Appendix C - Specialized Property Editors

7C.1 Aquifer Editor

The Aquifer Editor is invoked whenever a new aquifer object is created or an existing aquifer object is selected for editing. It contains the following data fields:

• Name: User assigned aquifer name.
• Porosity: Volume of voids / total soil volume (volumetric fraction).
• Wilting Point: Soil moisture content at which plants cannot survive (volumetric fraction).
• Field Capacity: Soil moisture content after all free water has drained off (volumetric fraction).
• Conductivity: Soil's saturated hydraulic conductivity (in/hr or mm/hr).
• Conductivity Slope: Average slope of log(conductivity) vs. soil moisture deficit (porosity minus moisture content) curve (unitless).
• Tension Slope: Average slope of soil tension versus soil moisture content curve (inches or mm).
• Upper Evaporation Fraction: Fraction of total evaporation available for evapotranspiration in the upper unsaturated zone.
• Lower Evaporation Depth: Maximum depth into the lower saturated zone over which evapotranspiration can occur (ft or m).
• Lower Groundwater Loss Rate: Rate of percolation from saturated zone to deep groundwater (in/hr or mm/hr).
• Bottom Elevation: Bottom elevation of aquifer (ft or m).
• Water Table Elevation: Elevation of the water table in the aquifer at the start of the simulation (ft or m).
• Unsaturated Zone Moisture: Moisture content of the unsaturated upper zone of the aquifer at the start of the simulation (volumetric fraction) (cannot exceed soil porosity).
• Upper Evaporation Pattern: Name of the monthly time pattern of adjustments applied to the upper evaporation fraction (optional – leave blank if not applicable).

C.2 Climatology Editor

The Climatology Editor is used to enter values for various climate-related variables required bycertain SWMM simulations. The dialog is divided into five tabbed pages, where each pageprovides a separate editor for a specific category of climate data.

Temperature Page

The Temperature page of the Climatology Editor dialog is used to specify the source of temperature data used for snowmelt computations. It is also used to select a climate file as a possible source for evaporation rates. There are three choices available:

• No Data: Select this choice if snowmelt is not being simulated and evaporation rates are not based on data in a climate file.
• Time Series: Select this choice if the variation in temperature over the simulation period will be described by one of the project's time series. Also enter (or select) the name of the time series.
• External Climate File: Select this choice if min/max daily temperatures will be read from an external climate file. Also enter the name of the file. If you want to start reading the climate file at a particular date in time that is different than the start date of the simulation (as specified in the Simulation Options), check off the “Start Reading File at” box and enter a starting date (month/day/year) in the date entry field next to it. Use this choice if you want daily evaporation rates to be estimated from daily temperatures or be read directly from the file.

Evaporation Page

The Evaporation page of the Climatology Editor dialog is used to supply evaporation rates, in inches/day (or mm/day), for a study area. There are five choices for specifying these rates:

• Constant: Use this choice if evaporation remains constant over time. Enter the value in the edit box provided.
• Time Series: Select this choice if evaporation rates will be specified in a time series. Enter or select the name of the time series in the dropdown combo box provided. Note that for each date specified in the time series, the evaporation rate remains constant at the value supplied for that date until the next date in the series is reached (i.e., interpolation is not used on the series).
• Directly From Climate File:This choice indicates that daily evaporation rates will be read from the same climate file that was specified for temperature. Enter values for monthly pan coefficients in the data grid provided.
• Computed from Temperatures: Hargreaves’ method will be used to compute daily evaporation rates from the daily air temperature record contained in the external climate file specified on the Temperature page of the dialog. This method also uses the site’s latitude, which can be entered on the Snowmelt page of the dialog even if snow melt is not being simulated.
• Monthly Averages: Use this choice to supply an average rate for each month of the year. Enter the value for each month in the data grid provided. Note that rates remain constant within each month.
• Evaporate Only During Dry Periods: Select this option if evaporation can only occur during periods with no precipitation.
• In addition this page allows the user to specify an optional Monthly Soil Recovery Pattern. This is a time pattern whose factors adjust the rate at which infiltration capacity is recovered during periods with no precipitation. It applies to all subcatchments for any choice of infiltration method. For example, if the normal infiltration recovery rate was 1% during a specific time period and a pattern factor of 0.8 applied to this period, then the actual recovery rate would be 0.8%. The Soil Recovery Pattern allows one to account for seasonal soil drying rates. In principle, the variation in pattern factors should mirror the variation in evaporation rates but might be influenced by other factors such as seasonal groundwater levels.

Wind Speed Page

The Wind Speed page of the Climatology Editor dialog is used to provide average monthly wind speeds. These are used when computing snowmelt rates under rainfall conditions. Melt rates increase with increasing wind speed. Units of wind speed are miles/hour for US units and km/hour for metric units. There are two choices for specifying wind speeds:

• From Climate File:Wind speeds will be read from the same climate file that was specified for temperature.
• Monthly Averages: Wind speed is specified as an average value that remains constant in each month of the year. Enter a value for each month in the data grid provided. The default values are all zero.

Snowmelt Page

The Snowmelt page of the Climatology Editor dialog is used to supply values for the following parameters related to snow melt calculations:

• Dividing Temperature between Snow and Rain: Enter the temperature below which precipitation falls as snow instead of rain. Use degrees F for US units or degrees C for metric units.
• ATI (Antecedent Temperature Index) Weight: This parameter reflects the degree to which heat transfer within a snow pack during non-melt periods is affected by prior air temperatures. Smaller values reflect a thicker surface layer of snow which results in reduced rates of heat transfer. Values must be between 0 and 1, and the default is 0.5.
• Negative Melt Ratio: This is the ratio of the heat transfer coefficient of a snow pack during non-melt conditions to the coefficient during melt conditions. It must be a number between 0 and 1. The default value is 0.6.
• Elevation above MSL: Enter the average elevation above mean sea level for the study area, in feet or meters. This value is used to provide a more accurate estimate of atmospheric pressure. The default is 0.0, which results in a pressure of 29.9 inches Hg. The effect of wind on snow melt rates during rainfall periods is greater at higher pressures, which occur at lower elevations.
• Latitude: Enter the latitude of the study area in degrees north. This number is used when computing the hours of sunrise and sunset, which in turn are used to extend min/max daily temperatures into continuous values. It is also used to compute daily evaporation rates from daily temperatures. The default is 50 degrees north.
• Longitude Correction: This is a correction, in minutes of time, between true solar time and the standard clock time. It depends on a location's longitude (θ) and the standard meridian of its time zone (SM) through the expression 4(θ -SM). This correction is used to adjust the hours of sunrise and sunset when extending daily min/max temperatures into continuous values. The default value is 0.

Areal Depletion Page

The Areal Depletion page of the Climatology Editor Dialog is used to specify points on the Areal Depletion Curves for both impervious and pervious surfaces within a project's study area. These curves define the relation between the area that remains snow covered and snow pack depth. Each curve is defined by 10 equal increments of relative depth ratio between 0 and 0.9. (Relative depth ratio is the ratio of an area's current snow depth to the depth at which there is 100% areal coverage).

Enter values in the data grid provided for the fraction of each area that remains snow covered at each specified relative depth ratio. Valid numbers must be between 0 and 1, and be increasing with increasing depth ratio.

Clicking the Natural Area button fills the grid with values that are typical of natural areas. Clicking the No Depletion button will fill the grid with all 1's, indicating that no areal depletion occurs. This is the default for new projects.

Adjustments

The Adjustments page of the Climatology Editor Dialog is used to supply a set of monthly adjustments applied to the temperature, evaporation rate, rainfall, and soil hydraulic conductivity that SWMM uses at each time step of a simulation:

• The monthly Temperature adjustment (plus or minus in either degrees F or C) is added to the temperature value that GeoSWMM would otherwise use in a specific month of the year.
• The monthly Evaporation adjustment (plus or minus in either in/day or mm/day) is added to the evaporation rate value that GeoSWMM would otherwise use in a specific month of the year.
• The monthly Rainfall adjustment is a multiplier applied to the precipitation value that GeoSWMM would otherwise use in a specific month of the year.
• The monthly Conductivity adjustment is a multiplier applied to the soil hydraulic conductivity used compute rainfall infiltration, groundwater percolation, and exfiltration from channels and storage units.

The same adjustment is applied for each time period within a given month and is repeated for that month in each subsequent year being simulated. Leaving a monthly adjustment blank means that there is no adjustment made in that month

C.3 Cross-Section Ed99itor

The Cross-Section Editor dialog is used to specify the shape and dimensions of a conduit's cross- section. When a shape is selected from the dropdown combo box an appropriate set of edit fields appears for describing the dimensions of that shape. Length dimensions are in units of feet for US units and meters for SI units. Slope values represent ratios of horizontal to vertical distance. The Barrels field specifies how many identical parallel conduits exist between its end nodes.

If an Irregular shaped section is chosen, a drop-down edit box will appear where the user can enter or select the name of a Transect object that describes the cross-section's geometry.

The Force Main shape option is a circular conduit that uses either the Hazen-Williams or Darcy- Weisbach formulas to compute friction losses for pressurized flow during Dynamic Wave flow routing. In this case the appropriate C-factor (for Hazen-Williams) or roughness height (for Darcy- Weisbach) is supplied as a cross-section property. The choice of friction loss equation is made on the Dynamic Wave Simulation Options dialog. Note that a conduit does not have to be assigned a Force Main shape for it to pressurize. Any of the other closed cross-section shapes can potentially pressurize and thus function as force mains using the Manning equation to compute friction losses.

C.4 Curve Editor

The Curve Editor dialog is invoked whenever a new curve object is created or an existing curve object is selected for editing. The editor adapts itself to the category of curve being edited (Storage, Tidal, Diversion, Pump, or Rating). To use the Curve Editor:

C.5 Events Editor

The Events Editor is activated when the Events sub-category of simulation Options is selected for editing from the GeoSWMM model object panel.

It is used to limit the periods of time in which a full unsteady hydraulic analysis of the drainage network is performed. For times outside of these periods, the hydraulic state of the network stays the same as it was at the end of the previous hydraulic event.  Although hydraulic calculations are restricted to these pre-defined event periods, a full accounting of the system's hydrology is still computed over the entire simulation duration. During inter-event periods any inflows to the network, from runoff, groundwater flow, dry weather flow, etc., are ignored. The purpose of only computing hydraulics for particular time periods is to speed up long-term continuous simulations where one knows in advance which periods of time (such as representative or critical storm events) are of most interest.

 The dialog consists of a table listing the start and end date of each event, plus a blank line at the end of the list used for adding a new event. The events do not have to be entered in chronological order. There are date and time selection controls below the table used to edit the dates of a selected event. Clicking the Replace Event button will replace the row with the entries in these controls. The Delete Event button will delete the selected event and the Delete All button will delete all events from the table. The first column of the table contains a check box which determines if the event should be used in the analysis or not.

• To identify event periods of interest, one can first run a simulation with Flow Routing turned off (from Simulation Options - General) and then perform a statistical frequency analysis on the system's rainfall record (see Viewing a Statistics Report).
• When a new event occurs, the water in a storage unit node will remain at the same level it had at the end of the previous event. Therefore one may want to choose event intervals long enough to minimize the effect that storage carryover might have.

C.6 Groundwater Flow Editor

The Groundwater Flow Editor dialog is invoked when the Groundwater property of a subcatchment is being edited. It is used to link a subcatchment to both an aquifer and to a node of the drainage system that exchanges groundwater with the aquifer. It also specifies coefficients that determine the rate of groundwater flow between the aquifer and the node. These coefficients (A1, A2, B1, B2 and A3) appear in the following equation that computes groundwater flow as a function of groundwater and surface water levels:

Where:

Q_gw = groundwater flow (cfs per acre or cms per hectare)

H_gw = height of saturated zone above bottom of aquifer (ft or m)

H_sw = height of surface water at receiving node above aquifer bottom (ft or m)

H^*= threshold groundwater height (ft or m).

The properties listed in the editor are as follows:

Aquifer Name: Name of aquifer object that supplies groundwater. Leave this field blank if you want the subcatchment not to generate any groundwater flow.

• Receiving Node: Name of node that receives groundwater from the aquifer.
• Surface Elevation: Elevation of ground surface for the subcatchment that lies above the aquifer in feet or meters.
• Groundwater Flow Coefficient: Value of A1 in the groundwater flow formula.
• Groundwater Flow Exponent: Value of B1 in the groundwater flow formula.
• Surface Water Flow Coefficient: Value of A2 in the groundwater flow formula.
• Surface Water Flow Exponent: Value of B2 in the groundwater flow formula.
• Surface-GW Interaction Coefficient: Value of A3 in the groundwater flow formula.
• Fixed Surface Water Depth: Fixed depth of surface water at the receiving node (feet or meters) (set to zero if surface water depth will vary as computed by flow routing). This value is used to compute HSW.
• Threshold Groundwater Elevation: Groundwater elevation that must be reached before any flow occurs (feet or meters). Leave blank to use the receiving node's invert elevation.

The values of the flow coefficients must be in units that are consistent with the groundwater flow units of cfs/acre for US units or cms/ha for metric units.

If groundwater flow is simply proportional to the difference in groundwater and surface water heads, then set the Groundwater and Surface Water Flow Exponents (B1 and B2) to 1.0, set the Groundwater Flow Coefficient (A1) to the proportionality factor, set the Surface Water Flow Coefficient (A2) to the same value as A1, and set the Interaction Coefficient (A3) to zero.

Note that when conditions warrant, the groundwater flux can be negative, simulating flow into the aquifer from the channel, in the manner of bank storage. An exception occurs when A3 ≠ 0, since the surface water - groundwater interaction term is usually derived from groundwater flow models that assume unidirectional flow. Otherwise, to ensure that negative fluxes will not occur, one can make A1 greater than or equal to A2, B1 greater than or equal to B2, and A3 equal to zero.

C.7 Infiltration Editor

The Infiltration Editor dialog is used to specify values for the parameters that describe the rate at which rainfall infiltrates into the upper soil zone in a subcatchment's pervious area. It is invoked when editing the Infiltration property of a subcatchment. The infiltration parameters depend on which infiltration model was selected for the project: Horton, Green-Ampt, or Curve Number. The choice of infiltration model can be made either by editing the project's Simulation Options or by changing the project's Default Properties.

Green-Ampt Infiltration Parameters

The following data fields appear in the Infiltration Editor for Green-Ampt infiltration:

• Suction Head: Average value of soil capillary suction along the wetting front (inches or mm).
• Conductivity: Soil saturated hydraulic conductivity (in/hr or mm/hr).
• Initial Deficit: Fraction of soil volume that is initially dry (i.e., difference between soil porosity and initial moisture content). For a completely drained soil, it is the difference between the soil's porosity and its field capacity.

Horton Infiltration Parameters

The following data fields appear in the Infiltration Editor for Horton infiltration:

• Max. Infil. Rate: Maximum infiltration rate on the Horton curve (in/hr or mm/hr). Representative values are as follows:
• • DRY soils (with little or no vegetation):
  • • Sandy soils: 5 in/hr
    • Loam soils: 3 in/hr
    • Clay soils: 1 in/hr
  • DRY soils (with dense vegetation):
  • • Multiply values in A. by 2
  • MOIST soils:
  • • Soils which have drained but not dried out (field capacity): Divide values from A and B by 3.
    • Soils close to saturation: Choose value close to min. infiltration rate.
    • Soils which have partially dried out: Divide values from A and B by 1.5 - 2.5. 
• Min. Infil. Rate: Minimum infiltration rate on the Horton curve (in/hr or mm/hr). Equivalent to the soil’s saturated hydraulic conductivity.
• Decay Const.: Infiltration rate decay constant for the Horton curve (1/hours). Typical values range between 2 and 7.
• Drying Time: Time in days for a fully saturated soil to dry completely. Typical values range from 2 to 14 days.
• Max. Infil. Vol.: Maximum infiltration volume possible (inches or mm, 0 if not applicable). It can be estimated as the difference between a soil's porosity and its wilting point times the depth of the infiltration zone.

Curve Number Infiltration Parameters

The following data fields appear in the Infiltration Editor for Curve Number infiltration:

• Curve Number: This is the SCS curve number which is tabulated in the publication SCS Urban Hydrology for Small Watersheds, 2nd Ed., (TR-55), June 1986. Consult the Curve Number Table for a listing of values by soil group, and the accompanying Soil Group Table for the definitions of the various groups.
• Conductivity: This property has been deprecated and is no longer used.
• Drying Time: The number of days it takes a fully saturated soil to dry. Typical values range between 2 and 14 days.

C.8 Inflows Editor

The Inflows Editor dialog is used to assign Direct, Dry Weather and RDII inflow into a node of the drainage system. It is invoked whenever the Inflows property of a Node object is selected in the Property Editor. The dialog consists of three tabbed pages that provide a special editor for each type of inflow.

Direct Inflows Page

The Direct page on the Inflows Editor dialog is used to specify the time history of direct external flow and water quality entering a node of the drainage system. These inflows are represented by both a constant and time varying component as follows:

Inflow at time t = (baseline value)*(baseline pattern factor) +(scale factor)*(time series value at time t)

The dialog consists of the following input fields:

• Constituent: Selects the constituent (FLOW or one of the project's specified pollutants) whose direct inflow will be described.
• Baseline: Specifies the value of the constant baseline component of the constituent's inflow. For FLOW, the units are the project's flow units. For pollutants, the units are the pollutant's concentration units if inflow is a concentration, or can be any mass flow units if the inflow is a mass flow (see Conversion Factor below). If left blank then no baseline inflow is assumed.
• Baseline Pattern: An optional Time Pattern whose factors adjust the baseline inflow on either an hourly, daily, or monthly basis (depending on the type of time pattern specified). If left blank, then no adjustment is made to the baseline inflow.
• Time Series: Specifies the name of the time series that contains inflow data for the selected constituent. If left blank, then no direct inflow will occur for the selected constituent at the node in question.
• Scale Factor: A multiplier used to adjust the values of the constituent's inflow time series. The baseline value is not adjusted by this factor. The scale factor can have several uses, such as allowing one to easily change the magnitude of an inflow hydrograph while keeping its shape the same, without having to re-edit the entries in the hydrograph's time series. Or it can allow a group of nodes sharing the same time series to have their inflows behave in a time-synchronized fashion while letting their individual magnitudes be different. If left blank the scale factor defaults to 1.0.
• Inflow Type: For pollutants, selects the type of inflow data contained in the time series as being either a concentration (mass/volume) or mass flow rate (mass/time). This field does not appear for FLOW inflow.
• Conversion Factor: A numerical factor used to convert the units of pollutant mass flow rate in the time series data into concentration mass units per second. For example, if the time series data were in pounds per day and the pollutant concentration defined in the project was mg/L, then the conversion factor value would be (453,590 mg/lb) / (86400 sec/day) = 5.25 (mg/sec) per (lb/day).

More than one constituent can be edited while the dialog is active by simply selecting another choice for the Constituent property. However, if the Cancel button is clicked then any changes made to all constituents will be ignored.

If a pollutant is assigned a direct inflow in terms of concentration, then one must also assign a direct inflow to flow, otherwise no pollutant inflow will occur. An exception is at submerged outfalls where pollutant intrusion can occur during periods of reverse flow.

If pollutant inflow is defined in terms of mass, then a flow inflow time series is not required.

Dry Weather Inflows Page

The Dry Weather page of the Inflows Editor dialog is used to specify a continuous source of dry weather flow entering a node of the drainage system. The dialog consists of the following input fields:

• Constituent: Selects the constituent (FLOW or one of the project's specified pollutants) whose dry weather inflow will be specified.
• Average Value: Specifies the average (or baseline) value of the dry weather inflow of the constituent in the relevant units (flow units for flow, concentration units for pollutants). Leave blank if there is no dry weather flow for the selected constituent.
• Time Patterns: Specifies the names of the time patterns to be used to allow the dry weather flow to vary in a periodic fashion by month of the year, by day of the week, and by time of day (for both weekdays and weekends). One can select a previously defined pattern from the dropdown list of each combo box. Up to four different types of patterns can be assigned.

More than one constituent can be edited while the dialog is active by simply selecting another choice for the Constituent property. However, if the Cancel button is clicked then any changes made to all constituents will be ignored.

RDII Inflow Page

The RDII page of the Inflows Editor dialog is used to specify RDII (rainfall-dependent infiltration/inflow) for the node in question. The editor contains the following two input fields:

• Unit Hydrograph Group: Enter (or select from the dropdown list) the name of the Unit Hydrograph group that applies to the node in question. The unit hydrographs in the group are used in combination with the group's assigned rain gage to develop a time series of RDII inflows per unit area over the period of the simulation. Leave this field blank to indicate that the node receives no RDII inflow.
• Sewershed Area: Enter the area (in acres or hectares) of the sewershed that contributes RDII to the node in question. Note this area will typically be only a small, localized portion of the subcatchment area that contributes surface runoff to the node.

C.9 Initial Buildup Editor

The Initial Buildup Editor is invoked from the Property Editor when editing the Initial Buildup property of a subcatchment. It specifies the amount of pollutant buildup existing over the subcatchment at the start of the simulation. The editor consists of a data entry grid with two columns. The first column lists the name of each pollutant in the project and the second column contains edit boxes for entering the initial buildup values. If no buildup value is supplied for a pollutant, it is assumed to be 0. The units for buildup are either pounds per acre when US units are in use or kilograms per hectare when SI metric units are in use. 

If a non-zero value is specified for the initial buildup of a pollutant, it will override any initial buildup computed from the Antecedent Dry Days parameter specified on the Dates page of the Simulation Options dialog.

C.10 Land Use Editor

The Land Use Editor dialog is used to define a category of land use for the study area and to define its pollutant buildup and washoff characteristics. The dialog contains three tabbed pages of land use properties:

• General Page (provides land use name and street sweeping parameters)
• Buildup Page (defines rate at which pollutant buildup occurs)
• Washoff Page (defines rate at which pollutant washoff occurs)

General Page

The General page of the Land Use Editor dialog describes the following properties of a particular land use category:

• Land Use Name: The name assigned to the land use.

• Description: An optional comment or description of the land use (click the ellipsis button or press Enter to edit).
• Street Sweeping Interval: Days between streets sweeping within the land use.
• Street Sweeping Availability: Fraction of the buildup of all pollutants that is available for removal by sweeping.
• Last Swept: Number of days since last swept at the start of the simulation.

If street sweeping does not apply to the land use, then the last three properties can be left blank.

Buildup Page

The Buildup page of the Land Use Editor dialog describes the properties associated with pollutant buildup over the land during dry weather periods. These consist of:

• Pollutant: Select the pollutant whose buildup properties are being edited.
• Function: The type of buildup function to use for the pollutant. The choices are NONE for no buildup, POW for power function buildup, EXP for exponential function buildup SAT for saturation function buildup, and EXT for buildup supplied by an external time series. Select NONE if no buildup occurs.
• Max. Buildup: The maximum buildup that can occur, expressed as lbs (or kg) of the pollutant per unit of the normalizing variable.

The following two properties apply to the POW, EXP and SAT buildup functions:

• Rate Constant: The time constant that governs the rate of pollutant buildup. For Power buildup its units are mass / days raised to a power, while for Exponential buildup its units are 1/days.
• Power/Sat. Constant: The exponent C3 used in the Power buildup formula, or the half-saturation constant C2 used in the Saturation buildup formula. For the latter case, its units are days.

The following two properties apply to the EXT (External Time Series) option:

• Scaling Factor: A multiplier used to adjust the buildup rates listed in the time series.
• Time Series: The name of the Time Series that contains buildup rates (as mass per normalizing variable per day).
• Normalizer (Normalizing Variable): The variable to which buildup is normalized on a per unit basis. The choices are either land area (in acres or hectares) or curb length. Any units of measure can be used for curb length, as long as they remain the same for all subcatchments in the project.

When there are multiple pollutants, the user must select each pollutant separately from the Pollutant dropdown list and specify its pertinent buildup properties.

Washoff Page

The Washoff page of the Land Use Editor dialog describes the properties associated with pollutant washoff over the land use during wet weather events. These consist of:

• Pollutant: The name of the pollutant whose washoff properties are being edited.
• Function: The choice of washoff function to use for the pollutant. The choices are:
• • NONE: no washoff
  • EXP: exponential washoff
  • RC: rating curve washoff
  • EMC: event-mean concentration washoff.
• Coefficient: This is the value of C1 in the exponential and rating curve formulas, or the event-mean concentration.
• Exponent: The exponent used in the exponential and rating curve washoff formulas.
• Cleaning Efficiency: The street cleaning removal efficiency (percent) for the pollutant. It represents the fraction of the amount that is available for removal on the land use as a whole (set on the General page of the editor) which is actually removed.
• BMP Efficiency: Removal efficiency (percent) associated with any Best Management Practice that might have been implemented. The washoff load computed at each time step is simply reduced by this amount.

As with the Buildup page, each pollutant must be selected in turn from the Pollutant dropdown list and have its pertinent washoff properties defined.

C.11 Land Use Assignment Editor

The Land Use Assignment editor is invoked from the Property Editor when editing the Land Uses property of a subcatchment. Its purpose is to assign land uses to the subcatchment for water quality simulations. The percent of land area in the subcatchment covered by each land use is entered next to its respective land use category. If the land use is not present its field can be left blank. The percentages entered do not necessarily have to add up to 100.

C.12 LID Control Editor

The LID Control Editor is used to define a low impact development control that can be deployed throughout a study area to store, infiltrate, and evaporate subcatchment runoff. The design of the control is made on a per-unit-area basis so that it can be placed in any number of subcatchments at different sizes or number of replicates. The editor contains the following data entry fields:

• Control Name: A name used to identify the particular LID control.
• LID Type: The generic type of LID being defined (bio-retention cell, rain garden, green roof, infiltration trench, permeable pavement, rain barrel, or vegetative swale). Process Layers: These are a tabbed set of pages containing data entry fields for the vertical layers and underdrain that comprise an LID control. They include some combination of the following, depending on the type of LID selected: Surface Layer, Pavement Layer, Soil Layer, Storage Layer, and Drain System or Drainage Mat.

The Surface Layer page of the LID Control Editor is used to describe the surface properties of bio-retention cells, porous pavement, infiltration trenches, and vegetative swales. These properties are:

• Storage Depth: When confining walls or berms are present this is the maximum depth to which water can pond above the surface of the unit before overflow occurs (in inches or mm). For LIDs that experience overland flow it is the height of any surface depression storage. For swales, it is the height of its trapezoidal cross section.
• Vegetative Cover Fraction: The fraction of the storage area above the surface that is filled with vegetation.
• Surface Roughness: Manning's n for overland flow over the surface of porous pavement or a vegetative swale. Use 0 for other types of LIDs.
• Surface Slope: Slope of porous pavement surface or vegetative swale (percent). Use 0 for other types of LIDs. 
• Swale Side Slope: Slope (run over rise) of the side walls of a vegetative swale's cross section. This value is ignored for other types of LIDs.

If either Surface Roughness or Surface Slope values are 0 then any ponded water that exceeds the storage depth is assumed to completely overflow the LID control within a single time step.

The Pavement Layer page of the LID Control Editor supplies values for the following properties of a porous pavement LID:

• Thickness: The thickness of the pavement layer (inches or mm). Typical values are 4 to 6 inches (100 to 150 mm).
• Void Ratio: The volume of void space relative to the volume of solids in the pavement for continuous systems or for the fill material used in modular systems. Typical values for pavements are 0.12 to 0.21. Here, porosity = void ratio / (1 + void ratio).
• Impervious Surface Fraction: Ratio of impervious paver material to total area for modular systems; 0 for continuous porous pavement systems.
• Permeability: Permeability of the concrete or asphalt used in continuous systems or hydraulic conductivity of the fill material (gravel or sand) used in modular systems (in/hr or mm/hr). The permeability of new porous concrete or asphalt is very high (e.g., hundreds of in/hr) but can drop off over time due to clogging by fine particulates in the runoff.
• Clogging Factor: Number of pavement layer void volumes of runoff treated it takes to completely clog the pavement. Use a value of 0 to ignore clogging. Clogging progressively reduces the pavement's permeability in direct proportion to the cumulative volume of runoff treated.

If one has an estimate of the number of years it takes to fully clog the system (Yclog), the Clogging Factor can be computed as: Yclog * Pa * CR * (1 + VR) * (1 - ISF) / (T * VR) where Pa is the annual rainfall amount over the site, CR is the pavement's capture ratio (area that contributes runoff to the pavement divided by area of the pavement itself), VR is the system's Void Ratio, ISF is the Impervious Surface Fraction, and T is the pavement layer Thickness.

As an example, suppose it takes 5 years to clog a continuous porous pavement system that serves an area where the annual rainfall is 36 inches/year. If the pavement is 6 inches thick, has a void ratio of 0.2 and captures runoff only from its own surface, then the Clogging Factor is 5 x 36 x (1+ 0.2) / 6 / 0.2 = 180.

The Soil Layer page of the LID Control Editor describes the properties of the engineered soil mixture used in bio-retention types of LIDs. These properties are:

• Thickness: The thickness of the soil layer (inches or mm). Typical values range from 18 to 36 inches (450 to900 mm) for rain gardens, street planters and other types of land-based bio-retention units, but only 3 to 6 inches (75 to 150 mm) for green roofs.
• Porosity: The volume of pore space relative to total volume of soil (as a fraction).
• Field Capacity: Volume of pore water relative to total volume after the soil has been allowed to drain fully (as a fraction). Below this level, vertical drainage of water through the soil layer does not occur.
• Wilting Point: Volume of pore water relative to total volume for a well dried soil where only bound water remains (as a fraction). The moisture content of the soil cannot fall below this limit.
• Conductivity: Hydraulic conductivity for the fully saturated soil (in/hr or mm/hr).
• Conductivity Slope: Slope of the curve of log(conductivity) versus soil moisture content (dimensionless). Typical values range from 5 for sands to 15 for silty clay.
• Suction Head: The average value of soil capillary suction along the wetting front (inches or mm). This is the same parameter as used in the Green-Ampt infiltration model.

Porosity, field capacity, conductivity and conductivity slope are the same soil properties used for Aquifer objects when modeling groundwater, while suction head is the same parameter used for Green-Ampt infiltration. Except here they apply to the special soil mixt used in a LID unit rather than the site's naturally occurring soil.

The Storage Layer page of the LID Control Editor describes the properties of the crushed stone or gravel layer used in bio-retention cells, porous pavement systems, and infiltration trenches as a bottom storage/drainage layer. It is also used to specify the height of a rain barrel (or cistern). The following data fields are displayed:

• Height: This is the height of a rain barrel or thickness of a gravel layer (inches or mm). Crushed stone and gravel layers are typically 6 to 18 inches (150 to 450 mm) thick while single family home rain barrels range in height from 24 to 36 inches (600 to 900 mm).

The following data fields do not apply to Rain Barrels.

• Void Ratio: The volume of void space relative to the volume of solids in the layer. Typical values range from 0.5 to 0.75 for gravel beds. Note that porosity = void ratio / (1 + void ratio).
• Filtration Rate: The maximum rate at which water can flow out the bottom of the layer after it is first constructed (in/hr or mm/hr). Typical values for gravels are 10 to 30 in/hr (250 to 750 mm/hr). If the layer contains a sand bed beneath it then the conductivity of the sand should be used. If there is an impermeable floor or liner below the layer then use a value of 0. The actual exfiltration rate through the bottom will be the smaller of this limiting rate and the normal infiltration rate into the soil below the layer.
• Clogging Factor: Total volume of treated runoff it takes to completely clog the bottom of the layer divided by the void volume of the layer. Use a value of 0 to ignore clogging. Clogging progressively reduces the Filtration Rate in direct proportion to the cumulative volume of runoff treated and may only be of concern for infiltration trenches with permeable bottoms and no under drains. 

LID storage layers can contain an optional underdrain system that collects stored water from the bottom of the layer and conveys it to a conventional storm drain. The Underdrain page of the LID Control Editor describes the properties of this system. It contains the following data entry fields:

• Drain Coefficient and Drain Exponent: Coefficient C and exponent n that determines the rate of flow through the underdrain as a function of height of stored water above the drain height. The following equation is used to compute this flow rate (per unit area of the LID unit):

Where is outflow (in/hr or mm/hr),height of stored water (inches or mm), andis the drain height. If the layer does not have an underdrain then set C to 0. A typical value for n would be 0.5 (making the drain act like an orifice). A rough estimate for C can be based on the time T required to drain a depth D of stored water. For n = 0.5, C = 2D^1/2/T.

• Drain Offset Height: Heightof any underdrain piping above the bottom of a storage layer or rain barrel (inches or mm).
• Drain Delay (for Rain Barrels only): The number of dry weather hours that must elapse before the drain line in a rain barrel is opened (the line is assumed to be closed once rainfall begins). This parameter is ignored for other types of LIDs.

C.13 LID Group Editor

The LID Group Editor is invoked when the LID Controls property of a Subcatchment is selected for editing. It is used to identify a group of previously defined LID controls that will be placed within the subcatchment, the sizing of each control, and what percent of runoff from the non-LID portion of the subcatchment each should treat.

The editor displays the current group of LIDs placed in the subcatchment along with buttons for adding an LID unit, editing a selected unit, and deleting a selected unit. Selecting Add or Edit will bring up an LID Usage Editor where one can enter values for the data fields shown in the Group Editor.

Note that the total % Of Area for all of the LID units within a subcatchment must not exceed 100%. The same applies to % From Impervious. Refer to the LID Usage Editor for the meaning of these parameters.

C.14 LID Usage Editor

The LID Usage Editor is invoked from a subcatchment's LID Group Editor to specify how a particular LID control will be deployed within the subcatchment. It contains the following data entry fields:

• Control Name: The name of a previously defined LID control to be used in the subcatchment. (LID controls are added to a project by using the Data Browser.)
• Number of Replicate Units: The number of equal size units of the LID practice (e.g., the number of rain barrels) deployed within the subcatchment.
• Area of Each Unit: The surface area devoted to each replicate LID unit (sq. ft or sq. m). If the LID Occupies Full Subcatchment box is checked, then this field becomes disabled and will display the total subcatchment area divided by the number of replicate units. The label below this field indicates how much of the total subcatchment area is devoted to the particular LID being deployed.
• Top Width of Overland Flow Surface: The width of the outflow face of each identical LID unit (in ft or m). This parameter only applies to LID processes such as Porous Pavement and Vegetative Swales that use overland flow to convey surface runoff off of the unit. (The other LID processes, such as Bio-Retention Cells and Infiltration Trenches simply spill any excess captured runoff over their berms.)
• % Initially Saturated: For Bio-Retention Cells this is the degree to which the unit's soil is initially filled with water (0 % saturation corresponds to the wilting point moisture content, 100 % saturation has the moisture content equal to the porosity). The storage zone beneath the soil zone of the cell is assumed to be completely dry. For other types of LIDs it corresponds to the degree to which their storage zone is initially filled with water.
• % of Impervious Area Treated: The percent of the impervious portion of the subcatchment's non-LID area whose runoff is treated by the LID practice. (E.g., if rain barrels are used to capture roof runoff and roofs represent 60% of the impervious area, then the impervious area treated is 60%). If the LID unit treats only direct rainfall, such as with a green roof, then this value should be 0. If the LID takes up the entire subcatchment then this field is ignored.
• Send Outflow to Pervious Area: Select this option if the outflow from the LID is returned onto the subcatchment's pervious area rather than going to the subcatchment's outlet. An example of where this might apply is a rain barrel whose contents are used to irrigate a lawn area. This field is ignored if the LID takes up the entire subcatchment.
• Detailed Report File: The name of an optional file where detailed time series results for the LID will be written. Click the () button to select a file using the standard Windows File Save dialog or click the delete () button to remove any detailed reporting. The detailed report file will be a text file that can be easily opened and viewed with any text editor outside of GeoSWMM.

C.15 Pollutant Editor

The Pollutant Editor is invoked when a new pollutant object is created or an existing pollutant is selected for editing. It contains the following fields:

• Name: The name assigned to the pollutant.
• Units: The concentration units (mg/L, ug/L, or #/L (counts/L)) in which the pollutant concentration is expressed.
• Rain Concentration: Concentration of the pollutant in rain water (concentration units).
• GW Concentration: Concentration of the pollutant in ground water (concentration units).
• I&I Concentration: Concentration of the pollutant in any Infiltration/Inflow (concentration units).
• DWF Concentration: Concentration of the pollutant in any dry weather sanitary flow (concentration units). This value can be overridden for any specific node of the conveyance system by editing the node's Inflows property.
• Decay Coefficient: First-order decay coefficient of the pollutant (1/days).
• Snow Only: YES if pollutant buildup occurs only when there is snow cover, NO otherwise (default is NO).
• Co-Pollutant: Name of another pollutant whose runoff concentration contributes to the runoff concentration of the current pollutant.
• Co-Fraction: Fraction of the co-pollutant's runoff concentration that contributes to the runoff concentration of the current pollutant.

An example of a co-pollutant relationship would be where the runoff concentration of a particular heavy metal is some fixed fraction of the runoff concentration of suspended solids. In this case suspended solids would be declared as the co-pollutant for the heavy metal.

C.16 Snow Pack Editor

The Snow Pack Editor is invoked when a new snow pack object is created or an existing snow pack is selected for editing. The editor contains a data entry field for the snow pack’s name and two tabbed pages, one for snow pack parameters and one for snow removal parameters.

Snow Pack Parameters Page

• The Parameters page of the Snow Pack Editor dialog provides snow melt parameters and initial conditions for snow that accumulates over three different types of areas: the impervious area that is plowable (i.e. subject to snow removal), the remaining impervious area, and the entire pervious area. The page contains a data entry grid which has a column for each type of area and a row for each of the following parameters: Min. Melt Coefficient: The degree-day snow melt coefficient that occurs on December 21. Units are either in/hr-deg F or mm/hr-deg C.
• Max. Melt Coefficient: The degree-day snow melt coefficient that occurs on June 21. Units are either in/hr-deg F or mm/hr-deg C. For a short term simulation of less than a week or so it is acceptable to use a single value for both the minimum and maximum melt coefficients. The minimum and maximum snow melt coefficients are used to estimate a melt coefficient that varies by day of the year. The latter is used in the following degree-day equation to compute the melt rate for any particular day:

• Base Temperature: Temperature at which snow begins to melt (degrees F or C).
• Fraction Free Water Capacity: The volume of a snow pack's pore space which must fill with melted snow before liquid runoff from the pack begins, expressed as a fraction of snow pack depth.
• Initial Snow Depth: Depth of snow at the start of the simulation (water equivalent depth in inches or millimeters).
• Initial Free Water: Depth of melted water held within the pack at the start of the simulation (inches or mm). This number should be at or below the product of the initial snow depth and the fraction free water capacity.
• Depth at 100% Cover: The depth of snow beyond which the entire area remains completely covered and is not subject to any areal depletion effect (inches or mm).
• Fraction of Impervious Area That is Plowable: The fraction of impervious area that is plowable and therefore is not subject to areal depletion.

Snow Removal Parameters Page

The Snow Removal page of the Snow Pack Editor describes how snow removal occurs within the Plowable area of a snow pack. The following parameters govern this process:

• Depth at which snow removal begins (in or mm): Depth which must be reached before any snow removal begins.
• Fraction transferred out of the watershed: The fraction of snow depth that is removed from the system (and does not become runoff).
• Fraction transferred to the impervious area: The fraction of snow depth that is added to snow accumulation on the pack's impervious area.
• Fraction transferred to the pervious area: The fraction of snow depth that is added to snow accumulation on the pack's pervious area.
• Fraction converted to immediate melt: The fraction of snow depth that becomes liquid water which runs onto any subcatchment associated with the snow pack.
• Fraction moved to another subcatchment: The fraction of snow depth which is added to the snow accumulation on some other subcatchment. The name of the subcatchment must also be provided.

The various removal fractions must add up to 1.0 or less. If less than 1.0, then some remaining fraction of snow depth will be left on the surface after all of the redistribution options are satisfied.

C.17 Time Pattern Editor

The Time Pattern Editor is invoked when a new time pattern object is created or an existing time pattern is selected for editing. The editor contains that following data entry fields:

• Name: Enter the name assigned to the time pattern.
• Type: Select the type of time pattern being specified.
• Description: You can provide an optional comment or description for the time pattern. If more than one line is needed, click the button to launch a multi-line comment editor.
• Multipliers: Enter a value for each multiplier. The number and meaning of the multipliers changes with the type of time pattern selected:
• • MONTHLY: One multiplier for each month of the year.
  • DAILY: One multiplier for each day of the week.
  • HOURLY: One multiplier for each hour from 12 midnight to 11 PM.
  • WEEKEND: Same as for HOURLY except applied to weekend days.

In order to maintain an average dry weather flow or pollutant concentration at its specified value (as entered on the Inflows Editor), the multipliers for a pattern should average to 1.0.

C.18 Time Series Editor

The Time Series Editor is invoked whenever a new time series object is created or an existing time series is selected for editing. To use the Time Series Editor:

• Enter values for the following standard items:
• • Name: Name of the time series.
  • Description: Optional comment or description of what the time series represents. Click the () button to launch a multi-line comment editor if more than one line is needed.

• Select whether to use an external file as the source of the data or to enter the data directly into the form's data entry grid.
• If the external file option is selected, click the () button to locate the file's name. The file's contents must be formatted in the same manner as the direct data entry option discussed below.
• For direct data entry, enter values in the data entry grid as follows:
• • Date Column: Optional date (in month/day/year format) of the time series values (only needed at points in time where a new date occurs). 
  • Time Column: If dates are used, enter the military time of day for each time series value (as hours: minutes or decimal hours). If dates are not used, enter time as hours since the start of the simulation.
  • Value Column: The time series’ numerical values.

A graphical plot of the data in the grid can be viewed in a separate window by clicking the View button. It allows cut, copy, insert, and paste selected cells in the grid as well as options to insert or delete a row.One can also click the Import button to enter curve data directly to the grid from an external file.

• Press OK to accept the time series or Cancel to discard the edits made.

Note that there are two methods for describing the occurrence time of time series data:

• Calendar date/time of day (which requires that at least one date, at the start of the series, be entered in the Date column)
• Elapsed hours since the start of the simulation (where the Date column remains empty).

C.19 Title/Notes Editor

The Title/Notes editor is invoked when a project’s Title/Notes data category is selected for editing. As shown above, the editor contains a multi-line edit field where a description of a GeoSWMM project can be entered.

C.20 Transect Editor

The Transect Editor is invoked when a new transect object is created or an existing transect is selected for editing. It contains the following data entry fields:

• Name: The name assigned to the transect.
• Description: An optional comment or description of the transect.
• Station/Elevation Data Grid: Values of distance from the left side of the channel along with the corresponding elevation of the channel bottom as one move across the channel from left to right, looking in the downstream direction. Up to 1500 data values can be entered.
• Roughness: Values of Manning's roughness for the left overbank, right overbank and main channel portion of the transect. The overbank roughness values can be zero if no overbank exists.
• Bank Stations: The distance values appearing in the Station/Elevation grid that mark the end of the left overbank and the start of the right overbank. Use 0 to denote the absence of an overbank.
• Modifiers:
• • The Stations modifier is a factor by which the distance between each station will be multiplied when the transect data is processed by SWMM. Use a value of 0 if no such factor is needed.
  • The Elevations modifier is a constant value that will be added to each elevation value.
  • The Meander modifier is the ratio of the length of a meandering main channel to the length of the overbank area that surrounds it. This modifier is applied to all conduits that use this particular transect for their cross section. It assumes that the length supplied for these conduits is that of the longer main channel. SWMM will use the shorter overbank length in its calculations while increasing the main channel roughness to account for its longer length. The modifier is ignored if it is left blank or set to 0.

It allows cut, copy, insert, and paste selected cells in the grid as well as options to insert or delete a row. Clicking the View button will bring up a window that illustrates the shape of the transect cross-section.

C.21 Treatment Editor

The Treatment Editor is invoked whenever the Treatment property of a node is selected from the Property Editor. It displays a list of the project's pollutants with an edit box next to each as shown below. Enter a valid treatment expression in the box next to each pollutant which receives treatment.

C.22 Unit Hydrograph Editor

The Unit Hydrograph Editor is invoked whenever a new unit hydrograph object is created or an existing one is selected for editing. It is used to specify the shape parameters and rain gage for a group of triangular unit hydrographs. These hydrographs are used to compute rainfall-dependent infiltration/inflow (RDII) flow at selected nodes of the drainage system. A UH group can contain up to 12 sets of unit hydrographs (one for each month of the year), and each set can consist of up to 3 individual hydrographs (for short-term, intermediate-term, and long-term responses, respectively) as well as parameters that describe any initial abstraction losses. The editor contains the following data entry fields:

• Name of UH Group: Enter the name assigned to the UH Group.
• Rain Gage Used: Type in (or select from the dropdown list) the name of the rain gage that supplies rainfall data to the unit hydrographs in the group.
• Hydrographs For: Select a month from the dropdown list box for which hydrograph parameters will be defined. Select All Months to specify a default set of hydrographs that apply to all months of the year. Then select specific months that need to have special hydrographs defined. Months listed with a (*) next to them have had hydrographs assigned to them.
• Unit Hydrographs: Select this tab to provide the R-T-K shape parameters for each set of unit hydrographs in selected months of the year. The first row is used to specify parameters for a short-term response hydrograph (i.e., small value of T), the second for a medium-term response hydrograph, and the third for a long-term response hydrograph (largest value of T). It is not required that all three hydrographs be defined and the sum of the three R-values do not have to equal 1. The shape parameters for each UH consist of: 
• • R: the fraction of rainfall volume that enters the sewer system
  • T: the time from the onset of rainfall to the peak of the UH in hours 
  • K: the ratio of time to recession of the UH to the time to peak 
• Initial Abstraction Depth: Select this tab to provide parameters that describe how rainfall will be reduced by any initial abstraction depth available (i.e., interception and depression storage) before it is processed through the unit hydrographs defined for a specific month of the year. Different initial abstraction parameters can be assigned to each of the three unit hydrograph responses. These parameters are:
• • Dmax: the maximum depth of initial abstraction available (in rain depth units) 
  • Drec: the rate at which any utilized initial abstraction is made available again (in rain depth units per day)
  • Do: the amount of initial abstraction that has already been utilized at the start of the simulation (in rain depth units).

If a grid cell is left empty its corresponding parameter value is assumed to be 0. It allows cut, copy and paste text to or from selected cells in the grid.

C.23 Calibration Data Manager

The Calibration Data Manager in GeoSWMM provides a user-friendly interface for managing observed time series data used to calibrate and validate model simulations. It allows users to assign observed data either manually or by importing from external files to specific Subcatchments, Nodes, or Links in the model. The calibration data can be visualized graphically and exported for further analysis. When viewed in the Time Series Plot under the Results section, observed data appears as Observed for comparison with simulated results.

• Name: The name of the Calibration Data Series.
• Object Category: Select Subcatchment, Node or Link.
• Object Name: Choose the specific object name from the dropdown list based on the selected category.
• Calibration Variable: Select the variable to be calibrated based on the object
• 1. 1. 1. Subcatchment: Runoff, Washoff, Groundwater flow, Groundwater Elevation, Snowpack
        2. Node: Water Depth, Water Quality, Lateral Inflow,
        3. Link: Flow Depth, Flow Velocity and Flow

Calibration Data Input and Visualization

• Users can import calibration data from an external file or enter it manually in the data grid.
• To import data, click the () button and select the file. The file format must match the structure of the data entry grid described in Appendix E Section E.7.
• Manual data format should follow this structure:
• • Date Column: Optional date in MM/DD/YYYY format. Enter only when a new date occurs in the series. 
  • Time Column: If dates are used, enter the time of day in 24-hour format (HH:MM) or decimal hours. If dates are not used, enter time as elapsed hours since the start of the simulation.
  • Value Column: Observed numerical values of the time series.
• Click the View () button to display a graph of the entered data in a separate window. The grid supports cut, copy, paste, insert, and delete operations for easy data management.
• Click the Import () button to load observed data directly from an external file into the grid.
• Click OK to save and apply the time series or cancel to discard changes.