From the National Geographic (Jennifer Pitt):
For one week now, the Colorado River has been flowing into its delta. It’s the first ever deliberate release of water here to benefit the environment.
That the river is flowing again in its delta is somewhat astounding, all the more remarkable because it’s happening as the result of cooperation between the United States and Mexico under a new collaborative agreement on river and water management.
These releases – lasting eight weeks – are being made from Morelos Dam, about 100 miles (160 kilometers) upstream from the river’s end at the Upper Gulf of California (Sea of Cortez). About 75 of those river miles (120 kilometers) are typically wet, either from a high groundwater table or the tides that make their way upstream. But a reach of about 25 miles of the channel have been dry for decades, hot sand baking in the desert sun.
For the Colorado River to flow all the way to the Upper Gulf it needs to cross that sandy reach, and on March 29, 2014 it had made it down about 20 of those 25 miles, and about 40% of the total flow volume had been released.