Disappearing Rio Grande

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Why Follow the Rio Grande

by Colin McDonald | Feb. 11, 2015

The Rio Grande is disappearing. Demand for water is growing as snow packs shrink, rain patterns shift and average temperatures rise faster than they ever have in the past 11,000 years.

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Time for a break at home, Day 154

Hugh Fitzsimons checks out the collection of dead and dying fish at the Pecos River boat ramp. The fish are dying by the hundreds because of a bloom of golden alga, according to an investigation by the Texas Parks and Wildlife Department. Photo by: Colin McDonald

For four days, dead and dying fish have washed ashore at the boat ramp at the mouth of the Pecos River.

The one advantage of the temperatures dropping near freezing every night was the stench of the rotting gar, largemouth bass, crappie, sunfish, shad and minnows was not too bad. The layer of slime that was growing on the cement ramp, however, was a bit treacherous. 

I took it as a sign it was time to go home. After spending two month on the river there is gear, relationships and injuries to mend. I also have to work out the logistics for the last 600 miles to work out.

I want to say thank you to Erich Schlegel, Jason Jones, David Lozano and Dan DiBona for their help, advice and companionship in getting from El Paso to Big Bend. That was the most difficult reach of the Rio Grande to travel and it took a toll on all of us.

I’ll head back to the confluence of the Pecos and Rio Grande on December 2 with photographer Mike Kane. We have talked about this project for more than five years. It’s a dream to be able to work with him. Wait until you see what he can do with a portrait.

The other advantage of heading back to the world of heated rooms with reliable phone and internet service is that it is easier to figure out what is going on. 

It turns out fish have died en masse in the salty Pecos River since at least 1985 due to golden alga, Prymnesium parvum, according to the Texas Parks and Wildlife Department.

Not much is known about the single-cell microscopic alga. It is found in salty and brackish water around the world. Texas biologists were the first to identify it in the Western Hemisphere in fresh water on the Pecos. It has since been found in the Brazos, Canadian, Colorado and Red River basins.

It is believed that golden alga produces a toxin to make catching bacteria and other alga, which the plant then eats, easier.

The problem for fish is that when the population of the golden alga grows exponentially, for reasons that are not understood, the toxin starts to kill the cells of their gills and internal organs one layer at a time.

“Fish behave as if there is not enough oxygen in the water,” said the TWPD website. “They travel at the top of the water surface or rest on the bottom in edges and shallow areas.”

That’s exactly what Hugh Fitzsimons, a supporter of this project, and I saw as we explored the flat water of the Pecos on Wednesday.

The fish were scattered over 3 miles of the wide river.  Some were floating belly up. Others were on their side with one fin slowly flapping above the water. Lucky for us, the toxin of the golden alga does not seem to have any impact on mammals or birds.

We saw close to a dozen ospreys dining on the fish along with a growing crowd of vultures.

It was good day for them, but I had enough of paddling amongst dead fish and hitched a ride home with Hugh. 

Disclosure: Hugh Fitzsimons is a major donor to The Texas Tribune. A complete list of Tribune donors and sponsors can be viewed here.

To comment on this post or ask a question, please visit the expedition's Facebook page.

Air temperature (°C)
Conductivity (µS/cm)
Depth of Measurement (meters)
Dissolved oxygen (mg/L)
E. coli colonies per 100 ml
pH level
Secchi disk transparency (meters)
Water temperature (°C)

What do these numbers mean?

As they travel, Colin and Erich are taking water samples for the following periodic water quality tests. In partnership with The Meadows Center for Water and the Environment’s Texas Stream Team Program at Texas State University, the results will be added to a public database it helps maintain for research and monitoring water quality.

Air/Water Temperature
Temperature impacts everything from the amount of oxygen in the water and the metabolism of aquatic species to how easily compounds dissolve. Most species can tolerate slow seasonal changes but can go into thermal stress or shock when temperatures change by more than one or two degrees Celsius in 24 hours.
pH Level
The pH scale measures water’s acidity and runs on a logarithmic scale from 1.0 to 14.0, with 7.0 considered neutral. Anything below 7 is acidic and anything above is basic. A pH range of 6.5 to 8.2 is optimal for most organisms.
Dissolved Oxygen
Oxygen is just as vital for life below the surface as it is above. The amount needed varies according to species and stage of life, but generally 5.0 to 6.0 milligrams per liter is required for growth and activity. Levels bellow 3.0 mg/L are stressful to most fish species and levels below 2.0 mg/L for an extended period of time will cause fish kills.
Conductivity levels depend mainly on how easily the rocks and soils a stream passes through dissolve. For example, high levels of conductivity are often found with water that passes through limestone and gypsum because it will pick up the calcium, carbonate and sulfate from those rock formations. However, discharges into a water body, such as a failing sewage system, can also raise the conductivity because of the presence of chloride, phosphate and nitrate.
Water Clarity
Turbid water can come from high levels of sediment or plankton. Both will block sunlight to aquatic plants and the sediments can carry pollution such as nutrients and pesticides. Low levels of turbidity may indicate a healthy and well-functioning ecosystem. High levels can be an indicator of runoff from eroding soils or blooms of microscopic plankton due to high levels of nutrients.
E. coli
E. coli bacteria are found in the colon of warm-blooded animals. If the pathogen is found in water it’s an indicator that fecal mater from humans, pets, livestock or wildlife is also present and may pose a public health threat. For drinking water the standard is to have no E. coli. But almost all non-treated water has some E. coli in it and at low levels it does not represent a substantial health threat to those who swim or wade in it. The Environmental Protection Agency has set the water quality standard for these types of activities at 126 colony forming units per 100 mL.
Secchi disk transparency
The Secchi disk is a plain white, circular disk used to measure water transparency in bodies of water. It is lowered into the water of a lake or other water body until it can be no longer seen. This depth of disappearance, called the Secchi disk transparency, is a conventional measure of the transparency of the water.


To report on and understand the haphazard irrigation system the Rio Grande has become and the changes it is going through, Colin decided the best approach would be to travel the length of the Rio Grande by foot and small boat.

He knew it would give him a unique perspective on a river that few understand. It did require many long days of moving slowly and camping on muddy riverbanks, but Colin likes that sort of thing.

The benefit was it provided access to people who wanted to share their stories and experiences with the Rio Grande. Via Facebook and chance encounters, Colin made instant friends who opened their homes. They provided help from loaning their trucks to their cell phone contact lists to help tell the story of the Rio Grande.

The trip would not have been possible without their help, along with the dedicated assistance of David Lozano, Jason Jones and Daniel Dibona, who drove thousands of miles to get people and boats in place.


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