Rock Creek Beach Lake
Jasper County, Iowa640 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Algal growth
- Public access
- Limited data
Rock Creek Beach Lake in Jasper County, Iowa is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.1 ft visibility. Surface area: 640 acres.
- Clarity
- 1.1 ft
- Typical in August
- 79°F
- Area
- 640 acres
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Rock Creek Beach Lake’s letter
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Free interactive depth-contour map of Rock Creek Beach Lake, reaching a maximum surveyed depth of 16 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Why Rock Creek Beach Lake has no grade
Rock Creek Beach Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Rock Creek Beach Lake is Not Rated — not an F. Its 1.1-foot median from 44 readings collected 2021–2024 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Iowa DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Rock Creek Beach Lake is a 640-acre lake in Jasper County, Iowa. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-27. Grade methodology: LakeQuality methodology.
What Rock Creek Beach Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedBacteria C
Based on E. coli testing, Rock Creek Beach Lake occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 7.5% of 106 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 measurements for Rock Creek Beach Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 1.1 ft of visibility. TSI 75.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.1 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 75 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Rock Creek Beach Lake typically sits around 79°F at the surface in August. Summer average is about 79°F. Usually warmest in Jul (about 82°F) and coldest in May (about 68°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 79 field readings (2010–2022) via the EPA Water Quality Portal. See the full Rock Creek Beach Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 640 acres |
| Public Access | Yes |
No bathymetric survey has been published for Rock Creek Beach Lake, so its depth is not documented here.
Recreation & Access
- Rock Creek WestPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Rock Creek Beach Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.011 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 Beach 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 (0.53 km)
EPA Impairment Status
Rock Creek Beach 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 (1.34 km)
Graded lakes near Rock Creek Beach Lake
Rock Creek Beach Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Jasper County
Frequently asked questions about Rock Creek Beach Lake
Where is Rock Creek Beach Lake?
- Rock Creek Beach Lake is a lake in Jasper County, Iowa. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Rock Creek Beach Lake?
- Rock Creek Beach Lake in Jasper County, Iowa is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.1 ft visibility. Surface area: 640 acres.
Is Rock Creek Beach Lake safe to swim in?
- Based on E. coli testing, Rock Creek Beach Lake occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 7.5% of 106 samples across 7 seasons. That works out to a bacteria swim-safety grade of C — a historical summary of past testing, not a current reading. Rock Creek Beach Lake is not rated for water quality — its monitoring record does not meet the evidence bar. 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 Beach Lake?
- Rock Creek Beach Lake typically sits around 79°F at the surface in August, from 79 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
Are there boat ramps on Rock Creek Beach Lake?
- Rock Creek Beach Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Rock Creek West. Public access is listed as yes.
Explore Rock Creek Beach 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
44 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_WQX44 samples · 2021–2024
Analytical methods
- Unknown
- 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
Named boat-access points from the USGS National Boat Ramps inventory