Paul R. Houser, Science Advisor

Reclamation Climate Change ActivitiesPaul R. Houser

Paul R. Houser, Science Advisor

The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public.

Reclamation Mission

Paul R. Houser, Science Advisor

Mote, 2003

TRENDS (1950-97) in April 1 snow-water content at western snow courses

Less spring snowpack

Earlier snowmelt runoff

Stewart et al., 2005

Earlier greenup

Cayan et al., 2001

Figs. M. Dettinger (USGS)

Observed Hydrology & Vegetation ChangesLess snow/more rain

Paul R. Houser, Science Advisor

Implications for water supplies, water demands, operating constraints?

• Supplies– warming

• less snowpack less controllable water supply • more landscape evapotranspiration (ET) less runoff

– precipitation change? could be + or - , help or worsen…

• Demands– warming

• Irrigation: increased seasonal water demand (longer season, more ET)• Electricity: increased summer demand, decreased winter demand

• Operating Constraints– Environment – instream flow requirements?

• Reduction in cold-water supplies– Flood Protection – storage reservation requirement?

• All other things equal, warming leads to greater area contributing runoff during western winter storm events – greater winter reservoir drafts?

• Storm intensification could be + or -, worsen or help…

Paul R. Houser, Science Advisor

Key Challenges for Reclamation

• Understand how climate variability and change can affect Western water supply and demand, and Reclamation delivery of water given operational constraints (i.e. environmental constraints, flood constraints)

• Bring science and technology to bear on the needs of water resources managers

• Address goals of internal programs and authorizations where climate change is a factor

Paul R. Houser, Science Advisor

West-Wide Climate Risk Assessments (WWCRA) - Hydrologic Projections (2011)

http://www.usbr.gov/WaterSMART/wwcra.html

112 Transient Climate Projections…http://gdo-dcp.ucllnl.org/downscaled_cmip3_projections/dcpInterface.html

8 “big basin” VIC hydrology model-apps from Univ. of WA…

112 Transient Hydrologic Projections covering western U.S.…

Analyses of Period-changes in climate and hydrology

SECURE Report to Congress, 2011 focus on median changes; future reports have broader scope

Technical Report, data-development (TSC 86-68210, March 2011)

Data-service, Reclamation and broader public use (Summer 2011)

Paul R. Houser, Science Advisor

• Funding• WaterSMART Basin

Study Program – West-Wide Climate Risk Assessment

• Supporting:• Secretarial Orders

3289 and 3297

SECURE Report Production

Paul R. Houser, Science Advisor

Future Climate / Hydrology

Baseline Change Through Time

Temp

Precip

Snow

2020s 2050s 2070s

Paul R. Houser, Science Advisor

Tying to Impacts Example Colorado Flow Timing

• Flow timing shifts towards additional cool season runoff.

• Reduced warm season runoff

Competing Questions• Floods - Increased drawdown

requirements to maintain risk objectives

• Storage - Able to refill to supply objectives

Paul R. Houser, Science Advisor

Tying to ImpactsColorado River Example

Environmental and Flood Control

Implications for Flood Control Objectives

Implications for Environmental Flow Objectives

HUGE CAVEAT – e.g. calibration, validation

1950 2000 2050 2100

50

100

150

Colorado River above Imperial Dam

Annu

al M

ax. W

eek

Run

off,

kcfs

Water Year

1950 2000 2050 2100

6

8

10

Colorado River above Imperial Dam

Annu

al M

in. W

eek

Run

off,

kcfs

Water Year

Paul R. Houser, Science Advisor

SE

CU

RE

Rep

ort:

Wes

twid

e Im

pact

s (e

.g. a

nnua

l and

sea

sona

l run

off)

annual Dec-Mar Apr-Jul

2020

s-19

90s

2050

s-19

90s

2070

s-19

90s

Paul R. Houser, Science Advisor

Colorado River Basin Water Supply and Demand Study

Paul R. Houser, Science Advisor

Annual Colorado River Water Supply & Use

Paul R. Houser, Science Advisor

Water Supply Scenarios *

Observed Resampled: future hydrologic trends and variability

will be similar to the past 100 yearsPaleo Resampled: future hydrologic trends and variability

are represented by the distant past (approximately 1250 years)

Paleo Conditioned: future hydrologic trends and variability

are represented by a blend of the wet dry states of the paleo-climate record but magnitudes are more similar to the observed period

Downscaled GCM Projected: future climate will continue to warm with

regional precipitation trends represented through an ensemble of future GCM projections

Water Demand Scenarios *

Current Trends: growth, development patterns, and

institutions continue along recent trendsEconomic Slowdown: low growth with emphasis on economic

efficiencyExpansive Growth: economic resurgence (population and

energy) and current preferences toward human and environmental values *

Enhanced Environment and Healthy Economy:

expanded environmental awareness and stewardship with growing economy*

* Additional “branches” possible depending upon assumed trajectory of specific socio-economic

factors.

* Preliminary – Subject to change

Paul R. Houser, Science Advisor

Integration of Supply and Demand Scenarios

Recent Trends Recent

Trends

Water Supply Scenarios (multiple realizations for each scenario)

Climate indexing for demands

Water Demand Scenarios

Observe

d Resa

mpled

Downscaled G

CM Projected

Paleo Conditio

nedPaleo Resa

mpled

Current T

rends

Expansiv

e Growth

Enhance

d Environment a

nd

Healthy E

conomy

Economic

Slowdown

Paul R. Houser, Science Advisor

Addressing an Uncertain Future

• The path of major influences on the Colorado River system is uncertain and can not be represented by a single view

• An infinite number of plausible futures exist

• A manageable and informative number of scenarios are being developed to explore the broad range of futures

Scenario Funnel

Paul R. Houser, Science Advisor

Thank YouQuestions?