San Gregorio Deep Lake
Rio Arriba County, New Mexico33 acresView mapDirections
NMED publishes the water-quality measurements for San Gregorio Deep Lake. Here is what has been measured.
- Impaired · Nutrients (phosphorus, nitrogen)
- Limited data
San Gregorio Deep Lake in Rio Arriba County, New Mexico has water-quality measurements published by NMED, shown here as reported. Water clarity: 4.3 ft visibility. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 33 acres.
San Gregorio Deep Lake is a 33-acre lake in Rio Arriba County, New Mexico. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, NMED, last sampled 2014-09-22. Methodology: how these readings are compared.
What San Gregorio Deep Lake is good for
From access and monitoring records, not editorial picks.
- Camping1 public campground nearby
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. San Gregorio Deep Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether San Gregorio Deep Lake is safe to swim in today is a call for the New Mexico Environment Department and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for San Gregorio Deep Lake
These are the measurements NMED publishes for San Gregorio Deep 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. Chlorophyll-a 8.5 µg/L. TSI 54.
| 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 | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | 8.5µg/L | Measured, not scored 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. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about San Gregorio Deep Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
33 acres
No bathymetric survey has been published for San Gregorio Deep Lake, so its depth is not documented here.
Recreation & Access
Public campgrounds near San Gregorio Deep Lake
- Clear Creek4.9 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
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Stays near San Gregorio Deep Lake
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Fishing San Gregorio Deep Lake
Water quality readings over time
3 seasons of samples on record (2013–2017). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
Chlorophyll-a
Worsening+2.34 µg/L/yr3 years
Reservoir Info (USACE NID)
San Gregorio Deep Lake is a man-made reservoir impounded by the San Gregorio Dam (completed 1947), built primarily for irrigation on the Clear Creek; earth-type dam, 28 ft tall and 1,074 ft long.
- Surface area
- 33 ac
- Normal storage
- 254 ac-ft
- Max storage
- 500 ac-ft
- Drainage area
- 3.6 sq mi
- Hazard class
- High
- Owner
- NACIMIENTO COMMUNITY IRRIGATION COMPANY AND NMDGF
All listed purposes: Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID NM00185 · Operator website · Matched by proximity (0.24 km)
EPA Impairment Status
San Gregorio Deep Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit NM-2106.B_10 · Official waterbody report
Nearby Lakes in Rio Arriba County
Frequently asked questions about San Gregorio Deep Lake
Where is San Gregorio Deep Lake?
- San Gregorio Deep Lake is a lake in Rio Arriba County, New Mexico. Its water-quality measurements are published by NMED and shown on this page as reported.
What is the water quality of San Gregorio Deep Lake?
- San Gregorio Deep Lake in Rio Arriba County, New Mexico has water-quality measurements published by NMED, shown here as reported. Water clarity: 4.3 ft visibility. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 33 acres.
Is San Gregorio Deep Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. San Gregorio Deep Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Are there campgrounds on San Gregorio Deep Lake?
- San Gregorio Deep Lake has 1 public campground from USGS The National Map within 5 km, including Clear Creek. 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 San Gregorio Deep Lake across LakeQuality
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4 thermal springs within 18 mi, nearest San Antonio Hot Spring
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Where this data comes from
9 measurements from 1 monitoring station, 2013–2014. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- NM Environmental Dept./SWQB
21NMEX_WQX9 samples · 2013–2014
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
Impairment status from EPA ATTAINS 303(d) database
Public campgrounds from USGS The National Map Structures, within about 3 miles