Module Basin

Overview

Module Basin works as an interface among the different modules of Mohid-Land. Indeed it manages fluxes between modules as precipitation, evapotranspiration, infiltration, etc and updates water column and concentration after each module call. This module is able to compute a water and mass balance for each property transported in all mediums.

Main Processes

The processes made in the Module Basin can be summarized as following:

• Reading entering data and grid construction
• Atmospheric processes (precipitation, leaf interception, leaf drainage, evaporation) in order to obtain the potential water column
• Call of Module PorousMedia giving potential water column and obtain the infiltration rate
• Update of the water column and send it to ModuleRunoff (the holder of water column)
• Call of Module PorousMediaProperties and update of water column concentrations send it to the ModuleRunoffProperties
• Call of Module Runoff giving the remaining water columns to be transported
• Call of Module RunoffProperties

(When Module Runoff and RunoffProperties run as they are the holders of water column and water column concentration, no update is needed).

• Call of Module DrainageNetwork to route the water in the river and the new transfered from groundwater and from runoff.
• Output of the different components of the water and property flux

Evapotranspiration

Some water may be extracted from the soil because of the evaporation and transpiration processes, which become a sink in soil water profile. These two processes are currently named Evapotranspiration and Potential Evapotranspiration may be modeled using the Penmann Monteith equation.

$\overset{\text{Energy flux rate}}{\lambda_v E=\frac{\Delta R_n + \rho_a c_p \left( \delta q \right) g_a }{\Delta + \gamma \left ( 1 + g_a / g_s \right)}}~ \iff ~ \overset{\text{Volume flux rate}}{ET_o=\frac{\Delta R_n + \rho_a c_p \left( \delta q \right) g_a } { \left( \Delta + \gamma \left ( 1 + g_a / g_s \right) \right) \lambda_v }}$

λ_v = Latent heat of vaporization. Energy required per unit mass of water vaporized. (J/g)

L_v = Volumetric latent heat of vaporization. Energy required per water volume vaporized. (L_v = 2453 MJ m^-3)

E = Mass water evapotranspiration rate (g s^-1 m^-2)

ET_o = Water volume evapotranspired (m³ s^-1 m^-2)

Δ = Rate of change of saturation specific humidity with air temperature. (Pa K^-1)

R_n = Net irradiance (W m^-2), the external source of energy flux

c_p = Specific heat capacity of air (J kg^-1 K^-1)

ρ_a = dry air density (kg m^-3)

δe = vapor pressure deficit, or specific humidity (Pa)

g_a = Hydraulic conductivity of air, atmospheric conductance (m s^-1)

g_s = Conductivity of stoma, surface conductance (m s^-1)

γ = Psychrometric constant (γ ≈ 66 Pa K^-1)

Also if vegetation exists a differentiation between Potential Transpiration and Potential Evaporation may be done using LAI:

$PotentialTrans = CropTransp * (1 - e^{-0.463 * LAI})$

Data File

Keywords

ATMOSPHERE                    : 0/1              [1]          !Use Module Atmosphere 
POROUS_MEDIA                  : 0/1              [1]          !Use Module Porous Media
POROUS_MEDIA_PROPERTIES       : 0/1              [1]          !Use Module Porous Media Properties
RUN_OFF                       : 0/1              [1]          !Use Module RunOff
RUN_OFF_PROPERTIES            : 0/1              [1]          !Use Module RunOff Properties
DRAINAGE_NET                  : 0/1              [1]          !Use Module Drainage Netork
DT_DURING_RAIN                : sec.             [60.]        !initial dt that is tried when rains in the time step
EVAPOTRANSPIRATION_METHOD     : integer          [1]          !1- evapotranspiration - everything in crops; 2- separate
                                                              !between evaporation (surface soil) and transpiration (in crops)
EVAP_FROM_CANOPY              : 0/1              [1]          !Evaporate from plant leafs
EVAP_FROM_WATER_COLUMN        : 0/1              [0]          !Evaporate from water column.
OUTPUT_TIME                   : sec. sec. sec.    -           !Output Time
TIME_SERIE_LOCATION           : char              -           !Path to time serie location file

Computed or user defined potential evapotranspiration
<beginproperty>
NAME                      : reference evapotranspiration
UNITS                     : mm/h
DESCRIPTION               : fao evapotranspiration
DEFAULTVALUE              : 0.0
REMAIN_CONSTANT           : 0
<endproperty>

Sample

ATMOSPHERE                : 1
EVAPOTRANSPIRATION        : 1
EVAPOTRANSPIRATION_METHOD : 1
VEGETATION                : 0
POROUS_MEDIA              : 1
POROUS_MEDIA_PROPERTIES   : 1
RUN_OFF                   : 1
RUN_OFF_PROPERTIES        : 1
DRAINAGE_NET              : 0

!OUTPUT_TIME              : 0 7200
TIME_SERIE_LOCATION       : ..\General Data\TimeSeries\TimeSeriesLocation2D_2.dat
VERIFY_MASS               : 1
CONTINUOUS                : 0
DT_DURING_RAIN            : 3600. 
 
EVAP_FROM_CANOPY          : 1
EVAP_FROM_WATER_COLUMN    : 0

<beginproperty>
NAME                      : reference evapotranspiration
UNITS                     : mm/h
DESCRIPTION               : fao evapotranspiration
DEFAULTVALUE              : 0.0
REMAIN_CONSTANT           : 0
<endproperty>