Big Hollow Lake
Des Moines County, Iowa178 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Big Hollow Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Algal growth
Big Hollow Lake in Des Moines County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.8 ft visibility. Phosphorus: 118 µg/L. Chlorophyll-a (algae): 46 µg/L. Surface area: 178 acres.
Free interactive depth-contour map of Big Hollow Lake, reaching a maximum surveyed depth of 44 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Big Hollow Lake is a 178-acre highly nutrient-loaded hypereutrophic lake in Des Moines County, Iowa. Phosphorus level is improving over recent sampling years. Compared to the 1 other monitored lakes in Des Moines County, Big Hollow Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-16. Methodology: how these readings are compared.
Swimming conditions
Readings onlyRecreation use not supported
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.
Based on E. coli testing, Big Hollow Lake routinely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 28.6% of 7 samples across 2 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Whether Big Hollow 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 Big Hollow Lake
These are the measurements Iowa DNR publishes for Big Hollow 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 1.8 ft of visibility. Phosphorus 118 µg/L. Chlorophyll-a 46 µg/L. TSI 70.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 118µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 46µg/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. | 70 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Big Hollow Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Big Hollow Lake typically sits around 71°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 81°F) and coldest in Sep (about 71°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (71°F) to its warmest (81°F).
Typical surface water temperature by month, from 23 field readings (2011–2023) via the EPA Water Quality Portal. See the full Big Hollow Lake water temperature breakdown →
Lake Details
Surface area
178 acres
No bathymetric survey has been published for Big Hollow Lake, so its depth is not documented here.
Stays via Stay22
Stays near Big Hollow Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Hollow Lake in Des Moines 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 Big Hollow Lake are listed below.
Top-rated places to stay near Big Hollow Lake
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Fishing Big Hollow Lake
Water Quality Trend: Stable
Based on 4 years of monitoring (2021–2024).
Water clarity
Stable4 years
Phosphorus
Improving-2.55 µg/L/yr4 years
Chlorophyll-a
Worsening+2.75 µg/L/yr4 years
Reservoir Info (USACE NID)
Big Hollow Lake is a man-made reservoir impounded by the Big Hollow Dam (completed 2008), built primarily for recreation on the Big Hollow Creek; earth-type dam, 60 ft tall and 795 ft long.
- Surface area
- 178 ac
- Normal storage
- 3,046 ac-ft
- Max storage
- 5,942 ac-ft
- Drainage area
- 7.5 sq mi
- Hazard class
- Significant
- Owner
- Des Moines County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA03551 · Operator website
EPA Impairment Status
Big Hollow Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 02-ICD-6496 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Big Hollow Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- United States Gypsum Company - MediapolisMediapolis · 3.7 mi away · NPDES IA0063606Recent 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.
Nearby Lakes in Des Moines County
Frequently asked questions about Big Hollow Lake
Where is Big Hollow Lake?
- Big Hollow Lake is a lake in Des Moines County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Big Hollow Lake?
- Big Hollow Lake in Des Moines County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.8 ft visibility. Phosphorus: 118 µg/L. Chlorophyll-a (algae): 46 µg/L. Surface area: 178 acres.
Is Big Hollow Lake safe to swim in?
- Based on E. coli testing, Big Hollow Lake routinely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 28.6% of 7 samples across 2 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Big Hollow Lake is safe to swim in today is a call for Iowa's water agency and the county health department; check their current beach advisories before you swim.
What is the water temperature of Big Hollow Lake?
- Big Hollow Lake typically sits around 71°F at the surface in September, from 23 EPA Water Quality Portal field readings (2011–2023). That is a typical value for the month, not a live reading.
Explore Big Hollow Lake across LakeQuality
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Where this data comes from
53 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX53 samples · 2021–2024
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)