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Streamflow Predictability

Streamflow Predictability

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Streamflow Predictability. Sources of Predictability. Model solutions to the streamflow forecasting problem…. Historical Data. SNOW-17 / SAC. Historical Simulation. SWE. SM. Q. Past. Future. - PowerPoint PPT Presentation

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Page 1: Streamflow  Predictability

Streamflow Predictability

Page 2: Streamflow  Predictability

Historical Simulation

Q

SWESM

Historical Data

Past Future

SNOW-17 / SAC

Sources of Predictability

1. Run hydrologic model up to the start of the forecast period to estimate basin initial conditions;

Model solutions to the streamflow forecasting problem…

Page 3: Streamflow  Predictability

Historical Simulation

Q

SWESM

Historical Data Forecasts

Past Future

SNOW-17 / SAC SNOW-17 / SAC

1. Run hydrologic model up to the start of the forecast period to estimate basin initial conditions;

2. Run hydrologic model into the future, using an ensemble of local-scale weather and climate forecasts.

Sources of PredictabilityModel solutions to the streamflow forecasting problem…

Page 4: Streamflow  Predictability

• Physically based conceptual model• Two-layer model

– Upper layer: surface and interception storages– Lower layer: deeper soil and ground water

storages• Routing: linear reservoir model• Integrated with snow17 model

Sacramento Soil Moisture Accounting (SAC-SMA) model

Rainfall - Evapotranspiration - Changes in soil moisture storage = Runoff

• Model parameters: 16 calibrated parameters

• Input data: basin average precipitation (P) and Potential Evapotranspiration (PET)

• Output: Channel inflow (Q)

Page 5: Streamflow  Predictability

Soil Tension and Free Water

Page 6: Streamflow  Predictability

Sacramento Model StructureE T Demand

Impervious Area

E T

E T

E T

E T

Precipitation Input

Px

Pervious Area

E T

Impervious Area

Tension Water

UZTW Free Water

UZFW

PercolationZperc. Rexp

1-PFREE PFREE

Free WaterTension Water P S

LZTW LZFP LZFS

RSERV

Primary Baseflow

Direct Runoff

Surface Runoff

Interflow

Supplemental Base flow

Side Subsurface Discharge

LZSK

LZPK

Upper Zone

Lower Zone

EXCESS

UZK

RIVA

PCTIM

ADIMP

Total Channel Inflow

Distribution Function Streamflow

Total Baseflow

Page 7: Streamflow  Predictability

Model ParametersPXADJ Precipitation adjustment factorPEADJ ET-demand adjustment factorUZTWM Upper zone tension water capacity (mm)UZFWM Upper zone free water capacity (mm)UZK Fractional daily upper zone free water withdrawal ratePCTIM Minimum impervious area (decimal fraction)ADIMP Additional impervious area (decimal fraction)RIVA Riparian vegetation area (decimal fraction)ZPERC Maximum percolation rate coefficientREXP Percolation equation exponentLZTWM Lower zone tension water capacity (mm)LZFSM Lower zone supplemental free water capacity (mm)LZFPM Lower zone primary free water capacity (mm)LZSK Fractional daily supplemental withdrawal rateLZPK Fractional daily primary withdrawal ratePFREE Fraction of percolated water going directly to lower zone free water storageRSERV Fraction of lower zone free water not transferable to lower zone tension waterSIDE Ratio of deep recharge to channel baseflowET Demand Daily ET demand (mm/day)PE Adjust PE adjustment factor for 16th of each month

Page 8: Streamflow  Predictability

State VariablesADIMC Tension water contents of the ADIMP area

(mm)UZTWC Upper zone tension water contents (mm)UZFWC Upper zone free water contents (mm)LZTWC Lower zone tension water contents (mm)LZFSC Lower zone free supplemental contents

(mm)LZFPC Lower zone free primary contents (mm)

Page 9: Streamflow  Predictability

How the SAC-SMA Model Works

Page 10: Streamflow  Predictability

Study site: Root River basin in MN

• Drainage area: 1593 km2

• Largely agricultural (72%), USDA

• Receives 29 to 33 inches of annual precipitation

Root River basin

Page 11: Streamflow  Predictability

Greens Bayou river basin in eastern Texas

• Hourly discharge data • Hourly Mean Areal Precipitation • Model running time step is hourly

• Drainage area: 178 km2

• Most of the basin is highly developed • Humid subtropical climate (890-1300 mm annual rain)

Data for SAC-SMA

Page 12: Streamflow  Predictability

SMADA Basins

Page 13: Streamflow  Predictability

Error Growth models

• Lorenz, 1982

∂E∂t

= α E 1 −EE∞

⎛⎝⎜

⎞⎠⎟

Page 14: Streamflow  Predictability

Greens Bayou Precip forcing fields – Nov 17, 2003 tornado

Page 15: Streamflow  Predictability