Dissolved Gas Abatement Study Background Due to the rapid decline in salmon runs and their listing as an endangered species, voluntary spill, at the eight Federal dams on the Lower Snake and Columbia Rivers, has been requested by the Pacific Northwest Region to help improve juvenile salmonid fish passage around the dams. However, total dissolved gas (TDG) supersaturation is generated when water is spilled over existing spillway configurations at large dams. High levels of TDG can cause mortality in juvenile and adult migratory fish, resident fish, and other organisms. Dissolved gas control was also a regional issue in the late 1970’s and several of the eight Federal dams were retrofitted with spillway deflectors to reduce the level of high TDG supersaturation. These spillway deflectors were designed for involuntary spillway releases that occur when river discharges exceed powerhouse hydraulic capacities. Recently, operation of the Federal projects has changed with the requirement for voluntary spill to assist fish passage and TDG supersaturation has again resurfaced as a major regional concern. Purpose of Study The purpose of the Dissolved Gas Abatement Study (DGAS) is to identify, evaluate, and recommend structural and or operational measures which will reduce river dissolved gas levels during involuntary spill operations and/or voluntary spill for juvenile fish passage. The study area includes the eight Corp’s dams on the Snake and Columbia Rivers in the States of Washington and Oregon. Study Management and Team Members The DGAS is a cooperative venture jointly managed by Portland and Walla Walla Districts of the U.S. Army Corps of Engineers. Scientists and engineers within the two districts and researchers at the Corps' Waterways Experiment Station in Vicksburg, Mississippi, are exploring structural measures that could be implemented to reduce the production of total dissolved gas during spilling operations at large dams on the Snake and Columbia rivers. In addition, the Corps has contracted with universities, other agencies and private firms to provide research and modeling capability to support the study effort. LINKS: DGAS Modeling Core Team Page (Univeristy of Washington) for meeting agendas and minutes. Walla Walla District: Home Page | Total Dissolved Gas Monitoring Reports (updated houlrly) | 1997 Fish Research CONTACT: DGAS Chris Pinney, Fisheries Biologist, Planning Division, Aquatic Resources Branch Rick Emmert, Technical Manager, Engineering Division, Design Branch Last Updated: 11:19 AM 5/9/2000 Privacy and Security Notice

The POC for this page: Rick Emmert, CENWW-ED 509-527-7536 Walla Walla, WA rick.l.emmert@usace.army.mil