GCDAMP Glen Canyon Dam

Operations of Glen Canyon Dam The Record of Decision (ROD) on the operation of Glen Canyon Dam was signed on October 9, 1996. It stipulated flows at Glen Canyon (via reference to the EIS(1)). A new operating criteria for Glen Canyon Dam was signed on February 24, 1997. According to the EIS, minimum flows of 8,000 cubic feet per second (cfs) during the day and 5,000 cfs at night were incorporated within the preferred alternative largely to maintaining the food base for the sport fishery (EIS, pg 223). The maximum flow of 25,000 cfs was imposed in order to conserve sediment in the Grand Canyon, especially in the Marble Canyon area. The maximum daily change limitation of 8,000 cfs (during “wet” months) was intended to benefit a variety of resources; sport fish, native fishes, recreation, riparian vegetation and habitat and cultural. The downramp limit of 1,500 cfs was mainly imposed to reduce the erosion of beaches (sand deposits) in the Marble Canyon reach due to rapid leaching of water in the sand (EIS, pg 204). The ROD and operating criteria include “emergency exception criteria” which continued over from “interim flows” as a recognition of the fact that the Glen Canyon Powerplant is connected to an electrical system. [1] Operating tier for WY2017 The operating tier for water year 2017, established in August 2016, is the Upper Elevation Balancing Tier, with an initial water year release volume of 8.23 maf and the potential for an April 2017 adjustment to equalization or balancing releases. Based on the current forecast, an April adjustment to balancing releases is projected to occur and Lake Powell is currently projected to release 9.0 maf in water year 2017. This projection will be updated each month throughout the water year. [2]

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Updates [3] USBR Monthly/Annual Reports Upper Colorado Region Water Operations site 24-Month Study Monthly Summaries Annual Operating Plans for Colorado River reservoirs Report to Congress Regarding Operations of Glen Canyon Dam 2015-2016 Report to Congress 2014-2015 Report to Congress 2013-2014 Report to Congress 2010-2011 Report to Congress 1999-2001 Report to Congress 1998-1999 Report to Congress

Links and Information 1997 Operating Criteria for Glen Canyon Dam 2007 Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead Operations of Glen Canyon Dam under the 1996 ROD Presentations and Papers 2017 February 2017 Glen Canyon Montly Operational Coordination Call Analysis of Water Losses and Impacts to the Grand Canyon Ecosystem of the "Fill Mead First" Proposal and PPT Basin Hydrology, and 2017-2018 Operations Basin Hydrology, Operations and 2018 Hydrograph 2016 FILL MEAD FIRST: A technical assessment (Summary) FILL MEAD FIRST: A technical assessment (Analysis) Basin Hydrology and Water Year (WY) 2017 Hydrograph August 2016 DOI-DOE Federal Family call on Glen Canyon Operations Basin Hydrology, Operations, and 2017 Hydrograph TWG: Basin Hydrology, Operations, and 2017 Hydrograph AMWG: Basin Hydrology, Operations, and 2017 Hydrograph Glen Canyon Dam operations during equalization 2015 2016 Annual Operating Plan AMWG: Basin Hydrology and WY 2016 Hydrograph TWG: Hydrology Update and 2016 Hydrograph Panel on Current Projects and Issues in Utah Central Utah Project Meeting the Mitigation Requirement for the Bonneville Unit CUP Current Projects and Issues in Utah Provo Area Office 2014 Colorado River Annual Operating Plan and Drought Contingency Planning Basin Hydrology, Operations DOI-DOE Hydrograph Development for Water Year 2015 Basin Hydrology, Operations, and 2015 Hydrograph and Development of Water Year 2015 Hydrograph Basin Hydrology, Operations, and 2015 Hydrograph Panel on the Potential Effects of Long-Term Drought on Colorado River Operations Near Term Risks: Options to Address Declining Reservoirs State of Nevada Concerns 2013 Colorado River Basin Hydrology and Projected Glen Canyon Dam Operations Operational Flexibility In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (mw) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,200 cfs above or below the hourly scheduled release rate. Under system normal conditions, fluctuations for regulation are typically short lived and generally balance out over the hour with minimal or no noticeable impacts on downstream river flow conditions. Releases from Glen Canyon Dam can also fluctuate beyond scheduled releases when called upon to respond to unscheduled power outages or power system emergencies. Depending on the severity of the system emergency, the response from Glen Canyon Dam can be significant, within the full range of the operating capacity of the power plant for as long as is necessary to maintain balance in the transmission system. Glen Canyon Dam typically maintains 30 mw (approximately 880 cfs) of generation capacity in reserve in order to respond to a system emergency even when generation rates are already high. System emergencies occur fairly infrequently and typically require small responses from Glen Canyon Dam. However, these responses can have a noticeable impact on the river downstream of Glen Canyon Dam. [4] Other Stuff Video of the construction of Glen Canyon Dam HOW ITS MADE - The Glen Canyon Dam 1983 flood videos and spillway repairs Challenge at Glen Canyon (Part 1) Challenge at Glen Canyon (Part 2) Challenge at Glen Canyon (Part 3) What is the total release (CFS) possible from Glen Canyon Dam? Total release during a HFE = Power plant capacity + 15,000 cfs through the bypass tubes Capacity depends on how many of the 8 units are available. [5]