Lake Pahoja is a 72-acre productive, nutrient-rich eutrophic lake in Lyon County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Water clarity 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 2024-09-09. Grade methodology: LakeGrade methodology.
Watch Lake Pahoja 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 1.7 ft of visibility. Chlorophyll-a: 44.8 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.7 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 44.8 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 72 acres |
| Public Access | Yes |
Where to stay near Lake Pahoja
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Fishing Lake Pahoja
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.127 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +8.27 µg/L/yr | 4 |
Recreation & Access
Water Temperature
Lake Pahoja averages about 75°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in May (about 67°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 31 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake Pahoja water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Lake Pahoja, reaching a maximum surveyed depth of 24 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 1 lakes in Lyon County
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More records, surveys & data sources
Reservoir Info (USACE NID)
Lake Pahoja is a man-made reservoir impounded by the Lake Pahoja Dam (completed 1974), built primarily for fire protection, stock, or small fish pond on the TR-KLONDIKE CREEK; earth-type dam, 50 ft tall and 1,305 ft long.
- Surface area
- 71.5 ac
- Normal storage
- 893 ac-ft
- Max storage
- 2,283 ac-ft
- Drainage area
- 6.09 sq mi
- Hazard class
- Significant
- Owner
- Lyon County Conservation Board
All listed purposes: Fire Protection, Stock, Or Small Fish Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID IA00604 · Operator website
EPA Impairment Status
Lake Pahoja is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 06-BSR-1532 · Official waterbody report
Regulated Pollution Sources Nearby
6 EPA-permitted facilities operate within about 5 miles of Lake Pahoja under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Larchwood 1447 LlcLarchwood · 4.3 mi away · NPDES IA0052919Recent violation
- Larchwood City Of StpLarchwood · 4.9 mi away · NPDES IA0047333Recent violation
- Damon Bahnson Combined OperationInwood · 3.9 mi away · NPDES IA0084239
- Thane Fluit FeedlotInwood · 4.3 mi away · NPDES IA0053196
- Austin FluitLarchwood · 4.6 mi away · NPDES IA0084204
- Novartis Animal Health Us, Inc. (Changed To Elanco, Changed To Avach)Larchwood · 4.7 mi away · NPDES IA0073831
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)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-09
Monitoring stations: 1