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Bob Moffitt www.nps.gov

Lake Powell is a long narrow meandering reservoir. When it's full the water seeps into banks outside the reservoir and are lost to the millions of Colorado River users.

Lakes Powell and Mead store Colorado River drinking water for the arid Southwest. This time of year they lose a lot of that water to evaporation. The Powell reservoir is also losing a lot of water through seepage, according to a new study.

Lake Powell, which is upstream of the Grand Canyon, is losing more water to seepage than Nevada’s annual Colorado River allotment.

About 380,000 acre-feet every year seeps into the porous Navajo sandstone, according to hydrologist Thomas Myers who studied the water loss and just published a paper about it in the Journal of the American Water Resources Association.

"You lose almost no water to seepage at Lake Mead," Myers said. "It’s a lot less fractured. It just doesn’t allow the water to flow miles and miles away from the reservoir like it does at Lake Powell."

The Glen Canyon Institute commissioned the study. It’s agenda is to restore Glen Canyon and a free flowing river. The institute would like to see more water stored in Lake Mead, which has a less porous foundation.