The Colorado River: Interim Guidelines for Lake Powell and Lake Mead National Integrated Drought Information System Workshop October 1, 2008

Colorado River Basin Operation governed by the “Law of the River” including: –Colorado River Compact (1922) –Boulder Canyon Project Act (1928) –U.S. Mexican Water Treaty (1944) –Colorado River Storage Project (1956) –Supreme Court Consolidated Decree (1964 and following) –Colorado River Basin Project Act (1968) System operated on a “tight margin” Variable hydrology Large amount of storage capacity

Short-term Scheduling Long-term Planning Mid-term Operations Real-time Control Spatial Resolution/ Time Horizon Operational ActivityDecisions Basin-wide over decades Basin-wide over 1-2 years Sub-basin over 4-6 weeks Single project over 1-7 days Operating Criteria and Guidelines Annual Operating Plan Water and Power Schedules Unit Commitment Economic Dispatch Automatic Generation and Control

In 2004, five years of unprecedented drought, coupled with increased water use, led to increased tensions among the Basin States There had never been a shortage in the Lower Basin and there were no shortage guidelines Operations between Lake Powell and Lake Mead were coordinated only at the higher reservoir levels (through “equalization”) Impetus for the Interim Guidelines

Interim Guidelines 1 - A Robust Solution Operations specified through the full range of operation for Lake Powell and Lake Mead Encourage efficient and flexible water use and management in the Lower Basin through the Intentionally Created Surplus (ICS) mechanism Strategy for shortages in the Lower Basin 2, including a provision for additional shortages if warranted In place for an interim period (through 2026) to gain valuable operational experience Basin States agree to consult before resorting to litigation 1.Issued in Record of Decision, dated December 13, 2007; available at Mexico water deliveries are not directly effected by these guidelines

Lake Powell & Lake Mead Operational Diagrams 1 Subject to April adjustments that may result in balancing releases or releases according to the Equalization Tier. 2 These are amounts of shortage (i.e., reduced deliveries in the United States). 3 If Lake Mead falls below elevation 1,025 ft msl, the Department will initiate efforts to develop additional guidelines for shortages at lower Lake Mead elevations.

Colorado River Basin Storage (as of September 29, 2008) Current Storage Percent Full MAF Elevation (Feet) Lake Powell60% Lake Mead46% Total System Storage 57%*34.10NA *Total system storage was maf or 54% this time last year

Min Power Pool 3,490 ft 3,627 ft maf (60% of Live Capacity) 3,370 ft Dead Pool Elevation Lake Powell Capacity 3,700 ft 24.3 maf Dead Pool (1.9 maf) Inactive Pool (4.0 maf) Not to scale 72 ft 138 ft As of Sep 29, ,636 ft 8 ft 3,575 ft Lower Elevation Balancing Tier Mid-Elevation Release Tier 3,525 ft Equalization Tier Upper Elevation Balancing Tier Equalization Elevation (WY 2008)

Lower SNWA Intake 1,000 ft 1,106 ft maf (46% of Live Capacity) 895 ft Dead Pool Elevation Lake Mead Capacity 1,219.6 ft 25.9 maf Dead Pool (2.0 maf) Inactive Pool (7.5 maf) Not to scale 115 ft As of Sep 29, ,145 ft 55 ft 1,075 ft Shortage Conditions 1,050 ft Surplus Conditions Normal or ICS Surplus Conditions Min Power Pool 15.9 maf

The Colorado River: Interim Guidelines for Lake Powell and Lake Mead For further information: