Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin © Conrad Gowell
Welcome to the Hot Water Report 2024: Warming Waters in the Lower Snake and Columbia Rivers.

 I. EXECUTIVE SUMMARY

• Toxic algal blooms have re-emerged on the lower Snake River. Whitman County Public Health and the Washington State Toxic Algae Monitoring Program confirmed that the toxic algal bloom in the river tested positive for microcystins, which is a liver toxin harmful to people and the river ecosystem and lethal to pets.
• For over 40 days, the lower Snake River has experienced hot water temperatures in which many of the reservoirs have continuously registered high temperatures between 70 - 72°F, well over the 68°F “harm threshold” –the biological and legal limit– set to protect migrating salmon and steelhead.
• The warm water and stagnant reservoirs that toxic algal blooms thrive in are also harmful to salmon and steelhead. Toxic algal blooms are a health risk to people, pets, and the river; and significantly reduce what are already quite limited recreational and fishing opportunities on the lower Snake River.
• Toxic algae is an additional stressor on already unhealthy and warming waters in the lower Snake River. By cooling down water temperatures and re-establishing currents, lower Snake River dam removal would reduce/eliminate toxic algal blooms, help restore a healthy river ecosystem that people can enjoy, and protect salmon and steelhead from extinction.

II. INTRODUCTION

Toxic algal blooms in the lower Snake River, October 2023 © LightHawk's pilot Dr. Judy Parrish

Before the lower Snake River dams were built, the pristine, clear, cold waters of the Snake River Basin were home to millions of adult salmon and steelhead, along with sturgeon, lamprey eel, and other native fishes. The once-abundant anadromous fish populations in the Columbia-Snake River Basin are struggling to survive today primarily due to harms caused by the federal dams and their reservoirs. The federal hydro-system creates conditions that harm and kill both juvenile and adult fish, including by elevating water temperatures in large, stagnant reservoirs in the summer months. These cold-water fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit.

In Issue 9, we report on toxic algal blooms recently found on the lower Snake River and tested positive for a liver toxin that is harmful to people and the river ecosystem and lethal to pets. These ‘blooms’ are visible across approximately 50 miles in two lower Snake reservoirs, and are expected to persist and expand in the months ahead.

During the summer, our Hot Water Report provides real-time water temperatures in the lower Snake and Columbia river reservoirs, with updates and reports from scientists, Tribal members, fishing guides, and other experts about the challenges facing these rivers, our opportunities to recover healthy, resilient fish populations, and the benefits they deliver to Northwest communities and other fish and wildlife populations.

View the Hot Water Report issues at wildsalmon.org/HWR

 III. Confirmed: Toxic Algal Blooms Re-emerge on the Lower Snake River

Toxic algal bloom at Central Ferry on the Snake River, 2023 © Whitman County Public Health

Water samples taken in the lower Snake River on August 12 and August 16 tested positive for toxic algae with microcystins, a liver toxin that harms people and the river ecosystem and is lethal to pets. Whitman County Public Health collected a toxic algal bloom sample in the Lower Granite Dam’s reservoir near a popular recreational spot, Granite Point. The toxic algal bloom has been spotted in different areas covering a roughly 50-mile stretch of river between Nisqually John Landing in the Lower Granite Dam’s reservoir and Little Goose Dam.

Toxic algal blooms thrive in warm, nutrient-rich water

Cyanobacteria, a type of algae, occur naturally in freshwater environments and are vital to the function of aquatic ecosystems.¹ However, while cyanobacteria can be good, too much cyanobacteria in the water is dangerous. Excessive growth of this single-cell organism can lead to “blooms” that may cause serious harm to freshwater habitats and human and animal health, earning them the name “harmful algal blooms,” also referred to as toxic algal blooms.²

According to the Whitman County Public Health, some environmental factors that contribute to these algal blooms include: sunny days, warm water temperatures, still water conditions (or slow-moving stagnant water), and an influx of nutrients (namely nitrogen and phosphorous) that enters a waterbody via runoff or other sources. The combination of these conditions are most likely to materialize in late summer and early fall, when water and air temperatures are often at their highest (and precipitation and snowpack at their lowest).

Warm, slow-moving/stagnant, and nutrient-rich waters create ideal conditions to generate toxic algal blooms. For over 40 days, the lower Snake River has experienced hot water temperatures in which many of the reservoirs have continuously registered high temperatures between 70 - 72°F, over the 68°F “harm threshold” –the biological and legal limit– set to protect migrating salmon and steelhead. The water in the lower Snake River is already dangerously hot for salmon throughout every summer, and now it is providing conditions for toxic algae - causing the river to become unsafe and hazardous for people and pets.

On the lower Snake River, toxic algal blooms have occurred for the second year in a row, with a couple of instances in previous years. A large toxic algal bloom happened between September 2023 - January 2024, where the blooms were found in Granite Point, Wawawai Landing, Central Ferry, and Wawawai County Park. This year, toxic algal blooms have been found earlier - in mid-August - between Nisqually John Landing in the Lower Granite Reservoir and Little Goose Dam.

Impacts of toxic algal blooms on human health, pets, and aquatic life

Toxic algal bloom samples © Whitman County Public Health

When toxic algal blooms form, they usually appear as blue-green scum, foam, froth, or a paint-like slick on the water body’s surface.³ Under the right set of conditions (including factors like light intensity, nutrient loads, and water temperature and salinity), these cyanobacterial blooms can become toxic, producing byproducts known as cyanotoxins.⁴ Cyanobacteria can produce many cyanotoxins, such as microcystins, which were found on the lower Snake River in 2023 and now again this year in mid-August.

Microcystins are very stable and can withstand environmental forces (such as sunlight or temperature variations) without breaking down, which means this toxin can last up to several months under these “favorable” conditions.⁵ Microcystins are a group of toxins that can harm the liver and are commonly responsible for human and animal poisonings, and habitat degradation such as:

Impacts on human health: Direct exposure to water contaminated by Microcystin (via drinking, swimming, boating, fishing, or other activities that may lead to contact or accidental consumption) can cause these short-term health effects: headache, sore throat, vomiting, nausea, diarrhea, pneumonia, lethargy, skin rash, muscle cramping, and muscle twitching.^6,7 Long-term exposure effects include tumor development, liver failure, and decreased sperm count and motility.⁸

Impacts on domestic animals (primarily dogs): Direct exposure to water contaminated by Microcystin (via drinking, swimming, or licking fur that has been exposed) can cause these health effects in dogs and livestock: vomiting, diarrhea, weakness, pale gums, excessive drooling, paralysis, difficulty breathing, lethargy, skin rash, muscle cramping, muscle twitching, seizures, and sudden death from cyanotoxin poisoning.^9,10

Impacts associated with habitat degradation caused by algal blooms: Significant increases in algae harm water quality, food resources, and habitats, and decrease the oxygen that fish and other aquatic life need to survive – particularly upon the death of blooms when decomposing algae absorb large quantities of oxygen. This oxygen depletion can lead to injury and death in fish, especially resident species. Algal blooms also block sunlight that submerged aquatic vegetation needed to survive (and produce oxygen via photosynthesis), another way blooms deplete oxygen in freshwater systems.¹¹

Restoring a free-flowing and cold lower Snake River to protect communities, ecosystems, and salmon

© Neil Ever Osborne

The lower Snake River dams create reservoirs with warm slackwater that is harmful or lethal for salmon throughout the summer. And now things are getting worse: these same reservoirs are now becoming a breeding ground for toxic algal blooms, adding yet a new threat to endangered native fish and communities along the lower Snake River.

A sick lower Snake River, where toxic algal blooms are a regular occurrence, increases the pressures on threatened and endangered salmon and steelhead. Already under stress as they migrate through the dams’ warm reservoirs, these coldwater fish must now also contend with toxic algal bloom-driven oxygen depletion and changes in pH – at the same time that the reservoirs are at their hottest.

Removing the four lower Snake River dams will once again allow cool waters to flow freely and support healthy salmon populations. It will also mean far fewer toxic algal blooms and a healthier Snake River overall – one that benefits fish, people, communities, watersheds, and cultures.

Resources:

• Toxic Algal Bloom Factsheet by Whitman County Public Health 

References:
1,2, 4,6,8 Harmful Algal Blooms (HABs) in Water Bodies, U.S. Environmental Protection Agency; webpage accessed on April 23, 2024.
3, 5, Toxic Algae Blooms, Benton-Franklin Health District; webpage accessed on April 25, 2024.
7,9 Toxic Algal Blooms website by Whitman County Public Health 
10. CDC: For Veterinarians: Harmful Algal Bloom-Associated Illnesses
11. Nutrient Pollution: Dead Zones and Harmful Algal Blooms, U.S. Environmental Protection Agency; webpage accessed on April 28, 2024.

 IV. READING THE DATA - LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES

INTRODUCTION TO THE WATER TEMPERATURE DATA:

• Throughout this summer, the Hot Water Report will provide, on a weekly basis, an update on real-time water temperatures in the lower Snake and Columbia River reservoirs.
• Data collection: The daily average and high water temperature data at the four reservoir forebays are measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dams in the lower Snake River and the lower Columbia River for 2024. The water temperatures are taken on the hour. Hourly temperatures are used to find the highest temperatures reached in each reservoir, and hourly temperature measurements are used to find the daily average temperatures.
• Average Water Temperature Graphs (below): Daily average temperatures are represented with solid lines, and the 10-year average (2014 - 2023) temperatures are with dashed lines of the same color. The dotted line across the graph represents the 68°F “harm threshold” for adult and juvenile fish.
• Weekly High Water Temperature Tables (below): This table outlines the highest water temperatures reported for each reservoir during the week and how many days water temperatures have exceeded 68°F.
• Hot water temperature effects to salmon: The longer and the higher water temperatures rise above 68°F, the greater the harm to salmon, including: migration disruption, increased metabolism, increased susceptibility to disease, reduced reproductive potential (by reducing egg viability), suffocation (warm water carries less oxygen), and in worst case - death.

 V. DISCUSSION OF DATA - LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES

LOWER SNAKE RIVER WATER TEMPERATURES: 8/17 - 8/23

Lower Snake River - 2024 Daily Average and 10-year Average.

Lower Snake River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir.

• Lower Snake River Water Temperatures: this week, the Ice Harbor Dam's reservoir reached a high average water temperature of 71.00°F on August 22.
• The Lower Monumental Dam's reservoir registered a high average temperature of 70.71°F on August 18.
• The Little Goose Dam’s reservoir registered 70.48°F on August 17.
• The Lower Granite reservoir registered a high average of 67.37°F. Lower Granite Dam’s reservoir’s average and high daily temperatures registered below 67°F due to the US Army Corps of Engineers’ continued cold water release effort from the reservoir behind Dworshak Dam. However, these cold water releases do not significantly cool/benefit the three downstream reservoirs on the lower Snake River.

WEEKLY HIGH TEMPERATURES IN THE LOWER SNAKE RIVER: 8/17 - 8/23

• The lower Columbia and Snake river reservoirs continue to reach above the 68°F “harm” threshold. This week, many of the reservoirs’ temperatures ranged between 70°F - 71°F.
• The Little Goose Dam's reservoir reached the highest water temperature of 71.73°F on August 17. Lower Monumental Dam’s reservoir registered a high water temperature of 71.31°F on August 17.
• The Ice Harbor Dam's reservoir registered a high temperature of 71.26°F.
• The Lower Granite Dam's reservoir registered a high water temperature of 68.29°F.
• Water temperatures in the Ice Harbor Dam reservoir have exceeded 68°F for 45 consecutive days, and ranged between 70°F - 72°F for 42 consecutive days. Both the Lower Monumental and Little Goose Dams’ reservoirs have exceeded 68°F for 47 days.

LOWER COLUMBIA RIVER WATER TEMPERATURES: 8/17 - 8/23

Lower Columbia River - 2024 Daily Average and 10-year Average.

Lower Columbia River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir

• Lower Columbia River Water Temperatures: this week, all four reservoirs on the lower Columbia River exceeded 68°F.
• The reservoir behind The Dalles Dam had a high average temperature of 71.24°F on August 17 and 18. The reservoir behind John Day Dam reached an average temperature of 71.06°F on August 17.

WEEKLY HIGH TEMPERATURES IN THE LOWER COLUMBIA RIVER: 8/17 - 8/23

• On the lower Columbia River, John Day Dam reservoir registered the highest temperature at 72.14°F on August 17. The Dalles Dam reservoir reached the second highest temperature at 71.60°F on August 17 and August 18.
• Bonneville Dam reservoir has spent 49 consecutive days above 68°F and both The Dalles Dam and John Day Dam reservoirs registered above 68°F for 48 days.

Data Sources: The 2024 lower Snake River and lower Columbia River water temperature data presented in the Hot Water Report are collected from the USGS, Columbia River DART program by Columbia Basin Research, University of Washington, using data courtesy of the U.S. Army Corps of Engineers (USACE). The 10-year average water temperature data is courtesy of the Fish Passage Center. Lower Monumental 10-year average water temperatures are unavailable. Graphs and tables are assembled by SOS Staff.

The Hot Water Report is a project of the Save Our wild Salmon Coalition, Association of Northwest Steelheaders, Columbia Riverkeeper, Earthjustice, Endangered Species Coalition, Idaho Conservation League, Idaho Rivers United, National Wildlife Federation, Natural Resources Defense Council, Northwest Sportfishing Industry Association, Orca Network, Sierra Club, Snake River Waterkeeper, and Wild Steelhead Coalition.

View previous Hot Water Report issues at wildsalmon.org/HWR