Texas v. New Mexico

Texas and New Mexico entered into the Pecos River Compact to resolve disputes about the Pecos River, which traverses both states. A River Master performs annual calculations of New Mexico's water delivery to ensure it complies with its Compact obligations. A party may seek the Supreme Court's review of the River Master's calculations within 30 days of its final determination. In 2014 and 2015, after heavy rainfall, a federally owned reservoir in New Mexico retained large amounts of flood waters in the Pecos Basin. When the reservoir's authority to hold the water expired, it began to release the water. Texas could not use the released water, so it also released the water to make room for water flowing from New Mexico. When the River Master calculated and reported New Mexico's obligations for 2014 and 2015, it did not reduce Texas's rights to delivery based on the evaporation of water stored in the federal reservoir in New Mexico that Texas could not use. The 30-day review period lapsed, and New Mexico filed no objection. However, in 2018, New Mexico filed a motion challenging the River Master's calculations. Rather than dismiss the untimely objection, the River Master modified the governing manual to allow retroactive changes to final reports, gave that modification retroactive effect, and amended the 2015 report to credit New Mexico for the evaporative loss.