Blue Hole
Santa Rosa, NM
Complete Field Guide
Elevation: 4600ft/ 1400 m ● Water temp: 63 F year round ● Visibility: 60-100 ft ● Depth: 83 ft/ 25 m ● Type: Artesian Karst Spring
● Diameter: ~ 80 ft/ 24m ● Water Flow: 3000 gal/min
Blue Hole is a small, nearly circular spring set into the desert just off historic Route 66. The water is cold, clear, and constantly renewed. Conditions are consistent day to day, which makes it one of the most controlled open-water environments in the Southwest.
Site Description:
Blue Hole is an 83 foot (25 m) deep vertical sinkhole, fed by flow coming upwards through a grate at the bottom. The grate blocks caves that extend 200 feet underwater almost straight down.
Two PVC training platforms are at depths of roughly 20 and 25 feet (6 and 7 m), an idea location for skills practice. A single line extending to the bottom has horizontal PVC pipes every 15 feet (3 m)
Currents/Hydrodynamics:
There are no strong currents in Blue Hole. While flow from the grate is approximately 3000 gpm, spread over the whole area of the grate this only results in an upward flow out of the grate of around just over 2 inches a second. However, you may feel slight currents occationally in some areas. Water leaves Blue Hole at the surface, into El Rito Creek.
We wanted to see what the flow was like in Blue Hole, so we set up some computer models. If Blue Hole was a perfect cylinder, the currents would look something like this idealized cross section, where the red is the slightly stronger flow coming up from the grate to the surface:
However, Blue Hole narrows around 40 feet, so this complicates the flow a bit. We can approximate this narrowing in a very simplified way, like this:
Now we see the flow is much more complex- which matches what we see in real life. All that being said, these flows are quite small- a few inches a second at the most- so you'll likely not feel anything at all unless you're trying to hover in one place.
At 4600 feet, Blue Hole is an altitude dive. In practice, this means to ascend more conservatively than usual (ascending at 30 ft/min rather than 60 ft/min) and that No-decompression limits are shorter than sea level. Use altitude tables or a computer set to altitude mode.
Altitude
Hydrogeology
What you see:
The exposed rock around Blue Hole is Santa Rosa Sandstone (Triassic), a reddish sandstone that forms the walls and bottom.
What formed it:
The sinkhole itself developed from dissolution of deeper Permian gypsum and limestone units (Yeso Formation evaporites and San Andres limestone), around 200 feet underground. Groundwater slowly dissolved those layers, creating subsurface cavities. When the sandstone roof collapsed, the basin opened at the surface.
Why the pool stays full:
Artesian discharge from the San Andres aquifer feeds the hole from below. Flow is substantial, with historical measurements reported up to ~3,000 gallons per minute.
Biology & Ecology
Blue Hole is cold, oligotrophic (low in nutients), and constantly flushed. That combination limits biological productivity.
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Fish populations (goldfish) are limited and inconsistent, and located mostly in the upper 10-15 feet due to low oxygen.
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Western Plains crayfish may be present along rocks and ledges
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Microbial/algal films dominate rock surfaces, with seasonal filamentous algae sometimes present
