Transcript No Slide Title

INCORPORATING LARGE-SCALE CLIMATE VARIABILITY INFORMATION INTO WATER
RESOURCES DECISION MAKING: A Case Study of the Truckee-Carson River System
Katrina Grantz, Balaji Rajagopalan, Edie Zagona, and Martyn Clark
CLIMATE DIAGNOSTICS
Climate diagnostics are used to identify large-scale climate features related to
flow in the Truckee and Carson rivers.
Climatology Analysis
Average Monthly Preciptation
The annual cycles of
streamflow and
precipitation indicate that
the basins are primarily
snowmelt dominated.
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Precipitation (in)
3.5
3
2.5
Figure 8. Forecasts without (left) and with (right) climate
information in wet (top) and dry (bottom) streamflow years
Forecasting Results- Fall
Figure 4. Climate composites of sea surface temperature (left) and vector
winds (right) for high minus low streamflow years in the Carson River
Truckee Fall Forecast
Carson Fall Forecast
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200
400
600
300
0 100
r=0.36
500
Median of Ensemble Forecast
Forecasts issued from fall are
based on Pacific climate
information alone. The
forecasts demonstrate the
ability to capture whether
spring runoff will be above or
below average six months in
advance.
r=0.28
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0 100
Observed Value
300
500
Observed Value
Figure 9. Scatterplots of median of fall ensemble forecast vs.
observed value in the Trucee (left) and Carson (right) rivers.
STOCHASTIC FORECAST
DECISION SUPPORT SYSTEM (DSS)
We utilize the nonparametric techniques of the modified k-nearest neighbor
(K-NN) algorithm to generate ensemble forecasts of spring streamflow.
Predictors, based on climate diagnostics, are SWE, SST, and 500mb
geopotential height from regions of highest correlation.
To test the utility of the new forecasting technique and impacts on
operations, forecasts will be input to the Truckee Operations RiverWare
model used by the USBR.
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1.5
1
0.5
0
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Month
Figure 1. Average monthly flow in the Truckee and Carson rivers (left) and
average monthly precipitation in the Sierra Nevada climate division.
Correlation Analysis- Winter
Because the basins are snowmelt dominated we correlate spring runoff with
climate signals over the Pacific Ocean the preceding winter and fall.
Yt=yt*+et*
yt*
et*
Figure 5. Figure illustrating local polynomial fit and
residual resampling for modified K-NN method
Water Available
For Irrigation
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100
200
Lahontan
300
Storage
500
300
0 100
r=0.87
R=0.87
R=0.92
0
200
400
600
Observed Value
Figure 2. Carson River (top) and Truckee River (bottom) spring streamflow
correlated with winter geopotential height 500mb (left) and sea surface
temperature (right)
800
0 100
300
500
Observed Value
Figure 7. Scatterplots of median of ensemble forecast vs.
observed value for each year in the Truckee River (left) and
Carson River (right).
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200
Truckee
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400
500
Diversion (kaf)
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0.015
Water Available
For Fish
0.005
Figure 10. Truckee RiverWare model (above) and seasonal
forecasting model results (right) for a dry year 1992. The solid
line represents model results using the ensemble forecast, the
dashed line represents model results using the climatological
forecast. The point depicts the value that would have occurred
given a perfect forecast.
Canal
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Median of Ensemble Forecast
200
400
600
800
Carson Forecast
r=0.92
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Median of Ensemble Forecast
Truckee Forecast
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PDF
The forecasting method is validated using standard cross-validation: dropping
one point from the forecasting model and then predicting it.
Figure 6. Forecasting results for Truckee (top) and Carson
(bottom) rivers for entire period of record. The solid line
represents the observed value, the boxplots represent the
ensemble forecast in each year and the horizontal lines
represent the 5th, 25th, 50th, 75th, and 95th percentile of the
historical data.
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0.005
PDF
Forecasting Results- All Years
400
(kaf)
Diversion Through
Truckee Canal
0.015
Spring streamflow in the
Truckee and Carson
rivers correlates strongly
with the 500mb
geopotential height
variable in the region off
the coast of Washington
and sea surface
temperature in the
northern Pacific the
preceding winter.
Regions of high
correlation are the same
for the Truckee and
Carson rivers.
The modified K-NN method uses a
local polynomial fit for the mean
forecast and bootstraps the residuals
to generate an ensemble forecast.
• assumes no underlying structure to
the data (no transformations needed)
• produces flows not seen in the
historical record
• perturbs the historical record within
its representative neighborhood
0.000 0.002 0.004 0.006 0.008 0.010
Incorporation
Into DSS
Streamflow composites of
the six wettest years minus
the six driest years show
the vector winds rotating
counter-clockwise around
the region off the coast of
Washington (bringing moist
air from the tropics to fall in
the mountians as snow)
and a SST pattern similar
to that in the correlation
plots.
PDF
Stocahstic
Forecast
Composite Analysis: High-Low Years
SWE & Large-Scale Climate
800
Diversions through the
Truckee Canal must
balance the interests of
the Newlands Project
farming district and the
endangered cui-cui and
Lahontan cutthroat trout
Figure 3. Carson River) spring streamfllow correlated with fall geopotential
height 500mb (left) and sea surface temperature (right)
SWE alone
600
Truckee Canal
Forecasts are improved when
climate information (e.g. SST
and geopotential height) is
incorporated into the forecast.
Forecasts without climate
information are based on SWE
alone. Wet and dry years are
compared to examine the utility
of the improved forecasts in
years of extreme streamflow.
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Climate
Diagnostics
Fall climate correlations
exhibit a persistence in
the atmospheric
circulation patterns seen
in the winter corrlation
analysis. This enhances
the prospect of longer
lead forecasts.
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USBR needs good seasonal forecasts on Truckee
and Carson Rivers (accurate and with long-lead time)
to determine reservoir releases and inter-basin
transfers through the Truckee Canal.
Forecasting Results- Use of Climate Information in the Forecast
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This poster summarizes recent work on using climate information to improve
seasonal forecasts in the Truckee and Carson rivers.
Correlation Analysis- Fall
Median of Ensemble Forecast
OVERVIEW
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100
Water
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Remaining
300
in Truckee
400
500
(kaf)
Seasonal Operations Model Because the Truckee RiverWare model is not
fully operational, we develop a simplified seasonal operations model. We test
decision variables such as Water Available for Irrigation, Diversion through the
Truckee Canal, and Water Available for Fish.
Funding Provided By:
 CIRES
 USBR- Lahontan Basin Area Office