The State of America’s Lakes 2026

How to read this edition

Every figure on this page is computed from the same lake records the rest of LakeQuality publishes. The universe is the 36 US states whose agencies report enough lake sampling to grade against — 33,763 named lakes with a public page. It is not every lake in the United States. Most US waterbodies have never been sampled for the nutrients this letter uses.

13 more state hubs — Maryland, Maine, South Carolina, California, Connecticut, New Hampshire, New Jersey, Rhode Island, Delaware, West Virginia, Louisiana, Mississippi, and Alaska — already have named-lake pages. They are not in this grade table, because their records have not yet cleared the same sampling minimum used everywhere else here. Ontario and Québec have their own pages and 0 letters. They are not US states. Ontario and Québec.

Two denominators appear throughout. Rated is the set with enough sampling for a letter (5,737 lakes, 17% of the edition). All monitored is every named lake in those 36 states, including Not Rated. A percentage of “good water” is always of the rated set. Treating Not Rated as F would invent 28,026 failing grades the samples do not support.

The national grade picture

The letter scores phosphorus, nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment 2022 ecoregion condition classes. Secchi depth is measured and shown because that is what a swimmer sees; it is not in the letter. The bar below is of every named lake in the edition, so the hatched Not Rated slice is part of 100% — a five-letter bar renormalized to 100 would quietly pretend 28,026 unmeasured lakes had been graded.

Of the 5,737 lakes that do carry a letter, the largest band is B (1,754 lakes). A and B together are 51.1% — nutrients and algae in the Good class for that ecoregion. D and F together are 31.2%. The C band is the everyday American lake: fair water, visible green in a warm July, generally usable and not the postcard clarity of a northern oligotrophic basin.

The tails are not symmetric. There are 1,178 A-graded lakes and 641 F-graded lakes. An A is a nutrient-and-algae statement, not a swimming clearance. An F is a nutrient-and-algae statement, not a condemnation of the shoreline. Both still need a same-day look at algae advisories and the lake's own page. Full method: methodology and how the grades work.

Trophic state — what the water is doing

Carlson's Trophic State Index classifies a lake by how much algae its nutrient load can support. We state a class as fact only on rated lakes, which is the same sampling requirement as the letter. Clarity-only TSI estimates exist on thousands of unrated waters; publishing those as “eutrophic” would say more than the samples support. Of the 5,735 classified lakes in this edition:

Eutrophic and hypereutrophic lakes together are 54% of the classified set. Oligotrophic lakes are 12.3%. That is the country's real split: most monitored US lakes are productive waters, not wilderness gin-clear basins. The oligotrophic share concentrates in deep glacial belts — Michigan, Minnesota's forested north, Vermont, and high-elevation western lakes. The eutrophic share is the agricultural Midwest and the naturally warm South. See trophic state explained.

Four regions, four lake countries

Census Bureau regions, counting only the states we cover in each. The Midwest holds 51.7% of the lakes in this edition. The Northeast has the highest A/B share among rated lakes (61.2%). A region average is a landscape average. Deep glacial water and shallow prairie reservoirs are not the same object, and the letter does not pretend they are.

Florida is the South's weight (3,122 lakes, 69.4% A/B of 1,302 rated). Almost all of those healthy letters are Bs (902), not As (1). That is the subtropical grading profile: Florida LAKEWATCH breakpoints, not Minnesota thresholds. A naturally productive warm-water lake should not flunk because it is not a glacial kettle. The same state is also heavily 303(d)-listed (55.1%) — the listing and the letter are answering different questions, which is the national pattern in miniature.

State by state

Ranked by the share of rated lakes earning A or B. A state average is treated as a ranking only when at least 20 lakes carry a letter (8 states fall below that bar and stay in the table with a note). Open any row for the named lakes behind the average.

The lakes that define the tails

National named-lake lists, US only, clean ranking names, complete grades. The state table is the typical lake. These lists are the exceptions. Each name links to the measurements.

Direction of travel

A trend is published only where a lake has enough repeated summer samples to call a direction on clarity, phosphorus, or chlorophyll-a. Of 7,206 lakes with a call, 2,784 are improving, 2,863 are declining, and 1,559 are stable. The two moving sides are nearly the same size. That is the honest national sentence: US lake water is not collapsing in this dataset, and it is not being rescued all at once either.

Among rankable states, 13 have more improving lakes than declining ones (Michigan, Wyoming, Wisconsin, Vermont, New York, Virginia, …). 13 have the opposite tilt (Florida, Massachusetts, Montana, Minnesota, Nebraska, Utah, …). Improvements usually mean fewer nutrients reaching the water — upgraded wastewater, shoreline buffers, phosphorus kept on the field. Declines run the other way: new shoreline, heavier farm runoff, warmer summers that lengthen the algae season. The named movers: comeback lakes and lakes that are slipping.

Impaired waters are a different list

5,719 lakes in this edition (16.9%) appear on an EPA/state 303(d) impaired-waters list (3,437 formally listed, 3,082 with a TMDL or cleanup plan). That rate is higher than the D/F rate because the two systems measure different things. The letter is nutrients and algae. The list is whatever designated use the state assessed — including toxics the grade never sees.

The most common listed cause is Mercury (2,516 lakes). Nutrients follow (2,102). Algal growth is listed on 1,010 lakes. Mercury in fish tissue is why an A-graded northern lake can still carry a consumption advisory. Pathogens are why a clear lake can still close a beach. Read the letter for nutrients and algae; read the 303(d) row and the fish-advisory explainer for everything the letter is blind to. Per-state lists start at /impaired/mn.

What this means if you use a lake

If you are choosing a place to swim, start with the A and B lakes in the state you can actually reach, then check a current advisory. The letter tells you where the water usually sits. It does not tell you whether a calm, hot week produced a scum this morning. The swimming guide is here; the seasonal algae picture is here.

If you are fishing, a long species list and a high grade can travel together or apart. Mercury and PFAS are tissue contaminants. A clean-looking lake can still be a catch-and-release water for the species you wanted to keep. Start from the lake page and the state advisory, not from the national average.

If you are looking at shoreline property, the useful move is the lake's own multi-year record — grade, trend, 303(d) causes, and how often algae is measured — not the state average. Neighboring lakes in the same county routinely sit two letter grades apart. The property checklist is here.