Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon

Fact Sheet 2016-3051

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The Hells Canyon Complex (HCC) is a hydroelectric project built and operated by the Idaho Power Company (IPC) that consists of three dams on the Snake River along the Oregon and Idaho border (fig. 1). The dams have resulted in the creation of Brownlee, Oxbow, and Hells Canyon Reservoirs, which have a combined storage capacity of more than 1.5 million acre-feet and span about 90 miles of the Snake River. The Snake River upstream of and through the HCC historically has been impaired by water-quality issues related to excessive contributions of nutrients, algae, sediment, and other pollutants. In addition, historical data collected since the 1960s from the Snake River and tributaries near the HCC have documented high concentrations of mercury in fish tissue and sediment (Harris and Beals, 2013). Data collected from more recent investigations within the HCC continue to indicate elevated concentrations of mercury and methylmercury in the water column, bottom sediments, and biota (Clark and Maret, 1998; Essig, 2010; Fosness and others, 2013). As a result, Brownlee and Hells Canyon Reservoirs are listed as impaired for mercury by the State of Idaho, and the Snake River from the Oregon and Idaho border through the HCC downstream to the Oregon and Washington border is listed as impaired for mercury by the State of Oregon.

Suggested Citation

Clark, G.M., Naymik, Jesse, Krabbenhoft, D.P., Eagles-Smith, C.A., Aiken, G.R., Marvin-DiPasquale, M.C., Harris, R.C., and Myers, Ralph, 2016, Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon: U.S. Geological Survey Fact Sheet 2016-3051, 6 p.,

ISSN: 2327-6932 (online)

Study Area

Table of Contents

  • Introduction
  • Mercury Cycling in the Environment
  • Mercury in the Hells Canyon Complex
  • References Cited

Additional publication details

Publication type:
Publication Subtype:
USGS Numbered Series
Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon
Series title:
Fact Sheet
Series number:
Year Published:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Idaho Water Science Center, Forest and Rangeland Ecosystem Science Center
6 p.
United States
Idaho, Oregon
Other Geospatial:
Brownlee Dam, Hells Canyon Dam, Oxbow Dam, Snake River
Online Only (Y/N):
Additional Online Files (Y/N):