Grand Canyon

Preliminary analysis indicates that last week’s manmade flood of the Grand Canyon was a success. The three day flood redistributed sediment in the canyon, modifying old sand bars and creating many new ones as well (some of which are the size of football fields).

From the article:

During the flood, flows in the Grand Canyon increased to 41,000 cubic feet per second for nearly three days - four to five times the normal amount of water released from the Glen Canyon Dam. Water levels along the river rose between 2 and 15 feet and left sediment behind when the four giant steel tubes releasing the water from the dam were closed.

Officials released similar manmade floods into the canyon in 1996 and in 2004.

But those floods actually resulted in a net reduction in overall sandbar size because they were conducted when the Colorado River was relatively sand-depleted, according to the U.S. Geological Survey. Officials believe this year’s flood will be beneficial because sand levels in the river are at a 10-year high and are three times greater than 2004 levels.

Whatever benefits come from this year’s flood, however, will be eroded within 18 months without additional floods every year to 18 months depending on the amount of sediment available, Martin said.

In its environmental assessment on Glen Canyon Dam releases, the U.S. Bureau of Reclamation calls for no other high-flow releases until after 2012.

The benefits of the flooding are obviously beneficial. It’s a shame they don’t actually have plans to do this every year (probably due to the demands that must be met by the Colorado River Compact).

Probably the most popular discussion that’s occurred in the geoblogosphere in the past week has been about the age of the Grand Canyon. While I read many of the articles and discussion related to the new findings, I neglected to post or comment on it myself.

Image Credit: Photo by Leviathor on Flickr.

However, while at work today, I decided to listen to some NPR podcasts that I’ve also been neglecting. Last week on Science Friday featured Victor Polyack, a senior research scientist at the University of New Mexico in Albuquerque, and one of the co-authors of the study. Coincidently, I happened to just be reading a post on the same subject by Brian over at Clastic Detritus who also just recently heard the NPR podcast.

Science Friday article on the Grand Canyon is here.
Science Friday podcast (mp3 file) on the age of the Grand Canyon is here. (~15 minutes in length)

Brian shares my opinions of the guest caller towards the end of the interview (who happened to be a retired USGS employee who disagrees with the new findings). It was a quite an interesting exchange. The USGS researcher raises some interesting questions that Polyack et al. need to figure out. That said, it’s definitely an interesting hypothesis, but I think their data is showing something else that’s not necessary related to downcutting.

Here are some other posts this week from the geoblogosphere summing up the research:

About.com - Geology - Andrew Alden was one of the first people I saw weigh in on the subject. His analysis is that the dates seem to be pretty solid, however they do not make the case for the age of the Grand Canyon by themselves since they simply represent ages of groundwater tables.

Clastic Detritus - As I mentioned, Brian talks about NPR Science Friday interview and the guest caller at the end of the interview.

NOVA Geoblog - Callan Bently has some interesting links in his post about the subject and goes into detail about what they actually did to find the dates and what the conclusions means in layman’s terms.

And of course, the here is the original Associated Press article posted on Physorg.

That wasn’t the only news related to the Grand Canyon last week. A man-made flood filled the canyon towards the end of last week to help restore the health of the Colorado River system as it flows through the canyon. However, some officials expressed concern and criticism.

In a statement, Public Employees for Environmental Responsibility condemned the flush as a “staged canyon greenwash” meant to attract television cameras while following a flood timeline that would “magnify the benefits for power production at the expense of environmental benefits.”

“The Bush administration is trying to extend its control through the term of its successor — a dead man’s hand throttling the Colorado River management,” said Jeff Ruch, executive director of the environmental group.