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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The Devils Problem

The color of the Devils River changes with depth from light and clear to dark blue. Photo by: Jessica Lutz

The Devils River flows clear as gin before it enters Lake Amistad and joins the Rio Grande. It’s the cleanest river in Texas, supports endangered fish and birds and is home to plants found nowhere else in the state.

It's less than 70 miles long and is arguably the most protected river in Texas. But despite the 38,000 acres of state natural area and the 160,000 acres of land and conservation easements along its banks that are held by the Texas chapter of The Nature Conservancy, a supporter of this project, the river’s most crucial aspect is not safeguarded. 

“If we protect the whole river basin but we have not protected the aquifer, it may not be enough,” said Nature Conservancy biologist John Karges. 

Karges explained that as a conservation organization, The Nature Conservancy now has to take a much broader look if it wants to protect places like the Devils River. The old model of putting a fence around the pretty parts is no longer enough. It is an important first step, but there also has to be protection for the broader system.

The Devils is an easy place to see this connection. The river is fed by springs that draw from the Trinity Edwards Aquifer.  If that aquifer is drawn down, there would be no springs and the Devils would become a dry arroyo. 

The loss would be more than just a difficult-to-access swimming hole. 

The only reason the Rio Grande does not remain a salty stream after it leaves Big Bend National Park is because of clear freshwater springs like those on the Devils that flow out of the Trinity Edwards. 

The challenge is that it is not understood exactly where and how those springs get their water and what the impact would be from increased pumping from the Trinity Edwards.

We spent Monday exploring the river and its springs with Karges, Taylor Bruecher, a geology graduate student at Sul Ross University who is doing her thesis on the springs of the Devils, and undergraduate research assistant Christine Cosby. 

We woke to sub-freezing temperatures and a steaming river. The water from the springs emerges from the ground between 68 and 72 degrees and keeps the pools near them the equivalent of temperature-controlled aquariums. Turtles paddle around just below the surface while schools of big mouth bass and sunfish swim in circles. Mosquito fish dart about and gar lurk in the shadows. 

It is a true oasis.

What is known is the springs emerge from the multi-layered limestone of the Trinity Edwards Aquifer, which stretches across and below most of Central and South Texas. Somewhere out there, rainwater is captured and gets to the aquifer.

Where exactly and how the water moves is still a mystery. 

Bruecher’s preliminary analysis shows the water leaving the springs is a mix of water that entered the aquifer between several thousand years to less than several decades ago. The springs also seem to be responding to the last decade of drought because the flow of the river has declined by more than a third.

That oscillation is expected, but the pipeline proposals to pump groundwater from near the Devils is what makes Karges concerned. Cities from San Antonio to San Angelo have considered such proposals and there would be no limit on how much they could pump under current regulation. As demand grows and the cost of water increases, there is little chance that pressure will ever go away.

And so the job of protecting the Devils River is now expanded to protecting and understanding the hydrology of an area larger than most states.  

Nothing is easy out here.

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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.

While making his way to the Gulf of Mexico, Colin will be periodically activating a device that uses satellite technology to share his current location. Use this map to see where he traveled on this day.

Check-In Time of Check-In (CST) Latitude Longitude
#1 11:59 a.m. 29.88172 -100.96304
#2 1:32 p.m. 29.8852 -100.99417
#3 2:11 p.m. 29.89025 -100.98651
#4 3:00 p.m. 29.89109 -100.98657
#5 6:21 p.m. 29.88454 -100.99377


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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