Low Lake Levels Reduce Amistad Dam Flood Release Risk for 2025

Evelio Siller, USA IBWC Area Operations Manager, points out Amistad Lake level measurements

With hurricane season approaching, annual flood warning notices have been circulated. The IBWC (International Boundary and Water Commission) recently issued notices to residents of Del Rio and Val Verde County within the Rio Grande River floodplain. However, Amistad Lake is currently experiencing significantly low water levels due to persistent drought conditions, minimizing the immediate risk of potential overflow.

Evelio Siller, USA IBWC Area Operations Manager, is an engineer by trade and said his “main job is to maintain safety” at the Amistad Dam. According to Siller, the railroad tracks, while not a precise marker, can serve as a general visual reference for the floodplain boundary. Del Rio’s subdivision most susceptible to flooding has been identified as Vega Verde, as it is situated entirely within the floodplain.

According to Siller, the railroad tracks, while not a precise marker, can serve as a general visual reference for the American-side floodplain boundary.

There are two types of potential flooding. The City of Del Rio stated flood warning notices are “due to potential overflow from local tributaries and Amistad Dam releases.” Local tributaries usually find their way back into the reservoir, but when the reservoir fills up, that is when intentional Amistad Dam flood releases are considered. The dam opens at the top to release water to manage high lake levels and mitigate potential flooding downstream along the Rio Grande. But 2025 lake levels are so low, it would take something like 3 back-to-back record breaking months of rain to fill the lake high enough to raise any concern of flood release.

The flood warning notice dated April 1, 2025 was simply the standard advisory distributed at the start of hurricane season. The Atlantic hurricane season runs from June 1st through November 30th. As of April 8, according to The National Hurricane Center (NOAA), there are no signs of cyclones in the Atlantic. As of April 8, 2025, according to the IBWC, the water level of Amistad Lake is at 25% capacity, approximately 66.28 feet below full pool (1050.72 feet msl)... 100% capacity is 1117.00 feet msl, full capacity is referred to as “conservation pool elevation.”

Siller advised, the most recent Amistad Dam flood release occurred 15 years ago in 2010, coinciding with Hurricane Alex. Del Rio experienced an exceptionally wet period in 2010, setting the stage for significant flooding and a subsequent release from Amistad Dam. As of May 1, 2010, historical data indicated that Amistad Lake was already near conservation pool elevation, signifying a nearly full reservoir. According to Weather.Gov, the month of May then brought unprecedented rainfall, becoming the wettest May on record with a total of 10.45 inches. Within this deluge, May 24th alone saw a remarkable 7.12 inches of rain, ranking as the fifth-wettest day in Del Rio's recorded history since 1905, with some areas near Lake Amistad receiving over 10 inches in a single event.

Siller demonstrating Amistad Dam flood release procedures on a miniature model of the dam

This already saturated region was then impacted by the remnants of Hurricane Alex, which made landfall in Mexico on June 30, 2010. Although downgraded to a tropical storm by the time it reached Del Rio, Alex brought further torrential rainfall, causing reservoirs along the U.S.-Mexico border, including Amistad Lake, to rise dramatically. With lake levels reaching their second-highest point ever recorded, the IBWC initiated a flood release from Amistad Dam on July 5, 2010. This action was necessary to manage the overwhelming water levels and mitigate potential flooding downstream along the Rio Grande. The controlled releases continued for an extended period until August 19, 2010.

It would likely take several storms of Hurricane Alex strength to drop enough rainfall on the region, to fill the Amistad Reservoir levels high enough, to trigger a flood release. In 2010, by the time Hurricane Alex hit Del Rio, Amistad Reservoir levels were already high prior to the back-to-back storm surges. Odds are, we don’t have to worry this year. Even if we broke another wettest month record, it wouldn’t be enough to cause a flood, because the lake levels are so low.