Crystal Lake Max Depth is a 10-acre productive, nutrient-rich eutrophic lake in Hancock County, Iowa. 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 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: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.6 ft of visibility. Chlorophyll-a: 50.3 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 50.3 µg/L | F |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 10 acres |
| Public Access | Yes |
Where to stay near Crystal Lake Max Depth
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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 |
| Chlorophyll-a | ↑ Improving | -17.83 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Crystal Lake Max Depth averages about 76°F at the surface in summer, 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 →
Location & Depth Map
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.
County Ranking
Ranked #1 of 2 lakes in Hancock County
Cleaner Lakes Within 30 Miles
Crystal Lake Max Depth holds Grade F. 3 nearby lakes hold higher grades.
- ABlue Pit LakeCerro Gordo County · 29.5 mi · Two grade letters higher (F → A)
- DClear LakeCerro Gordo County · 20.2 mi · Higher grade (F → D)
- DBlack Pit LakeCerro Gordo County · 29.3 mi · Higher grade (F → D)
Nearby Lakes in Hancock County
Explore Crystal Lake Max Depth across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
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)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-10-22
Monitoring stations: 1