Tools For Drought Management Water Management in the face of droughts require Skilful Hydrologic...

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

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

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

INDEPENDENCE

DONNERMARTIS

STAMPEDE

BOCA

PROSSER

TRUCKEERIVER

CARSONRIVER

CARSONLAKE

Truckee

CarsonCity

Tahoe City

Nixon

Fernley

DerbyDam

Fallon

WINNEMUCCALAKE (dry)

LAHONTAN

PYRAMID LAKE

NewlandsProject

Stillwater NWR

Reno/Sparks

NE

VA

DA

CA

LIF

OR

NIA

LAKE TAHOE

Study Area

TRUCKEE CANAL

Farad

Ft Churchill

NEVADA

CALIFORNIA

Carson

Truckee

Average Monthly Flows

• Primarily snowmelt driven basins

(April, May, June)

• Correlate Fall/ Winter Climate Signals with AMJ Streamflow

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 forirrigation

– How much water to divertfrom Truckee to Carson viathe Truckee Canal

– How much water will beavailable for Irrigation

Truckee Canal

Decision Variables

• Lahontan Storage Available for Irrigation

• Truckee River Water Available for Fish

• Diversion through the Truckee Canal

RiverWare – River and Reservoir Decision Support System

Inflow Forecast

OR

Historical Hydrology

OR

Stochastic inflows

Models interaction of

Hydrologic response of River /Reservoir system (includes

Hydropower)

With

Multi-objective operating policies

Operational Decisions

Predictions

Statistical Output

Economic Analysis

Environ analysis

Tradeoff Analysis

Truckee-Carson RiverWare Model

Winter Climate Link

500 mb Geopotential Height

Carson Spring Flow

• 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

High flow Years Low flow Years

• 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)

Forecasting ResultsTruckee RPSS results

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Nov 1st Dec 1st Jan 1st Feb 1st Mar 1st Apr 1st

Month

Med

ian

RP

SS

(al

l yea

rs)

GpH & SWE

SWE

Carson RPSS results

-0.2

0.0

0.2

0.4

0.6

0.8

1.0


Month

Med

ian

RP

SS

(al

l yea

rs)

GpH & SWE

SWE

Truckee Forecasted vs. Observed Correlation Coeff

0

0.2

0.4

0.6

0.8

1


Month

Co

rrel

atio

n C

oef

f

GpH & SWE

SWE

Carson Forecasted vs. Observed Correlation Coeff

0

0.2

0.4

0.6

0.8

1


Month

Co

rrel

atio

n C

oef

f.

GpH & SWE

SWE

Truckee Likelihood Results

0

0.5

1

1.5

2

2.5


Month

Med

ian

Lik

elih

oo

d (

all

year

s)

GpH & SWE

SWE

Carson Likelihood Results

0

0.5

1

1.5

2

2.5


Month

Med

ian

Lik

elih

oo

d (

all

year

s)

GpH & SWE

SWE

•Skills increase with decrease in lead-time

•Significant skill even on Jan 1st and Feb 1st (when snow infois partial)

Forecast Ensembles are Used to drive the Decision Support

System for the Truckee/Carson Baisn

(Forecast skills of the decision variables evaluated)

Decision Model

Results0 100 300 500

010

030

050

0

Perfect Forecast Irrigation Water (kaf)

Med

ian

of E

nsem

ble

Irrig

atio

n W

ater

(kaf

)

r=0.17

0 50 100 150

050

100

150

Perfect Forecast Diversion (kaf)

Med

ian

of E

nsem

ble

Div

ersi

on(k

af)

r=0.23

0 200 400 600

020

040

060

0

Perfect Forecast Fish Water (kaf)

Med

ian

of E

nsem

ble

Fis

h W

ater

(kaf

)

r=0.36

0 100 200 300 400 500

010

020

030

040

050

0


Med

ian

of E

nsem

ble

Irrig

atio

n W

ater

(kaf

)

r=0.54

0 50 100 150

050

100

150


Med

ian

of E

nsem

ble

Div

ersi

on(k

af)

r=0.38

0 200 400 600

020

040

060

0


Med

ian

of E

nsem

ble

Fis

h W

ater

(kaf

)

r=0.62

0 100 200 300 400 500

010

030

050

0


Med

ian

of E

nsem

ble

Irrig

atio

n W

ater

(kaf

)

r=0.79

0 50 100 150

050

100

150


Med

ian

of E

nsem

ble

Div

ersi

on(k

af)

r=0.78

0 200 400 600

020

040

060

0


Med

ian

of E

nsem

ble

Fis

h W

ater

(kaf

)

r=0.93

Canal Diversion Water for FishIrrigation Water

Dec 1st Forecast

Feb 1st Forecast

Apr 1st Forecast

Significant skillEspecially from Feb1stonwards

Dry Year: 1994April 1st February 1st December 1st

Truckee ForecastTruckee Forecast

Carson ForecastCarson Forecast

Storage for IrrigationStorage for Irrigation

Canal DiversionCanal Diversion

Water for FishWater for Fish

Wet Year: 1993April 1st February 1st December 1st






Normal Year: 2003April 1st February 1st December 1st






Exceedance Probabilities 1994 (Dry Year) Apr 1st Feb 1st Dec 1st Historical

Irrigation Water mean value (kaf) 94 161 214 264264 kaf Irrigation Water exceedance probability 4% 14% 18% 50%Fish Flow mean value (kaf) 0 42 39 19960.5 kaf Fish Flow exceedance probability 0% 57% 58% 87%Canal Diversion mean value (kaf) 52 107 121 84

1993 (Wet Year) Apr 1st Feb 1st Dec 1st Historical


2003 (Normal Year) Apr 1st Feb 1st Dec 1st Historical


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 theshort 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

AcknowledgementsMs. Katrina Grantz for

USBR Truckee Office for financial support of this study

CADSWES for computation and logistics support

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