The U.S. Supreme Court is wading into another water dispute between Texas and New Mexico over the Pecos River Compact, with oral arguments scheduled to be heard Monday.
At issue is a complaint from Texas that New Mexico received delivery credit for water that had evaporated.
In September 2014, rainfall from Tropical Storm Odile soaked West Texas and eastern New Mexico.
New Mexico held Pecos River water in Brantley Reservoir due to rising water levels. The U.S. Bureau of Reclamation operates the lake, near Carlsbad.
Hannah Riseley-White, deputy director of the New Mexico Interstate Stream Commission, said public safety concerns drove the decision.
“The call came from Texas that they were having widespread flooding just across the state line,” she said. “In November 2014, once the storm event and crisis had passed, and we were getting ready to release water, Texas requested we continue to hold the water. Red Bluff Reservoir was still full, and they wanted to be able to use the water at some future date.”
New Mexico eventually released the water in August 2015. By that time, 21,000 acre-feet, or about 6.8 billion gallons, had evaporated.
Discussion between the states indicated that Texas would assume evaporative losses on the water delivery.
But in 2017, Texas reversed course and appealed to the river master in charge of tallying water deliveries. The river master decided that New Mexico should receive delivery credit for about 16,000 acre-feet of the water that evaporated.
“Our perspective is that but for Texas’ request, that water would have been released in November to the state line, passed through gauges and been credited to New Mexico,” Riseley-White said. “It seems clear from a procedural standpoint and an equity standpoint that the decision was appropriate.”
Texas petitioned the U.S. Supreme Court to review the decision.
Texas will present first in Monday’s court proceedings, which will be conducted remotely. Texas says the river master’s decision was “clearly erroneous.”
“After coordinating with parties in both New Mexico and Texas, the bureau began releasing floodwater in August 2015,” the Texas motion for review says. “That timing confirms that the bureau was not holding the water for Texas’s use, but instead was storing the water for flood control.”
New Mexico will share argument time with the U.S. Solicitor General’s Office. The office filed an amicus curiae, or friend of the court, brief supporting New Mexico’s position.
New Mexico has a credit of more than 166,000 acre-feet under the Pecos compact. That will shrink by about 16,000 acre-feet if the court rules against New Mexico.
“Some people point out that we have such a huge credit, so why does New Mexico care?” Riseley-White said. “On the Rio Grande, 16,000 acre-feet might seem much more insignificant. But on the Pecos, it’s a significant amount – almost a third of our annual delivery obligation under the compact.”
A smaller credit could also affect agricultural water supply. If the credit falls below 115,000 acre-feet, less water is available for the Carlsbad Irrigation District under a 2003 Pecos settlement agreement.
The case marks the first time the Supreme Court has heard a challenge to a decision made by its appointed river master.