US Supreme Court settles long-running water dispute over dwindling Rio Grande

The settlement calls for reducing groundwater pumping along the dwindling river and retiring water rights from irrigated farmland in southern New Mexico. The states held up the proposal as a promise to restore order to an elaborate system of storing and sharing water between two vast irrigation districts in southern New Mexico and western Texas.

Researchers have warned that unsustainable use of the Rio Grande — which originates in Colorado and stretches south into Mexico — threatens water security for millions of people who rely on the binational river basin.

Farmers in southern New Mexico increasingly have turned to groundwater to irrigate pecan orchards and chile crops as hotter, drier conditions have reduced river flows and storage over recent decades. That pumping is what prompted Texas to sue in 2013, claiming the practice was cutting into water deliveries.

While the Colorado River gets all the headlines, experts say the situation along the Rio Grande is just as dire. Stretches of the river as far north as Albuquerque are expected to go dry again this year, marking the third time in five years.

Officials with the New Mexico Department of Justice and the state engineer's office did not immediately answers emails Wednesday about the court's order. They have previously said the agreements will allow water conservation decisions to be made locally while avoiding a doomsday scenario of billion-dollar payouts on water shortfalls.

The settlement package provides for a detailed accounting system for sharing water with Texas. New Mexico could rely on credits and debits from year to year to navigate through drought and wet periods, though it could be responsible for additional water-sharing obligations if deliveries are deferred too long.

Under the settlement, New Mexico must reduce annual groundwater depletions by 18,200 acre-feet, or about 5.9 billion gallons (22.3 billion liters).

Officials expect to achieve most of the necessary reductions from buying water rights from willing sellers, meaning more than 14 square miles (36 square kilometers) of farmland would be retired.

Other details — and the price tag — still are being worked out, but top water managers have repeatedly told New Mexico lawmakers that it will take “an all hands on deck approach.”

“The problems that we face with water are problems we can’t face unless we work together,” Hannah Riseley-White, director of the Interstate Stream Commission, told a group of water experts during a meeting in March.

She mentioned a combination of long-term fallowing programs, water conservation and more efficient irrigation infrastructure.