Difference between revisions of "Module RunoffProperties"
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===Keywords=== | ===Keywords=== | ||
Since water does not enter domain through boundary there is no need for property definition | Since water does not enter domain through boundary there is no need for property definition | ||
| + | |||
| + | ==Discharges== | ||
| + | In RunoffProperties the discharges may be positive or negative (RunoffProperties uses discharge flow and concentrarion) and are dealt with ModuleDischarges | ||
| + | |||
| + | If one property is not discharged than the assumption is that if a positive discharge exists that property concentration is zero. | ||
| + | |||
| + | ===Computation=== | ||
| + | The discharges are initialized in Construct phase reading its locations and checking if inside boundaries. | ||
| + | |||
| + | In Modification phase the discharges are explicit and computed before transport (they were not included in transport scheme). | ||
| + | |||
| + | ===Keywords=== | ||
| + | For positive discharges the discharge concentration is read from Discharges_X.dat and the following keyword needs to exist in the Runoff Properties_X.dat inside the property block of the discharged property: | ||
| + | DISCHARGES : 1 | ||
| + | |||
==Other Features== | ==Other Features== | ||
Revision as of 12:08, 17 January 2014
Contents
Overview
This is the module in Mohid Land that handles runoff properties, meaning that controls its transport (dependent on fluxes computed in module Runoff). In this module property transformation is not computed since runoff routing is usually a fast process and there is not time for microbiological activity or chemical equilibrium. This is also the module that handles erosion/deposition to compute sediment and particulate properties sources and sinks (from surface soil to runoff water and vice-versa). Standard units for Module RunoffProperties are mg/L for dissolved and particulated properties in the water column and kg/m2 when deposited in surface soil.
Main Processes
Property Transport
Time discretization of property transport in Module RunoffProperties can be explicit or implicit. If user chooses to use implicit formulation, fluxes between runoff cells are implicit computed and also Drainage Network interaction where sinks in runoff occur. Runoff interaction acting as source to runoff and sinks from vegetation (particulate organic material easily eroded from manure) are always computed explicitly.
Spatial discretization (horizontally and vertically) of property transport in Module RunoffProperties can be chosen from several options as in ModuleWaterProperties for each property (e.g. Upwind order 1 to 3, CentralDifferences, LeapFrog..)
In order to boost the computation, RunoffProperties has the option of choosing all the same discretization for all the properties (see keywords).
The property transport equation:
Failed to parse (unknown error): \frac{(V\times C_{i})^{t+\Delta t}-(V\times C_{i})^{t}}{\Delta t}=-\left (Q_{i+\frac{1}{2}}\times C_{i+\frac{1}{2}}^{*}-Q_{i-\frac{1}{2}}\times C_{i-\frac{1}{2}}^{*} \right )+\left (\gamma _{i+\frac{1}{2}}^{*}\times A_{i+\frac{1}{2}}\times \frac{C_{i+1}^{*}-C_{i}^{*}}{\Delta x_{i}} \: \; -\gamma _{i-\frac{1}{2}}^{*}\times A_{i-\frac{1}{2}}\times \frac{C_{i}^{*}-C_{i-1}^{*}}{\Delta x_{i}} \right )
where:
V is cell water volume (m3) - water column (m) * cell area (m2) C is cell property concentration (g/m3) Deltat is time step (s) Q is flow in cell face (m3/s) Gamma is diffusivity in cell face (m2/s) Deltaxi is cell spatial step in direction i (m) * is t in case of explicit model and t+deltat in case of implicit
Diffusivity in runoff is defined by molecular diffusivity and dispersion (associated to erratic motion)
where:
Gammaface is diffusivity in cell face (m2/s) Diffface is molecular diffusivity in cell face (m2/s) vface is velocity at the cell face (m/s) lambdaface is dispersivity (m)
Erosion/Deposition
Erosion and deposition are function of the shear stress at the soil surface, meaning that higher velocities will tend to erode material and lower velocities will tend to deposit. Sediment bed is simulated as a "fluff layer" representing the easy eroded material in soil.
The property erosion equation:
where:
Es is the flux of eroded property (kg.m-2.s-1) E is erosion factor (kg.m-2.s-1) Penr is property enrichment ratio to cohesive sediment that exists in sediment bed (kg.m-2Property / kg.m-2sediment) taub is shear stress at the sediment bed (Pa) tauce is the critical (minimum) shear stress for erosion to occur (Pa)
Erosion of properties occurs dependently on the enrichemt ratio of the property in sediment since the erosion rate (E) is dependent on sediment type and cohesion. It is assumed that erosion is a transfer process between sediment in bed to the water column where properties are adsorbed to.
And the property deposition equation:
where:
Ds is the flux of deposited property (kg.m-2.s-1) C is property concentration (g/m3) Ws is property deposition velocity (m/s) 1E-3 is the conversion from grams to kilograms taub is shear stress at the sediment bed (Pa) taucd is the critical (maximum) shear stress for deposition to occur (Pa) taucd has to be lower than tauce
Deposition of properties occurs independently on the proportion of the property in sediment. Each property may have a different deposition rate and the process will be proportional to the property concentration since higher concentration will promote flocculation and deposition.
Bottom Shear Stress
Bottom shear stress is the effective shear at the soil surface promoted by water transport in runoff
where:
taub is bottom shear stress (Pa or kg.m-1.s-2) rho is water density (kg.m-3) g is gravity acceleration (m.s-2) n is manning coefficient (s.m(-1/3)) v is velocity at the center of cell (m.s-1) h is water column (m)
Partition
Partition between particulated and dissolved species is done using a user ratio.
Boundary Conditions
In Runoff there is the option to define the boundary condition as an imposed level but water can only exit domain and not enter (e.g. obstacles to water) As so there is no need to define property values in the outside or boundary.
Computation
The boundary flow from Module Runoff is used to define transport coefficients for advection diffusion. In advection diffusion solving (if user chooses implicit) the fluxes are computed implicitly.
Keywords
Since water does not enter domain through boundary there is no need for property definition
Discharges
In RunoffProperties the discharges may be positive or negative (RunoffProperties uses discharge flow and concentrarion) and are dealt with ModuleDischarges
If one property is not discharged than the assumption is that if a positive discharge exists that property concentration is zero.
Computation
The discharges are initialized in Construct phase reading its locations and checking if inside boundaries.
In Modification phase the discharges are explicit and computed before transport (they were not included in transport scheme).
Keywords
For positive discharges the discharge concentration is read from Discharges_X.dat and the following keyword needs to exist in the Runoff Properties_X.dat inside the property block of the discharged property:
DISCHARGES : 1
Other Features
Outputs
Output is done in terms of timeseries and HDF following the MOHID standards.
References
Data File
Keywords
Units in runoff properties
Transported properties (soluble) : g/m3 (or mg/l)
Adsorbed properties (non soluble) : ug/kgsoil
Bottom layer Properties (bottom transition) : kg/m2
ADVDIFF_EXPLICIT : 0/1 [1] !REMARK: Horizontal diffusion is always explicit
(1 - horiz adv is explicit; 0 - horiz adv is implicit
NEW_FORMULATION : 0/1 [0] !if 1 then spatial methods will be the same for all properties
ADVDIFF_METHOD_H : integer [UpwindOrder1] !Spatial methods for horizontal advection
!UpwindOrder1 = 1, UpwindOrder2 = 2, UpwindOrder3 = 3, P2_TVD = 4,
CentralDif = 5, LeapFrog = 6 !
<beginproperty>
PARTICULATE : 0/1 [0] !Property physical state: 0 - Dissolved ; 1 - Particulate
EROSION : 0/1 [0] !Compute erosion (source/sink term) - only read if PARTICULATE : 1
DEPOSITION : 0/1 [0] !Compute deposition (source/sink) - only read if PARTICULATE : 1
WS_TYPE : integer [1] !1 -constant;2 -concentration function - only read if DEPOSITION : 1
WS_VALUE : real !Fall velocity value - only read if WS_TYPE : 1
ADVECTION_DIFFUSION : 0/1 [0] !Property advection - diffusion
ADVDIFF_METHOD_H : integer [UpwindOrder1] !Spatial methods for horizontal advection
!UpwindOrder1 = 1, UpwindOrder2 = 2, UpwindOrder3 = 3, P2_TVD = 4,
CentralDif = 5, LeapFrog = 6
ADVDIFF_TVD_LIMIT_H : integer [Superbee] !Horizontal advection non-linear stability conditions
MinMod = 1, VanLeer = 2, Muscl = 3, Superbee = 4, PDM = 5
ADVDIFF_VOLUME_RELATION_MAX : real 5. !The relation between adjacent volumes above which
!the advection is upwind
PARTITION : 0/1 [0] !Compute partition between dissolved-particulate phases
PARTITION_COUPLE : char + !Name of the property (oposite phase) to compute partition
PARTITION_FRACTION : real - !Percentage of mass of a property in a determined phase
PARTITION_RATE : real [1 s-1] !Kinetic rate of partition to reach equilibrium
USE_SED_REF_CONC : 0/1 [0] !Use cohesive sediment concentration as a reference
SED_REF_CONC : real [1] !Reference cohesive sediment concentration to partition
<endproperty>
Sample
OUTPUT_TIME : 0 3600
TIME_SERIE_LOCATION : ..\General Data\TimeSeries\TimeSeriesLocation2D_2.dat
!
!Advection diffusion options
ADVDIFF_EXPLICIT : 0
!(1 - adv explicit; 0 - adv implicit; diff always explicit)
NEW_FORMULATION : 1 !1 - do not use moduleadvectiondiffusion (removed advection computation); 0 - old formulation
ADVDIFF_METHOD_H : 1 !UpwindOrder1 = 1. UpwindOrder2 = 2. UpwindOrder3 = 3. P2_TVD = 4.
!CentralDif = 5. LeapFrog = 6
!Dispersion
<begin_dispersion_trans>
NAME : dispersion trans
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 0.0
REMAIN_CONSTANT : 1
<end_dispersion_trans>
!!!!!!!!!!BEGIN SHEAR EROSION/DEPOSITION PARAMETERS!!!!!!!!!!!
HMIN_CHEZY : 0.0001 !0.0005 !m
<begin_critical_shear_erosion>
NAME : critical shear for erosion
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 0.2 !Pa = N/m2
REMAIN_CONSTANT : 1
<end_critical_shear_erosion>
<begin_critical_shear_deposition>
NAME : critical shear for deposition
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 0.1 !Pa = N/m2
REMAIN_CONSTANT : 1
<end_critical_shear_deposition>
<begin_erosion_coefficient>
NAME : erosion coefficient for shear
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 5.0E-6 !5.0E-4 !kg m-2 s-1
REMAIN_CONSTANT : 1
<end_erosion_coefficient>
!!!!!!!!!!END SHEAR EROSION/DEPOSITION PARAMETERS!!!!!!!!!!!
!!!!!!!!!!BEGIN SPLASH EROSION PARAMETERS!!!!!!!!!!!
SPLASH_HCRITIC_COMPUTE : 1
SPLASH_HCRITIC : 0.1 !m water column height where exponent decay is about 40% of maximum value
SPLASH_EROSIVERAIN_METHOD : 2 ! 1-constant erosive rain ; 2-use real rain for erosive rain
SPLASH_EROSIVERAIN_VALUE : 30. ! mm/h for erosive rain (read if SPLASH_EROSIVERAIN_METHOD : 1)
<begin_soil_detach>
NAME : erosion coefficient for rain splash
INITIALIZATION_METHOD : CONSTANT
DEFAULTVALUE : 0.1 !g/J
REMAIN_CONSTANT : 1
<end_soil_detach>
!!!!!!!!!!END SPLASH EROSION PARAMETERS!!!!!!!!!!!
!
!Property declaration
<beginproperty>
NAME : nitrate
UNITS : mgN/l
ADVECTION_DIFFUSION : 1
DESCRIPTION : nitrate
DEFAULTVALUE : 1.0
ADVDIFF_MOLECULAR_DIFF_COEF : 0.0
TIME_SERIE : 1
OUTPUT_HDF : 1
<endproperty>
Properties needed to run erosion/depositio: cohesive sediment and each other particulate have to be marked as particulate and erosion deposition parameters defined.
<beginproperty>
NAME : cohesive sediment
UNITS : mg/l
DESCRIPTION : Calcium in soil solution
PARTICULATE : 1
ADVECTION_DIFFUSION : 1
EROSION : 1
DEPOSITION : 1
WS_TYPE : 1 !1 - constant; 2 - Concentration function
WS_VALUE : 1E-10 !1E-4 !m/s (read if WS_TYPE : 1)
SPLASH_EROSION : 0
DEFAULTVALUE : 2.8e-3 !mg/l
BOTTOM_CONC : 1.0 !kg/m2
ADVDIFF_MOLECULAR_DIFF_COEF : 0.0 ! 1.15741E-8
TIME_SERIE : 1
OUTPUT_HDF : 1
<endproperty>
