Watershed Modeling Approaches

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Watershed Modeling Approaches
Distributed CASC-2D (CSU, U Conn, WMS)

• overland flow 2-D diffusion wave with explicit
  FD
• channel flow 1-D diffusion wave with explicit
  FD, or 1-D dynamic wave with implicit Preissmann
  scheme
• infiltration Green-Ampt equation with
  redistribution
• evapotranspiration, interception, erosion
  (overland and channel)

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Watershed Modeling Approaches CASC-2D
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Watershed Modeling Approaches CASC-2D
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Watershed Modeling Approaches
Soil Moisture Routing Model (Cornell)

• subsurface 2-D Darcys Law / water balance,
  topography driven
• evapotranspiration
• deep percolation

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Watershed Modeling Approaches
DHSVM

• Grid-based subsurface routing, hydraulic
  gradient ground slope
• Power law subsurface hydraulic conductivity
  (transmissivity) function
• Unit hydrograph distribution of excess runoff
  (travel time for each pixel)
• Muskingum-Cunge network/channel routing

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Watershed Modeling Approaches
KINEROS2 (USDA-ARS)

• overland flow 1-D kinematic wave, 4-pt
  implicit FD wetted area factor in recession
• channel flow 1-D kinematic wave, 4-pt
  implicit FD
• infiltration Smith-Parlange, layered soils,
  redistribution, interactive (plane to plane),
  sub-grid effective parameters
• erosion and sedimentation 4-pt implicit FD
• interception

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Watershed Modeling Approaches KINEROS2
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Watershed Modeling Approaches KINEROS2
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Watershed Modeling Approaches KINEROS2
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Watershed Modeling Approaches
TOPMODEL

• Topographically Driven slope, contributing
  area, convergence
• Saturated zone hydraulic gradient assumed to be
  equal to slope
• Exponential decrease of hydraulic conductivity
  with depth
• Watershed outflow related to mean depth to
  water table
• Saturation and infiltration excess runoff
  generation
• Evapotranspiration
• Channel routing kinematic wave

K0 surface conductivity, f decay coef., b
ground slope
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Watershed Modeling Approaches Topmodel
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Watershed Modeling Approaches
SAC-SMA (part of NWSRFS)

• Physically-based conceptual model
• based on physical concepts that describe water
  movement trough a watershed
• Lumped
• Continuous
• Two-layer soil model (upper and lower zones)

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Watershed Modeling Approaches SAC-SMA
Components

• Tension water (unsaturated)
• Free water (saturated)
• Surface flow
• Lateral drainage
• Evapotranspiration
• Vertical drainage (percolation)

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Watershed Modeling Approaches SAC-SMA
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Watershed Modeling Approaches SAC-SMA
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Watershed Modeling Approaches

• SAC-SMA is a component of NWSRFS
• Snow models available
• Runoff over a time step distributed to
  watershed outlet using UH
• Channel routing lumped methods, distributed
  methods