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OPERATIONS OF GLEN CANYON DAM UNDER THE ROD usbr/wapa ///$/99 l ~ i ~ . I ~ .. S; ~: . , ~ I. Bac~l:J'ound: 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'). A new operating criteria for Glen Canyon Dam was signed on February 24, I 997 (copy attached). 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 of25,000 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 downrarop 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. ~ jo..~ ~y ;.," jc~j' On April 1st, 1998, the day Western changed the boundaries on its control areas, an incident of excess generation on the CRSP tranmission lines occurred which invoked the "emergency exception criteria" The operation of Glen Canyon Dam on that day exceeded the normal ROD flows. After this incident, members of the Adaptive Management Work Group (AMWG) and the Technical Work Group (TWG) asked Western and Reclamation to report on how these agencies were operating under the ROD. These reports led to a concern by some regarding the interpretation of the ROD. Specifically, that "regulation flows", to the extent that they caused releases to exceed the limitation outlined in the ROD and Operating Criteria, were a violation of the ROD. In early July, Western and Reclamation discussed this issue. Western agreed to limit "scheduled" downrarops to 1,450 cfs in order to reduce the likelihood that downrarops would exceed 1,500 cfs. Later, Western also moved 80% of regulation for CRSP loads to Hoover Dam during the times of the day in which Western would be downramping. .'-,.., ;~<: ~., fP f'" /~ ~';: ",t 1{ ~'. 10,- iJ .'.,., ~.~ L'i'" ~~ t". ~? r1 ~> . ::.{.>, ? .;" '\~ ~. ~~1 , US Department ofInterior, 1995. Operation of Glen Canyon Dam Final Environmental Impact Statement. US Department of Interior, Bureau of Reclamation, Upper Colorado Region, Salt Lake City, Utah. Hereinafter referred to as: "EIS,"