Mercury Cycling in the Hells Canyon Complex Active
The Hells Canyon Complex (HCC) is the largest privately owned hydroelectric power complex in the United States. Upstream are millions of acres of irrigated agricultural lands and Idaho’s largest metropolitan area clustered around the state capital Boise. Downstream lie confluences with the Salmon and Clearwater Rivers, critical habitat for threatened bull trout and fall chinook salmon.
Elevated concentrations of mercury and methylmercury in the water column, bottom sediments, and biota in this reach have resulted in two of the reservoirs, Brownlee and Hells Canyon, being listed as impaired for mercury by the state of Idaho, and the entire reach being listed as impaired for mercury by the state of Oregon. The objective of this study is to determine key processes controlling mercury transport, cycling, and bioaccumulation in the Hells Canyon Reach of the Snake River.
Although concentrations of inorganic mercury entering the HCC are typical in comparison to other sites in the U.S., biogeochemical conditions in Brownlee Reservoir, and to a lesser extent, Hells Canyon Reservoir, effectively promote the conversion of some of the mercury into the more toxic and bioaccumulative form, methylmercury. Fish tissue samples regularly exceed human health criteria for methylmercury set by states, such as Oregon and Idaho, and by the U.S. Environmental Protection Agency. Exposure to too much methylmercury can affect the human nervous system and can hamper a child’s development both in the womb and in early life.
A proposal to use cold water from Brownlee Reservoir’s lower layer to cool the Snake River downstream of the HCC raised concerns about exposing sensitive aquatic species to methylmercury-rich waters from deep in the reservoir. In 2012, the Idaho Water Science Center, with help from the Wisconsin Water Science Center, confirmed elevated mercury concentrations in water column and bed sediment core samples. In 2014, Idaho Power Company, the owner and operator of the HCC, asked the USGS for help to better understand the mercury dynamics in the reservoirs and how the proposed reservoir operations might affect downstream transport of methylmercury.
The scale of the study area and the multitude of research questions required a multidisciplinary approach. USGS Idaho Water Science Center hydrologist Greg Clark, who has since retired, invited Dave Krabbenhoft, leader of the USGS Mercury Research Laboratory, to help form a study team. As Dave puts it, “When Greg Clark and I started this effort, we had the opportunity to hand pick an all-star team, and we did!” Today, that team of USGS hydrologists, biologists, ecologists, chemists, and technicians from five states works alongside colleagues from the Idaho Power Company, Reed Harris Environmental, the University of Wisconsin, and Portland State University.
The hydrologic component of the study focuses on the mass loading of mercury and methylmercury into, within, and out of the HCC to better understand the hydrologic processes promoting methylmercury production and the fate of that methylmercury as the large reservoirs stratify and destratify seasonally. This part of the research team is composed primarily of scientists from the USGS Idaho and Wisconsin Water Science Centers and the Water Mission Area (WMA).
The biological component of the study is examining how methylmercury is bioaccumulating—and biomagnifying—through the food web from phytoplankton to predator sportfish such as largemouth bass. The biological research is led by Collin Eagles-Smith of the USGS Forest and Rangeland Ecosystem Science Center.
The geochemical component of the study is seeking to pinpoint mercury sources and to peer inside the processes of mercury methylation. This portion of the study is led by Dave Krabbenhoft, by Mark Marvin-DiPasquale of the USGS Water Resources Mission Area, and by Brett Poulin of the University of California-Davis.
The team is also developing a simulation model to help understand the present-day behavior of mercury in Hells Canyon Complex, especially factors leading to increases in fish mercury levels in the complex and predict the response of the system (and downstream) to future reservoir management scenarios. Mercury cycling is being added to CE-QUAL-W2, a well-established model originally developed by the US Army Corps of Engineers and maintained by Portland State University, that simulates hydrodynamics and water quality. The model will simulate mercury in water, sediments, and the food web.
As the Hells Canyon study continues, the project serves as a prime example of how integrated USGS science can bring nationwide expertise to bear on a significant issue of regional concern. It also shows how the USGS can collaborate effectively with academia and the private sector to help solve economic, environmental, and societal challenges.
Read our 2022 information sheet USGS Science to Protect Wildlife and Human Health (PDF)
The following data are associated with this project.
Mercury Stable Isotope Measurements in Water and Suspended Particulate Matter from Snake River Tributaries in Idaho and Oregon, USA
Hydrological, Chemical, and Biological Characterization of the Snake River and Associated Tributaries and Irrigation Drains from River Mile 448 to 346, 2022
Mercury in smallmouth bass from the Snake River, USA, 2013-2022
Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019
Chemical characterization of water and suspended sediment of the Snake River and Hells Canyon Complex (Idaho, Oregon) (ver. 3.0, November 2023)
Biogeochemical Data for Mercury and other Constituents in Surface Sediment and Deep Cores from the Hells Canyon Reservoir Complex, Idaho and Oregon 2014-2018
The following publications are associated with this project.
Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system
Mercury sources and budget for the Snake River above a hydroelectric reservoir complex
Metabolically diverse microorganisms mediate methylmercury formation under nitrate-reducing conditions in a dynamic hydroelectric reservoir
In-reservoir physical processes modulate aqueous and biological methylmercury export from a seasonally anoxic reservoir
Seasonal dynamics and interannual variability in mercury concentrations and loads through a three-reservoir complex
Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon
Archive of digital chirp subbottom profile data collected during USGS Cruise 13GFP01, Brownlee Dam and Hells Canyon Reservoir, Idaho and Oregon, 2013
Seismic profile analysis of sediment deposits in Brownlee and Hells Canyon Reservoirs near Cambridge, Idaho
Water column and bed-sediment core samples collected from Brownlee Reservoir near Oxbow, Oregon, 2012
These news items are related to this study.
Below are partners associated with this project.
- Overview
The Hells Canyon Complex (HCC) is the largest privately owned hydroelectric power complex in the United States. Upstream are millions of acres of irrigated agricultural lands and Idaho’s largest metropolitan area clustered around the state capital Boise. Downstream lie confluences with the Salmon and Clearwater Rivers, critical habitat for threatened bull trout and fall chinook salmon.
Elevated concentrations of mercury and methylmercury in the water column, bottom sediments, and biota in this reach have resulted in two of the reservoirs, Brownlee and Hells Canyon, being listed as impaired for mercury by the state of Idaho, and the entire reach being listed as impaired for mercury by the state of Oregon. The objective of this study is to determine key processes controlling mercury transport, cycling, and bioaccumulation in the Hells Canyon Reach of the Snake River.
Although concentrations of inorganic mercury entering the HCC are typical in comparison to other sites in the U.S., biogeochemical conditions in Brownlee Reservoir, and to a lesser extent, Hells Canyon Reservoir, effectively promote the conversion of some of the mercury into the more toxic and bioaccumulative form, methylmercury. Fish tissue samples regularly exceed human health criteria for methylmercury set by states, such as Oregon and Idaho, and by the U.S. Environmental Protection Agency. Exposure to too much methylmercury can affect the human nervous system and can hamper a child’s development both in the womb and in early life.
A proposal to use cold water from Brownlee Reservoir’s lower layer to cool the Snake River downstream of the HCC raised concerns about exposing sensitive aquatic species to methylmercury-rich waters from deep in the reservoir. In 2012, the Idaho Water Science Center, with help from the Wisconsin Water Science Center, confirmed elevated mercury concentrations in water column and bed sediment core samples. In 2014, Idaho Power Company, the owner and operator of the HCC, asked the USGS for help to better understand the mercury dynamics in the reservoirs and how the proposed reservoir operations might affect downstream transport of methylmercury.
The scale of the study area and the multitude of research questions required a multidisciplinary approach. USGS Idaho Water Science Center hydrologist Greg Clark, who has since retired, invited Dave Krabbenhoft, leader of the USGS Mercury Research Laboratory, to help form a study team. As Dave puts it, “When Greg Clark and I started this effort, we had the opportunity to hand pick an all-star team, and we did!” Today, that team of USGS hydrologists, biologists, ecologists, chemists, and technicians from five states works alongside colleagues from the Idaho Power Company, Reed Harris Environmental, the University of Wisconsin, and Portland State University.
The hydrologic component of the study focuses on the mass loading of mercury and methylmercury into, within, and out of the HCC to better understand the hydrologic processes promoting methylmercury production and the fate of that methylmercury as the large reservoirs stratify and destratify seasonally. This part of the research team is composed primarily of scientists from the USGS Idaho and Wisconsin Water Science Centers and the Water Mission Area (WMA).
The biological component of the study is examining how methylmercury is bioaccumulating—and biomagnifying—through the food web from phytoplankton to predator sportfish such as largemouth bass. The biological research is led by Collin Eagles-Smith of the USGS Forest and Rangeland Ecosystem Science Center.
The geochemical component of the study is seeking to pinpoint mercury sources and to peer inside the processes of mercury methylation. This portion of the study is led by Dave Krabbenhoft, by Mark Marvin-DiPasquale of the USGS Water Resources Mission Area, and by Brett Poulin of the University of California-Davis.
The team is also developing a simulation model to help understand the present-day behavior of mercury in Hells Canyon Complex, especially factors leading to increases in fish mercury levels in the complex and predict the response of the system (and downstream) to future reservoir management scenarios. Mercury cycling is being added to CE-QUAL-W2, a well-established model originally developed by the US Army Corps of Engineers and maintained by Portland State University, that simulates hydrodynamics and water quality. The model will simulate mercury in water, sediments, and the food web.
As the Hells Canyon study continues, the project serves as a prime example of how integrated USGS science can bring nationwide expertise to bear on a significant issue of regional concern. It also shows how the USGS can collaborate effectively with academia and the private sector to help solve economic, environmental, and societal challenges.
Read our 2022 information sheet USGS Science to Protect Wildlife and Human Health (PDF)
- Data
The following data are associated with this project.
Mercury Stable Isotope Measurements in Water and Suspended Particulate Matter from Snake River Tributaries in Idaho and Oregon, USA
This study was designed to examine mercury (Hg) stable isotope values in filtered water and suspended particulate matter from tributaries to the Snake River located in Oregon and Idaho. Water samples were collected from 21 tributary sites representing a range of watershed land use types (e.g., agriculture, forest, etc.) within the Snake River Basin. In 2018, water samples were collected at tributaHydrological, Chemical, and Biological Characterization of the Snake River and Associated Tributaries and Irrigation Drains from River Mile 448 to 346, 2022
This dataset includes field hydrologic measurements and laboratory analyses of surface and pore waters, sediments, benthic plants/biofilms, and biota along the Middle Snake River upgradient of the Hells Canyon Complex. The study region for this work focuses on a section of the Snake River heavily utilized for agriculture, with complex systems of irrigation diversion and return drainage, spanning 1Mercury in smallmouth bass from the Snake River, USA, 2013-2022
Comma-separated values (.csv) file containing data related to mercury in smallmouth bass (Micropterus dolomieu) collected from the Snake River, USA.Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019
This dataset describes biomass and methylmercury concentrations in zooplankton, other invertebrates, fish, and coarse and fine detritus samples collected at the outflow locations of Brownlee and Oxbow Reservoirs in the Snake River Hells Canyon Complex. Based on the sampling locations, the sampled materials were presumed to have flowed through the dam turbines or over the spillway, thereby represenChemical characterization of water and suspended sediment of the Snake River and Hells Canyon Complex (Idaho, Oregon) (ver. 3.0, November 2023)
This dataset includes laboratory analyses of surface water samples and sediment trap material collected from (1) locations upstream, downstream, and within the Hells Canyon Complex (Idaho, Oregon) of the Snake River, (2) tributaries of the Snake River, and (3) two reservoirs near Boise, Idaho, from 2014 to 2021. The study area spans approximately 232 river miles of the Snake River and includes: twBiogeochemical Data for Mercury and other Constituents in Surface Sediment and Deep Cores from the Hells Canyon Reservoir Complex, Idaho and Oregon 2014-2018
The Hells Canyon Complex (HCC) is comprised of a series of three consecutive reservoirs (Brownlee, Oxbow, and Hells Canyon) along a 145 km reach of the Snake River bordered by Idaho to the east and Oregon to the west. Due to concerns regarding mercury (Hg) contamination within the HCC, in cooperation with Idaho Power Company, the U.S. Geological Survey has been leading an investigation into the so - Publications
The following publications are associated with this project.
Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system
Impoundment is among the most common hydrologic alterations with impacts on aquatic ecosystems that can include effects on mercury (Hg) cycling. However, landscape-scale differences in Hg bioaccumulation between reservoirs and other habitats are not well characterized nor are the processes driving these differences. We examined total Hg (THg) concentrations of Smallmouth Bass (Micropterus dolomieuAuthorsJames Willacker, Collin Eagles-Smith, Jim Chandler, Jesse Naymik, Ralph Myers, David P. KrabbenhoftMercury sources and budget for the Snake River above a hydroelectric reservoir complex
Understanding sources of mercury (Hg) and methylmercury (MeHg) to a water body is critical for management but is often complicated by poorly characterized Hg inputs and in situ processes, such as inorganic Hg methylation. In this study, we determined inorganic Hg and MeHg concentrations and loads (filter-passing and particulate fractions) for a semi-arid 164-kilometer stretch of the Snake River abAuthorsAustin K. Baldwin, Sarah E. Janssen, Michael T. Tate, Brett Poulin, Alysa Muir Yoder, Jesse Naymik, Christopher F. Larsen, Charles Hoovestol, David P. KrabbenhoftMetabolically diverse microorganisms mediate methylmercury formation under nitrate-reducing conditions in a dynamic hydroelectric reservoir
Brownlee Reservoir is a mercury (Hg)-impaired hydroelectric reservoir that exhibits dynamic hydrological and geochemical conditions and is located within the Hells Canyon Complex in Idaho, USA. Methylmercury (MeHg) contamination in fish is a concern in the reservoir. While MeHg production has historically been attributed to sulfate-reducing bacteria and methanogenic archaea, microorganisms carryinAuthorsBenjamin D. Peterson, Brett A. Poulin, David P. Krabbenhoft, Michael T. Tate, Austin K. Baldwin, Jesse Naymik, Nick Gastelecutto, Katherine D. McMahonIn-reservoir physical processes modulate aqueous and biological methylmercury export from a seasonally anoxic reservoir
Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of mercury in aquatic food webs. Once formed within a reservoir, the timing and magnitude of the biological uptake of MeHg and the relative importance of MeHg export in water versus biological compartments remain poorly understood. WAuthorsAustin K. Baldwin, Collin Eagles-Smith, James Willacker, Brett Poulin, David P. Krabbenhoft, Jesse Naymik, Michael T. Tate, Dain Bates, Nick Gastelecutto, Charles Hoovestol, Christopher F. Larsen, Alysa Muir Yoder, James A. Chandler, Ralph MyersSeasonal dynamics and interannual variability in mercury concentrations and loads through a three-reservoir complex
The Hells Canyon Complex (HCC) along the Snake River (Idaho-Oregon border, USA) encompasses three successive reservoirs that seasonally stratify, creating anoxic conditions in the hypolimnion that promote methylmercury (MeHg) production. This study quantified seasonal dynamics and interannual variability in mercury concentrations (inorganic divalent mercury (IHg) and MeHg) and loads at four reservAuthorsAustin K. Baldwin, Brett Poulin, Jesse Naymik, Charles Hoovestol, Gregory M. Clark, David P. KrabbenhoftMercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon
Introduction 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 milesAuthorsGregory M. Clark, Jesse Naymik, David P. Krabbenhoft, Collin A. Eagles-Smith, George R. Aiken, Mark C. Marvin-DiPasquale, Reed C. Harris, Ralph MyersArchive of digital chirp subbottom profile data collected during USGS Cruise 13GFP01, Brownlee Dam and Hells Canyon Reservoir, Idaho and Oregon, 2013
From March 16 - 31, 2013, the U.S. Geological Survey in cooperation with the Idaho Power Company conducted a geophysical survey to investigate sediment deposits and long-term sediment transport within the Snake River from Brownlee Dam to Hells Canyon Reservoir, along the Idaho and Oregon border; this effort will help the USGS to better understand geologic processes. This report serves as an archivAuthorsArnell S. Forde, Shawn V. Dadisman, James G. Flocks, Ryan L. Fosness, Chris Welcker, Kyle W. KelsoSeismic profile analysis of sediment deposits in Brownlee and Hells Canyon Reservoirs near Cambridge, Idaho
The U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center, in cooperation with the USGS Idaho Water Science Center and the Idaho Power Company, collected high-resolution seismic reflection data in the Brownlee and Hells Canyon Reservoirs, in March of 2013.These reservoirs are located along the Snake River, and were constructed in 1958 (Brownlee) and 1967 (Hells Canyon). ThAuthorsJames Flocks, Kyle Kelso, Ryan Fosness, Chris WelckerWater column and bed-sediment core samples collected from Brownlee Reservoir near Oxbow, Oregon, 2012
The U.S. Geological Survey, in cooperation with Idaho Power Company, collected water-column and bed-sediment core samples from eight sites in Brownlee Reservoir near Oxbow, Oregon, during May 5–7, 2012. Water-column and bed-sediment core samples were collected at each of the eight sites and analyzed for total mercury and methylmercury. Additional bed-sediment core samples, collected from three ofAuthorsRyan L. Fosness, Jesse Naymik, Candice B. Hopkins, John F. DeWild - News
These news items are related to this study.
- Partners
Below are partners associated with this project.