Development and Implementation of a Protocol for High-Flow Experimental Releases from Glen Canyon Dam, Arizona, 2011 through 2020. Environmental Assessment

摘要

The Department of the Interior (Interior), acting through the Bureau of Reclamation (Reclamation), is proposing to develop and implement a protocol for high-flow experimental releases (HFEs) from Glen Canyon Dam to better determine whether and how sand conservation can be improved in the Colorado River corridor within Grand Canyon National Park. This experimental protocol builds on, and was developed, following analysis of a series of high flow experimental releases, particularly those conducted in 1996, 2004, and 2008. This experimental protocol is the next logical scientific investigation as part of the Departments efforts to improve conservation of limited sediment resources in the Colorado River below Glen Canyon Dam. The information gained through this experimental protocol cannot be developed in any other manner, and is essential to informing future decisions in an adaptive management setting. In the past fifteen years of scientific research and monitoring, scientists have learned much regarding the use of high flow releases from Glen Canyon Dam. This proposed protocol is based on that science and targets future monitoring and research so as to refine our ability to predict the outcomes of future management actions intended to benefit the Colorado River ecosystem. This protocol will evaluate short-duration, high-volume dam releases during sediment-enriched conditions for a 10-year period of experimentation, 20112020, to determine how multiple events can be used to better build sandbars and conserve sand over a long time period. Under the concept of HFEs, sand stored in the river channel is suspended by these dam releases and a portion of the sand is redeposited downstream as sandbars and beaches, while another portion is transported downstream by river flows. These sand features and associated backwater habitats can provide key wildlife habitat, potentially reduce erosion of archaeological sites, enhance riparian vegetation, maintain or increase camping opportunities, and improve the wilderness experience along the Colorado River in Grand Canyon National Park.