Tools For Drought Management

1
Tools For Drought Management

• Water Management in the face of droughts
• require
• Skilful Hydrologic Forecasting/Simulation Tool
• Statistical or Hydrologic Models (PRMS, SWAT,
  etc.)
• for seasonal time scales
• Stochastic Flow Simulation tools for longer term
  (multi-year, decades) planning and management
• Decision Support tool of the agriculture/water
  resources system
• RiverWare

2
Seasonal Streamflow Forecast/Simulation

• Hydrologic Models
• PRMS, SWAT
• Statistical Models
• Nonlinear Regression approach for ensemble
  forecasts
• incorporating large-scale land-ocean-atmospheric
  information, Grantz et al., 2005 Regonda et
  al., 2006
• Skilful, provides uncertainty estimates via
  ensembles

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Truckee / Carson Basin - Application

• Study Area
• Hydroclimatology, Management
• Spring Streamflow Forecast Models
• incorporating large-scale land-ocean-atmospheric
  information, Grantz et al., 2005
• Decision Support Model
• Drive the streamflow forecast through the
  decision model. Investigate skills in the
  decision variables

4
Study Area
NEVADA
Truckee
Carson
CALIFORNIA
TRUCKEE CANAL
Farad
Ft Churchill
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Average Monthly Flows

• Primarily snowmelt driven basins
• (April, May, June)
• Correlate Fall/ Winter Climate Signals with AMJ
  Streamflow

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Management Issues

• Irrigation/Agriculture decisions on the Newland
  Irrigation district are made in Feb much before
  the peak flow occurs
• So, skilful long-lead seasonal streamflow
  forecasts on Truckee and Carson Rivers are
  required
• Forecasts determine
• How storage targets will be met
• on the Lahonton reservoir for
• irrigation
• How much water to divert
• from Truckee to Carson via
• the Truckee Canal
• How much water will be
• available for Irrigation

7
Decision Variables

• Lahontan Storage Available for Irrigation
• Truckee River Water Available for Fish
• Diversion through the Truckee Canal

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RiverWare River and Reservoir Decision Support
System
Operational Decisions Predictions Statistical
Output Economic Analysis Environ
analysis Tradeoff Analysis
Inflow Forecast OR Historical Hydrology OR Stochas
tic inflows
Models interaction of Hydrologic response of
River /Reservoir system (includes
Hydropower) With Multi-objective operating
policies
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Truckee-Carson RiverWare Model
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Winter Climate Link
Low flow Years
High flow Years

• High flow years go with S.Westerly winds in the
  Basin
• during winter ? increased moisture/snow ?
  increased streamflow
• in spring.
• Vice-Versa for Low flow years Grantz et al.,
  2005 Water Resources Research

11

• Identified large scale land-ocean-atmosphere
  predictors for Truckee/Carson spring (April-June
  total) streamflow
• Used a Nonlinear regression framework (local
  polynomials) to generate ensemble of spring
  streamflow forecasts
• Forecasts issued on the 1st of each month
  starting from Nov 1st through April 1st
• Skills evaluated using correlation coefficient
  and RPSS
• (RPSS 1 implies categorical forecast, 0, no
  better than climatology)

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Forecasting Results

• Skills increase
• with decrease
• in lead-time
• Significant skill
• even on Jan 1st
• and Feb 1st
• (when snow info
• is partial)

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Forecast Ensembles are Used to drive the Decision
Support System for the Truckee/Carson
Baisn(Forecast skills of the decision variables
evaluated)
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Decision Model Results
Canal Diversion
Water for Fish
Irrigation Water
Dec 1st Forecast
Feb 1st Forecast
Significant skill Especially from Feb1st onwards
Apr 1st Forecast
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Dry Year 1994
April 1st
February 1st
December 1st
Truckee Forecast
Carson Forecast
Storage for Irrigation
Canal Diversion
Water for Fish
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Wet Year 1993
April 1st
February 1st
December 1st
Truckee Forecast
Carson Forecast
Storage for Irrigation
Canal Diversion
Water for Fish
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Normal Year 2003
April 1st
February 1st
December 1st
Truckee Forecast
Carson Forecast
Storage for Irrigation
Canal Diversion
Water for Fish
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Exceedance Probabilities
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Summary

• Developed a streamflow forecast framework
  incorporating large-scale ocean-atmospheric-land
  variables
• Skilful long-lead streamflow forecasts obtained
  on the Truckee/Carson river basin 4-5 months
  ahead of the spring peak flow
• Developed a Decision Support System that
  incorporates all the management aspects of the
  water resources system
• Skilful streamflow forecasts translated into
  skills in the decision variables especially the
  amount of flow available for irrigation
• The Integrated streamflow-Decision Support System
  provides a robust framework for effective
  management of droughts both in the
• short and longer time scales
• Streamflow scenarios can be generated conditioned
  on climate change, land use change, water use
  change etc. and management/decision strategies
  evaluated

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AcknowledgementsMs. Katrina Grantz for USBR
Truckee Office for financial support of this
studyCADSWES for computation and logistics
support