Colorado River discharge in the stretch that passes through the Grand Canyon increased dramatically as the result of planned ecological releases from upstream Glen Canyon Dam, built in 1963. Above is a graph showing how the release will increase flow and stage for an approximate 60-hr time span, as a way to mimic natural flows that renourish sand beds critical to the river corridor’s health.
Below is a graph showing Lake Powell and downstream Lake Meade stage. Note the dip in reservoir stage over the past 9 years. Both reservoirs are at about half their peak capacity. I think that’s around 20 million acre feet for Lake Powell and around 28 million acre feet for Lake Mead. Lake Okeechobee holds around 5 million acre feet at capacity in comparison.
It was interesting to hear Interior Secretary Dirk Kempthorne’s comparison of Powell’s release volume to the volume it takes to fill the Empire State Building in 20 minutes. Empire state building is around 1300 ft tall (not counting tower), and covers an area of around 2 acres on the ground, which is about the size of fair play in a major league baseball field. By comparison, evaporation extracts around 2 volumes of the Empire State Building every day from Lake Okeechobee.Click below to find out more on Grand Canyon’s big day:
Correction, and update (on 3/7): Below is a graph, courtesy of the US Geological Survey, showing instantaneous discharge levels of the Colorado through Grand Canyon. The US Geological Survey’s flow record at the Grand Canyon goes back to 1922! Flows are currently around 45,000 cfs. In comparison, exteme high discharges down the Caloosahatchee in 2003 and 2004 were just 16,000 cfs.