Macon County, Missouri · 39.75°N · Water Quality Report Card
Long Branch Lake
Long Branch Lake in Macon County, Missouri has a water quality grade of C (Fair). Water clarity: 1.8 ft visibility. Phosphorus: 43.5 µg/L. Chlorophyll-a (algae): 16.1 µg/L.
- Clarity
- 1.8 ft
- Mean depth
- ~49 ft est.
- Type
- Eutrophic
- Trend
- ↑ Improving
Long Branch Lake is a productive, nutrient-rich eutrophic lake in Macon County, Missouri with an estimated average depth of about 49 feet. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 1 other monitored lakes in Macon County, Long Branch Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-15. Grade methodology: LakeGrade methodology.
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Swimming Safety
Based on E. coli testing, Long Branch Lake rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 4.6% of 282 samples across 8 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Missouri’s current beach and health-department advisories before swimming.
Water Quality Grade: C (Fair)
Very murky, less than 1.8 ft of visibility. Phosphorus level: 43.5 µg/L. Chlorophyll-a: 16.1 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | |
| Phosphorus | 43.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 16.1 µg/L | Fair |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~49 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Missouri has not published bathymetry for Long Branch Lake.
Where to stay near Long Branch Lake
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Fishing Long Branch Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.008 m/yr | 5 |
| Phosphorus | → Stable | +0.18 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.36 µg/L/yr | 5 |
Location
County Ranking
Ranked #1 of 2 lakes in Macon County
Nearby Lakes in Macon County
Explore Long Branch Lake across LakeGrade
More Missouri Lake Rankings
Other Grade C Lakes in Missouri
Eutrophic Lakes in Missouri
More records, surveys & data sources
EPA Impairment Status
Long Branch Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MO_7168.00 · Official waterbody report · Matched by proximity (2.02 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Where this data comes from
208 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC208 samples · 2020–2024
Analytical methods
- Depth, Secchi disk in meters
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2024-09-15
Monitoring stations: 1