Summit Lake
Union County, Iowa202 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Summit Lake. Here is what has been measured.
- Hypereutrophic
- 57 ft max depth
- Public access
Summit Lake in Union County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.4 ft visibility. Phosphorus: 121 µg/L. Chlorophyll-a (algae): 45.7 µg/L. Surface area: 202 acres.
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. 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. Methodology: how these readings are compared.
What Summit Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyAlgae risk
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Summit Lake is safe to swim in today is a call for the Iowa Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Summit Lake
These are the measurements Iowa DNR publishes for Summit Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.4 ft of visibility. Phosphorus 121 µg/L. Chlorophyll-a 45.7 µg/L. TSI 71.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 121µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 45.7µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 71 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Summit Lake
Answers come straight from the public measurements and survey records on this page.
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.
Column height runs from this lake’s coldest month (70°F) to its warmest (80°F).
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
Max depth
~57 ft est.
Surface area
202 acres
Public access
Yes
Listed by Iowa DNR
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
Watershed (drainage) area
16 sq mi
HydroLAKES / HydroSHEDS
Shoreline
5 mi
HydroLAKES / HydroSHEDS
Elevation
1,240 ft
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
Stays via Stay22
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 readings cover nutrients and algae, not lodging. Cabins and rentals around Summit Lake are listed below.
Top-rated places to stay near Summit Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Summit Lake → · more Iowa lake trips
Follow Summit Lake’s readings
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Fishing Summit Lake
Water Quality Trend: Improving
Based on 5 years of monitoring (2020–2024).
Water clarity
Improving5 years
Phosphorus
Improving-15.89 µg/L/yr5 years
Chlorophyll-a
Improving-5.66 µg/L/yr5 years
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
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.
Nearby Lakes in Union County
Frequently asked questions about Summit Lake
Where is Summit Lake?
- Summit Lake is a lake in Union County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Summit Lake?
- Summit Lake in Union County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. 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.
Can I fish at Summit Lake?
- Summit Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Iowa's fish and wildlife agency, so check its current regulations before you go.
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 readings
Iowa's cleanest lakes, ranked on agency measurements
More lakes in Iowa
Other 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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
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