Palmyra-Modesto Lake
Macoupin County, Illinois37 acresView mapDirections
Illinois EPA publishes the water-quality measurements for Palmyra-Modesto Lake. Here is what has been measured.
- Eutrophic
- Impaired · Algal growth
- Public access
- Limited data
Palmyra-Modesto Lake in Macoupin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Phosphorus: 60 µg/L. Chlorophyll-a (algae): 29.6 µg/L. Surface area: 37 acres.
Palmyra-Modesto Lake is a 37-acre productive, nutrient-rich eutrophic lake in Macoupin County, Illinois. Limited fish-species data available. Public access is available. Compared to the 2 other monitored lakes in Macoupin County, Palmyra-Modesto Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2021-10-13. Methodology: how these readings are compared.
Palmyra-Modesto Lake covers about 37 acres in Macoupin County. Vrbo is where to look for cabins and lake homes around Palmyra-Modesto Lake, and Booking.com and Expedia search hotels near the lake for your dates.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Palmyra-Modesto Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), pesticides, taste, color, odor, trash, turbidity. Check local advisories before you swim.
Whether Palmyra-Modesto Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Palmyra-Modesto Lake
These are the measurements Illinois EPA publishes for Palmyra-Modesto Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 60 µg/L. Chlorophyll-a 29.6 µg/L. TSI 64.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 60µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 29.6µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 64 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Palmyra-Modesto Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Palmyra-Modesto Lake typically sits around 67°F at the surface in October. Summer average is about 73°F. Usually warmest in Aug (about 75°F) and coldest in Apr (about 52°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (52°F) to its warmest (75°F).
Typical surface water temperature by month, from 263 field readings (2011–2021) via the EPA Water Quality Portal. See the full Palmyra-Modesto Lake water temperature breakdown →
Lake Details
Surface area
37 acres
Public access
Yes
Listed by Illinois EPA
No bathymetric survey has been published for Palmyra-Modesto Lake, so its depth is not documented here.
Stays via Stay22
Stays near Palmyra-Modesto Lake
Compare lakeside cabins, hotels, and vacation rentals near Palmyra-Modesto Lake in Macoupin County, Illinois — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Palmyra-Modesto Lake are listed below.
Top-rated places to stay near Palmyra-Modesto Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Fishing Palmyra-Modesto Lake
Reservoir Info (USACE NID)
Palmyra-Modesto Lake is a man-made reservoir impounded by the Palmyra-Modesto City Lake Dam (completed 1965), built primarily for water supply on the TRIB NASSA CREEK; earth-type dam, 50 ft tall and 620 ft long.
- Surface area
- 37 ac
- Normal storage
- 565 ac-ft
- Max storage
- 967 ac-ft
- Drainage area
- 1.8 sq mi
- Hazard class
- Significant
- Owner
- PALMYRA-MODESTO WATER COMMISSION
Source: USACE National Inventory of Dams, NID ID IL00772 · Operator website · Matched by proximity (0.29 km)
EPA Impairment Status
Palmyra-Modesto Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Drinking water, Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RDZP · Official waterbody report
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Palmyra-Modesto Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Palmyra Stp, Village OfPalmyra · 3.1 mi away · NPDES IL0044831Recent violation
- Palmyra-Modesto Comm WtpPalmyra · 0.2 mi away · NPDES IL0044822
- Illini FeedersPalmyra · 1.6 mi away · NPDES IL0063436
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.
Nearby Lakes in Macoupin County
Frequently asked questions about Palmyra-Modesto Lake
Where is Palmyra-Modesto Lake?
- Palmyra-Modesto Lake is a lake in Macoupin County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Palmyra-Modesto Lake?
- Palmyra-Modesto Lake in Macoupin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Phosphorus: 60 µg/L. Chlorophyll-a (algae): 29.6 µg/L. Surface area: 37 acres.
Is Palmyra-Modesto Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Palmyra-Modesto Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), pesticides, taste, color, odor, trash, turbidity. Check local advisories before you swim.
What is the water temperature of Palmyra-Modesto Lake?
- Palmyra-Modesto Lake typically sits around 67°F at the surface in October, from 263 EPA Water Quality Portal field readings (2011–2021). That is a typical value for the month, not a live reading.
Can I fish at Palmyra-Modesto Lake?
- Public access to Palmyra-Modesto Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
44 measurements from 2 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX44 samples · 2021
Analytical methods
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)