Five questions. Every lake. Free. And five lists no lake community wants its name on.

Ask anyone who lives on a lake what they'd want to know before a summer weekend, and the answers converge on the same few things. Can we swim? Can we eat what we catch? Has the water gone green? Is something wrong with it? Is something living in it that shouldn't be?

State and federal agencies already track the answer to every one of those questions. They do it by keeping lists. The trouble is that the lists live on a dozen different agency websites, in formats built for regulators rather than residents, and almost nobody on the lake knows where to look.

Lake Atlas brings them together, for every one of the 484,442 lakes in the lower 48.

The five questions

1. Can we eat the fish? Answered from state fish consumption advisories. When a lake is on that list, it's because fish tissue sampling found something, often mercury or PCBs, at levels that warrant limits on how much people should eat.

2. Are there swimming advisories? Answered from beach and bacteria advisories. A listing usually means bacteria such as E. coli exceeded a threshold at a monitored beach.

3. Has a harmful algal bloom been reported? Answered from public bloom records. A record means a bloom was reported or confirmed in a given year.

4. Is the lake on the state's impaired waters list? Answered from the state's 303(d) list, reported to the EPA. A listing means the lake doesn't meet a water quality standard for its designated use, and it names the cause: phosphorus, mercury, bacteria and so on.

5. Are invasive species recorded? Answered from state and USGS invasive species records, including the species and the year it was first found.

How the answers read

Every answer is one of three things:

  • On list · Current. The lake appears on the agency list, with the cause or species and the year where available.
  • Not on list. No current listing was found.
  • No public record. The agency doesn't track this for the lake, or the record is missing.

Each answer shows its source and the date Lake Atlas last checked it. Lake Atlas is refreshed quarterly, not daily, and lakes can be added to or removed from agency lists in between, so always check with the issuing agency before you swim or eat fish.

Lake Atlas never calls a lake clean or safe, and never ranks one lake against another. "Not on list" means exactly that: no listing found. It isn't a clean bill of health.

Why these are the lists you don't want to be on

Each of these lists has consequences beyond the water. A swim advisory empties a beach. A fish advisory changes how a community fishes. An impaired-waters listing can follow a lake for years, and it surfaces in conversations about property, permits and grants. Invasive species, once recorded, rarely leave.

Nobody gets onto these lists overnight. The conditions build for seasons, often unmeasured, until an agency sample or a bad summer puts a name on them. Knowing where your lake stands today is the first step to staying off them, or getting off one.

Free, for everyone

The five answers are free on every Lake Atlas page, for every lake, for anyone. No account, no subscription. The data is public; we've only made it findable. Every page credits the state and federal agencies that gather it.

The history behind the answer

A current answer tells you where a lake stands now. It doesn't tell you how it got there. When was the lake first listed? Has it come off a list and gone back on? How many advisory seasons in the last decade?

That history sits scattered across state and federal sites, and piecing it together is slow work. Atlas Pass, the paid tier of Lake Atlas, assembles a lake's full advisory and listing history from those sources in one place. It's built for anyone who needs the long view: buyers and sellers, associations preparing a grant, consultants scoping a project, and agencies looking across many lakes.

Look up your lake in Lake Atlas · Get Atlas Pass

If your lake is on a list

Being listed isn't the end of the story. It's usually the start of a better-informed one. Lake communities that measure their own lake, consistently, are the ones that can show what's changing and whether their work is helping. That's what Lake Pulse is for.