Third Dam Lake
Cache County, Utah14 acresView mapDirections
Utah DWQ publishes the water-quality measurements for Third Dam Lake. Here is what has been measured.
- Oligotrophic
- Limited data
Third Dam Lake in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 4.3 ft visibility. Phosphorus: 10.4 µg/L. Chlorophyll-a (algae): 1.1 µg/L. Surface area: 14 acres.
Third Dam Lake is a 14-acre cold, clear oligotrophic lake in Cache County, Utah. Water clarity is declining over recent sampling years. Compared to the 8 other monitored lakes in Cache County, Third Dam Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2020-09-22. Methodology: how these readings are compared.
What Third Dam Lake is good for
From access and monitoring records, not editorial picks.
- Camping5 public campgrounds nearby
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. Check local advisories before you swim.
Whether Third Dam Lake is safe to swim in today is a call for the Utah Division of Water Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Third Dam Lake
These are the measurements Utah DWQ publishes for Third Dam 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 4.3 ft. Phosphorus 10.4 µg/L. Chlorophyll-a 1.1 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10.4µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 1.1µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Third Dam Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
14 acres
No bathymetric survey has been published for Third Dam Lake, so its depth is not documented here.
Recreation & Access
Public campgrounds near Third Dam Lake
- Spring Hollow Campground0.5 km
- Bridger Campground1.0 km
- Guinavah-Malibu Campground2.0 km
- Guinavah2.3 kmReserve
- Green Canyon3.9 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Stays via Stay22
Stays near Third Dam Lake
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Top-rated places to stay near Third Dam Lake
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Fishing Third Dam Lake
Water quality readings over time
2 seasons of samples on record (2019–2020). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Chlorophyll-a
Improving-3.4 µg/L/yr2 years
Reservoir Info (USACE NID)
Third Dam Lake is a man-made reservoir impounded by the Logan No. 3 (completed 1924), built primarily for hydroelectric on the Logan River; concrete-type dam, 32 ft tall and 108 ft long.
- Surface area
- 14 ac
- Normal storage
- 40 ac-ft
- Hazard class
- Low
- Owner
- Logan, City of
All listed purposes: Hydroelectric;Irrigation;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID UT00310 · Operator website · Matched by proximity (0.03 km)
Nearby Lakes in Cache County
Frequently asked questions about Third Dam Lake
Where is Third Dam Lake?
- Third Dam Lake is a lake in Cache County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Third Dam Lake?
- Third Dam Lake in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 4.3 ft visibility. Phosphorus: 10.4 µg/L. Chlorophyll-a (algae): 1.1 µg/L. Surface area: 14 acres.
Is Third Dam Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there campgrounds on Third Dam Lake?
- Third Dam Lake has 5 public campgrounds from USGS The National Map within 5 km, including Spring Hollow Campground, Bridger Campground, Guinavah-Malibu Campground, Guinavah. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Third Dam Lake across LakeQuality
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Where this data comes from
9 measurements from 1 monitoring station, 2019–2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX9 samples · 2019–2020
Analytical methods
- Field Measurements
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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.
Other records on this page
Public campgrounds from USGS The National Map Structures, within about 3 miles