Colorado River Basin Water Supply and Demand Study December 10, 2010

Colorado River Basin Study   Objectives: Define current and future imbalances in water supply and demand Assess the system reliability and risks to all Basin resources Develop and evaluate adaptation and mitigation strategies

CALIFORNIA NEW MEXICO COLORADO WYOMING UTAH ARIZONA NEVADA Colorado River Basin

Colorado River Basin Study   Phase 1: Water Supply Assessment   Phase 2: Water Demand Assessment   Phase 3: System Reliability Analysis   Phase 4: Develop & Evaluate Options to Balance Supply & Demand

Arizona Demand Study  Estimate current and future Colorado River water demand for which a long-term water supply has not yet been identified  Used along with demands from other Basin states to estimate supply & demand imbalance

Geographic Scope  Current Colorado River Contractors Mainstem Mainstem Central Arizona Central Arizona  Other Rural Areas North Central Arizona North Central Arizona Central Yavapai Highlands Central Yavapai Highlands Upper San Pedro Upper San Pedro

Arizona Demand Study

Miscellaneous Excess Users SCHEMATIC OF DELIVERY OF ARIZONA’S COLORADO RIVER ALLOCATION OF 2.8 MILLION ACRE-FEET (MAF) Priority 1 Contractors Priority 2 Contractors Priority 5 Contractors Priority 6 Contractors Priority 4 Mainstem Contractors Ak-Chin and Salt River Pima-Maricopa Indian Water Rights Settlements Indian Priority Subcontractors Municipal and Industrial Priority Subcontractors Excess Pool Non-Indian Agriculture Relinquished Pool Agricultural Settlement Pool AWBA and CAGRD Pool Indian Demand M & I Leases Indian Demand M & I Leases Indian Demand M & I Demand Priority 3 Contractors Priority 4 Contractors Priority 4 Central Arizona Project Priority 3 Central Arizona Project Unused Entitlement LAKE MEAD

Approach  Arizona Demand Study Focus: M&I water demand Focus: M&I water demand  Demand driver: Population growth Population growth  Energy water demand Linked to population growth Linked to population growth

Mainstem Assumptions  If projections indicate that an M&I contractor’s demand exceeds its entitlement, the projection is held to its entitlement, resulting in potential “unmet demand”  Mainstem contractors’ demand based on 2004 to 2008 averages from data reported in Reclamation accounting reports  Non-Indian agriculture acreage and consumptive use remain constant  Wildlife refuge use remains constant

Mainstem Study Area  ESTIMATED UNMET DEMAND IN 2060: APPROXIMATELY 30,000 ACRE-FEET

Other Rural Study Areas  North Central, Central Yavapai Highlands, and Upper San Pedro projections based in part on Arizona Water Atlas and Reclamation appraisal study data North Central Arizona Water Supply Study Report of Findings (Reclamation 2006) North Central Arizona Water Supply Study Report of Findings (Reclamation 2006) Augmentation Alternatives for the Sierra Vista Sub- watershed, Arizona, Appraisal Report (Reclamation 2007) Augmentation Alternatives for the Sierra Vista Sub- watershed, Arizona, Appraisal Report (Reclamation 2007) Central Yavapai Highlands Water Resources Management Study (Reclamation 2009) Central Yavapai Highlands Water Resources Management Study (Reclamation 2009)

Other Rural Study Area Assumptions  Municipal water demand based on study-predicted GPCD rates and population growth Industrial and agricultural uses based on study and/or Arizona Water Atlas projections Industrial and agricultural uses based on study and/or Arizona Water Atlas projections Agricultural use generally projected to decline over time Agricultural use generally projected to decline over time  Locally-available supplies based on study and Arizona Water Atlas data  Groundwater use projected to continue to increase; however, use above defined levels assumed to result in unmet demand

Other Rural Study Areas  ESTIMATED UNMET DEMAND IN 2060: APPROXIMATELY 65,000 ACRE-FEET

Central Arizona Study Area Assumptions  Phoenix, Pinal, and Tucson AMAs analyzed separately, with local supplies in one AMA assumed not to be available to other AMAs  Estimated unmet demand based on relationship between: Projected local demand in each AMA (municipal, industrial, agricultural use) Projected local demand in each AMA (municipal, industrial, agricultural use) Projected local supplies in each AMA (groundwater, surface water, effluent, and storage/recovery) Projected local supplies in each AMA (groundwater, surface water, effluent, and storage/recovery)  Aggregate GPCD based on ADWR Third Management Plan water use targets  Demand above locally-available supply assumed to be met via utilization of Colorado River water Overall demand exceeding available CAP supplies results in new demand for imported supplies Overall demand exceeding available CAP supplies results in new demand for imported supplies

Central Arizona Study Area Assumptions  Indian Water Use & Leasing Indian build-out of current CAP water supplies by 2025, with constant rates of use thereafter Indian build-out of current CAP water supplies by 2025, with constant rates of use thereafter Indian leasing based on what is authorized in settlements, and assumes approximately 225 kaf total use Indian leasing based on what is authorized in settlements, and assumes approximately 225 kaf total use

Central Arizona Study Area   ESTIMATED UNMET DEMAND IN 2060: APPROXIMATELY 530,000 ACRE-FEET

Arizona Demand Study   Initial baseline unmet demand estimate: 630,000 acre-feet   Arizona Baseline Demand Draft Report

Questions?

Uncertainty Analysis   Sensitivity Analysis Scenario approach for incorporating uncertainty

Uncertainty Approach   Demand Storylines for demand scenarios   Supply Analysis of future climate scenarios Analysis of climate connection and streamflow   Metrics Draft metrics for all categories

Uncertainty Approach   Scenario Approach Structured process and common language to discuss uncertainty Explore plausible futures Used to assess future risk and adaptation strategies Plausible Scenario Funnel

Elements of Scenario Analysis   Frame the Study Question   Identify and rank driving forces   Select and prioritize critical uncertainties   Group key uncertainties and develop storylines   Develop scenarios

Frame the Study Question   What is the future reliability of the Colorado River system to meet the needs of Basin resources?   What are the options and strategies to mitigate future risks to these resources?

Key Driving Forces   Four categories Natural systems (hydroclimate) Demographics and land use Technology and economics Social and Governance

Key Driving Forces   Demographics and Land Use Changes in population and distribution Changes in agricultural land use (e.g. irrigated agricultural areas, crop mixes, etc.)

Demand Storyline Developm ent   Storylines Plausible Logical, express coherent patterns Explore the range of uncertainty

Draft Demand Scenarios   “A” Current Trends Baseline scenario   “B” Economic Slowdown   “C” Expansive Growth   “D” Healthy Economy & Enhanced Environment

Demographics & Land Use Economics & Technology Social & Institutional D2 A D1 C1 B C2 Graphical Depiction of Driving Forces Categories and Scenarios Today

Questions?