AWBA Water Supply and Demand Study October 4, 2011 AWBA Meeting

Comparison 1997 Base to Base 1997 Base 1997 Reservoir Elevations 15,000 AF Indian Firming Indian Firming thru 2097 Pro Rata CAP/On-River Probability Base Shortage Determination Base 2012 Reservoir Elevation 23,724 AF Indian Firming Indian Firming Thru 2108 Shortage Sharing Proposal Stepped Shortage Determination

First Shortage Year Base vs Base

Shortage Volume Base vs Base

Number of Shortages Base vs Base

Credits Remaining Base vs Base

General Assumptions Starting Reservoir Elevation Jan Shortage Triggers CAP Shortage Distribution No Yuma Desalter M&I Firming thru 2097 Indian Firming thru 2108 Indian Firming 23,724 AF

Base vs. Scenarios Base On-River/CAP shortage distribution pro rata based on demand Scenarios Director’s Shortage Sharing Recommendation

Scenarios Scenario Upper Basin Depletion Schedule On-River Tribal Schedule Lake Mead Shortage Criteria Mexico Shares in Shortage Model Run Completed A AWBA Upper Basin Assumption Ten Tribes Interim Guidelines Extended Yes8/29/2011 B AWBA Upper Basin Assumption Ten Tribes Interim Guidelines Extended No8/29/2011 C AWBA Upper Basin Assumption ADWR Update Interim Guidelines Extended Yes8/30/2011 D AWBA Upper Basin Assumption ADWR Update Interim Guidelines Extended No E Upper Basin Schedule Ten Tribes Interim Guidelines Extended Yes8/29/2011 F Upper Basin Schedule Ten Tribes Interim Guidelines Extended No8/29/2011 G Upper Basin Schedule ADWR Update Interim Guidelines Extended Yes8/29/2011 H Upper Basin Schedule ADWR Update Interim Guidelines Extended No8/30/2011

Shortage Volume Base, Scenario A and Scenario C

First Shortage Year Base, Scenario A and Scenario C

Number of Shortages Base, Scenario A and Scenario C

Credits Remaining Base, Scenario A and Scenario C

Shortage Volume Median Traces

First Shortage Year Median Traces

Number of Shortages Median Trace

Credits Remaining Base, Scenario A and Scenario C

Discussion