Lake Mission Viejo
Orange County, California150 acresView mapDirections
SWRCB publishes the water-quality measurements for Lake Mission Viejo. Here is what has been measured.
- Limited data
Lake Mission Viejo in Orange County, California has water-quality measurements published by SWRCB, shown here as reported. Water clarity: 9.5 ft visibility. Surface area: 150 acres.
Lake Mission Viejo is a 150-acre lake in Orange County, California.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-07-05. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Lake Mission Viejo is safe to swim in today is a call for the California State Water Resources Control Board and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Mission Viejo
These are the measurements SWRCB publishes for Lake Mission Viejo, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 9.5 ft. TSI 45.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 9.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
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Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
150 acres
No bathymetric survey has been published for Lake Mission Viejo, so its depth is not documented here.
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Fishing Lake Mission Viejo
Reservoir Info (USACE NID)
Lake Mission Viejo is a man-made reservoir impounded by the Lake Mission Viejo (completed 1976), built primarily for water supply on the Oso Creek; earth-type dam, 123 ft tall and 1,750 ft long.
- Surface area
- 150 ac
- Max storage
- 4,300 ac-ft
- Drainage area
- 3.6 sq mi
- Hazard class
- High
- Owner
- Lake Mission Viejo Association, Inc.
All listed purposes: Water Supply;Recreation.
Source: USACE National Inventory of Dams, NID ID CA01122 · Operator website
Nearby Lakes in Orange County
Frequently asked questions about Lake Mission Viejo
Where is Lake Mission Viejo?
- Lake Mission Viejo is a lake in Orange County, California. Its water-quality measurements are published by SWRCB and shown on this page as reported.
What is the water quality of Lake Mission Viejo?
- Lake Mission Viejo in Orange County, California has water-quality measurements published by SWRCB, shown here as reported. Water clarity: 9.5 ft visibility. Surface area: 150 acres.
Is Lake Mission Viejo safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Lake Mission Viejo across LakeQuality
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Where this data comes from
4 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- North American Lake Management Society
NALMS4 samples · 2020–2023
Monitoring station identifiers (1)
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.