With illness reports floating in the news and blue-green algae mucking up your local lake, you figure you’re better safe than sorry. You search: “where safe to swim bay area.” You skip past the results from agencies you haven’t heard of and go straight to the state of California’s handy “Safe to Swim” map. Official. Easy. Except launching the map brings up a host of caveats. “The data can change at any time” and “is updated daily, depending on staff availability,” the website warns. It really “should not be used for any particular purpose other than general reference.” 

For a live map that’s meant to show where fecal contamination in water might make people sick it does not inspire confidence. It also doesn’t track harmful algal blooms (HABs), which can cause illnesses like rashes and fevers and even kill dogs. And what’s worse, clicking on the dot closest to you may reveal the “last sample date” was in 2014. The coastal beaches show recent testing, but most inland water bodies don’t.

Even Andrew Hamilton, an assistant deputy director at the State Water Boards’ Office of Information Management and Analysis, which publishes the map, recommends swimmers check elsewhere. He calls the Safe to Swim map “somewhat aspirational.”

Indeed, of the 6,107 monitoring sites visible on the map, only 611 have been updated in the past year. That’s just 10 percent, far from a statewide network of reliable water quality warnings. “If I’m in the San Francisco Bay, I would look at the local agencies,” Hamilton says. “Those will give you more current data.” And because there’s a separate reporting process and data pool for HABs, there’s a separate map for reports of algal bloom advisories.

So why don’t would-be swimmers have an easy way to find out where it’s safe to dive in? 

Part of the answer is out of the state’s hands: reporting is voluntary. Currently, no state law requires any of the local agencies that may do testing to report data, except for a very narrow definition of beaches: public, coastal saltwater stretches with 50,000 visitors or more a year, and only from April to November. (In the map above, look for the green dots along the coastline.) 

A child at a state-run swim camp at Lake Del Valle in Alameda County on July 24, 2026. As of Aug. 19, the East Bay Regional Park District’s website had an advisory for blue-green algae at the lake. Algal blooms don’t appear on the state’s Safe to Swim map. Melissa Sanchez Robinson / California Department of Water Resources

The other part of the answer lies in the 2024 state budget cuts, which “led to some hard decisions around program and project funding,” Hamilton said over email. Budgets supporting the Surface Water Ambient Monitoring Program (SWAMP), a statewide water quality initiative, were cut by 15–20 percent. The Central Valley Regional Water Board, a subagency of the statewide board, also announced a 5 percent reduction in the same year. 

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The required monitoring has been funded since 1997, when the Legislature passed a bill requiring health departments to monitor water quality. Currently, there’s $1.8 million a year in state funds and, with fluctuating federal grants via the Environmental Protection Agency, it evens out to about $2.3 million each year. 

On hot weekend days in the Sacramento Valley, thousands of people descend upon the lower American River to float in the cool water. The Central Valley waterboard stopped regular bacterial testing of this stretch in June last year. This year, dangerous levels of E. coli were found just upstream at Lake Natoma right before the Fourth of July weekend. Kate Golden

But for the inland areas (lakes, creeks, freshwater sources), there’s nothing.  

“There’s so much data gaps that we want to fill. And [the map] gives us that information of where we’re lacking the authority to collect that data,” Hamilton says. “Unfortunately, it’s just not something that we manage.”

When monitoring isn’t centralized and reliable, the public health impact can be dangerous. Last month, four families in Chico sued the city, alleging that their children were sickened by E. coli after swimming at a public pool where testing should have been done weekly. Four children were hospitalized after the outbreak.

Annalise Blum, a research fellow at Public Policy Institute California’s water policy center, says that having reliable info is essential for safe public access and recreation.

“It’s super important for anyone who wants to go swim in a waterbody or even go walk their dog next to it,” she says. “I have a toddler who likes to go and play in the water sometimes, and not knowing what the water quality is is a real detriment.” 

Some local agencies do test

Yet testing is being done at some water bodies, even if it doesn’t show up on the Safe to Swim map, even in places where the state doesn’t fund or require it.

Hal MacLean, water management supervisor at East Bay Regional Park District, often makes a 9 a.m. drive to the beach on Mondays—swapping sandals and surfboards for working boots, pipettes and tiny vials, labelled water bottles, and sterile gloves. 

He and the rest of the monitoring team sample eight beaches—six of them inland—and run tests for E. coli, Enterococcus, and cyanobacteria, which can cause harmful algal blooms. When test results exceed the state’s established thresholds, the team will post signs giving beachgoers a “yellow” or “red” light to warn against swimming.

Bacterial contamination is all that appears on the Safe to Swim map, but it isn’t the only reason swim spots close. Here, an algal bloom muddies the water on Sept. 13, 2024, at San Luis Reservoir near the Pacheco Pass—normally a place for boating, fishing, and swimming. Andrew Nixon / Department of Water Resources

But outside of their coastal reporting obligations, EBRPD has never shared the data they obtained with the Safe to Swim map, MacLean says. 

“We’re open to working with the state, but haven’t really been approached about it,” MacLean says. There’s a data portal, but it’s “problematic.” Glitchy, difficult, often requiring specific formats or data types. “Ideally, we’d just … send them our data,” he says, lightly. 

Sonoma County’s Environmental Health Department also maintains a fully up-to-date list of their freshwater beaches’ E. coli levels, alongside the mandated ocean water quality list. These sites were last updated on the Safe to Swim map in 2012. Christine Sosko, director of environmental health at the county, says that the health department never shared its sampling data with the state, and that reporting might been done by the water agency or a regional water quality board—partnerships that fell off over time. 

San Mateo County Health’s website mentions only Bay beaches, coastal beaches, and creek mouths as a part of its monitoring program. Per the map, inland rivers in the county, like San Mateo Creek or Belmont Creek used to be monitored by regional collaboratives, but efforts to update the data appear to have petered out by 2016.

Hamilton suspects that local agencies are feeling a budget squeeze. 

“The funding has been static for quite some time,” he says. “And with costs of analysis going up, the costs of personnel going up, that ability to maintain [monitoring] over time has not really been sustained.”

Before, Hamilton says, some local agencies were able to use state and federal funds to support additional non-obligatory monitoring. With shifting priorities, county departments likely started to focus on strictly necessary efforts—but even that, the Water Boards estimate, likely amounts to some $10 million statewide, nearly five times more than annual state and federal reimbursements. 

New waves on the horizon?

In 2021, the state Legislature tried to close the gap between coastal and inland monitoring, passing a bill that directed the California Water Quality Monitoring Council (a joint effort of the California Natural Resources Agency and the California Environmental Protection Agency) to put forth a new set of guidelines and potentially a budget for inland monitoring. But the directive did not come with funding. According to Hamilton, the council has yet to submit its work, which was due in 2023.

Which water bodies will fall under the new requirement, what indicators will be monitored, and who will do it are all questions waiting to be answered. Hamilton is hopeful that whatever comes next will result in monitoring that can uses the latest technology, that’s cohesive, that can maybe show algae blooms and bacterial testing in one place. 

“We think this map could be something that is of great value to Californians,” he says. “We recognize that it’s not perfect, and we look at it as an iterative process.”