Application of Climate Change research in CAP Planning activities

Mohammed MahmoudColorado River ProgramsCentral Arizona Project

• Historical Information– Authorized by 1968 Basin Project Act– Substantially completed in 1993– Responsible for repaying reimbursable costs to the U.S.

• Physical Characteristics– 336 mile aqueduct– 15 pumping plants– Lake Pleasant (system storage/release)– Primarily powered through Navajo Generating Station (NGS)– Diverts remainder of Arizona’s Colorado River

Apportionment

Colorado River Programs• Primary Questions of Concern:

– What factors influence the likelihood of shortage to CAP?– How do these factors influence the likelihood of shortage to

CAP?– What is the magnitude of likely shortage to CAP?

• Planning Issues of Importance:– Climate change– Upper Basin consumptive use– Higher priority Arizona users (Colorado On-River users)– System capacity for water deliveries– Projected growth in water use

• 92% of the Colorado River Basin's mean annual flow occurs above Lees Ferry (1906-2007)

• Mean annual flow is close to 15.0 MAF, ranging from 5.6 MAF to 25.2 MAF

• Upper Colorado and Green River are the most important tributaries: 75% of annual flow.

System Reservoirs

Lake Powell (Glen Canyon Dam)

Lake Mead (Hoover Dam)

System Vulnerabilities

Upper BasinPrecipitationSnowpackStreamflowUpper Basin UsesFlow Operations

Powell/MeadSide InflowFlow OperationsStorage

ArizonaOn-River Uses

CAPDelivery Infrastructure

CAP and Climate Change

• Winter regional-scale storm patterns drive snowpack which drives spring runoff in the Upper Colorado River Basin (90% of CAP supplies come from Upper Basin snowpack)

• Climate change is important to CAP because of our vulnerability in the Colorado River Basin

• Due to our junior priority, CAP is the most vulnerable in a vulnerable system

• Therefore it is important to explore the potential impacts of climate change to the Colorado River and to our system in order to better prepare for that possible eventuality

To put it in perspective…

Under current water use, a reduction of 7% in Colorado River water supply in the Lower Basin (Tier 3 short) results in a reduction of 30% for water available to Central Arizona (CAP)

30% Reduction

17%Reduction

Potential Impact of Climate Change

7%Reduction

Lower Colorado River Basin Arizona Central Arizona Project

Planning Models

• Colorado River Simulation System (CRSS)Addresses: – Climate change– Upper Basin uses– Projected growth

in water use

• Arizona On-River ModelAddresses:– Arizona higher

priority uses– Projected growth

in water use

Colorado River Hydrology

• Observed Resampled– Future hydrologic trends and variability similar to observed record– Mean: 15 MAF (Observed record)

• Paleo Resampled– Future hydrologic trends and variability based on streamflow

reconstructions of tree ring data– Mean: 14.7 MAF (Paleo record)

• Paleo Conditioned– Future hydrologic trends and variability represented by combined

statistics of both paleo and observed records– Mean: 15 MAF

• Downscaled GCM Projected– Future hydrologic conditions based on sustained climate warming – Mean: 13.6 MAF

Improving Predictability in the Colorado River Basin – Value of Combining Winter Synoptic Patterns with SST States(S. Rajagopal, Desert Research Institute)

WET/DRY?

Sea Surface Temp StatesAtmospheric Circulation Pattern Synoptic Storm Pattern