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Watershed Modeling Approaches

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

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Watershed Modeling Approaches

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  1. 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)

  2. Watershed Modeling Approaches: CASC-2D

  3. Watershed Modeling Approaches: CASC-2D

  4. Watershed Modeling Approaches Soil Moisture Routing Model (Cornell) • subsurface: 2-D Darcy’s Law / water balance, topography driven • evapotranspiration • deep percolation

  5. 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

  6. 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

  7. Watershed Modeling Approaches: KINEROS2

  8. Watershed Modeling Approaches: KINEROS2

  9. Watershed Modeling Approaches: KINEROS2

  10. 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

  11. Stream line Contour line Upslope contributing area a Watershed Modeling Approaches: Topmodel

  12. 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)

  13. Watershed Modeling Approaches: SAC-SMA Components: • Tension water (unsaturated) • Free water (saturated) • Surface flow • Lateral drainage • Evapotranspiration • Vertical drainage (percolation)

  14. Watershed Modeling Approaches: SAC-SMA

  15. Watershed Modeling Approaches: SAC-SMA

  16. 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

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