Terrapin Lake
Terrapin Lake in Washington County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 9.7 ft visibility.
- Clarity
- 9.7 ft
- Typical in August
- 74°F
- Max depth
- ~41 ft est.
- Public access
- No
- Ice-out
- Mar 20
Next lake in Washington County
Why Terrapin Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Terrapin Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Terrapin Lake is a lake in Washington County, Minnesota with an estimated average depth of about 41 feet. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-27. Grade methodology: LakeGrade methodology.
Watch Terrapin Lake water quality
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Terrapin Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Moderate clarity, visible to about 9.7 ft. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.7 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Terrapin Lake
Compare lakeside cabins, hotels, and vacation rentals near Terrapin Lake in Washington County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Terrapin Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Terrapin Lake typically sits around 74°F at the surface in August. Summer average is about 72°F. Usually warmest in Aug (about 74°F) and coldest in Apr (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 90 field readings (2011–2019) via the EPA Water Quality Portal. See the full Terrapin Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~41 ft est. |
| Average Depth | ~16 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Terrapin Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Terrapin Lake
Ice Season
Historical ice data from Minnesota DNR (4 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-19 (2012) | 2009-04-03 (2009) |
| Ice-In | 2012-11-23 (2012) | 2012-11-23 (2012) |
Most recent ice-out: 2012-03-19
Graded lakes near Terrapin Lake
Terrapin Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Washington County
Frequently asked questions about Terrapin Lake
What is the water quality grade for Terrapin Lake?
- Terrapin Lake in Washington County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 9.7 ft visibility.
Is Terrapin Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Terrapin Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Terrapin Lake?
- Terrapin Lake typically sits around 74°F at the surface in August, from 90 EPA Water Quality Portal field readings (2011–2019). That is a typical value for the month, not a live reading.
How deep is Terrapin Lake?
- No published bathymetric survey covers Terrapin Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 41 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
When does Terrapin Lake thaw?
- Terrapin Lake typically has ice-out around Mar 20.
Explore Terrapin Lake across LakeGrade
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Where this data comes from
3 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA3 samples · 2024
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate