Lakes Making a Water-Quality Comeback

Of 7,086 lakes across the 49 states and 2 Canadian provinces with several years of monitoring, 2,797 are improving and 2,791 are declining. A comeback here means a measured trend in the right direction, sustained over years of sampling.

What counts as a comeback

Every lake here carries a current grade and a trend built from repeated sampling over several years. The lakes worth calling comebacks are the ones improving while they still grade C, D, or F: the water is measurably getting better, and there is still a long way to go. A lake that already grades A and is getting slightly clearer is good news, but it is not a recovery — it never fell.

The longest-record lake in that recovering set is Hardy Ford Lake (VA), currently C on 15 years of samples, with phosphorus around 40 µg/L. The live improving list — including the already-clean lakes — is the improving ranking.

Recovery in progress: improving lakes that still grade C, D, or F

These are the lakes where the trend and the letter disagree in a useful way. The water is getting better. It is not yet Good for its ecoregion. That is the actual comeback window — and the one watershed work is trying to widen. Phosphorus is the usual lever; the chemistry is in Why Lakes Turn Green.

Lake	State	Grade	Clarity (ft)	Phosphorus (µg/L)	Years of data
Hardy Ford Lake	VA	C	3	40	15
Middle Blackwater River Lake	VA	C	5.9	20	15
Dam Lake	VA	C	8.5	20	15
Hales Ford Lake	VA	C	4.9	20	15
Peak Creek Lake	VA	C	5.6	20	15
State Park Lake	VA	C	7.5	20	15
Mouth Peak Cr. Lake	VA	C	6.9	20	15
Confl. Indian Cr. Lake	VA	C	4.6	20	15
Gills Creek Lake	VA	C	6.2	20	15
Dublin Water Works Lake	VA	C	7.2	10	15
Harry Strunk Lake	NE	C	2.5	68	13
Tennessee River Lake	TN	C	—	33	13

Already-clean lakes that are still improving

12 A- or B-graded lakes in the improving set still have an upward trajectory. The current head of that list is Rainy Lake (MN). These are not comebacks from poor condition. They are the less cinematic fact that a Good lake can still get clearer, which is worth knowing if the question is “is this watershed work doing anything?”

Lake	State	Grade	Clarity (ft)	Years of data
Rainy Lake	MN	A	13.9	6
Crane Lake	MN	A	9	6
East Fox Lake	MN	A	16.4	6
Deep Portage Lake	MN	A	15.4	6
Lower Hay Lake	MN	A	18.5	6
Big Lake	MN	A	10	6
Pelican Lake	MN	A	14.3	6
Birch Lake	MN	A	5.9	6
Birch Lake	MN	A	15	6
Round Lake	MN	A	13.5	6
Round Lake	MN	A	16.5	6
Round Lake	MN	A	18	6

What actually moves a lake

The EPA nutrient-pollution program is blunt about the inputs: fertilizer and manure from farm fields, urban stormwater, and leaking septics. Cut those and chlorophyll-a usually follows, slowly. The National Lakes Assessment keeps finding the same national pattern — excess phosphorus in about half of U.S. lakes — which is why a local restoration that never touches the watershed is a stall dressed up as a project.

Agricultural conservation (cover crops, buffer strips, manure timing) reduces the phosphorus walking off the field.
Wastewater and stormwater upgrades cut the urban and point-source share.
Shoreline buffers keep bank soil — and the phosphorus stuck to it — out of the water.
In-lake alum can bind sediment phosphorus when internal loading is the leftover problem. It is a treatment, not a substitute for the watershed work.

The other direction of the same dataset is The Lakes Where Water Quality Is Slipping. How a letter is assigned in the first place is Lake Water Quality Grades Explained.

Frequently Asked Questions

Monitoring records show the direction water quality is moving, not a letter grade for every past year, so no lake here is described as having gone “from F to A.” What the data does show is the trend: of 7,086 lakes with several years of sampling, 2,797 are improving. The most interesting are the ones improving while they still grade C, D, or F — recovery in progress rather than a lake that was already clean.

A lake is flagged improving only when it has several years of repeated sampling and the direction of phosphorus, chlorophyll-a, and/or clarity is getting better over that record. A single good summer is not a trend.

Measured in years to decades. Cutting the phosphorus coming in from the watershed is the durable step. Phosphorus already stored in bottom sediment can keep feeding algae after the farms and septics are cleaned up, which is why some lakes stall even after the obvious sources are gone.

Every improving lake — 2,797 of them right now — is listed at lakequality.org/ranking/improving. Lakes moving the other way are at lakequality.org/ranking/declining, with a companion article on where quality is slipping.