Sherman Reservoir
Sherman County, Nebraska2,868 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from C at the last regrade
- Mesotrophic
- Impaired · Mercury
- #2 of 2 in the county
- Public access
Sherman Reservoir in Sherman County, Nebraska has a water quality grade of A (Excellent). Water clarity: 2.4 ft visibility. Phosphorus: 99.7 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Surface area: 2868 acres.
- Clarity
- 2.4 ft
- Area
- 2,868 acres
- Type
- Mesotrophic
- Phosphorus
- 99.7 µg/L
- Chlorophyll-a
- 4.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Sherman Reservoir’s letter
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Sherman Reservoir is a 2,868-acre mesotrophic lake in Sherman County, Nebraska. Water quality is graded A based on 1 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 1 other monitored lakes in Sherman County, Sherman Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, NDEE, last sampled 2024-09-09. Grade methodology: LakeQuality methodology.
What Sherman Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
- Camping1 public campground nearby
- Big water2,868 acres
Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Sherman Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Very murky, less than 2.4 ft of visibility. Phosphorus 99.7 µg/L. Chlorophyll-a 4.4 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.4 ft | Not graded |
| Phosphorus | 99.7 µg/L | Not graded |
| Chlorophyll-a (Algae) | 4.4 µg/L | Good |
| Trophic State Index (TSI) | 60 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 2,868 acres |
| Public Access | Yes |
No bathymetric survey has been published for Sherman Reservoir, so its depth is not documented here.
Recreation & Access
- Marina BayPublic
- Thunder BayPublic
- Tradewinds MarinaSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Sherman Reservoir
- Sherman Reservoir State Recreation Area2.9 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Fishing Sherman Reservoir
Water Quality Trend: ↑ Improving
Based on 13 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.86 m/yr | 13 |
| Phosphorus | → Stable | +1.86 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.11 µg/L/yr | 12 |
Reservoir Info (USACE NID)
Sherman Reservoir is a man-made reservoir impounded by the Sherman Dam (completed 1962), built primarily for irrigation on the Oak Creek; earth-type dam, 134 ft tall and 4,450 ft long.
- Surface area
- 2,868 ac
- Normal storage
- 69,100 ac-ft
- Max storage
- 125,477 ac-ft
- Drainage area
- 37 sq mi
- Hazard class
- High
- Owner
- Farwell Irrigation District
Source: USACE National Inventory of Dams, NID ID NE01077 · Operator website
EPA Impairment Status
Sherman Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit NE-LO3-L0020 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Sherman County
Nearby Lakes in Sherman County
Frequently asked questions about Sherman Reservoir
Where is Sherman Reservoir?
- Sherman Reservoir is a lake in Sherman County, Nebraska. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Sherman Reservoir?
- Sherman Reservoir in Sherman County, Nebraska has a water quality grade of A (Excellent). Water clarity: 2.4 ft visibility. Phosphorus: 99.7 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Surface area: 2868 acres.
Is Sherman Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Sherman Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Are there boat ramps on Sherman Reservoir?
- Sherman Reservoir has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Marina Bay, Thunder Bay, Tradewinds Marina. Public access is listed as yes.
Are there campgrounds on Sherman Reservoir?
- Sherman Reservoir has 1 public campground from USGS The National Map within 5 km, including Sherman Reservoir State Recreation Area. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Sherman Reservoir across LakeQuality
More Nebraska Lake Rankings
Other Grade A Lakes in Nebraska
Mesotrophic Lakes in Nebraska
Where this data comes from
173 measurements from 2 monitoring stations, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Nebraska Department of Environment and Energy
21NEB001_WQX173 samples · 2012–2024
Analytical methods
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
- Total Phosphorus After Block Digestion
Monitoring station identifiers (2)
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
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory
Public campgrounds from USGS The National Map Structures, within about 3 miles