To: All Annual Operating Plan Recipients
From: Lower Colorado Region
Boulder Canyon Operations Office
River Operations Group
Daniel Bunk
P.O. Box 61470
Boulder City, NV 89006-1470
Phone: 702-293-8013
The operation of Lake Powell and Lake Mead in this October 2017 24-Month Study is pursuant to the December 2007 Record of Decision on Colorado River
Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines) and reflects the 2017 Annual Operating Plan (AOP) and draft 2018 AOP. Pursuant to the Interim Guidelines, the August 2017 24-Month Study projections of the January 1, 2018, system storage and reservoir water surface elevations set the operational tier for the coordinated operation of Lake Powell and Lake Mead during 2018.
Consistent with Section 6.B of the Interim Guidelines, the Lake Powell operational tier for water year 2018 will be governed by the Upper Elevation Balancing Tier, with an initial water year release volume of 8.23 maf and the potential for an April adjustment to equalization or balancing releases in April 2018. This
October 2017 24-Month Study indicates that, consistent with Section 6.B.4 of the Interim Guidelines, an April adjustment to balancing releases is projected to occur and Lake Powell is projected to release 9.0 maf in water year 2018.
Consistent with Section 2.B.5 of the Interim Guidelines, the Intentionally Created Surplus (ICS) Surplus Condition is the criterion governing the operation of Lake Mead for calendar years 2017 and 2018. The 2018 operational tier determinations will be documented in the 2018 AOP, which is currently in the final stages of development.
The Interim Guidelines are available for download at:
http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
The 2017 AOP is available for download at:
http://www.usbr.gov/lc/region/g4000/aop/AOP17.pdf
The draft 2018 AOP is available for download at:
https://www.usbr.gov/lc/region/g4000/AOP2018/AOP18_draft.pdf
Current runoff projections into Lake Powell are provided by the National Weather Service’s Colorado Basin River Forecast Center and are as follows:
Observed unregulated inflow into Lake Powell for the month of September was 0.196 maf or 48 percent of the 30-year average from 1981 to 2010. The forecast for October unregulated inflow into Lake Powell is 0.510 maf or 100 percent of the 30-year average. The observed 2017 April through July unregulated inflow is 8.173 maf or 114 percent of average.
In this study, the calendar year 2017 diversion for Metropolitan Water District of Southern California (MWD) is projected to be 0.652 maf. The calendar year 2017 diversion for the Central Arizona Project (CAP) is projected to be 1.394 maf. Consumptive use for Nevada above Hoover (SNWP Use) is projected to be 0.248 maf for calendar year 2017.
Due to changing Lake Mead elevations, Hoover’s generator capacity is adjusted based on estimated effective capacity and plant availability. The estimated
effective capacity is based on projected Lake Mead elevations. Unit capacity tests will be performed as the lake elevation changes. This study reflects these
changes in the projections.
Hoover, Davis, and Parker historical gross energy figures come from PO&M reports provided by the Lower Colorado Region’s Power Management Office, Bureau of Reclamation, Boulder City, Nevada. Questions regarding these historical energy numbers can be directed to Eric Carty at (702) 293-8129.