Heron Lake Shallow
Rio Arriba County, New MexicoView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from B at the last regrade
- Mesotrophic
- Impaired · Temperature
- #4 of 5 in the county
- Limited data
Heron Lake Shallow in Rio Arriba County, New Mexico has a water quality grade of C (Fair). Water clarity: 2.5 ft visibility. Phosphorus: 32 µg/L. Chlorophyll-a (algae): 2.1 µg/L.
- Clarity
- 2.5 ft
- Type
- Mesotrophic
- Phosphorus
- 32 µg/L
- Chlorophyll-a
- 2.1 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Heron Lake Shallow
Compare lakeside cabins, hotels, and vacation rentals near Heron Lake Shallow in Rio Arriba County, New Mexico — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Heron Lake Shallow
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at New Mexico’s top lakes →
Watch Heron Lake Shallow’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Heron Lake Shallow is a mesotrophic lake in Rio Arriba County, New Mexico. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 4 other monitored lakes in Rio Arriba County, Heron Lake Shallow ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, NMED, last sampled 2024-09-17. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The C is nutrients and algae, not a swimming clearance. Heron Lake Shallow is listed impaired under Clean Water Act §303(d) (IR 5) for temperature. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Very murky, less than 2.5 ft of visibility. Phosphorus 32 µg/L. Chlorophyll-a 2.1 µg/L. TSI 52. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | Not graded |
| Phosphorus | 32 µg/L | Fair |
| Chlorophyll-a (Algae) | 2.1 µg/L | Fair |
| Trophic State Index (TSI) | 52 | Mesotrophic |
Moderate nutrients, good water quality
Fishing Heron Lake Shallow
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.234 m/yr | 3 |
| Phosphorus | ↑ Improving | -1.69 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.77 µg/L/yr | 2 |
EPA Impairment Status
Heron Lake Shallow is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit NM-2117_10 · Official waterbody report · Matched by proximity (0.24 km)
County Ranking
Ranked #4 of 5 lakes in Rio Arriba County
Nearby Lakes in Rio Arriba County
Frequently asked questions about Heron Lake Shallow
Where is Heron Lake Shallow?
- Heron Lake Shallow is a lake in Rio Arriba County, New Mexico. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Heron Lake Shallow?
- Heron Lake Shallow in Rio Arriba County, New Mexico has a water quality grade of C (Fair). Water clarity: 2.5 ft visibility. Phosphorus: 32 µg/L. Chlorophyll-a (algae): 2.1 µg/L.
Is Heron Lake Shallow safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Heron Lake Shallow is listed impaired under Clean Water Act §303(d) (IR 5) for temperature. Check local advisories before you swim.
Explore Heron Lake Shallow across LakeQuality
24.2 mi away · recorded at 81°F
Species activity outlook by water temperature and season
Where to stay at New Mexico's top lakes, each with its grade
Moderate nutrients, good water quality
New Mexico's cleanest and most-polluted lakes, ranked
More New Mexico Lake Rankings
Other Grade C Lakes in New Mexico
Mesotrophic Lakes in New Mexico
Where this data comes from
15 measurements from 1 monitoring station, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- NM Environmental Dept./SWQB
21NMEX_WQX15 samples · 2012–2024
Analytical methods
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database