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.,~ 002545 '" '\ FINAL DISCUSSION PAPER REVIEWED and ADOPTED 11/6/97 Technical Work Group Meeting Phoenix, AZ POTENTIAL SPRING 1998 BEACHlHABITAT-BUll..DING FLOW INTRODUCTION Colorado River basin runoff is anticipated to be at or above normal levels during Water Year 1998 (WY98), Both Lake Powell and Lake Mead are nearly full and a pronounced E1 Niilo/Southern Oscillation pattern is developing that may result in high inflows to Lake Powell in WY98, The goal of adaptiveIy managing the Colorado River ecosystem is to use the best scientific information to plan and accomplish preservation and enhancement of Colorado River ecosystem resources, and to mitigate the undesirable impacts of Glen Canyon Dam (GCD) releases on those resources. Given the potential that releases from GCD above 25,000 cfs may be required in WY98, the AdaptiveManagement Work Group (AMWG) has asked the Grand Canyon Monitoring and Research Center (GCMRC) to work with them in initiating early planning efforts aimed at preparing for managing these flows, In response, GCMRC has developed information regarding a Beach/Habitat-BuiIding Flow (BHBF) alternative for GCD releases in WY98, ( PURPOSE The BHBF presented below is intended to provide information for use by the AMWG in discussing and planning for a Spring 1998 BHBF, While in some sense, the impetus for developing the BHBF is to provide the AMWG with a plan for releases from GCD that might mitigate the negative impacts on sediment resources of high steady flows, the initiation of this planning process is intended to result in a BHBF that has the potential to benefit physical, biological, cultural, socio-economic and recreational resources of Glen Canyon Recreation Area and Grand Canyon National Park. Implementing such a BHBF will allow the AMWG to test these hypotheses. Included in this document is a description of a likely WY98 hydrological scenario and a proposed iterative planning process and schedule. BACKGROUND Lqal Framework. A provision for a BHBF was included in the preferred alternative of the Glen Canyon Dam Final Environmental Impact Statement (GCDEIS). As discussed in the GCDEIS (p, 40), the BHBF was intended to comprise releases in excess ofpowerplant capacity in low (8,23 mat) water years, The Record of Decision (ROD) on the GCDEIS signed by the Secretary of the Interior modified these conditions and established a framework for implementing BHBFs in high water years using releases in excess of powerpIant capacity for dam safety purposes, Flows above the 25,000 cfs level established in the ROD can occur to avert emergency hydrologic situations, Beach/Habitat-Building flows, and Habitat Maintainence flows,