Dale Maffitt Reservoir is a 230-acre mesotrophic lake in Dallas County, Iowa. Water quality is graded B based on 2 sampling years through 2022. Overall water quality is improving over recent sampling years. Compared to the 1 other monitored lakes in Dallas County, Dale Maffitt Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2022-09-07. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 9.8 ft. Chlorophyll-a: 2.5 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.8 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 2.5 µg/L | A |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 230 acres |
Where to stay near Dale Maffitt Reservoir
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Fishing Dale Maffitt Reservoir
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.5 m/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.3 µg/L/yr | 3 |
Water Temperature
Dale Maffitt Reservoir averages about 78°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in Jun (about 72°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 9 field readings (2018–2022) via the EPA Water Quality Portal. See the full Dale Maffitt Reservoir water temperature breakdown →
Location
County Ranking
Ranked #1 of 2 lakes in Dallas County
Cleaner Lakes Within 30 Miles
Dale Maffitt Reservoir holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Dallas County
Explore Dale Maffitt Reservoir across LakeGrade
More Iowa Lake Rankings
Other Grade B Lakes in Iowa
Mesotrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Dale Maffitt Reservoir is a man-made reservoir impounded by the Maffitt Reservoir Dam (completed 1944), built primarily for water supply on the TR-RACCOON RIVER; earth-type dam, 79 ft tall and 1,800 ft long.
- Surface area
- 230 ac
- Normal storage
- 5,200 ac-ft
- Max storage
- 6,700 ac-ft
- Drainage area
- 1.41 sq mi
- Hazard class
- High
- Owner
- Des Moines Water Works
Source: USACE National Inventory of Dams, NID ID IA01338 · Operator website
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Dale Maffitt Reservoir under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- West Des Moines Water Works 88TH Street AsrWest Des Moines · 4 mi away · NPDES IA0053682Recent violation
- Cumming City Of StpCumming · 3.1 mi away · NPDES IA0071935
- Iowa Dot Rest Area #21 & #22 I80 WaukeeWaukee · 4.8 mi away · NPDES IA0068888
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-07
Monitoring stations: 1