In 1949, Texas and New Mexico entered into the Pecos River Compact under which the states would share in the water flowing through the Pecos River – essentially, New Mexico agreed to “deliver” a certain amount of water to Texas by that river. In 2014, a tropical storm hit the area, and to avoid flooding Texas asked New Mexico to temporarily store some of the water, which New Mexico agreed to do. Later, New Mexico released the water to Texas, but some of it had evaporated while in storage. New Mexico wanted delivery credit for the evaporated water, which was granted by the River Master appointed by the Court. Texas objected.

In Texas v. New Mexico, the Court, in a decision by Justice Kavanaugh (Justice Barrett recused), held that New Mexico was entitled to that credit under the River Master Manual approved by the Court in 1988, which explicitly granted delivery credit to “reservoir losses attributable to . . . storage” by New Mexico at Texas’ request. Justice Alito concurred in part, but dissented as to the result, saying that he would have sent the case back for redetermination since it was unclear that Texas was involved in the storage of the water, and there needed to be a more “coherent picture” of the events developed.

A link to the case is here: https://www.supremecourt.gov/opinions/20pdf/22o65_dc8e.pdf