NATURE NOTES:
In the Big Bend, River Runners Paddle at the Confluence of Politics and Ecology

By Andrew Stuart

photograph by Drew Stuart. A great blue heron takes flight over the Rio Grande, deep in the desert wilderness of the Big Bend. 

Record-breaking heat and drought strained West Texas this year – and made many outdoors activities daunting. Yet one group of Big Bend outdoorspeople have had it pretty good.

Michael Camacho, of Marfa, is a veteran boater of West Texas rivers.

“This by far was my favorite Rio Grande trip, in terms of water levels,” Camacho said of an October trip in Colorado Canyon. “Typically, every time I’ve done the river it’s been pretty low – dragging boats. I think it was about 1,000 cfs when we did it. It was awesome – we really delayed it. It was like, ‘Let’s paddle 5 or 6 miles today, and we’re done. We’ll just make camp, and play cards.’” 

Camacho – like other river enthusiasts – savored a rise in water levels on the Rio Grande here this fall. The river’s Big Bend reach can be a parched, bony stretch of water, and high flows are a special recreational opportunity. They’re also part of a larger picture – one of complex binational politics. And they invite us to take a closer look at a singular resource – and what might be done to sustain, and even restore it.

It’s been a year of brutal drought in the Southwest. The Rio Grande could run dry in New Mexico this year. Yet since late summer, the river in the Big Bend has flowed at well above 600 cfs – or cubic-feet-per-second – when flows of 100 cfs, or less, are routine. What accounts for this surge?

The answer lies in Mexico – and the dictates of a 75-year-old treaty. 

In 1944, the U.S. and Mexico signed a treaty to manage two binational waterways. The U.S. would provide 1.5 million acre-feet of water to Mexico each year from the Colorado River. Mexico, in turn, would deliver 1.75 million acre-feet to the Rio Grande every five years – an average of 114 billion gallons a year. 

One of the five-year cycles ended October 24th. As the deadline approached, Texas and U.S. officials stepped up pressure on their Mexican counterparts to meet the treaty obligation. Mexican water deliveries had been scarce in the preceding years, and South Texas farmers and cities rely on the river’s water.

In response, Mexican water managers “opened the taps” at dams on the Rio Conchos – a major tributary which joins the Rio Grande at the twin border cities of Presidio, Texas, and Ojinaga, Mexico.

The move triggered conflict in Chihuahua. Alarmed that the releases could presage a permanent loss of their water rights, farmers there seized control of one of the Conchos dams. In clashes with the national guard, two protesters were killed. 

Ultimately, Mexico met the treaty obligation not by deliveries on the Conchos, but by a “paper transfer” of water held at the Amistad and Falcon reservoirs, near Del Rio. 

It’s a bloody backdrop for a paddler’s idyll. Clearly, when it comes to managing the Rio Grande, livelihoods and communities hang in the balance. There’s also the river itself. What ecological impact do these releases have?

Jeff Bennett, of Alpine, is now a conservation specialist with the American Bird Conservancy. He was Big Bend National Park hydrologist for 15 years.

“Despite the fact that there’s 600 cfs in the river – that’s enough to go boating, but that’s not enough to maintain an ecosystem – for this time of year,” Bennett said. “That’d be a great flow in March or February. In September, or October, we should have been up to 2,000, 2,500 for several weeks.”

Bennett and his colleagues did pioneering science on the river.

Part of that science was reconstructing what might be called the “prehistory” of the Rio Grande. What were the river’s dynamics and patterns before it, and its tributaries, were dammed, a century ago?

The research shows that the Big Bend reach of the Rio Grande was unique among rivers in the American West. 

On other great Western rivers – the Colorado, the Columbia, the Missouri – peak flows are associated with spring snowmelt, and the resulting “freshet.” The Rio Grande’s main stem rises in the Rocky Mountains, and, historically, snowmelt did swell the river in the Big Bend. But the river’s peak here was always tied to the summer monsoon – especially in Mexico’s Sierra Madre Occidental, at the headwaters of the Rio Conchos.

The Big Bend stretch of the river supports 40 native fish species – most of which are found nowhere else. They include the Chihuahua shiner, the Mexican stoneroller, the speckled chub, the Rio Grande blue sucker. There are other rare aquatic creatures – mussels and clams like the Salina mucket, the Tampico pearlymussel, the endangered Texas hornshell.

In their reproduction, and other critical aspects of their life cycles, each creature is adapted to the river’s ancient patterns.

“The historic hydrograph would have been some sort of flow of snowmelt coming down, and a rise from the low flows of winter,” Bennett said. “The fish would’ve noticed that and said, ‘Hey, get to work.’ Then there would have been a little drop in that, and then the monsoon comes on and it’s even bigger than it was with snowmelt. Everything was cued to that.”

The ancient rhythms also shaped the river’s form. The annual monsoon pulse would have moved out sediment carried in by tributaries, opening up backwaters and side channels. These areas were biological “hot spots” – nutrient-rich places where native plants flourished and fish spawned.

With upstream diversion and impoundment, the river’s dynamism and complexity decreased.

“It goes from a wide, open channel with lots of types of water levels and flow velocities, to an irrigation canal,” Bennett said, “and it no longer functions like a river. It functions like an irrigation canal.” 

That comes at a cost to humans, as well. When floods do come, the river leaps its narrow channel and inundates communities, as it did in the Big Bend in 2008.  

Since the 1970s, scientists have been refining a concept of “environmental flows” – of modifying dam operations to maintain river ecosystems. The Rio Grande will likely never see the flows it did 200 years ago. Yet releases could be timed to mimic ancient patterns – creating a “mini-me” version of the former river, Bennett said. 

It would give the region’s distinctive river creatures a fighting chance at survival. And it could be done without adversely impacting the human communities that rely on the river.

“The question we’ve always been trying to ask.” Bennett said, “is how do we use the water that we have, and meet the obligations we all have to each other, to the greatest environmental benefit, to get the biggest return from our ecosystems, while maintaining the health and security of our communities?” 

A new generation of Mexican officials may be embracing the idea: releases on the Conchos have increasingly been timed to mimic the former monsoonal surges.

The Big Bend reach of the Rio Grande is designated a “wild and scenic river,” and rightfully so. It’s also a thoroughly managed river. Human choices will shape its future.