Crystal Lake Max Depth
Hancock County, Iowa10 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #1 of 2 in the county
- 58 ft max depth
- Public access
Crystal Lake Max Depth in Hancock County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 99 µg/L. Chlorophyll-a (algae): 50.3 µg/L. Surface area: 9.7 acres.
- Clarity
- 1.6 ft
- Typical in September
- 70°F
- Max depth
- ~58 ft est.
- Area
- 10 acres
- Type
- Hypereutrophic
- Phosphorus
- 99 µg/L
- Chlorophyll-a
- 50.3 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
Stays via Stay22
Stays near Crystal Lake Max Depth
Compare lakeside cabins, hotels, and vacation rentals near Crystal Lake Max Depth in Hancock 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 Crystal Lake Max Depth are listed below.
Top-rated places to stay near Crystal Lake Max Depth
Prices for Sep 11–13, 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 whole trip? See where to stay at Iowa’s top lakes →
Watch Crystal Lake Max Depth’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Free interactive depth-contour map of Crystal Lake Max Depth, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Crystal Lake Max Depth is a 10-acre highly nutrient-loaded hypereutrophic lake in Hancock County, Iowa with an estimated average depth of about 58 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. Compared to the 1 other monitored lakes in Hancock County, Crystal Lake Max Depth ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-22. 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 F is nutrients and algae, not a swimming clearance. Crystal Lake Max Depth is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth, turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus 99 µg/L. Chlorophyll-a 50.3 µg/L. TSI 70. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 99 µg/L | Poor |
| Chlorophyll-a (Algae) | 50.3 µg/L | Poor |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Crystal Lake Max Depth typically sits around 70°F at the surface in September. Summer average is about 76°F. Usually warmest in Jul (about 80°F) and coldest in May (about 59°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 Crystal Lake Max Depth water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~58 ft est. |
| Average Depth | ~14 ft est. |
| Surface Area | 10 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 Crystal Lake Max Depth.
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.
Fishing Crystal Lake Max Depth
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.004 m/yr | 5 |
| Phosphorus | ↑ Improving | -4.45 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -17.83 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Crystal Lake Max Depth is a man-made reservoir impounded by the Crystal Lake Sediment Control Dam (completed 2003) on the Tr- West Fork Iowa River; earth-type dam, 27 ft tall and 625 ft long.
- Surface area
- 9.7 ac
- Normal storage
- 89 ac-ft
- Max storage
- 148 ac-ft
- Drainage area
- 0.36 sq mi
- Hazard class
- Low
- Owner
- Iowa Department of Natural Resources
Source: USACE National Inventory of Dams, NID ID IA03525 · Operator website · Matched by proximity (0.82 km)
EPA Impairment Status
Crystal Lake Max Depth 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 02-IOW-781 · Official waterbody report · Matched by proximity (0.15 km)
County Ranking
Ranked #1 of 2 lakes in Hancock County
Nearby Lakes With Higher Grades
Crystal Lake Max Depth holds Grade F. 2 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 Hancock County
Frequently asked questions about Crystal Lake Max Depth
Where is Crystal Lake Max Depth?
- Crystal Lake Max Depth is a lake in Hancock County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Crystal Lake Max Depth?
- Crystal Lake Max Depth in Hancock County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 99 µg/L. Chlorophyll-a (algae): 50.3 µg/L. Surface area: 9.7 acres.
Is Crystal Lake Max Depth safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Crystal Lake Max Depth is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth, turbidity. Check local advisories before you swim.
What is the water temperature of Crystal Lake Max Depth?
- Crystal Lake Max Depth typically sits around 70°F at the surface in September, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Crystal Lake Max Depth?
- No published bathymetric survey covers Crystal Lake Max Depth, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 58 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 9.7 acres.
Explore Crystal Lake Max Depth across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
76 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_WQX76 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
Lake size & watershed from HydroLAKES (HydroSHEDS)