Rock Creek Max Depth Lake
Jasper County, Iowa640 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #2 of 2 in the county
Rock Creek Max Depth Lake in Jasper County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.1 ft visibility. Phosphorus: 167.5 µg/L. Chlorophyll-a (algae): 107.5 µg/L. Surface area: 640 acres.
- Clarity
- 1.1 ft
- Typical in September
- 67°F
- Area
- 640 acres
- Type
- Hypereutrophic
- Phosphorus
- 167.5 µg/L
- Chlorophyll-a
- 107.5 µg/L
- Trend
- ↑ Improving
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Compare lakeside cabins, hotels, and vacation rentals near Rock Creek Max Depth Lake in Jasper 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 Rock Creek Max Depth Lake are listed below.
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Rock Creek Max Depth Lake is a 640-acre highly nutrient-loaded hypereutrophic lake in Jasper County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 1 other monitored lakes in Jasper County, Rock Creek Max Depth Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-05. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria A
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.
Based on E. coli testing, Rock Creek Max Depth Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 25 samples across 7 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.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.1 ft of visibility. Phosphorus 167.5 µg/L. Chlorophyll-a 107.5 µg/L. TSI 77. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.1 ft | Not graded |
| Phosphorus | 167.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 107.5 µg/L | Poor |
| Trophic State Index (TSI) | 77 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Rock Creek Max Depth Lake typically sits around 67°F at the surface in September. Summer average is about 79°F. Usually warmest in Jul (about 81°F) and coldest in Sep (about 67°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 33 field readings (2010–2023) via the EPA Water Quality Portal.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 640 acres |
No bathymetric survey has been published for Rock Creek Max Depth Lake, so its depth is not documented here.
Fishing Rock Creek Max Depth Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.012 m/yr | 5 |
| Phosphorus | ↑ Improving | -12.2 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -2.11 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Rock Creek Max Depth Lake is a man-made reservoir impounded by the Rock Creek Dam, built primarily for recreation on the ROCK CREEK; earth-type dam, 33 ft tall and 1,500 ft long.
- Surface area
- 640 ac
- Normal storage
- 5,500 ac-ft
- Max storage
- 13,700 ac-ft
- Drainage area
- 41.4 sq mi
- Hazard class
- Significant
- Owner
- Iowa Department of Natural Resources
Source: USACE National Inventory of Dams, NID ID IA00537 · Operator website · Matched by proximity (0.19 km)
EPA Impairment Status
Rock Creek Max Depth Lake 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 03-NSK-865 · Official waterbody report · Matched by proximity (1.73 km)
County Ranking
Ranked #2 of 2 lakes in Jasper County
Nearby Lakes With Higher Grades
Rock Creek Max Depth Lake holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Jasper County
Frequently asked questions about Rock Creek Max Depth Lake
Where is Rock Creek Max Depth Lake?
- Rock Creek Max Depth Lake is a lake in Jasper County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Rock Creek Max Depth Lake?
- Rock Creek Max Depth Lake in Jasper County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.1 ft visibility. Phosphorus: 167.5 µg/L. Chlorophyll-a (algae): 107.5 µg/L. Surface area: 640 acres.
Is Rock Creek Max Depth Lake safe to swim in?
- Based on E. coli testing, Rock Creek Max Depth Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 25 samples across 7 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Rock Creek Max Depth Lake has a water quality grade of F (Algae-prone). Bacteria levels can spike quickly after heavy rain, so always check Iowa's current beach and health-department advisories before you swim.
What is the water temperature of Rock Creek Max Depth Lake?
- Rock Creek Max Depth Lake typically sits around 67°F at the surface in September, from 33 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Rock Creek Max Depth Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
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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
- 2130 B ~ Nephelometric Method
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