EFFECTS OF MINE DRAINAGE IN THE UPPER COLORADO RIVER BASIN IN COLORADO
By Lori E. Apodaca, U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO, 80225
In the Upper Colorado River Basin in Colorado, many streams are affected by metals and other elements as a result of drainage from inactive mine adits, tunnels, and waste piles. The headwaters of the Uncompahgre River and the Blue River are being investigated to determine the effects of mine drainage on water quality. Stream-water samples were collected during low-flow and high-flow conditions in the 1996 water year to determine the concentrations of metals in the water column and in the suspended sediment. Bed-sediment samples also were collected to determine the regional distribution of metals in bed sediment in these rivers. Zinc tends to remain in the dissolved phase during low-flow and high-flow conditions; its concentrations ranged from less than 10 micrograms per liter to several thousand micrograms per liter. Elements (such as arsenic, cadmium, and lead) in suspended sediment and bed sediment were orders of magnitude greater than element concentrations in the water column. Concentrations of some metals in the water column, suspended sediment, and bed sediment exceeded standards and guidelines for adverse effects on aquatic life. Understanding the source and transport of metals in mining areas can help to assess remediation alternatives and to determine the effects of metals on plants, animals, and humans.
KEY TERMS: water quality, mining, surface water, metals, sediment, Colorado.