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sensitivity of the reconstruction to different calibration years and the quality of
gauge data.
Denver Water engineers are still in the process of incorporating these results
into their water system model, a major undertaking. The general approach used is
to pair pre-gauge reconstructed estimates with the closest analog year in the set
of 45 years (1947-1991) with known daily hydrology for the model's 450 loca-
tions to obtain the input needed for their model. In cases where reconstructed years
have no analog, values for the closest year are scaled accordingly. In this way,
the extended records from the streamflow reconstructions are being incorporated
into the Denver Water's water system model, ultimately allowing the system to be
tested by using a longer record of hydroclimatic variability than is afforded by the
gauge record. A companion reconstruction of water demand, which largely reflects
maximum summer temperatures and the occurrence of rainfall events at two thresh-
olds, was also generated, allowing a comparison of long-term records of supply and
demand, and the frequency of a joint concurrence of high demand and low flow to be
assessed.
8.3.4 Informing the Public
Dendrohydrologic reconstructions of streamflow have played an important role in
raising awareness among water managers, policy makers, and the general public
that the range of variability in gauge records is just a subset of the long-term natu-
ral variability over multiple centuries. The late 1990s through early 2000s drought
in the western United States caught the attention of many, and because it was the
worst drought on record in many areas (depending on variable and length of time
considered), it led to questions such as, 'How often do we have a drought this severe
and have there been worse droughts in the past?' The public interest level was high,
especially where outdoor water use was restricted, and was further heightened by
media attention to the drought. Water managers had a practical interest in getting
answers to these questions, while policy makers were made acutely aware that water
resource and drought planning needed to consider more than the worst drought in
the twentieth century.
This situation created a rare window of opportunity for dendrohydrologists to
assist in addressing these questions. It also presented an excellent opportunity
to inform the general public about the usefulness of tree-ring reconstructions of
hydroclimatic variability. Many groups—from the Audubon Society to the local
soil conservation district to continuing education law students—were interested in
hearing about droughts of the past. The challenge was to present information on
the tree-ring-based reconstructions regarding the current drought and droughts of
the past in a way that was readily understandable by a range of audiences. New
approaches to data display and visualization were considered to improve ways
to convey information about hydrological reconstructions. For example, the time
series of reconstructed streamflow typically shown are not readily understood by
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