Dale Maffitt Reservoir
Dallas County, Iowa230 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from B at the last regrade
- Mesotrophic
- #1 of 2 in the county
Dale Maffitt Reservoir in Dallas County, Iowa has a water quality grade of A (Excellent). Water clarity: 9.8 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 230 acres.
- Clarity
- 9.8 ft
- Typical in September
- 76°F
- Area
- 230 acres
- Type
- Mesotrophic
- Phosphorus
- 20 µg/L
- Chlorophyll-a
- 2.1 µg/L
- Trend
- ↑ Improving
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Watch Dale Maffitt Reservoir’s letter
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Dale Maffitt Reservoir is a 230-acre mesotrophic lake in Dallas County, Iowa. Water quality is graded A 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: LakeQuality methodology.
What Dale Maffitt Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water9.8 ft of visibility
Swimming Safety
Grade onlyLow algae
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.
The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 9.8 ft. Phosphorus 20 µg/L. Chlorophyll-a 2.1 µg/L. TSI 43. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.8 ft | Not graded |
| Phosphorus | 20 µg/L | Good |
| Chlorophyll-a (Algae) | 2.1 µg/L | Good |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Dale Maffitt Reservoir typically sits around 76°F at the surface in September. Summer average is about 78°F. 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 230 acres |
No bathymetric survey has been published for Dale Maffitt Reservoir, so its depth is not documented here.
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 |
| Phosphorus | ↑ Improving | -0.9 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.4 µg/L/yr | 3 |
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.
County Ranking
Ranked #1 of 2 lakes in Dallas County
Nearby Lakes in Dallas County
Frequently asked questions about Dale Maffitt Reservoir
Where is Dale Maffitt Reservoir?
- Dale Maffitt Reservoir is a lake in Dallas County, Iowa. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Dale Maffitt Reservoir?
- Dale Maffitt Reservoir in Dallas County, Iowa has a water quality grade of A (Excellent). Water clarity: 9.8 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 230 acres.
Is Dale Maffitt Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Dale Maffitt Reservoir?
- Dale Maffitt Reservoir typically sits around 76°F at the surface in September, from 9 EPA Water Quality Portal field readings (2018–2022). That is a typical value for the month, not a live reading.
Explore Dale Maffitt Reservoir across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Iowa's top lakes, each with its grade
Moderate nutrients, good water quality
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Where this data comes from
36 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX36 samples · 2020–2022
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- ISU modification of APHA 2130-B
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)