Arrowhead Lake
Sac County, Iowa110 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↑ up from C at the last regrade
- Eutrophic
- Impaired · Algal growth
- #1 of 2 in the county
- Public access
Arrowhead Lake in Sac County, Iowa has a water quality grade of B (Good). Water clarity: 5.6 ft visibility. Phosphorus: 26 µg/L. Chlorophyll-a (algae): 7.1 µg/L. Surface area: 110 acres.
- Clarity
- 5.6 ft
- Typical in August
- 79°F
- Area
- 110 acres
- Type
- Eutrophic
- Phosphorus
- 26 µg/L
- Chlorophyll-a
- 7.1 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Free interactive depth-contour map of Arrowhead Lake, reaching a maximum surveyed depth of 22 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Arrowhead Lake is a 110-acre productive, nutrient-rich eutrophic lake in Sac County, Iowa. Water quality is graded B based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 1 other monitored lakes in Sac County, Arrowhead Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-04. Grade methodology: LakeQuality methodology.
What Arrowhead Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming Safety
Grade onlyBacteria advisory
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 B is nutrients and algae, not a swimming clearance. Arrowhead Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, pathogens (E. coli, fecal), turbidity. Check local advisories before you swim.
Water Quality Grade: B (Good)
Murky, only visible to about 5.6 ft. Phosphorus 26 µg/L. Chlorophyll-a 7.1 µg/L. TSI 51. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | 26 µg/L | Good |
| Chlorophyll-a (Algae) | 7.1 µg/L | Good |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Arrowhead Lake typically sits around 79°F at the surface in August. Summer average is about 78°F. Usually warmest in Jul (about 80°F) and coldest in May (about 64°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. See the full Arrowhead Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 110 acres |
| Public Access | Yes |
No bathymetric survey has been published for Arrowhead Lake, so its depth is not documented here.
Recreation & Access
- Black Hawk Wildlife AreaPublic
- Black Hawk Wildlife AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Arrowhead Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.016 m/yr | 5 |
| Phosphorus | ↑ Improving | -10.3 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -4.99 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Arrowhead Lake is a man-made reservoir impounded by the Provost Bay Dam, built primarily for other on the unnamed tributary; earth-type dam, 10 ft tall and 650 ft long.
- Surface area
- 110 ac
- Max storage
- 257 ac-ft
- Drainage area
- 0.54 sq mi
- Hazard class
- Low
- Owner
- Iowa Department of Natural Resources
Source: USACE National Inventory of Dams, NID ID IA04396 · Operator website · Matched by proximity (0.67 km)
EPA Impairment Status
Arrowhead Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-RAC-1134 · Official waterbody report · Matched by proximity (2.12 km)
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Arrowhead Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- Lake View City Of StpLake View · 1.1 mi away · NPDES IA0041998Recent violation
- Wall Lake City Of StpWall Lake · 3.1 mi away · NPDES IA0033065Recent violation
- Western Iowa Energy, LlcWall Lake · 3.5 mi away · NPDES IA0079855Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #1 of 2 lakes in Sac County
Nearby Lakes in Sac County
Frequently asked questions about Arrowhead Lake
Where is Arrowhead Lake?
- Arrowhead Lake is a lake in Sac County, Iowa. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Arrowhead Lake?
- Arrowhead Lake in Sac County, Iowa has a water quality grade of B (Good). Water clarity: 5.6 ft visibility. Phosphorus: 26 µg/L. Chlorophyll-a (algae): 7.1 µg/L. Surface area: 110 acres.
Is Arrowhead Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Arrowhead Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, pathogens (E. coli, fecal), turbidity. Check local advisories before you swim.
What is the water temperature of Arrowhead Lake?
- Arrowhead Lake typically sits around 79°F at the surface in August, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Are there boat ramps on Arrowhead Lake?
- Arrowhead Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Black Hawk Wildlife Area, Black Hawk Wildlife Area. Public access is listed as yes.
Explore Arrowhead Lake across LakeQuality
More Iowa Lake Rankings
Other Grade B Lakes in Iowa
Eutrophic Lakes in Iowa
Where this data comes from
60 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX60 samples · 2020–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory