There are complex issues that surround hydroelectricity, as with any other form of energy generation. Finding answers about hydro’s role in the Northwest’s communities and environment can be a challenge. While there is always new research and information being available, we compiled some of the most frequently asked questions and searched for answers backed by analysts, experts, and scientists as part of our commitment to science-based solutions.

Did the lower Snake River dams cause Snake River Chinook and sockeye to become threatened?2020-02-24T22:42:58+00:00

After the last federal dam on the Snake River was completed in 1975, adult salmon returns dwindled, many people believed it must be the fault of the dams. However, during the same timeframe, ocean conditions dramatically shifted from cooler-than-normal temperatures to warmer-than-normal temperatures. This type of shift is a leading indicator of reduced adult salmon returns.

University of Washington – PDO Index
Kintama Research – The coast-wide collapse in marine survival of west coast Chinook and steelhead: slow-moving catastrophe or deeper failure?
NOAA Northwest Fisheries Science Center – Outlook for Adult Returns
SalmonRecovery.gov – Citizens Guide

Who uses hydropower?2020-02-24T21:51:57+00:00

Almost every electric utility customer in the Northwest uses at least some amount of hydropower, since it produces roughly half of the region’s electricity. The Bonneville Power Administration markets most of the most hydropower in the Northwest. BPA’s customers are mostly not-for-profit organizations, like cooperatives, municipalities, and public utilities. Generating clean, affordable energy is important to these organizations. They also aid in protecting cities and homes from flooding, providing irrigation for farms, enabling low-carbon transportation in the form of barging, allowing for recreation, and aiding in fish passage.

NWPCC – BPA Electricity
NWPCC – Dam History

Is hydropower an important part of our clean energy future?2020-02-24T22:31:18+00:00

Hydropower is essential to our region’s bold clean energy goals. The State of Washington just passed Senate Bill 5116 into law. The law commits the state to a path for no coal generation by 2025 and 100% clean energy by 2045. Washington recognizes hydropower as a critical source of generation in order to meet this goal.

Similarly, Oregon is contemplating its own climate action. The city of Portland set a 100% carbon-free goal within its borders, and individual utilities in the Northwest are embarking on similar efforts.

Hydropower is critical to the region’s ability to meet these goals because it is carbon-free and because of its energy storage capabilities. Dams store energy in the form of the water built up behind the dams. When the water is released through turbines, electricity is generated. This ability to store and quickly release energy allows hydropower to fill in the gaps for intermittent resources, like wind and solar power, which balances the grid.

WA Senate Bill 5116

Are Southern Resident orcas being harmed by the existence of the lower Snake River dams?2020-02-24T22:37:54+00:00

Southern Resident orcas spend most of their time in the coastal inland waters of the Salish Sea. As a result, a NOAA Fisheries analysis showed that Chinook from the rivers that feed into Salish Sea—not the Columbia or Snake rivers which drain directly into the Pacific Ocean—are the top priority salmon stock for Southern Resident orcas. While the Columbia and Snake rivers saw a record number of adult Chinook salmon returns this past decade, Chinook populations critical for orcas did not rebound. Biologists have indicated that due to geography and timing, Snake River salmon are not the “key limiting resource or prey” for Southern Resident Orcas.

Scientists point to a loss of habitat and a population explosion of seals and sea lions in the as contributing factors to the struggles of these the salmon that orcas feed on. Researches also identified the measurable amounts of prescription and illicit drugs and other chemicals found in Salish Sea salmon populations as cause for concern.

NOAA Fisheries found that the hatchery Chinook in the Columbia and Snake river basins more than compensate for fish lost as a result of dams in terms of availability for orca whales.

NOAA Fisheries – Southern Resident Killer & West Coast Chinook Salmon
Encyclopedia of Puget Sound – Study says predators may play major role in chinook salmon declines
Protecttheharvest.com – news
OPB, “To Save Orcas, Removing Snake River Dams May Not Be The Answer, Feds

Seattle Times, “Drugs found in Puget Sound salmon from tainted wastewater”
Defenders of Wildlife – CONNECTING THE DOTS: Orcas, Salmon, and Toxic Chemicals in the Salish Sea”
CBC, “How toxic food and toxic water could be killing the killer whales”
King 5, “Will cutting salmon out of our diets save the Puget Sound orcas?”
NOAA Northwest Fisheries Science Center – Technical Memo

Are Northwest dams a source of methane gas?2020-02-24T21:54:52+00:00

Northwest dams and reservoirs do not create significant methane emissions.

US Army Corps of Engineers – Response to Methane Study

Are dams slowing down juvenile travel times on the lower Snake and lower Columbia rivers?2020-02-24T22:11:00+00:00

Data show that juvenile salmon typically migrate from the Lower Granite Dam located near the Idaho-Washington border through the Bonneville Dam near Portland, Oregon in approximately two weeks. This is only a few days longer than their migration without the dams.

University of Washington – Columbia Basin Research – Data Access in Real Time

Are fewer salmon returning to dammed rivers compared to free-flowing rivers?2020-02-24T22:44:51+00:00

Nearly all rivers along the entire North Pacific Coast—from southeast Alaska to southern Oregon—are experiencing similar or worse trends in Chinook salmon returns when compared to the lower Columbia and lower Snake rivers. This applies to coastal inland rivers in British Columbia and the Puget Sound as well. These poor returns are being observed in rivers with dams and without dams, and even includes rivers with nearly pristine habitat.

(Chinook, sockeye, and steelhead are the three species that are experiencing these lower returns. Other salmon species, like chum and pink, have remained more stable.)

Scientists theorize the problem is occurring in the ocean. Some believe growing numbers of seals and sea lions, which feed on the fish, are behind the declines. Others say the warming and acidifying of the ocean is killing off the prey that the salmon depend on. There is strong evidence that ocean conditions, including ocean temperatures, are an important predictor of adult salmon returns.

Outdoor Life, “Why are Alaska’s chinook salmon runs crashing? It’s a big mystery that a salty group of researchers aim to crack”
CBC, “More than a dozen B.C. chinook salmon populations in decline, scientists say”
Anchorage Daily News, “Southeast Alaska’s king salmon are disappearing, and fishermen are grappling with the consequences”
NOAA Fisheries Fact Sheet – Southern Resident Killer & West Coast Chinook Salmon

Have dams created a haven for salmon predators?2020-02-24T21:58:07+00:00

Salmon predation has become a major factor up and down the Pacific coast and is not limited to rivers or dams. Protections put into place for birds and marine mammals have allowed these salmon predator populations to expand in the past few decades. To support their greater numbers, salmon predators, such as sea lions, have invaded areas where they weren’t previously observed, including rivers. To help counter this problem, anti-predation programs are in place to protect salmon. Still, predation remains an area where more work needs to be done.

Encyclopedia of Puget Sound – Study says predators may play major role in chinook salmon declines
Protecttheharvest.com – news
Govtrack.us “Endangered Salmon and Fisheries Predation Prevention Act”

Has dam breaching been an effective method for recovering wild salmon?2020-02-24T22:21:38+00:00

There are examples of dams being removed where modern fish bypass systems weren’t in place and where it was easier to remove the dams than to modernize them, such as the Elwha River in Washington. That said, according to the Washington Policy Center, the Elwha River hasn’t shown improvement in overall salmon returns or in wild adult salmon returns, post-dam breaching. The communities along the Elwha also haven’t seen an increase in tourism or fishing.

NOAA Northwest Fisheries Science Center: Elwha River
The myth of Elwha Dam removal’s success

Do hydroelectric dams lead to significant mortality for salmon?2020-02-24T22:40:40+00:00

Data shows that fish survival past modernized dams can be as good or better than naturally flowing rivers. Technological improvements at dams, including scientifically engineered fish ladders and surface passage systems—like removable spillway weirs—help fish safely navigate the dams. Research by NOAA Fisheries shows that with the improvements that have been made, the survival of juvenile fish past the eight dams on the lower Columbia and lower Snake rivers is better now than when the Snake River was free flowing.

Proceedings of the National Academy of Sciences of the USA – Ocean and dam influences on salmon survival
Public Library of Science – Survival of Migrating Salmon Smolts in Large Rivers with and Without Dams

Would breaching dams on the lower Snake River be helpful to salmon there?2020-02-24T22:20:34+00:00

Dam breaching is likely ineffective where major fish passage improvements have already been made, such as on the lower Columbia and lower Snake rivers. Since 2001, the U.S. Army Corps of Engineers has invested close to $2 billion in new fish-passage technology at these dams. They’ve even developed new advancements that are a model for hydroelectric dams around the world. As a result, NOAA Fisheries has found that the operation of these dams is unlikely to jeopardize endangered salmon, steelhead, or orcas.

There are also some concerns about what dam breaching might look like for salmon in the Snake River. It is likely that there would be a severe decrease in water quality from the increased flow of pollution and sediment. Prior studies done by the U.S. Army Corps of Engineers surrounding the 2002 EIS suggest that toxic chemicals and sediment would be released into the river following dam breaching, leading to lower water quality. It is safe to assume that more toxins have built up since then, along with pollution and plastic, and that their release could have a negative impact on salmon recovery.

Bonneville Power Administration Fact Sheet: Many Paths to the Ocean
2019 NOAA Fisheries Biological Opinion
Army Corps of Engineers 1999 “Lower Snake River Juvenile Salmon Migration Feasibility Study”
Amount of trash found in Columbia River cleanup surprised some local divers

Can dams offset the effects of warmer water temperatures?2020-02-24T22:14:40+00:00

Dams with large storage reservoirs can help mitigate warmer downstream temperatures. Cold water from Dworshak Dam just upstream of the Snake River is released each summer to cool the water temperatures downstream.

Climate change is major driver of dangerous temperatures that warm rivers. Pulling out carbon-free resources—like hydroelectric dams—may worsen that problem long-term.

Army Corps of Engineers – Dworshak Dam Water Releases

Can batteries become a substitute for hydropower in the Northwest?2020-02-24T22:29:42+00:00

Batteries and Northwest hydropower operate on much different scales. Currently, the largest planned battery in the Northwest (planned for operation in 2021) will be able to release 30 megawatts of electricity for four consecutive hours. A battery that size represents an exciting development for our region. However, in comparison, the lower Snake River dams can generate up to 2,650 megawatts over a period of 10 hours per day for five consecutive days. That is enough electricity to power roughly 2 million homes during heat waves or cold snaps.

With thousands of megawatts of coal and natural gas-fired generation set to be retired in the Northwest over the coming decades due to climate concerns, we will likely need all of our existing hydropower, plus new sources of energy paired with batteries, to keep up with regional electricity needs. Rather than comparing batteries to hydropower, it will be important to use a combination of both.

Portland General Electric – Wheatridge Renewable Facility
Bonneville Power Administration – A Northwest energy solution: Regional power benefits of the lower Snake River dams

If dams aren’t the problem for salmon survival, what is behind the salmon population declines?2020-02-24T21:56:51+00:00

Scientists theorize the problem is occurring in the ocean. A recent peer-reviewed study shows that roughly 85% of the total historical vegetated estuary area for the West Coast has been lost. Losses were highest for major river deltas.

Some scientists have also pointed to the growing numbers of seals and sea lions, which feed on the fish, as behind the declines.

Others say the warming and acidifying of the ocean are killing off the prey that the salmon depend on. There is strong evidence that ocean conditions, including ocean temperatures, are an important predictor of adult salmon returns.

Insights into estuary habitat loss in the western United States using a new method for mapping maximum extent of tidal wetland
12-3-2018 CBC News “More than a dozen B.C. chinook salmon populations in decline, scientists say”
NOAA Northwest Fisheries Science Center Outlook for Salmon Returns

Are Northwest dams creating dangerous river temperatures for fish?2020-02-24T22:18:02+00:00

Climate change is causing warming ocean and river temperatures that can be harmful to fish. Damaging water temperatures can and do occur both in free-flowing rivers and rivers with dams. As an example, due to record high water temperatures, approximately 466,000 adult fish perished in the undammed Fraser River before reaching their spawning grounds in 1994.

The science is mixed on the direct effect that dams have on river temperatures. A 2003 EPA study indicated that dams may exacerbate temperature issues on the rivers, but a 2002 study performed by Pacific Northwest National Laboratory showed that dams within the Columbia and Snake river basins moderate extreme water temperatures.

The PNNL study concluded that “…the reservoirs decrease the water temperature variability. The reservoirs also create a thermal inertia effect that tends to keep water cooler later into the spring and warmer later into the fall compared to the unimpounded [i.e., free-flowing] river condition.”

A graph from the study, representing conditions at Ice Harbor Dam helps to illustrate the effect of dams on water temperatures.

Climate change effects on stream and river temperatures across the northwest U.S. from 1980–2009 and implications for salmonid fishes
2-28-2019 New York Times, “The World Is Losing Fish to Eat as Oceans Warm, Study Finds”
EPA – Climate change indicators
Foreman, M & B. James, C & C. Quick, M & Hollemans, Peter & Wiebe, Edward. (1997). Flow and Temperature Models for the Fraser and Thompson Rivers. Atmosphere-ocean
US Army Corps of Engineers – Lower Snake River Dams
Summary: Regional Scale Simulation of Water Temperature in the Columbia River Basin
Richmond, et al: Regional Scale Simulation of Water Temperature and Dissolved Gas Variations in the Columbia River Basin

How effective are hatcheries and habitat restoration efforts?2020-02-24T21:53:15+00:00

While several salmon stocks are still endangered, data show that the Columbia and Snake River are producing significantly improved numbers of juvenile salmon. According to NOAA Fisheries, “…the Columbia and Snake Rivers may now produce more juvenile salmon than they did prior to dams and development, when hatchery fish are included.”  Adult returns also saw significant improvements in the last decade, but poor ocean conditions reduced those numbers once again. Like the Snake River, undammed rivers from Southern Oregon to Alaska are seeing worsening returns of adult salmon, which is a cause for concern.


NOAA Fisheries Fact Sheet: Southern Resident Killer & West Coast Chinook Salmon
University of Washington–Columbia Basin Research–Data Access in Real Time
SalmonRecovery.gov–Citizens Guide

Have the Northwest’s hydroelectric dams resulted in significant habitat loss for salmon?2020-02-24T22:09:12+00:00

The building of dams and other human-related activities are a significant source of habitat loss for salmon. Specifically, hydroelectric dams on the Columbia and Snake rivers have contributed to habitat loss for key species, mainly Chinook, sockeye, and steelhead. That said, hydropower-funded programs have helped to restore and protect that same important habitat. In 2018 alone, the Bonneville Power Administration spent over $123 million on habitat restoration and protection programs. BPA has spent close to $17 billion since 1981 on fish and wildlife-related activities.

2018 Columbia River Basins Fish and Wildlife Program Costs Report


For access to even more information and research, visit our resources page.

Go to Top