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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
NR

Union County Lake Quality

New Mexico, 10 lakes — no lake here has enough monitoring data for a grade

Union County has 10 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. No lake in Union County has enough sampling behind it for an A–F grade yet. The 10 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.

Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.

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Where to stay near Union County

Top-rated places to stay near Union County

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Quick Answers for Union County

Cleanest lakes in Union County →Safest swimming lakes in New Mexico →

Planning a trip? Check special fishing regulations for Clayton Lake Deep Dam — or check the official New Mexico fishing regulations.

All Lakes in Union County

10 lakes · 0 graded, 10 not rated0 graded lakes · 10 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
NRClayton Lake Deep DamUnionNR3.9 ftNo recent samples10.3 µg/LNo recent samples✓ Public
NRAntelope Spring LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHorse LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMorris LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRShields LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRWeatherly LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMalpie LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRPasamonte LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMaestas LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLowry LakeUnionNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded

NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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Other Counties in New Mexico

San Miguel County

9 lakes · Avg grade A

Guadalupe County

6 lakes · Avg grade A

Rio Arriba County

24 lakes · Avg grade C

Sandoval County

11 lakes · Avg grade C

Otero County

7 lakes · Avg grade C

Lincoln County

6 lakes · Avg grade D

See how Union County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..

Source: EPA National Aquatic Resource Surveys, 2026.