Lost Valley Lake
Gasconade County, Missouri39 acresView mapDirections
Missouri DNR publishes the water-quality measurements for Lost Valley Lake. Here is what has been measured.
- Mesotrophic
- 44 ft max depth
Lost Valley Lake in Gasconade County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 3.9 ft visibility. Phosphorus: 22.7 µg/L. Chlorophyll-a (algae): 6.6 µg/L. Surface area: 39 acres.
Lost Valley Lake is a 39-acre mesotrophic lake in Gasconade County, Missouri with an estimated average depth of about 44 feet. Overall water quality is improving over recent sampling years. Compared to the 2 other monitored lakes in Gasconade County, Lost Valley Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2022-09-22. Methodology: how these readings are compared.
Swimming conditions
Readings onlyModerate algae
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. Check local advisories before you swim.
Whether Lost Valley Lake is safe to swim in today is a call for the Missouri Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lost Valley Lake
These are the measurements Missouri DNR publishes for Lost Valley Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.9 ft. Phosphorus 22.7 µg/L. Chlorophyll-a 6.6 µg/L. TSI 52.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 22.7µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 6.6µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 52 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lost Valley Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lost Valley Lake typically sits around 84°F at the surface in August. Summer average is about 84°F. Usually warmest in Jul (about 86°F) and coldest in May (about 75°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (75°F) to its warmest (86°F).
Typical surface water temperature by month, from 16 field readings (2019–2022) via the EPA Water Quality Portal. See the full Lost Valley Lake water temperature breakdown →
Lake Details
Max depth
~44 ft est.
Surface area
39 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Missouri has not published bathymetry for Lost Valley Lake.
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.3 mi
HydroLAKES / HydroSHEDS
Elevation
719 ft
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.
Stays via Stay22
Stays near Lost Valley Lake
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Top-rated places to stay near Lost Valley Lake
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Fishing Lost Valley Lake
Water quality readings over time
3 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
Phosphorus
Improving-1.55 µg/L/yr3 years
Chlorophyll-a
Improving-1.8 µg/L/yr3 years
Reservoir Info (USACE NID)
Lost Valley Lake is a man-made reservoir impounded by the Lost Valley Lake Dam (completed 1974), built primarily for recreation on the TR-BIG BRCH-BOEUF CREEK; earth-type dam, 30 ft tall.
- Surface area
- 39 ac
- Normal storage
- 455 ac-ft
- Max storage
- 626 ac-ft
- Drainage area
- 1,300 sq mi
- Hazard class
- High
- Owner
- RON DOLPH
Source: USACE National Inventory of Dams, NID ID MO30757 · Operator website
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lost Valley Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Lost Valley Lake ResortOwensville · 0.2 mi away · NPDES MO0103161Recent violation
- Country Living Apartments WwtfOwensville · 2.1 mi away · NPDES MO0134376Recent violation
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 Gasconade County
Frequently asked questions about Lost Valley Lake
Where is Lost Valley Lake?
- Lost Valley Lake is a lake in Gasconade County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of Lost Valley Lake?
- Lost Valley Lake in Gasconade County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 3.9 ft visibility. Phosphorus: 22.7 µg/L. Chlorophyll-a (algae): 6.6 µg/L. Surface area: 39 acres.
Is Lost Valley Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Lost Valley Lake?
- Lost Valley Lake typically sits around 84°F at the surface in August, from 16 EPA Water Quality Portal field readings (2019–2022). That is a typical value for the month, not a live reading.
How deep is Lost Valley Lake?
- No published bathymetric survey covers Lost Valley Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 44 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 39 acres.
Explore Lost Valley Lake across LakeQuality
More lakes in Missouri
Other Lakes in Missouri
Mesotrophic Lakes in Missouri
Where this data comes from
59 measurements from 2 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC58 samples · 2020–2022 - Missouri Dept. of Natural Resources
MDNR1 sample · 2021
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
- Nitrogen and Phosphorus, Total, Whole-water, Alkaline Persulfate Digest
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)