Upper Pat Mayse Reservoir
Lamar County, TexasView mapDirections
Nutrients and algae sit mid-range for this region.
- Eutrophic
- Impaired · Algal growth
- #1 of 3 in the county
- Public access
- Limited data
Upper Pat Mayse Reservoir in Lamar County, Texas has a water quality grade of C (Fair). Water clarity: 3.1 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 20.4 µg/L.
- Clarity
- 3.1 ft
- Type
- Eutrophic
- Phosphorus
- 30 µg/L
- Chlorophyll-a
- 20.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Upper Pat Mayse Reservoir’s letter
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Upper Pat Mayse Reservoir is a productive, nutrient-rich eutrophic lake in Lamar County, Texas. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 7 public boat landings. Compared to the 2 other monitored lakes in Lamar County, Upper Pat Mayse Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, TCEQ, last sampled 2025-09-10. Grade methodology: LakeQuality methodology.
What Upper Pat Mayse Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch7 documented ramps
Swimming Safety
Grade onlyLimited data
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 C is nutrients and algae, not a swimming clearance. Upper Pat Mayse Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Very murky, less than 3.1 ft of visibility. Phosphorus 30 µg/L. Chlorophyll-a 20.4 µg/L. TSI 58. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.1 ft | Not graded |
| Phosphorus | 30 µg/L | Good |
| Chlorophyll-a (Algae) | 20.4 µg/L | Fair |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Recreation & Access
- Lamar Point - 1Public
- Lamar Point - 2Public
- Clay BluffPublic
- FM 1499Public
- Pat Mayse West Recreation Area (West)Public
- Pat Mayse West Recreation Area (East)Public
Showing 6 of 7 documented landings from the USGS National Boat Ramps inventory.
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Upper Pat Mayse Reservoir
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | 0 m/yr | 6 |
| Phosphorus | → Stable | -0.43 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.79 µg/L/yr | 5 |
EPA Impairment Status
Upper Pat Mayse Reservoir 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 TX-0209_02 · Official waterbody report · Matched by proximity (2.04 km)
County Ranking
Ranked #1 of 3 lakes in Lamar County
Nearby Lakes in Lamar County
Frequently asked questions about Upper Pat Mayse Reservoir
Where is Upper Pat Mayse Reservoir?
- Upper Pat Mayse Reservoir is a lake in Lamar County, Texas. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Upper Pat Mayse Reservoir?
- Upper Pat Mayse Reservoir in Lamar County, Texas has a water quality grade of C (Fair). Water clarity: 3.1 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 20.4 µg/L.
Is Upper Pat Mayse Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Upper Pat Mayse Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Are there boat ramps on Upper Pat Mayse Reservoir?
- Upper Pat Mayse Reservoir has 7 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lamar Point - 1, Lamar Point - 2, Clay Bluff, FM 1499, among others. Public access is listed as yes.
Explore Upper Pat Mayse Reservoir across LakeQuality
More Texas Lake Rankings
Other Grade C Lakes in Texas
Eutrophic Lakes in Texas
Where this data comes from
60 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Texas Commission on Environmental Quality
TCEQMAIN60 samples · 2020–2025
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
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory