New Mexico’s state engineer is backing the proposed agreement that would end a yearslong legal battle with Texas over who has taken an unfair share of Rio Grande water, contending it will avoid future conflicts and create a more stable supply amid a changing climate.

New Mexico, Texas and Colorado proposed the settlement in October after a federal judge appointed by the Supreme Court ordered the case to trial when the parties failed to resolve the litigation dating to 2013.

The proposal, unsealed in January after being kept under wraps for months, calls for changing how and where river flows are measured to determine the three states’ portions under the 84-year-old Rio Grande Compact.

NEW MEXICO, TEXAS, COLORADO PROPOSE SETTLEMENT OVER RIO GRANDE MANAGEMENT

State Engineer Mike Hamman, the state’s top water official, called the proposed consent decree critical for the future of the Lower Rio Grande basin south of Elephant Butte Reservoir.

"It sets out the equitable apportionment for both states in the Lower Rio Grande, settles the interstate dispute that has lasted 10 years, and sets the stage for a known sustainable water supply for both New Mexico and Texas under the challenges of persistent drought and climate change," Hamman wrote in an email to the Santa Fe New Mexican.

Under the agreement, New Mexico would pay no penalties for water Texas had accused it of improperly diverting. Officials had feared the state, if it lost the court battle, would have to shell out as much as $2 billion, plus legal fees.

The decadelong legal tussle has cost New Mexico and Texas an estimated $31 million combined and is emblematic of battles springing up across the West as water supplies diminish under a climate becoming warmer and drier.

Rio Grande in Texas

New Mexico officials are backing a settlement with Texas and Colorado over the allocation of water from the Rio Grande. (CHANDAN KHANNA/AFP via Getty Images)

The Supreme Court must approve the deal before it’s finalized. New Mexico and Texas officials earlier this week implored Judge Michael Melloy, known as a special master, to support the deal and recommend it to the high court.

A key provision under the consent decree would be to gauge Texas’ water deliveries near El Paso instead of 120 miles upstream at Elephant Butte.

Some water managers believe this will help resolve an issue at the heart of the dispute — Texas’ claim that New Mexico irrigators pumped groundwater south of Elephant Butte, diverting water that belonged to the Lone Star State.

The decree also revises how water deliveries are calculated. It lays out pages of formulas aimed at preventing disputes if too little or too much water goes to a particular state in a given year.

But the U.S. Department of Justice and some irrigation districts have criticized the proposed settlement, saying it’s not a viable solution.

In its opposition brief to the court, the federal government contends "the decree would not provide any concrete or specific assurances that New Mexico will actually reduce groundwater pumping or be able to meet its delivery requirement."

State officials argue that as long as Texas receives its portion of water under the compact, federal agencies have no reason to be concerned or to get involved in how New Mexico delivers it.

In an email, the state attorney general’s spokeswoman wrote the consent decree would equitably divide water below Elephant Butte and ensure farmers and municipalities receive their fair share.

"Unfortunately, the United States opposes the consent decree because it wants to dictate the manner in which New Mexico complies with the compact and impose specific restrictions on New Mexico water users," spokeswoman Lauren Rodriguez wrote. "The federal government’s insistence on micromanaging how New Mexico meets its obligations under the consent decree is disappointing."

Still, the state hopes the special master will support the agreement because it would settle the dispute between Texas and New Mexico, she added.

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In a letter to the court, Hamman echoed Attorney General Raúl Torrez’s position.

Hamman wrote the consent decree would ensure New Mexico would receive its fair share of water in the Lower Rio Grande between Elephant Butte and the Texas state line.

It also would make clear the amount of groundwater that irrigators could pump in the Rincon and Mesilla valleys south of Elephant Butte without violating the compact, he wrote.

Hamman pointed to measures the state could use to ensure its water deliveries to Texas don’t fall short.

It will work with municipal and agricultural users to bolster water conservation and, in turn, decrease the amount of surface and groundwater consumed, Hamman wrote.

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At the same time, he wrote that the state will buy water rights to permanently retire wells and implement programs to pay farmers not to cultivate food, reducing the amount of irrigation water used in a growing season.