Module Basin

Overview

Module Basin is a connection among the different modules of Mohid-Land. Indeed it manages the entering data, namely the water column, that is updated after each call of each module. The final results of this module is the different water fluxes due to evapotranspiration, infiltration, groundwater and runoff flow with river, computing, if asked, a water and mass balance for each property transported.

Main Processes

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

• Reading entering data and grid construction
• Atmospheric processes (leaf interception, leaf drainage, evporation) in order to obtain the potential water column from the precipitation
• 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 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>