Dam releases on the Rio Conchos lead to sustained flooding on the Rio Grande

SOUTH PRESIDIO & BREWSTER COUNTIES — After weeks of heavy rain, Mexican reservoirs on the Rio Conchos — a major tributary of the Rio Grande — exceeded capacity, leading to a large release of water. Though the rain has slowed down, the river has held steady at flood stage for weeks thanks to the infusion from the Conchos. 

Typically, water is released from the reservoirs on the Conchos to fulfill a long-standing water use treaty between Mexico and the United States — since 1944, Mexico must release a certain amount of water from its reservoirs every five years to satisfy the treaty. Earlier this summer, the Rio Grande ran dry in several places as prolonged drought and a series of drier monsoon seasons took their toll. 

The nearest reservoir to Presidio-Ojinaga, Luis Leon — about halfway between Chihuahua City and Ojinaga — has hovered between 10 and 20% full since the last series of releases in 2020. This summer’s weather event, a collision between a cold front and a tropical storm system, recharged the Mexican reservoirs. At press time, Luis Leon held 150% of its typical capacity. 

Lori Kuczmanski, public information officer for the International Water and Boundary Commission (IBWC), explained that this particular release isn’t part of the water debt cycle. “In this particular situation, the treaties don’t apply,” she said. As the dam settles down to a manageable capacity, folks who live along the river have been battening down the hatches and keeping an eye on flood warnings from the National Weather Service. 

For Terry Bishop, a Presidio farmer, this year’s flood season hasn’t been as bad as the legendary flood of 2008 — but that doesn’t mean it hasn’t come with its own challenges. A stretch of IBWC-maintained levee runs through his property, so he’s been able to keep a careful watch on the water’s rise and fall. “The levee that the government built, to my knowledge it’s never failed,” he explained. 

The Presidio levees — originally constructed in 1975 — help protect the riverfront from run-of-the-mill flood events. The last time the water went up and over the levee was in 2008, and the IBWC made repairs as soon as the water receded. Bishop predicts that this year the situation will be reversed — heavy rainfall caused drainages that don’t normally run to overflow, colliding with the levee on the opposite side. “There was just too much water,” he said. 

Before 2008, the family maintained a golf course on the east side of the levee — in 2015, Bishop refashioned the space into a privately-owned, publicly-accessible park that’s set to receive a cash infusion from grants secured with the help of the Big Bend Conservation Alliance. The main attraction is a patch of artificial wetlands, charged with treated wastewater from the city. The desert oasis is home to some of the best birding in the state. 

The space is still too flooded for Bishop to access, and his maintenance to-do list keeps piling up. One particularly frustrating situation: this year’s flood season brought with it an invasive species of plant picked up by the floodwater. “I didn’t know what it was and none of my guys knew what it was, and we’re all from here,” he explained. 

Texas Parks and Wildlife identified the culprit as coffeeweed, an invasive species that can be toxic to people and livestock. The region around Presidio and Ojinaga is the most heavily populated area in the Big Bend region and home to numerous cattle ranching operations and smaller farms. “Apparently it’s a real problem for rice farmers, and there aren’t rice farmers anywhere near here,” Bishop said. 

Further downstream in Terlingua, business for the beleaguered river tours industry has picked up again after years of drought. Gay Davidson at Big Bend River Tours (BBRT)  said that customers and guides alike were pleased by all the water. Because of risky flood conditions, Big Bend National Park has temporarily shuttered permits for private boaters — commercial outfitters like BBRT have been enjoying the overflow, so to speak. 

All of the companies are running rafts, making a day on the river more accessible to folks who might be turned off by the traditional Rio Grande canoe or kayak excursion. The high flows have opened up dozens of opportunities for one-day floats through Santa Elena — a bucket-list trip that declining water conditions have made nearly impossible over the past decade. “We have guests that have been waiting five or six years just to get in there,” Davidson explained. 

The high water hasn’t been all fun and games and dizzying canyon views. As the water rises and falls, it leaves long stretches of gloopy mud in its wake, washing out some of the traditional take-outs and making starting and ending a river trip difficult. “We let our guests know that it’s going to be a muddy situation — don’t bring your best shoes, because you may not ever wear them again,” Davidson said.