Saturday, August 02, 2008

Is there enough sand to rebuild Grand Canyon sandbars?

An article in the August issue of GSA Today magazine asks, "Is there enough sand" to rebuild eroding sandbars on the Colorado River in the Grand Canyon.

[right: Example of a recirculating eddy and sandbar formed around the flow reattachment point along the Colorado River below Glen Canyon Dam. Image on right reproduced from Webb et al. (2005). GSA Today.]

The authors conclude that under the bset-case scenario for operating Glen Canyon Dam, it may be possible to supply about as much sand to the system as is lost to the dam system. However, optimum conditions may be difficult to achieve: "the optimal dam operation for accumulating tributary sand inputs is a constant, steady flow over the entire year." And the "optimal annual release volume for accumulating tributary sand is ahte minimum volume stipuated by the various agreements that govern water delivery between the upper and lower Colorado River basins."

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