The Rio Grande along the South Texas and Mexico border has experienced historic water levels since July 6, 2010 following 10 to 20 inches of rainfall in Mexico from the remnants of Hurricane Alex. The river at Laredo reached 42.45 feet on July 9th 2010, the highest since 38.98 feet on June 30th 1971. Further downstream the Falcon Reservoir pool level topped at 309.31 feet on July 17, surpassing the previous record of 308.10 feet on October 19, 1958. At Rio Grande City, the level rose to 57.31 feet, the highest since September 27, 1972 when it reached 65.78 feet. Water releases on the Falcon Reservoir have been as high as 60,000 CFS. This excessive flow and resultant releases have filled waterways not previously observed by forecasters. A MODIS image courtesy of NASA SPoRT depicted this vividly with a pass on July 18, 2010. Note the the yellow circle on the image dated 1646 UTC 18 July 2010 and the normal river basin in green. A map of the Rio Grande system is also included for reference.
More information on the flood: http://www.srh.noaa.gov/crp/?n=riograndeflood