It's a life-giving stream in a desert land, that for millennia has sustained human communities and creatures found nowhere else on Earth. The deep canyons it's carved are among the most remote and spectacular places on the continent. Its great sweep through the borderlands gives a region its name.
But this April and May, the Rio Grande has gone dry in large parts of Big Bend National Park. It's not the first time it's happened. But the forces that have killed the river this spring aren't likely to abate. What's happening now could become a regular occurrence.
Raymond Skiles was Big Bend National Park wildlife biologist for 30 years, and retired in 2018.
“It's a bizarre scene to witness,” Skiles said, “especially for someone that knows the river quite well over many years. It's astonishing. It's sad. It's not a river.”
In mid-April, Skiles traveled to Mariscal Canyon, at Big Bend's southern tip. The photos he captured there – of a bone-dry riverbed, and a few isolated pools – alarmed and outraged devotees of the park.
Skiles had taken similar photos in 2003. The stretch of river that includes Mariscal Canyon – referred to as the “Great Unknown” – is remote even by Big Bend standards. And when there's no water for boating, almost no Americans see it.
But the conditions Skiles witnessed may be impacting 75 miles of the river or more. A gauge in this area registered zero flow on April 15, and for a two-week period beginning April 19. Upstream, the gage at Presidio also registered zero flows in April.
How did it come to this for the “Great River”?
David Dean, of the U.S. Geological Survey, has studied the river here for years.
“I think it's primarily climate driven,” Dean said, “but once you add the layer of human infrastructure on top of that, it just makes things worse. If climatic conditions don't change, I could see the Big Bend reach of the Rio Grande being extremely low – at least in the winter months – for a long time to come.”
The last two decades have been the driest in the American West in the last 1,200 years, and Dean said that “mega-drought” is certainly affecting the Rio Grande. But there are also human impacts, which have a long history.
Historically, the Rio Grande here swelled in late spring, as snowmelt coursed down from the Rockies. High flows continued, as summer monsoons filled the Rio Conchos, which joins the Rio Grande from Mexico at Presidio-Ojinaga.
That ancient pattern changed in the 1870s, when irrigated agriculture boomed on the river, from Colorado to El Paso. The first stream records – from the early 20th century – show that the river went dry most years below El Paso.Since then, the Rio Conchos has been the primary source of water for the Big Bend Rio Grande. And, of course, communities and farmers in Mexico make their own demands of the Conchos.
As Skiles notes, no water is allocated – either from the Conchos, or the upstream Rio Grande – to ensure flowing water here.
“It's no longer a free-flowing river ,” Skiles said. “It's a plumbing system for managing the water rights that people have to extract the water. The plumbing is to deliver it from Point A to Point B for human uses. There's not a little bit of river that's dedicated to keeping it a river, and keeping the living things of the river, not even healthy, but surviving.”
Beginning at the east end of Big Bend National Park, springs supplement the river, providing a base flow, and a toehold for the river's aquatic life. But upstream, the short-term prospects for the Rio Grande are bleak, Dean said.
“It's really going to depend on the monsoon season to bring the river back to life,” Dean said, “and hopefully we get a strong one, and it makes the river boat-able and not hike-able any more.”
In the meantime, there's the stark reality of a great river run dry.
“This is happening in a national park,” Skiles said. “This is happening in a component of the United States' Wild and Scenic River system. I have to think – what world is this okay in, for the river just to stop because of human extraction and depletion of the river?”
On next week's Nature Notes, we explore the impacts on the river's aquatic life.
