Climate Change Streamflow Scenarios Designed for Critical Period Water Resources Planning Studies

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Climate Change Streamflow Scenarios Designed for
Critical Period Water Resources Planning Studies

• Alan F. Hamlet
• Dennis P. Lettenmaier
• Amy K. Snover
• Department of Civil and Environmental Engineering
• And
• Climate Impacts Group
• University of Washington
• European Geophysical Society
• Nice
• April 7, 2003

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Changing Awareness of Climate Change in the Water
Management Community
1985 Global warming? 1995 Is global
warming real? 1997 What are the expected
impacts of climate change for our region and
our water system? 2002 How do we include
climate change and climate uncertainty in long
term planning to reduce risks?
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Climate Change Scenarios for the PNW
2.5 C
1.7 C
Somewhat wetter winters and perhaps somewhat
dryer summers
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The primary impact pathway in the western US
less snow
2020s
2040s
Current Climate
Snow Water Equivalent (mm)
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Columbia River at The Dalles for
Middle-of-the-Road Scenarios
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Effects to Moderate Elevation Basins in the
Cascades
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Critical Period Planning Methods for Water Studies
Observed Streamflows
Planning Models
System Demands
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Incorporating Climate Change in Critical Period
Planning
Long term planning for climate change may include
a stronger emphasis on drought contingency
planning, testing of preferred planning
alternatives for robustness under various climate
change scenarios, and increased flexibility and
adaptation to climate and streamflow uncertainty.
Observed Streamflows
Planning Models
Altered Streamflows
Climate Change Scenarios
System Demands
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Project Goals

• Create climate change streamflow scenarios that
  cover the same period of record and are
  numerically consistent with the historic record
  of streamflows traditionally used in water
  planning studies.
• Make these streamflow scenarios freely available
  on the web for a large number of river locations
  to facilitate the incorporation of climate change
  information into existing water planning efforts.

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Changes in Mean Temperature and Precipitation or
Bias Corrected Output from GCMs
ColSim Reservoir Model
VIC Hydrology Model
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Issues with Hydrologic Model Bias
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Quantile-Based Bias Correction (Wood et al. 2002)
VIC Input 19000
Bias Corrected Output 10000
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Bias Correction Objectives
Raw
Bias Corrected
Result Bias corrected hydrologic simulations
are quite consistent with observed streamflows in
absolute value and climate change signals are
translated without significant distortion.
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Web-Based Data Archive
http//www.ce.washington.edu/hamleaf/climate_chan
ge_streamflows/CR_cc.htm
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Goals and Objectives of Two Regional-Scale Pilot
Studies in the Pacific Northwest
Northwest Power Planning Council Primarily
focused on reliability of the Columbia River
hydropower system. Study will use the GENESYS
model. Idaho Department of Water
Resources Primarily focused on sustainability
of irrigated agriculture in the Snake River
basin and water allocation amongst different
uses.
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Current Streamflow Locations
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• Planned Project Extensions
• Extend the period of record of the data to
  1928-1999.
• Extend the number of climate change scenarios
  and the downscaling methods used.

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Summary and Conclusions Water policy workshops
(Skamania 2001) have highlighted the need to
inject climate change information into existing
river basin planning activities where possible
and to provide access to free streamflow
scenarios to help reduce costs. Because most
planning studies currently use a critical period
framework, our project produces adjusted
realizations of the historic streamflow record
based on simulations from a physically based
hydrologic model driven by simple climate change
scenarios. The methods are flexible and portable
and can be used to create streamflow scenarios
deriving from different climate model scenarios,
different downscaling methods, or different
hydrologic models.