Summit Lake
Union County, Iowa202 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #4 of 6 in the county
- 57 ft max depth
- Public access
Summit Lake in Union County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.4 ft visibility. Phosphorus: 121 µg/L. Chlorophyll-a (algae): 45.7 µg/L. Surface area: 202 acres.
- Clarity
- 1.4 ft
- Typical in September
- 70°F
- Max depth
- ~57 ft est.
- Area
- 202 acres
- Type
- Hypereutrophic
- Phosphorus
- 121 µg/L
- Chlorophyll-a
- 45.7 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Stays near Summit Lake
Compare lakeside cabins, hotels, and vacation rentals near Summit Lake in Union County, Iowa — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Summit Lake are listed below.
Top-rated places to stay near Summit Lake
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Watch Summit Lake’s letter
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Free interactive depth-contour map of Summit Lake, reaching a maximum surveyed depth of 10 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Summit Lake is a 202-acre highly nutrient-loaded hypereutrophic lake in Union County, Iowa with an estimated average depth of about 57 feet. Water quality is graded F 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 1 public boat landing. Compared to the 5 other monitored lakes in Union County, Summit Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-30. Grade methodology: LakeQuality methodology.
What Summit Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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 F is nutrients and algae, not a swimming clearance. Summit Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, pCBs, turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.4 ft of visibility. Phosphorus 121 µg/L. Chlorophyll-a 45.7 µg/L. TSI 71. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.4 ft | Not graded |
| Phosphorus | 121 µg/L | Poor |
| Chlorophyll-a (Algae) | 45.7 µg/L | Poor |
| Trophic State Index (TSI) | 71 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Summit Lake typically sits around 70°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 80°F) and coldest in Sep (about 70°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 Summit Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~57 ft est. |
| Average Depth | ~14 ft est. |
| Surface Area | 202 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Summit Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Summit LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Summit Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.042 m/yr | 5 |
| Phosphorus | ↑ Improving | -15.89 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -5.66 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Summit Lake is a man-made reservoir impounded by the Summit Lake Dam (completed 1935), built primarily for recreation on the TR-WEST PLATTE RIVER; earth-type dam, 26 ft tall and 1,000 ft long.
- Surface area
- 202 ac
- Normal storage
- 1,410 ac-ft
- Max storage
- 2,680 ac-ft
- Drainage area
- 15.7 sq mi
- Hazard class
- Low
- Owner
- Creston Waterworks
Source: USACE National Inventory of Dams, NID ID IA01379 · Operator website
EPA Impairment Status
Summit Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 05-PLA-1470 · Official waterbody report · Matched by proximity (1.17 km)
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Summit Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Cromwell, City-Stp -SirwaCromwell · 3.5 mi away · NPDES IA0074063Recent violation
- Creston City Water Treatment PlantCreston · 0.1 mi away · NPDES IA0078514
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 6 lakes in Union County
Nearby Lakes With Higher Grades
Summit Lake holds Grade F. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Union County
Frequently asked questions about Summit Lake
Where is Summit Lake?
- Summit Lake is a lake in Union County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Summit Lake?
- Summit Lake in Union County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.4 ft visibility. Phosphorus: 121 µg/L. Chlorophyll-a (algae): 45.7 µg/L. Surface area: 202 acres.
Is Summit Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Summit Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, pCBs, turbidity. Check local advisories before you swim.
What is the water temperature of Summit Lake?
- Summit Lake typically sits around 70°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.
How deep is Summit Lake?
- No published bathymetric survey covers Summit Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 57 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 202 acres.
Are there boat ramps on Summit Lake?
- Summit Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Summit Lake. Public access is listed as yes.
Explore Summit Lake 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
Very high nutrients, dense algae, poor clarity
Iowa's cleanest and most-polluted lakes, ranked
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
58 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_WQX58 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)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory