By Jeffrey R. Deacon and Nancy E. Driver, U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO, 80225

Abstract

Natural and human factors have affected water quality and biological communities in streams of the Upper Colorado River Basin in Colorado. Bed-sediment and fish-tissue samples were collected in fall 1995 and 1996 to determine the occurrence and distribution of selected trace elements in the basin. Thirty-six sites were sampled for trace elements in bed sediment, and fourteen of these sites were sampled for trace elements in fish tissue. In mining areas of the basin, bed-sediment concentrations of trace elements, such as arsenic, cadmium, copper, lead, and zinc, exceeded current Canadian guidelines for severe effect levels (SEL) on sediment-dwelling organisms. Fish-tissue concentrations for these elements also were high in streams that drain mined areas. Bed-sediment concentrations of several trace elements in areas of urban and mixed land uses and at background sites exceeded the concentrations for the lowest effect level (LEL) on sediment-dwelling organisms. Trace-element concentrations in fish tissue were mid-range compared to all trace-element concentrations for these same land-use categories. High concentrations at background sites indicate that natural geologic conditions can affect trace-element concentrations. Concentrations of trace elements at agricultural sites were low compared to other land-use settings.

KEY TERMS: water quality; trace elements; bed sediment; fish tissue; Colorado

¹Hydrologist, U.S. Geological Survey, Water Resources Division, Colorado District, MS 415, Box 25046, Denver Federal Center, Lakewood, Colorado, 80225-0046, Phone: 303-236-2101 ext. 222, Fax: 303-236-4912, E-mail: jrdeacon@usgs.gov, nedriver@usgs.gov