Decision support experiments and evaluations using seasonal to ...

leaders in considering climate change. SPU is
a “receptive audience” for climate tools in that
it has a wide range of management and longterm
capital investment responsibilities that
have clear connections to climate conditions.
Further, SPU is receptive to new management
approaches due to public pressure and the risk
of legal challenges related to the protection of
fish populations who need to move upstream
to breed.
Specific lessons include: (1) access to skillful
seasonal forecasts enhances credibility of using
climate information in the Pacific Northwest,
even with relatively long lead times; (2)
monitoring of snowpack moisture storage and
mountain precipitation is essential for effective
decision making and for detecting long-term
trends that can affect water supply reliability;
and (3) while SPU has worked with the research
community and other agencies, it also
has significant capacity to conduct in-house
investigations and assessments. This provides
confidence in the use of information.
Experiment 5:
Using Paleoclimate Information to Examine
Climate Change Impacts
The Experiment
Can an expanded estimate of the range of
natural hydrologic variability from tree ring
reconstructions of streamflow, a climate change
research tool, be used effectively as a decisionsupport
resource for better understanding SI
climate variability and water resource planning?
Incorporation of tree ring reconstructions
of streamflow into decision making was
accomplished through partnerships between
researchers and water managers in the intermountain
West.
Background and Context
Although water supply forecasts in the intermountain
West have become increasingly sophisticated
in recent years, water management
planning and decision making have generally
depended on instrumental gage records of flow,
most of which are less than 100 years in length.
Drought planning in the Intermountain West
has been based on the assumption that the 1950s
drought, the most severe drought in the instrumental
record, adequately represents the full
Decision-Support Experiments and Evaluations using Seasonal to
Interannual Forecasts and Observational Data: A Focus on Water Resources
range of natural variability and, thus, a likely
worst-case scenario.
The recent prolonged drought in the western
United States prompted many water managers
to consider that the observational gage records
of the twentieth century do not contain the full
range of natural hydroclimatic variability possible.
Gradual shifts in recent decades to more
winter precipitation as rain and less as snow,
earlier spring runoff, higher temperatures, and
unprecedented population growth have resulted
in an increase in vulnerability of limited water
supplies to a variable and changing climate.
The paleoclimate records of streamflow and
hydroclimatic variability provide an extended,
albeit indirect, record (based on more than 1000
years of record from tree rings in some key
watersheds) for assessing the potential impact
of a more complete range of natural variability
as well as for providing a baseline for detecting
possible regional impacts of global climate
change.
Implementation/Application
Several years of collaborations between scientists
and water resource partners have explored
possible applications of tree ring reconstructed
flows in water resource management to assess
the potential impacts of drought on water
systems. Extended records of hydroclimatic
variability from tree ring based reconstructions
reveal a wider range of natural variability than
in gage records alone, but how to apply this
information in water management planning has
not been obvious. The severe western drought
that began in 2000 and peaked in 2002 provided
an excellent opportunity to work with water
resource providers and agencies on how to incorporate
paleoclimate drought information in
planning and decision making. These partnerships
with water resource managers have led to
a range of applications evolving from a basic
change in thinking about drought, to the use of
tree ring reconstructed flows to run a complex
water supply model to assess the impacts of
drought on water systems.
The extreme five-year drought that began in
2002 motivated water managers to ask these
questions: How unusual was 2002, or the
2000-2004 drought? How often do years or
droughts like this occur? What is the likelihood
Several years of
collaborations
between scientists
and water resource
partners have
explored possible
applications
of tree ring
reconstructed flows
in water resource
management to
assess the potential
impacts of drought
on water systems.
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