dilute contaminants in streams. Alteration of the natural flow regime has degraded native aquatic habitat along streams. Reuse of surface and ground water for irrigation has resulted in increased salinity in the lower South Platte River and surrounding alluvial aquifer.
High salinity can be detrimental to irrigation and drinking-water supplies.
High concentrations of uranium and radon in the South Platte River Basin are directly related to local geology. Median uranium concentrations were highest in shallow ground water from the alluvial aquifer in the plains, whereas, median radon concentrations were highest in ground water from the crystalline aquifer in the forested mountain areas. However, the potential for degraded ground-water quality is likely to increase as mountain communities grow. Surface-water quality generally was better in forested mountain areas than in other land uses. Development in mountain drainages correlated with elevated concentrations of dissolved solids, suspended sediment, and nutrients in surface water.