In the last month of 2013, the US Solicitor General filed a strongly worded brief as amicus curiae expressing the US Government’s view that the Supreme Court should grant the State of Texas’s motion for leave of the Court to file a complaint against the States of New Mexico and Colorado for alleged violations of the 1938 Rio Grande Compact (Compact) by New Mexico.

The Rio Grande Basin is defined in the Compact as “all of the territory drained by the Rio Grande and all its tributaries in Colorado, in New Mexico, and in Texas above Fort Quitman.” The Elephant Butte Reservoir, part of the US Department of Reclamation’s Rio Grande Project, was completed in 1916 and a lower storage system, the Caballo Reservoir, was completed in 1938. The Compact was entered by Colorado, New Mexico, and Texas to help address concerns that development upstream of Elephant Butte was depleting water supplies to the Project.

The current dispute involves a disagreement between Texas and New Mexico over certain terms of the Compact that appear to restrict New Mexico’s ability to withdraw and divert water in the region between Elephant Butte and the New Mexico border with Texas border 105 miles to the south. Simply put, New Mexico believes that the Compact only requires that it deliver water to Elephant Butte and the failure of any water to reach the Texas border is not New Mexico’s problem. However, Texas believes that New Mexico is diminishing water and return flows that Texas is entitled to by allowing water to be diverted and pumped below Elephant Butte in excess of Project allocations. The Solicitor’s brief indicates a similar position to that of Texas, noting that Reclamation water delivery contracts include seepage and return flows, therefore interference with the “release and delivery of Project water” by New Mexico would violate the Compact.

Of course, it is unclear what the final outcome will be. If New Mexico prevails, water deliveries to Texas will continue to diminish, creating greater challenges for the region. If Texas prevails, water users in Texas and Mexico may ultimately benefit to some degree from increased supplies, but the practical impacts on water users in the 105-mile region between Elephant Butte and the Texas border could be significant. Either way, any solution will be difficult both technically and politically, and may only provide temporary relief for the victor if drought continues to persist.

Like the water dispute between Florida and Georgia that we discussed in November, we will continue to monitor this case and provide updates as they develop.