EVAPOTRANSPIRATION PACKAGE

  • View
    49

  • Download
    0

Embed Size (px)

DESCRIPTION

EVAPOTRANSPIRATION PACKAGE. EVAPOTRANSPIRATION PACKAGE. The Evapotranspiration (ET) Package simulate the effects of plant transpiration and direct evapotranspiration in removing water from the saturated groundwater regime. - PowerPoint PPT Presentation

Text of EVAPOTRANSPIRATION PACKAGE

  • EVAPOTRANSPIRATION PACKAGE

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThe Evapotranspiration (ET) Package simulate the effects of plant transpiration and direct evapotranspiration in removing water from the saturated groundwater regime.In practice, the modeler treats evapotranspiration from a riparian zone with the ET Package, and the recharge from an application of irrigation water with the Recharge Package.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThe approach used by the ET Package is based on the following assumptions,When the water table is at or above a specified elevation, termed the ET surface, evapotranspiration loss from the water table occurs at a maximum rate (QETM) specified by the user.When the depth of the water table below the ET surface exceed a specified interval, termed the Extinction depth (d), the evapotranspiration from the water table ceases.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEBetween these limits, evapotranspiration from the water table varies linearly with water table elevation.Mathematically,RETij be the rate of loss per unit surface area (DELRjDELCi) of the water table due to evapotranspiration [L/t].RETMij be the maximum possible value of RETij [L/t].hSij be the ET surface elevation.dij be the extinction depth [L].And let,QETij = RETij DELRjDELCiand QETMij = RETMij DELRjDELCi

    EVT6

  • EVAPOTRANSPIRATION PACKAGE whereQETij is the evapotranspiration [L3/t] through the area, DELRjDELCi. QETMij is the maximum value of QETij and is in terms of volumetric discharge.Thus,

    ET is drawn from only one cell in the vertical column beneath the map area DELRjDELCi.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThe maximum ET rate (QETM) of an area is a function of,1.Species type (cottonwoods, willows,),2.Species size (small, medium,),3.Species size and type fraction (fraction of specie of type t and size s, fsts),4.Surface density of total plant life (Total number of all plants per unit area, DTot [1/L2]) 5. Maximum Volumetric ET rate per species type and size (Qsetmts, [L3/t]),6.Size of the area [L2],

    Maximum Volumetric ET Rate (Qsetmts)

    EVT6

  • EVAPOTRANSPIRATION PACKAGE

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThe area polygons are subdivided into grid cells.The i,j cell area that is designated to have ET is assigned the value RETMij,

    where Anm is the area DELRnDELCmAnm is the horizontal surface area of all the cells that cover the polygon.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThe extinction depth is a function of specie type and size.If a cell horizontal surface contains a mixture of specie type and size, the previous plot of volumetric ET as a function of head will over estimate some ET loss and under estimate others.Plant can be given too much water along with to little, therefore heads in the aquifer above the ET surface may produce a decline in ET (see two graphs on the right).

    EVT6

  • EVAPOTRANSPIRATION PACKAGEThere are two options for the user to designate the cell in a vertical column that receives the ET.

    Option 1ET is always drawn from the uppermost layer of the Model.Option 2the user specifies the cell, within the vertical column at i,j, from which the ET is to be taken.Option 1Option 2Cross-section

    EVT6

  • EVAPOTRANSPIRATION PACKAGENPEVTis the number of evapotranspiration parameters.NEVTOPis the Evapotranspiration option code.NEVTOP=1, ET is only to the top grid layer. NEVTOP=2, vertical distribution of evapotranspiration specified in layer variable IEVT.IEVTCBis a flag and a unit number.IRCHCB > 0, the unit number to which cell-by-cell terms will be written when SAVE BUDGET or a non-zero value of ICBCFL is specified in output control.IEVTCB 0, cell-by-cell flow terms will not be written.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEPARNAMis the name of a parameter. This name can consist of 1 to 10 characters, and is not case specific.PARTYPis parameter type. There is only one parameter type for the ET Packagethe maximum ET flux, EVT.Parvalis the parameter value.NCLUis the number of clusters required to define a parameter. Each repetition of Item 4 is a cluster.There is usually only one cluster used to define a EVT parameter, but it is acceptable to have more.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEMltarris the name of the multiplier array to be used to define cell values that are determined by parameters.The name NONE means that there is no multiplier array, and the cell value will be set to Parval.Zonarris the name of the zone array to be used to define cell values that are associated with a parameters.The name ALL means that there is no zone array, and all cells in the layer are associated with the parameter.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEIZis up to ten zone numbers (specified by spaces) the define the cells that are associated with a parameter.These values are not used if Zonarr is specified as ALL.Values can be negative, but not zero.The end of line, a zero value, or a non-numeric entry terminates the list of values.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEINSURFis the ET Surface (SURF) read flag INSURF0, a layer variable containing the ET surface elevation, SURF, is readINSURF
  • EVAPOTRANSPIRATION PACKAGEIf parameters are used (NPEVT>0)INEVTR>0, INEVTR is the number of parameters that will be used to define EVTR in the current stress period. Item 8 defines the names of the parameters.INEVTR
  • EVAPOTRANSPIRATION PACKAGEINEXDPis the extinction depth (EXDP) read flag. INSURF0, a layer variable containing the ET surface elevation, SURF, is readINSURF
  • EVAPOTRANSPIRATION PACKAGEEVTRis the maximum ET flux [L/t]. Read only if INEVTR0 and if NPEVT=0.Pnameis the name of the parameter the will be used to define the EVTR variable in the current stress period.Read INEVTR values if NPEVT>0 and INEVTR>0IEVTPFis an optional format code for printing the EVTR variable after it has been defined by parameters.The format codes are the same as those used in the U2DREL array reading utility module.

    EVT6

  • EVAPOTRANSPIRATION PACKAGEEXDPis the extinction depth. This variable is read only if INEXPD0.IEVTis the layer number variable that defines the horizontal location where ET is removedRead only if NEVTOP=2 and if INIEVT0.

    EVT6

  • EVAPOTRANSPIRATION PACKAGE No ParametersOption 1Option 2

    EVT6

  • EVAPOTRANSPIRATION PACKAGE Parameters

    EVT6