Due to upstream flood conditions and rising reservoir levels, the International Boundary and Water Commission, United States and Mexico, began the release of floodwaters from Falcon Dam, located at Falcon Heights, Texas-Nueva Ciudad Guerrero, Tamaulipas late Wednesday afternoon. 

Water will be released into the Rio Grande at the rate of 15,000 cubic feet per second (425 cubic meters per second). This water will flow downstream into the Lower Rio Grande Valley where the Commission has a system of flood control levees, diversion dams, and floodways. 

Releases at this rate are well within the capacity of the United States flood control system, according to IBWC spokersperson Sally Spener. Residents in the Rio Grande Basin should continue to monitor National Weather Service warnings and forecasts for any updated information about flood conditions. 

The International Boundary and Water Commission expects to begin diverting floodwaters at Anzalduas Diversion Dam in Hidalgo County into the U.S. interior floodway during the night of July 7. 

These flows originated in the San Juan River, a Mexican tributary affected by heavy precipitation from Hurricane Alex and the spill of floodwaters from Marte R. Gomez Dam in Mexico. The initial volumes to be diverted into the U.S. interior floodway are expected to be low but will increase as flows from Falcon Dam arrive in the region on July 8. 

Diversions into Mexico’s interior floodway at Retamal Dam are also expected. 

Rio Grande flow at BrownsvilleMatamoros  is expected to be limited to 7062 cubic feet per second (200 cubic meters per second); U.S. levees in that reach are designed to contain a flow of 20,000 cubic feet per second (570 cubic meters per second).

The U.S. interior floodway includes channels known as the Banker Floodway, Main Floodway, North Floodway, and Arroyo Colorado through portions of Hidalgo, Cameron, and Willacy Counties.  The last time the International Boundary and Water Commission diverted water into the U.S. floodway was in 1988 due to the effects of Hurricane Gilbert.

To prepare for flood conditions, crews from the U.S. Section of the International Boundary and Water Commission (USIBWC) on July 3 began closing all drainage and irrigation structures that pass through USIBWC levees in order to prevent floodwaters from the Rio Grande and interior floodway from flowing into adjacent communities.  Once the structures are closed, drainage from the land side of the levee that would normally flow into the river or floodways will be blocked so any local storm water flows will need to be pumped over the levee by the community or drainage district responsible for local storm water management. 

As conditions warrant, USIBWC staff will move into Flood Fight Operations, Spener said.  During this phase of response, crews work 24 hours per day to patrol flood control levees to identify and respond to any problems that could arise such as erosion along the levees, freeboard encroachment, or seepage on the land side of the levees.

Emergency Operations Centers at USIBWC Headquarters in El Paso and the Lower Rio Grande Flood Control Project Office in Mercedes were established last week to provide round-the-clock response and coordination with the Mexican Section of the Commission.

The Commission is managing its flood control infrastructure taking into account prudent operation of the reservoirs, existing flood conditions in parts of the Rio Grande and its tributaries in the United States and Mexico, impact to property, and forecasts for additional rainfall in the basin, including the potential for additional tropical weather impacts.

As part of its flood operations, the USIBWC exchanges information with the Mexican Section of the Commission regarding flood conditions.  The USIBWC provides data about Mexico’s Rio Grande tributaries to the National Weather Service, which uses this and U.S. data to formulate flood forecasts.

Information about Rio Grande flow as well as storage and release data from U.S. and Mexican reservoirs in the Rio Grande basin is available on the USIBWC web page at:  http://www.ibwc.gov/Water_Data/Reports/RG_Flow_data.html