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BASINS 3.0

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SWAT stands for Soil and Water Assessment Tool. Spatial Scale: watershed or river basin ... SWAT model computes evaporation from soils and. plants by Eo = 128 (ho) ... – PowerPoint PPT presentation

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Title: BASINS 3.0


1
BASINS 3.0 SWAT Model
  • Kristina Schneider
  • Kristi Shaw

2
Focus of Presentation
3
SWAT An Overview
  • SWAT stands for Soil and Water Assessment Tool
  • Spatial Scale watershed or river basin
  • Data Organization subbasins or hydrologic
    response units (HRUs)
  • Time scale Continuous time model (long term
    yield model)
  • based on a daily scale
  • Not for a single event
  •  
  • Data Inputs weather, soil properties,
    topography,
  • vegetation, and land management
    practices
  •   From the BASINS databases

4
SWAT An Overview
  • SWAT separates soil profiles into 10 layers to
    model inter
  • and intra-movement between layers.
  • The model is applied to each soil layer
    independently starting
  • at the upper layer.
  • SWAT soil water routing feature consists of four
    main pathways
  • 1. soil evaporation
  • 2. plant uptake and transpiration
  • 3. lateral flow
  • 4. percolation.

5
Soil Evaporation
  • Actual soil water evaporation stimulated using
    exponential
  • functions of soil depth and water
    content.
  • Potential soil water evaporation considering
    ground covering
  • Es potential soil water evaporation rate
    (mm/day)
  • EAsoil cover index
  • Eopotential evaporation rate at the surface
    (mm/day) 
  • Potential soil water evaporation for a layer
  • SEV potential soil water evaporation rate for
    layer (mm/day)
  • EVtotal soil water evaporation in mm from
    soil of depth Z in mm

6
Plant Uptake and Transpiration
  • SWAT model computes evaporation from soils and
  • plants by Eo 128 (ho)
  • Plant transpiration function potential
  • Evapotranspiration and
  • Leaf area index (area of plant leaves relative
    to
  • area of the HRU
  •  
  • Potential evapotranspiration calculated with
  • Hargreaves
  • Priestley-Taylor
  • Penman-Monteith.

7
Lateral Flow
  • The stream flow contribution below the surface
  • but above saturated zone.
  • It is calculated simultaneously with
    redistribution
  • using a kinematic storage model.
  • The model accounts for variation in
    conductivity,
  • slope, soil water content, and allows flow
    upward to surface.

  • Kinematic storage model finite difference mass
    continuity equation

8
Percolation
  • Storage routing technique combined with a
    crack-flow model to predict flow
    through each soil layer
  • Cracked flow model allows percolation of
    infiltrated rainfall though soil water content
    is less than field capacity.
  • Portion that does become part of layer stored
    water cannot percolate until storage exceeds
    field capacity.
  • Storage routing technique based on the
    following equation
  • Swisoil water contents at end of the day
    (mm)
  • Swoisoil water contents at beginning of the
    day
  • TTtravel time through layer (hr)

9
Summary
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