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LakeQuality

Eutrophic lakes — TSI 50 to 70 — are nutrient-rich and productive, with persistent summer algal communities that drive visible reductions in clarity. These conditions are not failures; they reflect a lake doing what nutrient-loaded waters do. 18 Wyoming lakes register as eutrophic. Only 0% are deep — eutrophy correlates with shallowness, agricultural watersheds, and the kind of nutrient-input history that takes decades to shift.

Eutrophic lakes typically carry higher phosphorus and chlorophyll-a readings. The same nutrient richness that defines the trophic class shows up in those numbers.

#LakeCountyClarityDepthTSI
1Seminoe Reservoir Riverine PelagicCarbon4.4 ft-55
2Glendo Reservoir Riverine PelagicPlatte1.4 ft-68
3Glendo Reservoir Lacustrine PelagicPlatte5.2 ft-50
4Alcova Reservoir Riverine PelagicNatrona5.8 ft-52
5Greyrocks ReservoirPlatte5.4 ft-50
6Guernsey ReservoirPlatte4.9 ft-51
7Glendo Reservoir Transitional PelagicPlatte5.3 ft-53
8Ocean LakeFremont2.2 ft-58
9Mavrakis PondSheridan0.9 ft-69
10Bighorn LakeBig Horn--62
11City ReservoirPark--64
12Unnamed ReservoirBig Horn--64
13South Crow ReservoirLaramie--53
14Hawk Springs ReservoirGoshen1.1 ft-68
15Sloans LakeLaramie2 ft-63
16Brooks LakeFremont6.3 ft-56
17Yellowtail Reservoir RpdBig Horn--70
18Rawlins ReservoirCarbon--63

Source: EPA National Aquatic Resource Surveys, 2026.