EDITOR'S NOTE: This script has been updated to reflect the full quantity of U.S. water storage, which is 18.95%. The previous figure of 18.41% represents the total “useable” quantity of U.S. water in storage

The water supply for nearly 2 million people on the U.S. side of the Rio Grande emptied to unprecedented levels this May. The supply of water available to U.S. communities in Falcon and Amistad Reservoirs dropped to a 53-year low, preceded only by the years following the creation of Amistad Reservoir.

The latest record, released Friday by the U.S. section of the International Boundary and Water Commission, showed the level dropped to 18.95%.

That reading collected on May 25 officially put the reservoir levels at a lower point than the historic low set in August 1998, said Sonny Hinojosa, Water Advocate for Hidalgo County Irrigation District No. 2.

"This volume of water is the lowest U.S. share of ownership at the Amistad/Falcon Reservoir System the U.S. has experienced since both Falcon and Amistad were constructed," said Sonny Hinojosa, Water Advocate with Hidalgo County Irrigation District #2.

Reservoir levels dropped steadily over the last several weeks, as temperatures increased, raising evaporation along this portion of the watershed, which spans about 600 miles from West Texas to the Rio Grande Valley. The Amistad and Falcon reservoirs supply communities in the Rio Grande Valley and other border communities.

Reservoir levels dropped about .4 percent a week, in recent weeks, said Hinojosa. For the first four weeks of May, use was about 13 to 15 thousand acre feet. But that number jumped to 25,745 in the last week of May, he said. 

Upriver, at Amistad Reservoir, the current surface elevation is 1049 feet, the lowest it has been since the dam was commissioned in 1968.