At Spanaway Lake, toxic algal blooms mean the lake closes for recreation to keep people safe. Ecology is starting a rulemaking to address toxins produced during harmful algal blooms in freshwater.
Washington’s lakes, rivers, streams, and reservoirs are some of the state’s most prized resources for recreation, drinking water, fish, and wildlife. They’re central to many communities’ identities and economies.
These important waters, however, face a wide range of pollution problems, including excess nutrients and toxic algal blooms. These two issues are related and often combine forces to make waterbodies unusable at certain times of the year. When too many nutrients such as nitrogen and phosphorus enter freshwater, algae can grow out of control, which causes a domino effect of problems. Some algal blooms produce toxins that can harm people, pets, fish, and wildlife.
We are starting two rulemakings to update the state’s water quality standards for freshwater. These efforts will help us identify polluted waters, guide cleanup efforts, and help communities qualify for funding to improve water quality.
These rules will support the ongoing efforts by local health jurisdictions, state agencies, and others who manage lakes and other freshwater recreation areas that can have harmful algal blooms. These organizations take samples of algal blooms so laboratory testing can determine if the blooms are harmful. These organizations can then make decisions about closing or restricting access to the water based on state and federal guidelines. Ecology provides technical assistance and funding for the state’s freshwater algae bloom monitoring program. We also provide grant funding for organizations working to address algal blooms in their local water through the freshwater algae control grant program.
Why we're acting now
We heard strong support for working on these updates from Tribes, local governments, and the public during our recent Triennial Review of water quality standards.
These two rules would be relevant across Washington. Harmful algal bloom criteria, which would be new for Washington state, would protect recreational designated uses, like swimming and boating. Nutrient criteria for lakes and reservoirs would protect a broader list of uses, including aquatic life, drinking water, and recreation.
Having specific criteria will help sampling and monitoring efforts needed to protect these uses from nutrient pollution. This helps Ecology prioritize the state’s clean water work and can provide more funding options for local efforts to understand and improve water quality. These criteria will also help build resilience into local waters against the effects of warming from climate change, as warming can lead to more frequent and more intense harmful algal blooms.
Rulemaking 1: harmful algal blooms
Some, but not all, types of algae can produce dangerous toxins that threaten human and animal health. When algal blooms release toxins — confirmed only through testing — officials may close the area to recreation to protect public health. In Washington, harmful algal blooms can limit swimming and boating opportunities during hot summer months.
This video is one example of what a harmful algal bloom could look like. These toxic blooms can be different textures and colors.
Through this first rulemaking, we are proposing to add new freshwater recreational criteria for addressing toxins that are produced during harmful algal blooms.
We are considering:
- Setting numeric criteria for two toxins, microcystins and cylindrospermopsin, based on EPA’s 2019 recommendations.
- Reviewing whether criteria are also needed for other cyanotoxins, including anatoxin-a and saxitoxin, which can occur in Washington fresh waters.
These new criteria would set statewide rules for when freshwater is considered polluted with these toxins. This will support ongoing efforts to measure and track harmful algae blooms.
We expect to share draft rule language for public review in fall 2026.
Rulemaking 2: nutrient criteria for lakes and reservoirs
Hog Lake in Spokane County
In a separate rulemaking, we are proposing to set new water quality criteria for lakes and reservoirs to protect aquatic life, recreation, and drinking water sources from nutrient pollution. Nutrient pollution can contribute to harmful algal blooms and other problems in lakes and reservoirs.
There are many sources of excess nutrients. Our everyday activities can combine to add too much nitrogen or phosphorus to a lake, including overuse of lawn and garden fertilizers, leaking or failing septic systems, and improperly managing pet and livestock waste. For some lakes and reservoirs, humans have altered the flow of the water in ways that causes the pollution to build up, instead of dispersing.
We will review EPA’s 2021 recommended nutrient criteria for total nitrogen, total phosphorus, and chlorophyll a, and evaluate how Washington-specific data can make criteria best reflect and protect our unique lake ecosystems.
We expect to share draft rule language for this rulemaking in fall 2027.
How these rules are connected
Nutrient pollution and harmful algal blooms often go hand-in-hand.
- The harmful algal bloom rule focuses on setting limits for toxins that affect human health.
- The nutrient criteria rule addresses the nutrients that can contribute to these blooms in the first place.
Working on both of these rules recognizes the bigger picture of clean water and the connections within an ecosystem.
Ecology's William Hobbs samples Hog Lake as part of a study looking at whether cyanotoxins bind and persist in nearshore lake sediments, posing a longer-term health threat.
As we start drafting rule language, we’ll be working others, including the Washington State Department of Health. Their experience developing guidance for freshwater algal toxins will be a big help in this work. They are also our partner in responding to harmful algal blooms throughout the year.
We know that many communities are concerned about harmful algal blooms in their local water, and they are already working with Ecology to try to improve water quality. We look forward to working with these groups during the rulemaking process. We will reach out to Tribes, local governments, and the public to gather input throughout our process. We plan to hold an informational webinar in early 2026 and are happy to connect before then.
We’re also conducting an Environmental Justice Assessment for both rules. This work helps us understand how our decisions affect overburdened communities and vulnerable populations. The insights we gain will guide us in making sure environmental benefits are shared more equitably, reducing environmental harms, and addressing health disparities across the state.
How you can get involved
We invite anyone interested in these rulemakings to participate in this multi-year process. We will host multiple opportunities for input, including webinars, and comment periods.
Visit our rulemaking webpages for meeting notices, opportunities to share your ideas, and to sign up for email updates:
We will continue engaging partners and the public throughout both rulemakings to make sure our work reflects the best available science and community input.