Roberts Creek Lake is a 296-acre productive, nutrient-rich eutrophic lake in Marion 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 6 public boat landings.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-17. Grade methodology: LakeGrade methodology.
Watch Roberts Creek Lake water quality
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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 1.5 ft of visibility. Chlorophyll-a: 44.6 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 44.6 µg/L | F |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 296 acres |
| Public Access | Yes |
Where to stay near Roberts Creek Lake
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Fishing Roberts Creek Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.036 m/yr | 5 |
| Chlorophyll-a | ↑ Improving | -11.27 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Roberts Creek Lake averages about 78°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in Sep (about 69°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 Roberts Creek Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Roberts Creek Lake, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 1 lakes in Marion County
Cleaner Lakes Within 30 Miles
Roberts Creek Lake holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Marion County
Explore Roberts Creek Lake across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Monroe County · Clarity: 1.3 ft
Lucas County · Clarity: 1.6 ft
Jasper County · Clarity: 1.1 ft
Jasper County · Clarity: 1.1 ft
Poweshiek County · Clarity: 1.3 ft
Lucas County · Clarity: 1.6 ft
Eutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Roberts Creek Lake is a man-made reservoir impounded by the Roberts Creek Dam (completed 1968), built primarily for recreation on the Roberts Creek; earth-type dam, 60 ft tall and 2,400 ft long.
- Surface area
- 296 ac
- Normal storage
- 3,043 ac-ft
- Max storage
- 21,863 ac-ft
- Drainage area
- 13.28 sq mi
- Hazard class
- Significant
- Owner
- Marion County Board of Supervisors
All listed purposes: Recreation;Other.
Source: USACE National Inventory of Dams, NID ID IA00655 · Operator website
EPA Impairment Status
Roberts Creek Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 04-LDM-1019 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Roberts Creek Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Park Hills Wastewater FacilityOtley · 1.4 mi away · NPDES IA0075434Recent violation
- Lake Red Rock - Whitebreast Sewage LagoonKnoxville · 3.1 mi away · NPDES IA0083402Recent violation
- Lake Red Rock - North Overlook Sewage LagoonKnoxville · 4.9 mi away · NPDES IA0083399
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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: 2024-09-17
Monitoring stations: 1