Swimming is now off-limits for people and pets on the Silver Springs side of Lahontan Reservoir after state testing turned up a cyanotoxin concentration officials describe as the highest ever recorded in Nevada. Camping, boating and other recreation remain permitted at Lahontan State Recreation Area, but the water itself is now considered too dangerous for contact.
The Nevada Division of Environmental Protection found toxin concentrations of about 25,000 micrograms per liter at Silver Springs, according to KTVN. That reading is more than 12 times higher than Nevada's own Danger Advisory threshold of 2,000 µg/L, according to the Nevada Division of State Parks, and it dwarfs the federal benchmark for recreational safety: the U.S. Environmental Protection Agency recommends issuing water advisories once microcystin levels pass 8 µg/L, putting the Silver Springs number at more than 3,100 times that health-protective standard, per the U.S. Environmental Protection Agency.
The Fallon side of the reservoir remains under a separate Danger Advisory, and the state agency will continue testing and monitoring conditions across the lake, per the same station's report. Restrictions will stay in place until testing shows toxin levels have come back down.
Why the Ban Goes Beyond Swimmers
Harmful algal blooms produce cyanotoxins that can cause skin and eye irritation, nausea, vomiting, diarrhea and other health effects in people, the station notes, and the risk to pets is especially severe. Cyanotoxin poisoning can trigger acute gastrointestinal distress, liver damage, kidney damage and neurological impairment in humans, alongside extreme mortality risk for animals, according to the Nevada Office of State Epidemiology — dogs are especially vulnerable because they tend to drink the water directly and lick toxic scum off their fur.
Nevada State Parks Administrator Jonathan Brunjes said visitors should follow posted restrictions and take precautions around the water until conditions improve, the article notes. Brunjes also said the ban exists not just to protect visitors and pets but to keep first responders safe, since emergency water rescues would force personnel into direct contact with toxic water, according to the Nevada Division of State Parks.
Visitors are being told to avoid any discolored water, and fishing is not recommended in areas where a bloom is present. Kevin Netcher said anglers who do fish should thoroughly wash their catch before cleaning or processing it and steer clear of visibly affected water, per the same account.
A Statewide Pattern, Not an Isolated Bloom
Lahontan is not the only Nevada waterbody dealing with this problem this summer. Nevada environmental and public health agencies reported monitoring 11 active harmful algal blooms statewide in 2026, with advisories also posted at Rye Patch Reservoir, Washoe Lake, Wild Horse Reservoir and Marlette Lake, according to the Nevada Office of State Epidemiology. Late-summer heat and stagnant water regularly trigger blue-green algae growth across the state's high-desert basins.
Residents can track the situation through the Nevada Division of Environmental Protection's interagency Harmful Algal Bloom Task Force, which runs a public hotline at 888-331-6337 and an online dashboard at nevadahabs.org for reporting suspected blooms and checking weekly advisories, per the Nevada Division of Environmental Protection.
A Second, Older Hazard Beneath the Surface
Even without the algal bloom, eating fish caught at Lahontan carries risk. Consumption is discouraged because of elevated mercury levels, and public health advisories against eating Lahontan fish date back to 1997, backed by historic testing that found a 1981 striped bass carrying 23.65 parts per million of mercury — roughly 51 times safe limits — and a 1998 walleye with 16 ppm, according to the U.S. Government Accountability Office.
That contamination traces back to the 19th century. Lahontan Reservoir forms Operating Unit 2 of the Carson River Mercury Superfund Site, designated by the EPA in 1990 after Comstock Lode-era gold and silver processing dumped toxic mercury tailings into the Carson River watershed, according to the U.S. Environmental Protection Agency. Decades of mine waste settled into the reservoir bed sediments, a legacy that persists independent of any given summer's algae conditions.
A Major Recreation Hub Under Pressure
Lahontan Dam was completed in 1915 as part of the federal Newlands Reclamation Project, one of the nation's earliest federal irrigation efforts following the Reclamation Act of 1902, and it impounds the Carson and Truckee rivers to deliver irrigation water to roughly 60,000 agricultural acres around Fallon, according to the Nevada Division of State Parks. Summer irrigation withdrawals lower lake levels and create the warm, shallow conditions that help algal blooms take hold.
Today, Lahontan State Recreation Area spans more than 28,000 acres across Lyon and Churchill counties with 69 miles of shoreline, making it one of northwestern Nevada's primary aquatic recreation destinations, per Travel Nevada. The Silver Springs side provides major public access points right off U.S. Route 50, putting the closure directly in the path of the area's heaviest visitor traffic.
