Rio Grande
Rio Grande Water Rights (1900–present)

Following the approval of the Rio Grande Project by federal lawmakers in 1905, the waters of the Rio Grande were to be divided between the states of New Mexico and Texas based on their respective amount of irrigable land. The project also accorded 60,000 acre-feet (74 million cubic meters) of water annually to Mexico in response to the country's demands. This was meant to put an end to the many years of disagreement concerning rights to the river's flow and the construction of a dam and reservoir at various location on the river between the agricultural interests of the Mesilla Valley and those of El Paso and Juárez. In the agreement provisions were made to construct Elephant Butte dam on public lands. This act was the first occurrence of congressionally directed allocation of an interstate river (although New Mexico would not achieve statehood till 1912).

Following the admittance of New Mexico into the union, the increased settlement of the Rio Grande farther north in Colorado and near Albuquerque, the 1938 Rio Grande Compact developed primarily because of the necessary repeal of the Rio Grande embargo among other issues. Though both Colorado and New Mexico were initially eager to begin negotiations, they broke down over whether Texas should be allowed to join negotiations in 1928, though it had representatives present. In an effort to avoid litigation of the matter in the Supreme Court a provisional agreement was signed in 1929 which stated that negotiations would resume once a reservoir was built on the New Mexico-Colorado state line. The construction of this was delayed by the Market Crash of 1929. With negotiations remaining stagnant, Texas sued New Mexico over the issue in 1935, prompting the intervention of the president who set up the Rio Grande Joint Investigation the findings of which helped lead to the final agreement. The 1938 Rio Grande Compact provided for the creation of a compact commission, the creation of gaging stations along the river to ensure flow amounts by Colorado to New Mexico at the state line and by New Mexico to Elephant Butte Reservoir, the water once there would fall under the regulation of the Rio Grande Project which would guarantee provision to Texas and Mexico. A system of debits and credits was created to account for variations in the water provided. The compact remains in effect today, though it has been amended twice.

In 1944, the US and Mexico signed a treaty regarding the river. Due to drought conditions which have prevailed throughout much of the 21st century, calls for a reexamination of this treaty have been made by locals in New Mexico, Mexico, and Texas. Texas, being the state with the least amount of control over the waterway, has routinely seen an under-provision of water since 1992.

In 1997, the US designated the Rio Grande as one of the American Heritage Rivers. Two portions of the Rio Grande are designated National Wild and Scenic Rivers System, one in northern New Mexico and the other in Texas, at Big Bend National Park.

In mid-2001, a 328-foot (100 m) -wide sandbar formed at the mouth of the river, marking the first time in recorded history that the Rio Grande failed to empty into the Gulf of Mexico. The sandbar was dredged, but reformed almost immediately. Spring rains the following year flushed the reformed sandbar out to sea, but it returned in mid-2002. By late 2003, the river once again reached the Gulf.
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