Decision support experiments and evaluations using seasonal to ...

a sub-seasonal lead time, the singlevalued
outlook may be justified by the
planned management strategy. In such
a case, the lake level is a constraint that
requires transferring uncertainty in
lake inflows to a different variable in
the reservoir system, such as lake outflow.
Alternatively, the deterministic
depiction may result from an effort to
simplify probabilistic information in
the communication of the lake outlook
to the public.
2.2.2.2 State and regional
Regionally-focused agencies such
as the U.S. Bureau of Reclamation
(USBR), the Bonneville Power Administration
(BPA), the Tennessee Valley Authority
(TVA), and the Great Lakes Environmental
Research Laboratory (GLERL) also produce
forecasts targeting specific sectors within their
priority areas. Figure 2.8 shows an example of
an SI lead forecast of lake levels produced by
GLERL. GLERL was among the first major
public agencies to incorporate climate forecast
information into operational forecasts using
hydrologic and water management variables.
Forecasters use coarse-scale climate forecast
information to adjust climatological probability
distribution functions (PDFs) of precipitation
and temperature that are the basis for generating
synthetic ensemble inputs to hydrologic and
water management models, the outputs of which
include lake level as shown in the figure. In this
case, the climate forecast information is from
the CPC seasonal outlooks (method described
in Croley, 1996).
The Bonneville Power Administration (BPA),
which helps manage and market power from
the Columbia River reservoir system, is both
a consumer and producer of hydrologic forecast
products. The BPA generates their own
ENSO-state conditioned ESP forecasts of reservoir
system inflows as input to management
decisions, a practice supported by research
into the benefits of ENSO information for
water management (Hamlet and Lettenmaier,
1999).
A number of state agencies responsible for
releasing hydrologic and water resources
forecasts also make use of climate forecasts in
Decision-Support Experiments and Evaluations using Seasonal to
Interannual Forecasts and Observational Data: A Focus on Water Resources
Figure 2.7 A deterministic five-week forecast of reservoir levels in Lake Lanier, Georgia,
produced by USACE .
the process of producing their own hydrologic
forecasts. The South Florida Water Management
District (SFWMD) predicts lake (e.g.,
Lake Okeechobee) and canal stages, and makes
drought assessments, using a decision tree in
which the CPC seasonal outlooks play a role.
SFWMD follows GLERL’s lead in using the
Croley (1996) method for translating the CPC
seasonal outlooks to variables of interest for
their system.
2.2.2.3 local
At an even smaller scale, some local agencies
and private utilities may also produce forecasts
or at least derive applications-targeted forecasts
from the more general climate or hydrology
forecasts generated at larger agencies or centers.
Figure 2.8 Probabilistic forecasts of future lake levels disseminated by GLERL.
From: .
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