Resource Management


For centuries, the Rio Grande regularly flowed over its banks blanketing the Lower Rio Grande Valley, replenishing resacas, spreading rich nutrients and assuring life for the flood forest.

The Rio Grande’s waters would find their way from Colorado to the Gulf of Mexico. The spring snow melt flowed, joining other river flows along the way and bringing seasonal flood waters to the most southern tip of Texas in excess of 35 feet above the normal flow level. When overflowing its banks, the Rio Grande would carve new channels through the loamy-clay soils creating oxbows, locally known as “resacas.” As the river retreated, the newly formed bodies of water and rich soils brought by the flooding would remain. This helped establish lush, tall trees and plants dependent on the flooding regime. 

With human settlement came the need to curb the flooding, as well as the need to access fresh ground water. In 1953, Falcon Dam was built to tame the Rio Grande. It was the first of many agreements that would dam and divert river waters further upstream. Soon after, an impressively engineered system of irrigation canals allowed people to prosper on the farming of the rich soils. The habitat was cleared and today more than 95% of the lower four counties of Texas have been developed. Surrounded by farm-fields, Santa Ana National Wildlife Refuge gleams like an island in a sea of cleared and altered lands. It reminds us of what the land used to look like. 

To maintain this living piece of history, refuge staff strives to mimic the historic seasons of the Rio Grande. Pumps draw waters from the river to blanket the refuge’s resacas. Conversely, as happened historically, the resacas are drawn down and allowed to go dry. During this time, biologists treat invasive and exotic plants so that when the waters return, resacas will be rich with native plants beneficial to wildlife. 

During the summer months, resacas are managed to provide wetland habitat for species such as the clay-colored thrush, groove-billed ani, tropical parula, great kiskadee and altamira oriole. In the winter, water levels in the resacas are maintained to provide habitat for least and pied-billed grebes, various wading birds, mottled ducks, sandpipers, rails and other winter waterfowl.

While nature did it best, the refuge’s seasonal management efforts assure continued life for the flood forest, nesting and feeding habitat for birds, watering holes for animals, and homes for a fascinating medley of insects, reptiles and amphibians.