Satellite imagery plays a key role in monitoring the effects of a type of controlled flooding called pulse flow in an attempt to reinvigorate the lower Colorado River ecosystem.
Due to increasing demand for Colorado River water by the United States and Mexico, the final stretch of the Lower Colorado has virtually disappeared. It has been decades since the Colorado flowed all the way through Mexico to the Gulf of California. Major spring floods are a rarity, and the lower reaches of the river only flow after rainstorms or when agricultural runoff drains into the dried riverbed.
The effects on the delta ecosystem have been profound. Willow and cottonwood forests that used to thrive along the Colorado’s banks and in its wetlands now struggle to survive, while a drought-adapted invasive salt cedar (tamarisk) shrub dominates. Populations of birds and other animals have dwindled. According to ecologists, only 10 percent of the Colorado’s original wetlands remain, with just 3 percent of cottonwood and willow forests surviving.
On March 23, 2014, researchers and water managers opened the floodgates of the Morelos Dam outside of Yuma, Ariz., for a pilot project to release water from the Colorado River into its parched delta in Mexico’s northwestern Baja California state. Storage dams upriver released water earlier this year, and the Morelos dam is the last barrier before the delta.
Edward Glenn, an environmental scientist from the University of Arizona, is among a group of scientists who first argued that relatively modest pulse floods could have a major impact on downstream ecosystems. Glenn and colleagues analyzed decades of Landsat imagery and found that the willows and cottonwoods responded surprisingly well to sporadic floods that occurred in the 1990s during wet El Niño years.
Glenn plans to use Landsat 8 and other satellite imagery to monitor changes this time as well. “What we’re trying to do here is a really big deal,” he said. “Nobody has done an international restoration project using a pulse flow on such a large scale before.”
Image courtesy of NASA.