Tuesday, November 12, 2013

Glen Canyon Dam high flow releases

For over 5 years the SFPUC and NPS have collaborated on experimental flood releases from O'Shaughnessy Dam to support development of a new instream flow management plan for the upper Tuolumne River between the dam and Early Intake.  The releases have primarily been conducted to test flow thresholds for sediment transport and Poopenaut Valley wetland inundation.  Similar flood release experiments have been underway on other rivers; among the most widely reported are the releases from Glen Canyon Dam into the Grand Canyon on the Colorado River.

The Glen Canyon Dam Adaptive Management Program began in 1997 as an effort to use high flow releases to manage sediment (primarily sand) for the benefit of backwater habitats that provide key fish and wildlife habitat, reducing erosion of archaeological sites, restore and enhancing riparian vegetation, and restoring sand bar beaches for recreational boating and camping.  The releases maintain water supply obligations by releasing less water during other parts of the year, mimicking pre-dam flows and water temperatures.

This week, the Glen Canyon program is conducting a second high flow experimental release from Glen Canyon Dam under a protocol approved in 2012. The protocol calls for conducting more frequent high flow experimental releases from the dam timed to occur following sediment inputs to the Colorado River from downstream tributaries. Large amounts of sediment were deposited over the summer due to major rainstorms.  The volume of sediment available is about three times larger than the volume available during the last high flow release in the fall of 2012.

Read more on the 2013 releases from the LA Times and the US Bureau of Reclamation. Also, checkout some of the science and multimedia products the USGS is producing related to the high flow releases.