Blackwater Lake
Cass County, Minnesota, near Longville. DNR lake ID 11027400.
Blackwater Lake is a 766.7-acre lake in Cass County, Minnesota, near Longville. Its deepest point reaches 67 ft, and about 44% of the lake is shallower than 15 feet. Summer water clarity averages 14.4 feet in Minnesota Pollution Control Agency monitoring, which places it in the mesotrophic nutrient class. It is not on the DNR infested waters list as of September 2026. DNR surveys document walleye, northern pike, largemouth bass, smallmouth bass, black crappie, bluegill.
Buying or selling on Blackwater Lake? Ask us what lakeshore here actually sells for, which stretches of shoreline buyers compete for, and what’s coming up before it’s listed.
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Quick facts
| DNR lake ID | 11027400 |
|---|---|
| County | Cass County, near Longville |
| Surface area | 766.7 acres |
| Maximum depth | 67 ft |
| Share under 15 ft | 44% |
| Water clarity (summer) | 14.4 ft through 2025 |
| Phosphorus (summer) | 12.3 µg/L |
| Algae, chlorophyll-a (summer) | 4.0 µg/L |
| Nutrient class | Mesotrophic |
| Clarity trend | Steady (2016 to 2025) |
| Invasive species | Not on DNR infested waters list (Sept 2026) |
| Public water accesses | 1 |
Water quality
Summer averages from Minnesota Pollution Control Agency monitoring through 2025: clarity 14.4 ft, phosphorus 12.3 µg/L, algae (chlorophyll-a) 4.0 µg/L. Using the Carlson trophic state index, Blackwater Lake rates as mesotrophic. Summer clarity trend 2016 to 2025: steady.
Fishing on Blackwater Lake
The most recent DNR standard fish survey was in 2019 (7 years ago). Catch per net is compared with the DNR’s typical range for lakes of the same type.
| Species | Net | Catch per net | Typical range |
|---|---|---|---|
| Walleye | gill | 1.92 | 1.3 to 5.5 |
| Walleye | trap | 0.09 | 0.2 to 0.7 |
| Northern pike | gill | 12.5 | 3.1 to 8.5 |
| Northern pike | trap | 0.18 | n/a |
| Yellow perch | gill | 1.5 | 2.5 to 24.2 |
| Yellow perch | trap | 0.18 | 0.5 to 2.7 |
| Black crappie | gill | 0.17 | 0.5 to 2.7 |
| Black crappie | trap | 0.64 | 0.7 to 3.2 |
| Bluegill | gill | 2.5 | n/a |
| Bluegill | trap | 23.64 | 5.6 to 42.3 |
| Largemouth bass | gill | 1.67 | 0.3 to 1.2 |
| Largemouth bass | trap | 1.27 | 0.3 to 1.1 |
| Smallmouth bass | gill | 0.17 | 0.2 to 1.0 |
| Smallmouth bass | trap | 0.45 | 0.1 to 0.4 |
| Tullibee (cisco) | gill | 0.42 | 0.7 to 6.5 |
| Pumpkinseed | gill | 2.5 | n/a |
| Pumpkinseed | trap | 2.91 | 1.7 to 8.2 |
| Rock bass | gill | 2.08 | 0.3 to 2.0 |
| Rock bass | trap | 2.09 | 0.6 to 2.5 |
| Hybrid sunfish | trap | 3.09 | n/a |
Walleye catch was within the typical range for similar lakes in that survey.
Largest fish measured in recent DNR samples: Largemouth bass 17.0 in (2019), Northern pike 32.0 in (2019), Smallmouth bass 18.0 in (2019), Walleye 23.0 in (2019).
Game and panfish documented since 2005: Walleye, Northern pike, Largemouth bass, Smallmouth bass, Black crappie, Bluegill, Yellow perch, Pumpkinseed, Hybrid sunfish, Rock bass, Tullibee (cisco), Bowfin, White sucker, Yellow bullhead, Brown bullhead, Black bullhead.
Fishing regulations
No lake-specific regulation found in Minnesota Rules or the DNR sunfish list. Statewide and zone regulations apply.
Regulations change. Confirm with the DNR before fishing.
Invasive species
Not on the Minnesota DNR infested waters list as of September 2026. That means no confirmed listing, not a guarantee the lake is free of invasive species.
Public boat access
- Black Water Lake: 1 concrete slab launch ramp, 1 dock, 10 trailer spaces. 7 mi SW of Longville on Hwy 84, then 0.5 mi W on Co Rd 11, then .25 mile S on Woodrow Twp Rd 11. Directions
DNR water access records (2023). Confirm current conditions with the DNR.
Nearby lakes
- IXL Lake 1.5 mi, Cass County
- Widow Lake 1.5 mi, Cass County
- Island Lake 1.6 mi, Cass County
- Sand Lake 1.7 mi, Cass County
- Sand Lake 1.7 mi, Cass County
- Mule Lake 1.9 mi, Cass County
- Squeedunk Lake 2.4 mi, Cass County
- Little Woman Lake 2.8 mi, Cass County
Questions about Blackwater Lake
How deep is Blackwater Lake?
Blackwater Lake reaches a maximum depth of 67 ft according to Minnesota DNR records. About 44% of the lake is shallower than 15 feet.
How big is Blackwater Lake?
Blackwater Lake covers about 766.7 acres in Cass County, Minnesota.
How clear is Blackwater Lake?
Summer water clarity on Blackwater Lake averages 14.4 feet (Secchi depth) in MPCA monitoring through 2025. Its trophic state is mesotrophic.
Does Blackwater Lake have zebra mussels or other invasive species?
Blackwater Lake is not on the Minnesota DNR infested waters list as of September 2026. That means there is no confirmed listing; it is not a guarantee the lake is free of invasive species.
What fish are in Blackwater Lake?
Minnesota DNR surveys document walleye, northern pike, largemouth bass, smallmouth bass, black crappie, bluegill, yellow perch, pumpkinseed, hybrid sunfish, rock bass in Blackwater Lake. The most recent standard survey was in 2019.
Where is the public boat access on Blackwater Lake?
Blackwater Lake has 1 public water access site on DNR record: Black Water Lake.
How is the walleye population on Blackwater Lake?
In Minnesota DNR net surveys from 1995 to 2019, walleye numbers on Blackwater Lake ran mostly within the typical range for similar lakes. Nets measure how many fish a lake holds, not where they’re biting, so local guides are the best source for current fishing.
Are there lake homes for sale on Blackwater Lake?
Homes on Blackwater Lake come up for sale throughout the year, and some sell before they’re ever publicly advertised. Tell us what you’re looking for and our agents will run a custom search and send you matching homes on Blackwater Lake and nearby lakes, including off-market opportunities when available.
What is it like to live on Blackwater Lake?
A mid-size lake with room for boating and fishing, about 44% shallow shoreline under 15 feet, and summer clarity around 14.4 feet. Conditions vary by property, so walk the frontage and ask us what similar homes have sold for.
Are there special fishing regulations on Blackwater Lake?
No lake-specific regulation was found for Blackwater Lake in Minnesota Rules or the DNR sunfish list. Statewide and zone regulations apply.
Ask us about Blackwater Lake
Whether you’re buying, selling, or just curious, our team works Cass County lakes every day. Send us a note or call (218) 656-6469.
Sources: Minnesota DNR LakeFinder records, DNR fish surveys (latest 2019), DNR infested waters list (Sept 2026), Minnesota Rules 6264.0400 (April 2026), MPCA monitoring via the Water Quality Portal, DNR water access records (2023), LAGOS-US. Lakewide information from public data; it does not describe any specific property. Verify shoreline, bottom type, and depth at any frontage.