What is the water quality grade for Sweet Briar Dam-Mid Reservoir?

Sweet Briar Dam-Mid Reservoir in Morton County, North Dakota received a water quality grade of F (Very Poor). Water clarity: 3 ft visibility. Chlorophyll-a (algae): 36.9 µg/L. Maximum depth: 29.9 ft. Surface area: 278 acres.

Is Sweet Briar Dam-Mid Reservoir safe to swim in?

Avoid swimming, very poor water quality, potential algae toxins. Sweet Briar Dam-Mid Reservoir has an overall water quality grade of F. Algae concentration (chlorophyll-a) is 36.9 µg/L. Always check local health department advisories before swimming.

How deep is Sweet Briar Dam-Mid Reservoir?

Sweet Briar Dam-Mid Reservoir has a maximum depth of 29.9 feet and an average depth of 10 feet. The lake covers 278 acres.

Morton County, North Dakota

Sweet Briar Dam-Mid Reservoir

Grade FVery Poor · 3 ft clarity

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Eutrophic

Sweet Briar Dam-Mid Reservoir is a 278-acre productive, nutrient-rich eutrophic lake in Morton County, North Dakota with a maximum depth of 30 feet (10-foot average). Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. The lake supports 8 documented fish species including Walleye, Yellow Perch, and Black Crappie. Public access is available with 1 public boat landing. Compared to the 3 other monitored lakes in Morton County, Sweet Briar Dam-Mid Reservoir ranks #3 for water quality.

Source: EPA Water Quality Portal sampling records, North Dakota DNR, last sampled 2024-08-06. Grade methodology: LakeGrade methodology.

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Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

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Water Quality Grade: F, Very Poor

Very murky, less than 3 ft of visibility. Chlorophyll-a: 36.9 µg/L. Trophic State Index: 64.

Metric	Value	Grade
Water Clarity (Secchi Depth)	3 ft	F
Phosphorus	No data
Chlorophyll-a (Algae)	36.9 µg/L	F
Trophic State Index (TSI)	64	Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

Characteristic	Value
Maximum Depth	29.9 ft
Average Depth	10 ft
Surface Area	278 acres
Shoreline Length	10.5 mi
Public Access	Yes

Where to stay near Sweet Briar Dam-Mid Reservoir

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Fish Species

Walleye Yellow Perch Black Crappie Bluegill Northern Pike Black Bullhead Common Carp Channel Catfish

Click a species to see every graded lake where it is documented.

Fishing Sweet Briar Dam-Mid Reservoir

Water Quality Trend: ↑ Improving

Based on 3 years of monitoring data (2020-2025).

Metric	Trend	Change/Year	Years
Water Clarity	↑ Improving	+0.32 m/yr	2
Chlorophyll-a	↑ Improving	-29.3 µg/L/yr	3

Recreation & Access

Boat Landings

Yes

Public Access

Water Temperature

Sweet Briar Dam-Mid Reservoir averages about 64°F at the surface in summer, usually warmest in Jun (about 74°F) and coldest in Oct (about 44°F). These are typical values by month — not a live reading.