From this morning’s Journal, the struggle to help a river get to its destination when it doesn’t really want to go there on its own (sub/ad req):
RATTLESNAKE POINT — Without Jason Thibodaux’s help, the Rio Grande would have a hard time making it past this sediment-choked desert flood plain.
Around a bend in the muddy, shallow river, a heavy equipment operator supervised by Thibodaux scooped sand from the main channel, building a berm on the east bank.
The goal, Thibodaux explained, was to keep the river flowing downstream toward Elephant Butte Reservoir. Without the help, the river would peter out into the flatlands on either side of its narrow channel.
State and federal water agencies began the project nine years ago when drought dropped water levels at Elephant Butte, the Rio Grande’s largest water storage reservoir. Elephant Butte “became disconnected from the river,” explained Chris Stageman, who manages the work for the New Mexico Interstate Stream Commission.
Each year crews have had to return, digging and shaping the channel to coax the river’s water supply downstream to the reservoir.
Without the effort, the water in this stretch of river would just spread across the flood plain and disappear, said Mike Harvey, a Colorado hydrologist who has worked in the area. “It’s just hung out to dry, basically,” Harvey said. “It just evaporates.”
update: Eric Perramond has a nice look at the key meta issue here:
The challenge for EB is keeping the Rio Grande channelized enough so that water eventually reaches the actual reservoir, instead of spreading out in a typical distributary delta like so many others that occur around the world, when a river meets ultimate base level (the sea). Here, it’s the constant battle between slope, sediment supply, and the currents of the river that dictate where the river struggles to make it to the dead pool of the dam. And unlike the Nile or the Mississippi deltas that are slowly disappearing, this inland Rio Grande near-delta actually re-forms every year. Given the amount of sediment thrown from semi-arid mountain landforms, it’s no surprise that flood and sediment control are a major concern. Throw in impervious cover, and you speed up the work that water can actually do in carrying sediment long distances in New Mexico.