Watershed Modeling Approaches Distributed: CASC-2D (CSU, U Conn, WMS) overland flow: 2-D diffusion...
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Transcript of Watershed Modeling Approaches Distributed: CASC-2D (CSU, U Conn, WMS) overland flow: 2-D diffusion...
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)
Watershed Modeling Approaches: CASC-2D
Watershed Modeling Approaches: CASC-2D
Watershed Modeling Approaches
Soil Moisture Routing Model (Cornell)
• subsurface: 2-D Darcy’s Law / water balance, topography driven• evapotranspiration• deep percolation
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
jijiji Tq ,,, tan
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
Watershed Modeling Approaches: KINEROS2
Watershed Modeling Approaches: KINEROS2
Watershed Modeling Approaches: KINEROS2
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
tanzfo ef
Kq
K0 = surface conductivity, f = decay coef., = ground slope
Upslope contributing area a
Stream line
Contour line
Watershed Modeling Approaches: Topmodel
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)
• Tension water (unsaturated)• Free water (saturated)• Surface flow• Lateral drainage• Evapotranspiration• Vertical drainage (percolation)
Watershed Modeling Approaches: SAC-SMA
Components:
Watershed Modeling Approaches: SAC-SMA
Watershed Modeling Approaches: SAC-SMA
E 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
SurfaceRunoff
Interflow
Supplemental Base flow
Side SubsurfaceDischarge
LZSK
LZPK
Upper Zone
Lower Zone
EXCESS
UZK
RIVA
PCTIM
ADIMP
TotalChannelInflow
DistributionFunction Streamflow
TotalBaseflow
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