The Department of the Interior today initiated another high-flow release from Glen Canyon Dam in Arizona--the second release under an innovative science-based experimental plan approved in May 2012. The goal of the releases is to help restore the environment in Grand Canyon National Park and Glen Canyon National Recreation Area while continuing to meet water and power needs and allowing continued scientific experimentation and monitoring on the Colorado River.
"These releases herald a new era in which protecting water supplies and protecting river resources are compatible," said Secretary of the Interior Sally Jewell. "Today's 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."
By sending enough water downstream to fill an Olympic-sized swimming pool every few seconds, the 96-hour-release will pick up enough sand from river channels to fill a building as big as a football field and as tall as the Washington Monument, all the way to the brim. Then these hundreds of thousands of tons of sediment from river channels will be re-deposited along downstream reaches as sandbars and beaches along the Colorado River.
The high-volume experimental releases are designed to restore sand features and associated backwater habitats to provide key fish and wildlife habitat, potentially reduce erosion of archaeological sites, restore and enhance riparian vegetation, increase beaches, and enhance wilderness values along the Colorado River in Glen Canyon National Recreation Area and Grand Canyon National Park. The annual volume of water to be sent toward Lake Mead this year will not change as a result of the experiment -- water releases in other months will be reduced to ensure the annual volume is unchanged.
Former Secretary of the Interior Ken Salazar triggered the first release under the experimental long-term protocol in November 2012. The protocol calls for conducting more frequent high-flow experimental releases, timing them to occur following sediment inputs to the Colorado River downstream from Glen Canyon Dam.
Due to recent rainstorms, the sediment resources currently available for today's experiment have reached historic levels--approximately three times larger than the sediment volume available a year ago. Scientists estimate the sediment deposited by the Paria River since late July at approximately 1.5 million metric tons.
Based on the best available science, including careful evaluation of impacts on key resources including water and power, Assistant Secretary of the Interior for Water and Science Anne Castle directed the Bureau of Reclamation to initiate the experimental high-flow release beginning today, based on a recommendation from scientists and resource specialists and the consensus of an Interior leadership team.
"We're able to react quickly when favorable sediment conditions exist to maximize the benefits to downstream resources as a result of the framework provided by the high-flow protocol," said Castle, who spoke at the event. "This is the essence of adaptive management -- using science to guide our actions and responding within a framework that was developed with many collaborators to support balanced stewardship of the Colorado River and the Grand Canyon."
Once Glen Canyon Dam power plant reached full capacity, each of the four river outlet tubes was opened at successive intervals so that the project will reach the peak release of 34,100 cubic-feet-per-second for a total of 96 hours.
Recognizing the importance of annual water deliveries, the Grand Canyon Protection Act of 1992 (Public Law 102-575) also directed the Secretary of the Interior to manage Glen Canyon Dam in such a way as to "protect, mitigate adverse impacts to and improve the values for which Grand Canyon National Park and Glen Canyon National Recreation Area were established."
The flexible framework provided by the high-flow release protocol of 2012 is intended to better distribute sediment to conserve downstream environmental resources, while continuing to meet the water storage, delivery and hydropower production needs vital to western communities, agriculture and industry. Refinements to the 2013 experiment were made within that framework including consideration of power marketing conditions for the Western Area Power Administration.
The additional water released during the high-flow experiment is part of the total annual water delivery from Glen Canyon Dam to Lake Mead determined in August of each year based on the projected hydrology and forecasted reservoir elevations identified in the August 24-Month Study. The release does not change the annual amount of water released: high flow experimental release flows are included in the total annual volume and are offset by making slight adjustments to the monthly release volumes during other times of the water year.
"The current operations plan based on the August 24-Month Study calls for releasing 7.48 million acre-feet of water from the dam to meet delivery obligations to the Lower Colorado River Basin and Mexico," said Reclamation Commissioner Michael Connor. "This reduced volume is the result of declining reservoir levels driven by the drought and is fully in accordance with the 2007 Interim Guidelines."
The 2012 protocol calls for experimental releases from the dam through 2020 to send sediment downstream based on a number of conditions and parameters. Similar experimental releases were conducted in 1996, 2004, 2008, and 2012. These releases produced extensive collaboration and scientific research, monitoring, and data collection by and among various agencies of Interior including U.S. Geological Survey's Grand Canyon Monitoring and Research Center, the Bureau of Reclamation, the National Park Service, the U.S. Fish and Wildlife Service and the Bureau of Indian Affairs.