Tale of water, sand
|All four of Glen Canyon Dam's bypass tubes were opened during the high-flow experiment Nov. 11 to 16. (Photos by Lynn Jeka)|
By Lisa Meiman
The Bureau of Reclamation Upper Colorado Region has learned that the best way to push sand around is to use water—lots of concentrated, fast-flowing water.
For five days in November 2013, enough water to fill an Olympic-sized swimming pool was drained every two seconds from Lake Powell into the Colorado River during a high-flow experiment designed to rebuild sandbars, beaches and backwaters in the iconic Grand Canyon.
“Looking directly at the flow of water coming from the four bypass tubes, and hearing the thunderous sound as it hit the river, I truly came to appreciate the power of water,” said Colorado River Storage Project Management Center Manager Lynn Jeka, who witnessed the peak release of the HFE Nov. 11.
Six of Glen Canyon’s eight turbines were pumping at full capacity and all four dam bypass tubes were opened from Nov. 11 to 16 to release the maximum amount of water possible. Reclamation attempts to mimic natural flood patterns in the Colorado River by altering dam operations like this.
Significant rainfall and monsoons this summer, storm systems that also flooded parts of Colorado, created the right conditions for a high-flow experiment at Glen Canyon Dam in Arizona. Unlike the November 2012 experiment, which sought to flush a mere 500,000 metric tons of sediment from the tailwater beneath Glen Canyon Dam into the Grand Canyon, this HFE intended to excavate more than 1.5 million metric tons downstream.
This is the second such release under a 10-year experimental plan protocol approved in May 2012 to conduct HFEs, when certain sediment conditions are met. The HFEs are designed to develop wildlife habitat, potentially reduce erosion of archaeological sites, restore and enhance riparian vegetation and improve beaches along the Colorado River in Glen Canyon National Recreation Area and Grand Canyon National Park.
After observing dam operations, Jeka drove to Lees Ferry, about 15 miles below the dam, to meet with CRSP MC and Grand Canyon Monitoring and Research Center scientists to see the impact of the manmade flood. “A sandbar we stood on the night before was completely submerged. That sand was being moved further downstream to help rebuild beaches for recreational and environmental purposes.”
Secretary of the Interior Sally Jewell, who also attended the event, stated, “These releases herald a new era in which protecting water supplies and protecting river resources are compatible. [The] experimental release is consistent with our obligations to water users but will substantially benefit the downstream environment. Although the Colorado River Basin is experiencing the worst 14-year drought in the past century, we continue to honor our commitment to conservation when times are tough—healthy waterways are critical to tourism, recreation, habitat, cultural sites and local economies.”
HFE effect on power
Although there was a large amount of water surging out of Lake Powell during the experiment, the annual amount of water that will pass through Glen Canyon Dam did not change. “The high flows do not change the total annual delivery of water from Lake Powell to Lake Mead; they modify the timing of delivery,” said CRSP MC Administrative Officer David Bennion. “More water is released at a single time rather than evenly measured throughout the year.”
However, timing of water releases can have a big impact on hydropower production at Glen Canyon Dam, one of five powerplants in CRSP that represented nearly 87 percent of that project’s hydropower output in Fiscal Year 2012.
“Water released during HFEs takes away CRSP’s hydropower production potential over the rest of the year,” said Bennion. “CRSP has to make up for that by purchasing power from the market in order to meet customers’ needs.” Bennion and the rest of the CRSP MC staff estimate the HFE will have an economic impact of about $1.7 million. This expense will be taken out of the CRSP Basin Fund, a revolving fund that covers CRSP’s annual expenses, which has the potential to affect customers.
Stakeholders coordinate to strike balance
| During the 96-hour peak release about 34,100 cubic feet of water per second was drained from Lake Powell into the Colorado River, the equivalent of an Olympic-sized swimming pool every other second.|
Conducting experiments like these, which have far-reaching impacts to many interested stakeholders, including Western and its customers, requires a lot of coordination and compromise. Western participates in the Adaptive Management Working Group, which brings scientists, government agencies, recreational users, conservationists and Native American tribes together to discuss how to operate Glen Canyon Dam in a way that protects all its important uses and downstream resources in the best possible way.
“Western communicated with Reclamation frequently while planning this HFE to minimize the impact of the experiment on hydropower,” said Bennion. The conversations helped Reclamation and the Department of Interior, including the Assistant Secretary for Water and Science, understand the impact of the HFE, and DOI implemented changes that reduced the overall cost of the experiment for Western.”
“It helps that Western has fostered these relationships for decades,” said CRSP MC Environmental Specialist Clayton Palmer. “Western has been involved in this collaboration with Glen Canyon stakeholders since its inception in the early 1990s.”
CRSP MC staff represent Western and customer interests in developing the timing, magnitude, frequency and duration of the HFEs. “We believe our participation in these groups and the partnerships we have formed there help create a good balance between hydropower and protecting the Colorado River in the Grand Canyon,” said Jeka.
Learn more about the HFE at the Bureau of Reclamation’s Upper Colorado Region website. Also, check out photos and videos of the 2013 HFE at Western’s YouTube and Flickr channels.