Lake of the Hills
Scott County, Iowa657 acresView mapDirections
Nutrients and algae sit mid-range for this region.
- Eutrophic
- Impaired · Algal growth
- #4 of 5 in the county
Lake of the Hills in Scott County, Iowa has a water quality grade of C (Fair). Water clarity: 5.1 ft visibility. Phosphorus: 53 µg/L. Chlorophyll-a (algae): 16.8 µg/L. Surface area: 657 acres.
- Clarity
- 5.1 ft
- Typical in September
- 69°F
- Area
- 657 acres
- Type
- Eutrophic
- Phosphorus
- 53 µg/L
- Chlorophyll-a
- 16.8 µg/L
- Trend
- ↑ Improving
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Watch Lake of the Hills’s letter
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Free interactive depth-contour map of Lake of the Hills, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Lake of the Hills is a 657-acre productive, nutrient-rich eutrophic lake in Scott County, Iowa. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 4 other monitored lakes in Scott County, Lake of the Hills ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-26. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyAlgae risk
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 C is nutrients and algae, not a swimming clearance. Lake of the Hills is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Murky, only visible to about 5.1 ft. Phosphorus 53 µg/L. Chlorophyll-a 16.8 µg/L. TSI 58. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.1 ft | Not graded |
| Phosphorus | 53 µg/L | Fair |
| Chlorophyll-a (Algae) | 16.8 µg/L | Fair |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Lake of the Hills typically sits around 69°F at the surface in September. Summer average is about 79°F. Usually warmest in Jul (about 79°F) and coldest in Sep (about 69°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 26 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake of the Hills water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 657 acres |
No bathymetric survey has been published for Lake of the Hills, so its depth is not documented here.
Fishing Lake of the Hills
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.415 m/yr | 4 |
| Phosphorus | ↑ Improving | -41.11 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -51.81 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Lake of the Hills is a man-made reservoir impounded by the Lake of The Hills Dam (completed 1972), built primarily for other on the BLACKHAWK CREEK; earth-type dam, 48 ft tall and 2,400 ft long.
- Surface area
- 657 ac
- Normal storage
- 613 ac-ft
- Max storage
- 1,950 ac-ft
- Drainage area
- 2.6 sq mi
- Hazard class
- High
- Owner
- Iowa Department of Transportation,SCOTT COUNTY CONSERVATION
All listed purposes: Other;Recreation.
Source: USACE National Inventory of Dams, NID ID IA00978 · Operator website
EPA Impairment Status
Lake of the Hills is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 01-NEM-68 · Official waterbody report
Regulated Pollution Sources Nearby
12 EPA-permitted facilities operate within about 5 miles of Lake of the Hills under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 9 facilities have a reported Clean Water Act violation in the past three years.
- Davenport City Of StpDavenport · 3.2 mi away · NPDES IA0043052MajorRecent violation
- Rock Island Main Stp, City OfRock Island · 4.4 mi away · NPDES IL0030783MajorRecent violation
- West Lake ParkDavenport · 0.3 mi away · NPDES IA0066974Recent violation
- Lakeside Manor Mobile Home CommunityDavenport · 1.3 mi away · NPDES IA0064718Recent violation
- Davenport Estates MhcDavenport · 3.2 mi away · NPDES IA0063339Recent violation
- Texpar Energy, LlcDavenport · 3.9 mi away · NPDES IA0001180Recent 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 #4 of 5 lakes in Scott County
Nearby Lakes in Scott County
Frequently asked questions about Lake of the Hills
Where is Lake of the Hills?
- Lake of the Hills is a lake in Scott County, Iowa. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake of the Hills?
- Lake of the Hills in Scott County, Iowa has a water quality grade of C (Fair). Water clarity: 5.1 ft visibility. Phosphorus: 53 µg/L. Chlorophyll-a (algae): 16.8 µg/L. Surface area: 657 acres.
Is Lake of the Hills safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Lake of the Hills is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth. Check local advisories before you swim.
What is the water temperature of Lake of the Hills?
- Lake of the Hills typically sits around 69°F at the surface in September, from 26 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Lake of the Hills across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Iowa's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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Other Grade C Lakes in Iowa
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Where this data comes from
42 measurements from 1 monitoring station, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX42 samples · 2022–2024
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)