Sweetwater Lake
Ramsey County, North DakotaView mapDirections
ND DEQ publishes the water-quality measurements for Sweetwater Lake. Here is what has been measured.
- Eutrophic
- 50 ft max depth
- Limited data
Sweetwater Lake in Ramsey County, North Dakota has water-quality measurements published by ND DEQ, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 655.5 µg/L. Chlorophyll-a (algae): 10.7 µg/L.
Sweetwater Lake is a productive, nutrient-rich eutrophic lake in Ramsey County, North Dakota with an estimated average depth of about 50 feet. Phosphorus level is declining over recent sampling years. Compared to the 7 other monitored lakes in Ramsey County, Sweetwater Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-17. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Sweetwater Lake is safe to swim in today is a call for the North Dakota Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Sweetwater Lake
These are the measurements ND DEQ publishes for Sweetwater Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3 ft of visibility. Phosphorus 655.5 µg/L. Chlorophyll-a 10.7 µg/L. TSI 71.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 656µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 10.7µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 71 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Sweetwater Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Sweetwater Lake typically sits around 45°F at the surface in October. Summer average is about 70°F. Usually warmest in Jul (about 73°F) and coldest in Feb (about 34°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (34°F) to its warmest (73°F).
Typical surface water temperature by month, from 254 field readings (2010–2023) via the EPA Water Quality Portal. See the full Sweetwater Lake water temperature breakdown →
Lake Details
Max depth
~50 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. North Dakota has not published bathymetry for Sweetwater Lake.
Lake Size & Watershed
Watershed (drainage) area
5 sq mi
HydroLAKES / HydroSHEDS
Surface area
262 acres
HydroLAKES / HydroSHEDS
Shoreline
3.7 mi
HydroLAKES / HydroSHEDS
Elevation
1,447 ft
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.
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Stays near Sweetwater Lake
Compare lakeside cabins, hotels, and vacation rentals near Sweetwater Lake in Ramsey County, North Dakota — 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 Sweetwater Lake
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Fishing Sweetwater Lake
Water Quality Trend: Stable
Based on 4 years of monitoring (2020–2023).
Water clarity
Stable3 years
Phosphorus
Worsening+187.79 µg/L/yr3 years
Chlorophyll-a
Improving-42.12 µg/L/yr4 years
Nearby Lakes in Ramsey County
Frequently asked questions about Sweetwater Lake
Where is Sweetwater Lake?
- Sweetwater Lake is a lake in Ramsey County, North Dakota. Its water-quality measurements are published by ND DEQ and shown on this page as reported.
What is the water quality of Sweetwater Lake?
- Sweetwater Lake in Ramsey County, North Dakota has water-quality measurements published by ND DEQ, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 655.5 µg/L. Chlorophyll-a (algae): 10.7 µg/L.
Is Sweetwater Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Sweetwater Lake?
- Sweetwater Lake typically sits around 45°F at the surface in October, from 254 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Sweetwater Lake?
- No published bathymetric survey covers Sweetwater Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 50 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Sweetwater Lake across LakeQuality
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Where this data comes from
31 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS North Dakota Water Science Center
USGS-ND31 samples · 2020–2023
Analytical methods
- P, wu, WCA, persulfate CF color
- Plant pigments, sonication & 445
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Depth, fish, and access data from North Dakota Game & Fish