As the summer snow melt continues, reservoir water levels in the Western U.S. should continue to rise. Look the top graph. This shows the dramatic rise in the water level of Lake Powell.
Lake Powell is the pond behind the Glen Canyon Dam. The dam, which is in far northern Arizona, is 710 feet high The Lake behind the dam stretches back 186 miles along the Colorado River. The dam wasn’t completed until 1963. The lake has a combined 1,900 miles of shoreline. At the dam, the water is 583 feet deep, nearly 3 times the maximum depth of Lake Erie.
This is a desert. At the dam, they get only 6.36″ of rain per year. That includes about 1″ of snow. Afternoon temperatures are in the mid-upper 40s and it can soar to 115° in the hottestworst summer heat waves. It’s been as cold as 2 below zero F in the winter.
Snowfall has been up to 2 to 3 times average in the Colorado Basin and the melting snow has caused some rivers to rise to above average flow. The Colorado River at Potash, Utah currently has a flow of 23,500 cubic feet per second. Average flow there is 13,800 cfs for early June. So the current flow is 170% of average flow. Lake Powell has risen 45.8 feet since April 12 and it’s now 32.3 feet higher than one year ago. To get to full volume, the lake would have to rise another 134.19 feet. The water level of the lake rose 2″ in the last 24 hours (as I write this).
Downstream from the Glen Canyon Dam is the Grand Canyon. The Colorado River at the Grand Canyon is slightly above average flow – currently at 20,000 cfs – average is 19,100 cfs.
Beyond the Grand Canyon is Lake Mead. It’s been holding a pretty steady water level in the last couple weeks. The level is up 8.68 ft. since April 5 and it’s 7.58 ft higher than one year ago. As Lake Powell continues to fill, they’ll be able to release a bit more water downstream into Lake Mead.
The water level of Shasta Lake in California is holding steady at at time when reservoir levels usually have started their summer decline. The water level is only 3.68 feet below full pool. The level has gone up 134 feet since Jan. 1 and is now 117 feet higher than one year ago.
As you can see, most reservoirs in California are at or close to capacity and river levels across much of the state are well above average levels..
The Truckee River at Truckee CA has a current flow of 1,070 cfs, compared to an average flow of 2,630 cfs. The San Joaquin River at Vernalis has a flow of 27,100 cfs compared to an average flow of 3,010 cfs and the Sacramento River at Freeport has a flow of 33,600 cfs compared an average flow of 14,399 cfs.