How is the Volume Calculated in the SWMM 5 Groundwater Component?

Subject:   How is the Volume Calculated in the SWMM 5 Groundwater Component?

How is the Volume Calculated in the SWMM 5 Groundwater Component? by dickinsonre Subject:   How is the Volume Calculated in the SWMM 5 Groundwater Component?  The groundwater component of SWMM 5 is found in the gwater.c code.  It (as is all of SWMM 5) is excellently written in small functions by Lew Rossman of the EPA during the SWMM 5 development process.  However, code being code sometimes it is easier to see how the code is functioning.  This blog or note tries to show that function.   The groundwater component consists of groundwater data (gw in the equation) and aquifer data (a) in the equation.  The equation for the groundwater volume is shown in Figure 1.   The volume is the water content (theta) times the upper depth and the porosity of the aquifer times the lower depth (Figure 2).  Figure 1.  Groundwater Volume Calculations    Figure 2.  Lower and Upper Depth of the Groundwater Compartrment   via Blogger http://www.swmm5.net/2013/08/how-is-volume-calculated-in-swmm-5.html

Aquifer and Groundwater Objects in SWMM 5

Subject:   Aquifer and Groundwater Objects in SWMM 5

Aquifer and Groundwater Objects in SWMM 5 by dickinsonre Subject:   Aquifer and Groundwater Objects in SWMM 5  There are two types of data objects in SWMM 5 to describe the Groundwater flow component.  There is a Groundwater data object associated with a Subcatchment that describes flow equations, the interaction between the Subcatchment infiltration and the Groundwater component and an Aquifer data object that describes the characteristics of the Aquifer that may span one or more Subcatchments.  The Groundwater data is specific to one Subcatchment but the Aquifer may    via Blogger http://www.swmm5.net/2013/08/aquifer-and-groundwater-objects-in-swmm.html

SWMM 5 Fixed Surface Water Depth Boundary Condition

Subject:  SWMM 5 Fixed Surface Water Depth Boundary Condition

A large difference between SWMM 5 and SWMM 4 is how the Groundwater Aquifer interacts with the drainage network.  In SWMM 4 since the hydrology was simulated in the Runoff Block, the results saved to an interface file and the hydraulics were simulated in the Extran Block it was not possible to have a time step to time step interaction between the Aquifer and the Open Channels.  SWMM 5 has integrated hydrology and hydraulics so it is possible to use either a Fixed Surface Water Depth for each Subcatchment or the Receiving Nodes Node Depth Invert Elevation – the Aquifer Bottom Elevation.  The groundwater thus flows either to a fixed boundary condition as in SWMM 4 or to a time varying boundary condition.

SWMM 5 Threshold Groundwater Elevation

Subject:  SWMM 5 Threshold Groundwater Elevation

A large difference between SWMM 5 and SWMM 4 is how the Groundwater Aquifer interacts with the drainage network.  In SWMM 4 since the hydrology was simulated in the Runoff Block, the results saved to an interface file and the hydraulics were simulated in the Extran Block it was not possible to have a time step to time step interaction between the Aquifer and the Open Channels.  SWMM 5 has integrated hydrology and hydraulics so it is possible to use either a fixed Threshold Groundwater Elevation for each Subcatchment or the Receiving Nodes Invert Elevation.

Aquifers in SWMM 5

Subject:   Aquifers in SWMM 5

Aquifers in SWMM 5 by dickinsonre Subject:   Aquifers in SWMM 5  Groundwater in SWMM 5 is modeled as two zones: (1) Saturated and (2) Unstaturated.  The data for the Groundwater Simulation consists of physical data in an Aquifer and elevation and flow coefficient and exponent data in the GroundwaterData.  The Aquifer data object can be applied to multiple Subcatchments but each Subcatchment has its own set of Groundwaterdata.  For example, in this model all of the Subcatchments share the same Aquifer data but each Subcatchment has different elevation and flow data – the labels on the basin are the groundwater elevations. via Blogger http://www.swmm5.net/2013/08/aquifers-in-swmm-5.html

The new features in SWMM 5.0.021

Note: The new features in SWMM 5.0.021, which really are the new features in SWMM 5.0.019, 5.0.020 and 5.0.021 because of the way in which it was released. The big structural changes were made to the subcatchment, node, groundwater, infiltration and evaporation routines so that there is better continuity between the rainfall that falls on the pervious area of a watershed, the BMP/LID’s of the subcatchment (unlimited per subcatchment), evaporation, infiltration and storage nodes/ponds/lakes. A watershed or subcatchment is now simulated in layers:

· Pervious and Impervious Area surface runoff,

· Shallow Water Aquifer for Infiltration,

· Surface ponds with evaporation and infiltration,

· BMP and LID coverage under the pervious area,

· Two layer Groundwater Aquifer for flow to canals and manholes.

SWMM5 Groundwater Flow Components

Note: There are three sub flow components in the calculation of the groundwater flow from a SWMM 5 Subcatchment.
1^st Component: Flow = Groundwater Flow Coef. * (LowerDepth – Aquifer Bottom to Node Invert) ^ Groundwater Flow Exponent
2 ^nd Component: Flow = SurfaceWater Flow Coef. * (Aquifer Bottom to Water Surface – Aquifer Bottom to Node Invert) ^ SurfaceWater Flow Exponent
3^rd Component: Flow = SurfaceWater-Groundwater Flow Coef. * (Aquifer LowerDepth * Aquifer Bottom to Node Invert)
The total flow is the sum of all three components.

SWMM 5 Aquifer has a Saturated and Unsaturated Zone

SWMM 5 Aquifer has a Saturated and Unsaturated Zone by dickinsonre Note:  The unsaturated upper zone soil moisture varies between the initial upper zone moisture fraction to the porosity fraction for the soil.  The soil moisture content is for the SWMM5 Aquifer which can cover more than one Subcatchment in your simulation network. via Blogger http://www.swmm5.net/2013/07/swmm-5-aquifer-has-saturated-and.html

SWMM 5 View Variables

SWMM 5 View Variables

There are four types of graphical variables in SWMM 5: (1) Subcatchements, (2) System, (3) Nodes and (4) Links.  The SWMM 5 Hydrology binary graphics file consists of 21 view variables for each subcatcment simulation in SWMM 5.  The variables are:
    

Subcatchment Variables	Description
SUBCATCH_RAINFALL	rainfall intensity
SUBCATCH_SNOWFALL	snowfall intensity
SUBCATCH_RUNOFF	total runoff flow rate
SUBCATCH_RUNOFF_IMPZero	runoff flow rate from zero imp area feb 2007
SUBCATCH_RUNOFF_IMP	runoff flow rate from imp area feb 2007
SUBCATCH_RUNOFF_Pervious	runoff flow rate from pervious area feb 2007
SUBCATCH_LOSSES	total losses (infil)
SUBCATCH_EVAP	watershed evaporation loss
SUBCATCH_DEPTH	watershed depth
SUBCATCH_GW_FLOW	groundwater flow rate to node
SUBCATCH_GW_FLOW_A1	groundwater flow rate to node
SUBCATCH_GW_FLOW_A2	groundwater flow rate to node
SUBCATCH_GW_FLOW_A3	groundwater flow rate to node
SUBCATCH_GW_ELEV	elevation of saturated gw table
SUBCATCH_GW_THETA	soil moisture
SUBCATCH_GW_PERCOLATION	aquifer deep percolation
SUBCATCH_SNOWMELT	watershed snow melt
SUBCATCH_SNOWDEPTH	watershed snow depth
SUBCATCH_FREEWATER	watershed snow depth
SUBCATCH_COLD	watershed cold content
SUBCATCH_SNOWAREA	watershed snow coverage
SUBCATCH_UL	soil thickness
SUBCATCH_FTOT	infiltration during an event
SUBCATCH_FU	current value of F
SUBCATCH_FUMAX	maximum value of F
SUBCATCH_MOISTURE	current soil mositure (less than porosity)
SUBCATCH_IMD	current IMD (Porisity - Moisture)
SUBCATCH_IMDbyEvent	IMD at the beginning of an event
SUBCATCH_SAT	Flag for saturation (1 is saturated)
SUBCATCH_INFIL_TIME	GA infiltration time
SUBCATCH_WLMAX	current infiltration RATE
SUBCATCH_NETPRECIP	rainfall intensity
SUBCATCH_BUILDUP	pollutant buildup concentration
SUBCATCH_WASHOFF	pollutant washoff concentration

The SWMM 5 system binary graphics file consists of 25 variables on one line for each system variable simulated in SWMM 5.  The variables are:

System Variables	Description
SYS_TEMPERATURE	air temperature
SYS_WINDSPEED	wind speed
SYS_RAINFALL	rainfall intensity
SYS_SNOWFALL	snow depth
SYS_RUNOFF	runoff flow
SYS_LOSSES	evap + infil
SYS_EVAP	evap
SYS_DWFLOW	dry weather inflow
SYS_GWFLOW	ground water inflow
SYS_IIFLOW	RDII inflow
SYS_EXFLOW	external inflow
SYS_INFLOW	total lateral inflow
SYS_FLOODING	flooding outflow
SYS_OUTFLOW	outfall outflow
SYS_STORAGE	storage volume
SYS_CE	continuity error for the basin
SYS_ITERATIONS	average iterations over the basin
SYS_SNOWDEPTH	snow depth
SYS_COLD	cold storage for the basin
SYS_SNOWMELT	snowmelt for the basin
SYS_RAINMELT	rainmelt for the basin
SYS_TS	time steps during the simulation
SYS_DWFLoad	total K3 line DWF load
SYS_WWFLoad	total K3 line WWF load
SYS_WWFLoadExtra	agency extra WWF Load

The SWMM 5 Node graphics binary file consists of 20 variables on one line for each junction/storage/outfall/divider  simulated in SWMM 5.  The variables are:

Node Variables	Description
NODE_DEPTH	water depth above invert
NODE_HEAD	hydraulic head
NODE_VOLUME	volume stored & ponded
NODE_LATFLOW	lateral inflow rate
NODE_IIFLOW	total rdii inflow rate
NODE_UH1	total rdii inflow rate from UH 1
NODE_UH2	total rdii inflow rate from UH 2
NODE_UH3	total rdii inflow rate from UH 3
NODE_DWFFLOW	total DWF inflow rate
NODE_INFLOW	total inflow rate
NODE_OUTFLOW	total outflow rate
NODE_OVERFLOW	overflow rate
NODE_CE	node ce
NODE_AREA	node surface area
NODE_DQDH	node surcharge dqdh
NODE_DENOM	node surcharge dqdh
NODE_ITERATIONS	node iterations to this time step
NODE_TIMESTEP	node iterations to this time step
NODE_CONVERGENCE	node iterations to this time step
NODE_QUAL	concentration of each pollutant

Link Variables