Overview: During the 20th century, the earth`s mean average annual

Proposal to the Coordinating Committee from the
Climate Change Technical Committee
Objectives: The Climate Change Technical Committee has agreed that climate change
should be explicitly considered in evaluating regional water supply, related instream
flows, and forecasting water demands. To facilitate this consideration, the Committee
has identified fourteen questions and concerns that should addressed, to the extent
possible, during the regional planning process. In addition, the Committee has developed
an evolving number of “Climate Change Building Blocks,” which are short, factual
statements about our knowledge of climate change and its impacts. In addition, the
Committee will identify knowledge and/or information that will lead to better decisionmaking and will share this information with the other technical committees and
professionals, stakeholders, and other interested parties in the region.
Vision: To achieve portions of the goals stated above, the Climate Change Technical
Committee is seeking funding from the Coordinating Committee, among other sources, to
evaluate the impacts of climate change on regional water resources. This evaluation
would be based upon a consistent methodology applied throughout the region. The
approach would be watershed specific, and include portions of WRIAs 7, 8, 9, and 10 in
which major municipal water supplies exist. WRIA 5, which does not have any major
municipal water supplies, will be evaluated if requested and if resources exist. The
evaluation would make use of current climate forecasts from the Intergovernmental Panel
on Climate Change (IPCC) (those used for the 2007 Assessment) to arrive at projected
climate conditions and streamflows.
Scope: This effort will have three primary tasks and work products.
Task 1 will develop a database of climate variables to represent a range of projected
climate change conditions. Three scenarios will be used in the forecast to provide a
range of impacts. These scenarios will be based upon combinations of three different
climate models and two different emissions scenarios to bracket the range of potential
impacts on water resources in the Puget Sound, as recommended by Dr. Phil Mote,
the Washington State Climatologist. These scenarios consist of the IPSL A2 model
for the “pessimistic” scenario, the GISS B1 model for the “optimistic” scenario, and
the ECHAM5 A2 as the “average” scenario. Three periods in the future will be
investigated: 2025, 2050, and 2075. The future periods have been selected to ensure
appropriate water supply planning in both the shorter-term and longer-term. The 2100
period may also be investigated depending upon the final recommendations of the
Climate Change Technical Committee and the availability of funds, with the
understanding that emissions projections in 2100 will be less certain than those made
for the other periods. Using the three scenarios and time periods, future temperature
and precipitation data will be developed using statistical downscaling techniques for
selected sites (associated with Weather Service observation stations) as daily time
series. For each of these scenarios (9 or 12), a seventy-five year sequence of daily
climate variables will be generated that will provide information about projected
Climate Change Committee Proposal – Page 1
average conditions and seasonal and inter-annual variability. The process used to
develop the projected climate datasets will include a quality assurance/quality control
(QA/QC) procedure to ensure the consistency and reproducibility of the downscaling
process. This may be accomplished, in part, by having team members not responsible
for the original calculations selectively evaluate any codes and results. The methods,
assumptions, data validation and results of this task will be documented in a technical
Deliverables – Task 1
 Technical memorandum documenting the methods used, key assumptions, QA/QC
efforts and results.
 Database of climate variables for defined scenarios and future years for specific
Task 2 will translate the forecasted climate variables from Task 1 into streamflows at
selected sites within the WRIA watersheds. Of highest priority is the estimation of
inflows into the reservoirs that currently serve (or are anticipated to serve) as major water
supplies. This will include the inflows into the Howard Hanson Reservoir, Lake Tapps,
Chester Morse Reservoir, the South Fork Tolt Reservoir, and the Spada Reservoir. In
addition, incremental flows will be generated below the reservoir sites to the extent that is
necessary to model environmental flows and system operations. The Distributed
Hydrology Soils Vegetation Model will be used to translate the temperature and
precipitation data into streamflows appropriate for use in water supply analysis. This
model has been applied to all of the basins of interest, and has been previously calibrated
for two of the basins. Similar to Task 1, this task will also include QA/QC procedures to
identify and correct any errors that may occur in the modeling and calibration process.
Also, the methods, assumptions, model calibration, and results of this task will be
documented in a technical memorandum.
Deliverables – Task 2
 Technical memorandum - for each portion of the WRIAs, documenting the
methods used, key assumptions, model calibration and validation, QA/QC efforts
and results.
 For each of the climate change scenarios, database of projected streamflows into
local reservoirs.
 For each of the climate change scenarios, database of projected streamflows
associated with environmental flows or other operational components.
Task 3 will develop a framework for estimating the impacts that future climate change
may have on municipal water demand and water supply. The Climate Change
Committee expects to work with and provide technical support and advice to the
Municipal Water Demand Forecast and Water Supply Assessment Advisory Committees.
The framework will be provided in a timely fashion to ensure that the other committees
have the opportunity to incorporate the framework into their analysis.
Climate Change Committee Proposal – Page 2
Deliverables – Task 3
 Framework for estimating potential future climate change impacts on municipal
water demand and supply.
 Support to Municipal Water Demand Forecast and Water Supply Assessment
Advisory Committees.
Cost: The cost of generating this information will be a function of the overall final scope,
which considers the number of WRIA’s that are included, the actual number of climate
scenarios investigated, the number of forecast years (2025, 2050, etc.) generated, the size
of the watersheds, and the degree to which watershed models have already been
developed, calibrated, and validated, and the amount of documentation and QA/QC
required. The cost estimates included reflect the assumptions that have been provided in
the text above. Funding will be requested from the Coordinating Committee and other
agencies that have expressed interest in participating and who will benefit from the
results. This may include the State Department of Ecology, the Cascade Water Alliance,
and Seattle Public Utilities. Tables 1-2 provide estimated costs of activities by watershed
or utility, and these are summarized in Table 3 by task and deliverables.
Timetable: The timetable for work will also be a function of the scope. It is anticipated
that the work will be staged to address the highest priorities first. This would allow
incremental outputs throughout the duration of the project. Completion of the climate
impacts study on all four WRIAs is estimated to be concluded within twelve months after
the project begins.
Climate Change Committee Proposal – Page 3
Table 1: Climate Data and Statistical Downscaling for DHSVM Runs
with Three Models and 3 Futures
Downscale Climate
Data and Generate
Streamflows into
Reservoirs and Other
Downstream Locations
Source of
Modeling and
Table 2: Develop Framework to Support Water Demand and
Water Supply Technical Committees
Everett Public Works Department
Seattle Public Utilities
Tacoma Water
Cascade Water Alliance
Framework for including
Climate Impacts on
Demand and Supply
Source of
K/C*/ Cascade*
Table 3: Summary of Costs by Task
Task 1 - Costs
Task 2 - Costs
Task 3 - Total
Total Cost
1. Quality Assurance/Quality Control [include in Task 1 and 2]
2. Report Writing [include in Task 1 and2]
* Current estimate is that 50-60% of budget would be requested from the $250,000
Allocated to King County(K/C) and remainder would be sought from other agencies.
Climate Change Committee Proposal – Page 4