United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
(EPA) Storm Water Management Model (SWMM) is a dynamic rainfall–
runoff
Runoff, run-off or RUNOFF may refer to:
* RUNOFF, the first computer text-formatting program
* Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed
* Runoff or run-off, a stock market ...
simulation
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or proc ...
of the surface/subsurface hydrology quantity and
quality
Quality may refer to:
Concepts
*Quality (business), the ''non-inferiority'' or ''superiority'' of something
*Quality (philosophy), an attribute or a property
*Quality (physics), in response theory
*Energy quality, used in various science discipli ...
from primarily urban/suburban areas. It can simulate the Rainfall- runoff, runoff, evaporation, infiltration and groundwater connection for roots, streets, grassed areas, rain gardens and ditches and pipes, for example. The hydrology component of SWMM operates on a collection of subcatchment areas divided into impervious and pervious areas with and without depression storage to predict runoff and
pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...
loads from precipitation, evaporation and
infiltration
Infiltration may refer to:
Science, medicine, and engineering
*Infiltration (hydrology), downward movement of water into soil
*Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings
*Infiltration (me ...
losses from each of the subcatchment. Besides, low impact development (LID) and best management practice areas on the subcatchment can be modeled to reduce the impervious and pervious runoff. The routing or hydraulics section of SWMM transports this water and possible associated
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
constituents through a system of closed pipes, open channels, storage/treatment devices, ponds, storages, pumps, orifices, weirs, outlets, outfalls and other regulators.
SWMM tracks the quantity and quality of the flow generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period composed of multiple fixed or variable time steps. The water quality constituents such as water quality constituents can be simulated from buildup on the subcatchments through washoff to a
hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
network with optional first order decay and linked pollutant removal, best management practice and low-impact development (LID) removal and treatment can be simulated at selected storage nodes. SWMM is one of the
hydrology transport model
An hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s a ...
s which the EPA and other agencies have applied widely throughout North America and through consultants and universities throughout the world. The latest update notes and new features can be found on the EPA website in the download section. Recently added in November 2015 were the EPA SWMM 5.1 Hydrology Manual (Volume I) and in 2016 the EPA SWMM 5.1 Hydraulic Manual (Volume II) and EPA SWMM 5.1 Water Quality (including LID Modules) Volume (III) + Errata.
Program description
The EPA storm water management model (SWMM) is a dynamic rainfall-runoff-routing simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas. The runoff component of SWMM operates on a collection of subcatchment areas that receive precipitation and generate runoff and pollutant loads. The routing portion of SWMM transports this runoff through a system of pipes, channels, storage/treatment devices, pumps, and regulators. SWMM tracks the quantity and quality of runoff generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period divided into multiple time steps.
SWMM accounts for various hydrologic processes that produce runoff from urban areas. These include:
# time-varying rainfall
# evaporation of standing surface water
# snow accumulation and melting
# rainfall interception from depression storage
# infiltration of rainfall into unsaturated soil layers
# percolation of infiltrated water into groundwater layers
# interflow between groundwater and the drainage system
# nonlinear reservoir routing of overland flow
# capture and retention of rainfall/runoff with various types of low impact development (LID) practices.
SWMM also contains a flexible set of hydraulic modeling capabilities used to route runoff and external inflows through the drainage system network of pipes, channels, storage/treatment units and diversion structures. These include the ability to:
# handle networks of unlimited size·
# use a wide variety of standard closed and open conduit shapes as well as natural channels·
# model special elements such as storage/treatment units, flow dividers, pumps, weirs, and orifices·
# apply external flows and water quality inputs from surface runoff, groundwater interflow, rainfall-dependent infiltration/inflow, dry weather sanitary flow, and user-defined inflows
# utilize either kinematic wave or full dynamic wave flow routing methods·
# model various flow regimes, such as backwater, surcharging, reverse flow, and surface ponding·
# apply user-defined dynamic control rules to simulate the operation of pumps, orifice openings, and weir crest levels.
Spatial variability in all of these processes is achieved by dividing a study area into a collection of smaller, homogeneous subcatchment areas, each containing its own fraction of pervious and impervious sub-areas. Overland flow can be routed between sub-areas, between subcatchments, or between entry points of a drainage system.
Since its inception, SWMM has been used in thousands of sewer and stormwater studies throughout the world. Typical applications include:
# design and sizing of drainage system components for flood control
# sizing of detention facilities and their appurtenances for flood control and water quality protection·
# flood plain mapping of natural channel systems, by modeling the river hydraulics and associated flooding problems using prismatic channels·
# designing control strategies for minimizing Combined Sewer Overflow (CSO) and Sanitary Sewer Overflow (SSO)·
# evaluating the impact of inflow and infiltration on sanitary sewer overflows·
# generating non-point source pollutant loadings for waste load allocation studies·
# evaluating the effectiveness of BMPs and Subcatchment LID's for reducing wet weather pollutant loadings. Rainfall-runoff modeling of urban and rural watersheds
# hydraulic and water quality analysis of storm, sanitary, and combined sewer systems
# master planning of sewer collection systems and urban watersheds
# system evaluations associated with USEPA's regulations including NPDES permits, CMOM, and TMDL
# 1D and 2D (surface ponding) predictions of
flood
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
levels and flooding volume
EPA SWMM is
public domain software
Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, ...
that may be freely copied and distributed. The SWMM 5 public domain consists of C engine code and Delphi SWMM 5 graphical user interface code. The C code and Delphi code are easily edited and can be recompiled by students and professionals for custom features or extra output features.
History
SWMM was first developed between 1969–1971 and has undergone four major upgrades since those years. The major upgrades were: (1) Version 2 in 1973-1975, (2) Version 3 in 1979-1981, (3) Version 4 in 1985-1988 and (4) Version 5 in 2001-2004. A list of the major changes and post-2004 changes are shown in Table 1. The current SWMM edition, Version 5/5.2.1, is a complete re-write of the previous Fortran releases in the programming language C, and it can be run under
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
,
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...
,
Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearly ...
,
Windows 8
Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on August 1, 2012; it was subsequently made available for downl ...
,
Windows 10
Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...
and also with a recompilation under
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
. The code for SWMM5 is
open source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
and
public domain
The public domain (PD) consists of all the creative work
A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...
code that can be downloaded from the EPA website.
EPA SWMM 5 provides an integrated graphical environment for editing watershed input data, running hydrologic, hydraulic, real time control and water quality simulations, and viewing the results in a variety of graphical formats. These include color-coded thematic drainage area maps, time series graphs and tables, profile plots, scatter plots and statistical frequency analyses.
The last rewrite of EPA SWMM was produced by the Water Supply and Water Resources Division of the U.S. Environmental Protection Agency's National Risk Management Research Laboratory with assistance from the consulting firm of CDM Inc under a Cooperative Research and Development Agreement (CRADA). SWMM 5 is used as the computational engine for many modeling packages plus components of SWMM5 are in other modeling packages. The major modeling packages that use all or some of the SWMM5 components are shown in the Vendor section. The update history of SWMM 5 from the original SWMM 5.0.001 to the current version SWMM 5.2.1 can be found at the EPA website. SWMM 5 was approved FEMA Model Approval Page in May 2005, with a note about the versions that are approved on the FEMA Approval Page SWMM 5 Version 5.0.005 (May 2005) and up for
NFIP
The National Flood Insurance Program (NFIP) is a program created by the Congress of the United States in 1968 through the National Flood Insurance Act of 1968 (P.L. 90-448). The NFIP has two purposes: to share the risk of flood losses through floo ...
modeling. SWMM 5 is used as the computational engine for many modeling packages (see the SWMM 5 Platform Section of this article) and some components of SWMM5 are in other modeling packages (see the SWMM 5 Vendor Section of this article).
SWMM conceptual model
SWMM conceptualizes a drainage system as a series of water and material flows between several major environmental compartments. These compartments and the SWMM objects they contain include:
The Atmosphere compartment, from which precipitation falls and pollutants are deposited onto the land surface compartment. SWMM uses Rain Gage objects to represent rainfall inputs to the system. The rain gage objects can use time series, external text files or NOAA rainfall data files. The Rain Gage objects can use precipitation for thousands of years. Using the SWMM-CAT Addon to SWMM5 climate change can now be simulated using modified temperature, evaporation or rainfall.
The Land Surface compartment, which is represented by one or more Subcatchment objects. It receives precipitation from the Atmospheric compartment in the form of rain or snow; it sends outflow in the form of infiltration to the Groundwater compartment and also as surface runoff and pollutant loadings to the Transport compartment. The Low Impact Development (LID) controls are part of the Subcatchments and store, infiltrate or evaporate the runoff.
The
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
compartment receives
infiltration
Infiltration may refer to:
Science, medicine, and engineering
*Infiltration (hydrology), downward movement of water into soil
*Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings
*Infiltration (me ...
from the Land Surface compartment and transfers a portion of this inflow to the Transport compartment. This compartment is modeled using Aquifer objects. The connection to the Transport compartment can be either a static boundary or a dynamic depth in the channels. The links in the Transport compartment now also have seepage and evaporation.
The Transport compartment contains a network of conveyance elements (channels, pipes, pumps, and regulators) and storage/treatment units that transport water to outfalls or to treatment facilities. Inflows to this compartment can come from surface runoff, groundwater interflow, sanitary dry weather flow, or from user-defined hydrographs. The components of the Transport compartment are modeled with Node and Link objects.
Not all compartments need to appear in a particular SWMM model. For example, one could model just the transport compartment, using pre-defined hydrographs as inputs. If kinematic wave routing is used, then the nodes do not need to contain an outfall.
Model parameters
The simulated model parameters for subcatchments are surface roughness, depression storage, slope, flow path length; for Infiltration: Horton: max/min rates and decay constant; Green-Ampt: hydraulic conductivity, initial moisture deficit and suction head; Curve Number: NRCS (SCS) Curve number; All: time for saturated soil to fully drain; for Conduits: Manning’s roughness; for Water Quality: buildup/washoff function coefficients, first-order decay coefficients, removal equations. A study area can be divided into any number of individual subcatchments, each of which drains to a single point. Study areas can range in size from a small portion of a single lot up to thousands of acres. SWMM uses hourly or more frequent rainfall data as input and can be run for single events or in a continuous fashion for any number of years.
Hydrology and hydraulics capabilities
SWMM 5 accounts for various hydrologic processes that produce surface and subsurface runoff from urban areas. These include:
# Time-varying rainfall for an unlimited number of rain gages for both design and continuous hyetographs
# evaporation of standing surface water on watersheds and surface ponds
# snowfall accumulation, plowing, and melting
# rainfall interception from depression storage in both impervious and pervious areas
# infiltration of precipitation into unsaturated soil layers
# percolation of infiltrated water into groundwater layers
# interflow between groundwater and pipes and ditches
# nonlinear reservoir routing of watershed overland flow.
Spatial variability in all of these processes is achieved by dividing a study area into a collection of smaller, homogeneous watershed or subcatchment areas, each containing its fraction of pervious and impervious sub-areas. Overland flow can be routed between sub-areas, between subcatchments, or between entry points of a drainage system.
SWMM also contains a flexible set of hydraulic modeling capabilities used to route runoff and external inflows through the drainage system network of pipes, channels, storage/treatment units and diversion structures. These include the ability to:
# Simulate drainage networks of unlimited size
# use a wide variety of standard closed and open conduit shapes as well as natural or irregular channels
# model special elements such as storage/treatment units, outlets, flow dividers, pumps, weirs, and orifices
# apply external flows and water quality inputs from surface runoff, groundwater interflow, rainfall-dependent infiltration/inflow, dry weather sanitary flow, and user-defined inflows
# utilize either steady, kinematic wave or full dynamic wave flow routing methods
# model various flow regimes, such as backwater, surcharging, pressure, reverse flow, and surface ponding
# apply user-defined dynamic control rules to simulate the operation of pumps, orifice openings, and weir crest levels
Infiltration is the process of rainfall penetrating the ground surface into the unsaturated soil zone of pervious subcatchments areas. SWMM5 offers four choices for modeling infiltration:
Classical infiltration method
This method is based on empirical observations showing that infiltration decreases exponentially from an initial maximum rate to some minimum rate over the course of a long rainfall event. Input parameters required by this method include the maximum and minimum infiltration rates, a decay coefficient that describes how fast the rate decreases over time, and the time it takes a fully saturated soil to completely dry (used to compute the recovery of infiltration rate during dry periods).
Modified Horton Method
This is a modified version of the classical Horton Method that uses the cumulative infiltration in excess of the minimum rate as its state variable (instead of time along the Horton curve), providing a more accurate infiltration estimate when low rainfall intensities occur. It uses the same input parameters as does the traditional Horton Method.
Green–Ampt method
This method for modeling infiltration assumes that a sharp wetting front exists in the soil column, separating soil with some initial moisture content below from saturated soil above. The input parameters required are the initial moisture deficit of the soil, the soil's hydraulic conductivity, and the suction head at the wetting front. The recovery rate of moisture deficit during dry periods is empirically related to the hydraulic conductivity.
Curve number method
This approach is adopted from the NRCS (SCS) curve number method for estimating runoff. It assumes that the total infiltration capacity of a soil can be found from the soil's tabulated curve number. During a rain event this capacity is depleted as a function of cumulative rainfall and remaining capacity. The input parameters for this method are the curve number and the time it takes a fully saturated soil to completely dry (used to compute the recovery of infiltration capacity during dry periods).
SWMM also allows the infiltration recovery rate to be adjusted by a fixed amount on a monthly basis to account for seasonal variation in such factors as evaporation rates and groundwater levels. This optional monthly soil recovery pattern is specified as part of a project's evaporation data.
In addition to modeling the generation and transport of runoff flows, SWMM can also estimate the production of pollutant loads associated with this runoff. The following processes can be modeled for any number of user-defined water quality constituents:
# Dry-weather pollutant buildup over different land uses
# pollutant washoff from specific land uses during storm events
# direct contribution of wet and dry rainfall deposition
# reduction in dry-weather buildup due to street cleaning
# reduction in washoff load due to BMPs and LIDs
# entry of dry weather sanitary flows and user-specified external inflows at any point in the drainage system
# routing of water quality constituents through the drainage system
# reduction in constituent concentration through treatment in storage units or by natural processes in pipes and channels.
Rain Gages in SWMM5 supply precipitation data for one or more subcatchment areas in a study region. The rainfall data can be either a user-defined time series or come from an external file. Several different popular rainfall file formats currently in use are supported, as well as a standard user-defined format. The principal input properties of rain gages include:
# rainfall data type (e.g., intensity, volume, or cumulative volume)
# recording time interval (e.g., hourly, 15-minute, etc.)
# source of rainfall data (input time series or external file)
# name of rainfall data source
The other principal input parameters for the subcatchments include:
# assigned rain gage
# outlet node or subcatchment and routing fraction
# assigned land uses
# tributary surface area
# imperviousness and zero percent imperviousness
# slope
# characteristic width of overland flow
# Manning's n for overland flow on both pervious and impervious areas
# depression storage in both pervious and impervious areas
# percent of impervious area with no depression storage.
# infiltration parameters
# snowpack
# groundwater parameters
# LID parameters for each LID Control Used
Routing options
Steady-flow routing represents the simplest type of routing possible (actually no routing) by assuming that within each computational time step flow is uniform and steady. Thus it simply translates inflow hydrographs at the upstream end of the conduit to the downstream end, with no delay or change in shape. The normal flow equation is used to relate flow rate to flow area (or depth).
This type of routing cannot account for channel storage, backwater effects, entrance/exit losses, flow reversal or pressurized flow. It can only be used with dendritic conveyance networks, where each node has only a single outflow link (unless the node is a divider in which case two outflow links are required). This form of routing is insensitive to the time step employed and is really only appropriate for preliminary analysis using long-term continuous simulations.
Kinematic wave
In gravity and pressure driven fluid dynamical and geophysical mass flows such as ocean waves, avalanches, debris flows, mud flows, flash floods, etc., kinematic waves are important mathematical tools to understand the basic features of the associ ...
routing solves the continuity equation along with a simplified form of the momentum equation in each conduit. The latter requires that the slope of the water surface equal the slope of the conduit.
The maximum flow that can be conveyed through a
conduit
Conduit may refer to:
Engineering systems
* Conduit (fluid conveyance), a pipe suitable for carrying either open-channel or pressurized liquids
* Electrical conduit, a protective cover, tube or piping system for electric cables
* Conduit curre ...
is the full normal flow value. Any flow in excess of this entering the inlet node is either lost from the system or can pond atop the inlet node and be re-introduced into the conduit as capacity becomes available.
Kinematic wave routing allows flow and area to vary both spatially and temporally within a conduit. This can result in attenuated and delayed outflow hydrographs as inflow is routed through the channel. However this form of routing cannot account for backwater effects, entrance/exit losses, flow reversal, or pressurized flow, and is also restricted to dendritic network layouts. It can usually maintain numerical stability with moderately large time steps, on the order of 1 to 5 minutes. If the aforementioned effects are not expected to be significant then this alternative can be an accurate and efficient routing method, especially for long-term simulations.
Dynamic wave routing solves the complete one-dimensional
Saint Venant
Saint-Venant ( vls, Papingem) is a commune in the Pas-de-Calais department (administrative division) in the Hauts-de-France region of France.
Geography
Saint-Venant is situated some northwest of Béthune and west of Lille, at the junction of ...
flow equations and therefore produces the most theoretically accurate results. These equations consist of the continuity and momentum equations for conduits and a volume continuity equation at nodes.
With this form of routing it is possible to represent pressurized flow when a closed conduit becomes full, such that flows can exceed the full normal flow value. Flooding occurs when the water depth at a node exceeds the maximum available depth, and the excess flow is either lost from the system or can pond atop the node and re-enter the drainage system.
Dynamic wave routing can account for channel storage, backwater, entrance/exit losses, flow reversal, and pressurized flow. Because it couples together the solution for both water levels at nodes and flow in conduits it can be applied to any general network layout, even those containing multiple downstream diversions and loops. It is the method of choice for systems subjected to significant backwater effects due to downstream flow restrictions and with flow regulation via weirs and orifices. This generality comes at a price of having to use much smaller time steps, on the order of a minute or less (SWMM can automatically reduce the user-defined maximum time step as needed to maintain numerical stability).
Integrated hydrology/hydraulics
One of the great advances in SWMM 5 was the integration of urban/suburban
subsurface flow
Subsurface flow, in hydrology, is the flow of water beneath earth's surface as part of the water cycle.
In the water cycle, when precipitation falls on the earth's land, some of the water flows on the surface forming streams and rivers. The rema ...
with the hydraulic computations of the drainage network. This advance is a tremendous improvement over the separate subsurface hydrologic and hydraulic computations of the previous versions of SWMM because it allows the modeler to conceptually model the same interactions that occur physically in the real open channel/shallow aquifer environment. The SWMM 5 numerical engine calculates the surface runoff, subsurface hydrology and assigns the current climate data at either the wet or dry hydrologic time step. The hydraulic calculations for the links, nodes, control rules and boundary conditions of the network are then computed at either a fixed or variable time step within the hydrologic time step by using interpolation routines and the simulated hydrologic starting and ending values. The versions of SWMM 5 greater than SWMM 5.1.007 allow the modeler to simulate climate changes by globally changing the rainfall, temperature, and evaporation using monthly adjustments.
An example of this integration was the collection of the different SWMM 4 link types in the runoff, transport and Extran blocks to one unified group of closed conduit and open channel link types in SWMM 5 and a collection of node types (Figure 2).
SWMM contains a flexible set of hydraulic modeling capabilities used to route runoff and external inflows through the drainage system network of pipes, channels, storage/treatment units, and diversion structures. These include the ability to do the following:
Handle drainage networks of unlimited size. Use a wide variety of standard closed and open conduit shapes as well as natural channels. Model special elements, such as storage/treatment units, flow dividers, pumps, weirs, and orifices. Apply external flows and water quality inputs from surface runoff, groundwater interflow, rainfall-dependent infiltration/inflow, dry weather sanitary flow, and user-defined inflows. Utilize either kinematic wave or full dynamic wave flow routing methods. Model various flow regimes, such as backwater, surcharging, reverse flow, and surface ponding. apply user-defined dynamic control rules to simulate the operation of pumps, orifice openings, and weir crest levels. Percolation of infiltrated water into groundwater layers. Interflow between groundwater and the drainage system. Nonlinear reservoir routing of overland flow. Runoff reduction via LID controls.
Low-impact development components
The low-impact development (LID) function was new to SWMM 5.0.019/20/21/22 and SWMM 5.1+ It is integrated within the subcatchment and allows further refinement of the overflows, infiltration flow and evaporation in
rain barrel
A rainwater tank (sometimes called a rain barrel in North America in reference to smaller tanks, or a water butt in the UK) is a water tank used to collect and store rain water runoff, typically from rooftops via pipes. Rainwater tanks are devices ...
,
swale
Swale or Swales may refer to:
Topography
* Swale (landform), a low tract of land
** Bioswale, landform designed to remove silt and pollution
** Swales, found in the formation of Hummocky cross-stratification
Geography
* River Swale, in North ...
s,
permeable paving
Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques ...
,
green roof
A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage ...
,
rain garden
Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites t ...
,
bioretention
Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. The main objective of the bioretention cell is to attenuate peak runoff as well as to remove stormwater runoff pollutants.
Construction of ...
and
infiltration trench
A percolation trench, also called an infiltration trench, is a type of best management practice (BMP) that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake ...
. The term Low-impact development (Canada/US) is used in Canada and the United States to describe a land planning and engineering design approach to managing stormwater runoff. In recent years many states in the US have adopted LID concepts and standards to enhance their approach to reducing the harmful potential for storm water pollution in new construction projects. LID takes many forms but can generally be thought of as an effort to minimize or prevent concentrated flows of storm water leaving a site. To do this the LID practice suggests that when impervious surfaces (concrete, etc.) are used, they are periodically interrupted by pervious areas which can allow the storm water to infiltrate (soak into the earth)
A variety of sub-processes in each LID can be defined in SWMM5 such as: surface, pavement, soil, storage, drainmat and drain.
Each type of LID has limitations on the type of sub-process allowed by SWMM 5. It has a good report feature and a LID summary report can be in the rpt file and an external report file in which the surface depth can be seen, soil moisture, storage depth, surface inflow, evaporation, surface infiltration, soil percolation, storage infiltration, surface outflow and the LID continuity error. There can be multiple LID's per subcatchment and no issues have been had because of having many complicated LID sub networks and processes inside the Subcatchments of SWMM 5 or any continuity issues not solvable by a smaller wet hydrology time step. The types of SWMM 5 LID compartments are: storage, underdrain, surface, pavement and soil. a bio-retention cell has storage, underdrain and surface compartments. an infiltration trench lid has storage, underdrain and surface compartments. A porous pavement LID has storage, underdrain and pavement compartments. A rain barrel has only storage and underdrain compartments and a vegetative swale LID has a single surface compartment. Each type of LID shares different underlying compartment objects in SWMM 5 which are called layers.
This set of equations can be solved numerically at each runoff time step to determine how an inflow hydrograph to the LID unit is converted into some combination of runoff hydrograph, sub-surface storage, sub-surface drainage, and infiltration into the surrounding native soil. In addition to Street Planters and Green Roofs, the bio-retention model just described can be used to represent Rain Gardens by eliminating the storage layer and also Porous Pavement systems by replacing the soil layer with a pavement layer.
The surface layer of the LID receives both direct rainfall and runon from other areas. It loses water through infiltration into the soil layer below it, by evapotranspiration (ET) of any water stored in depression storage and vegetative capture, and by any surface runoff that might occur. The soil layer contains an amended soil mix that can support vegetative growth. It receives infiltration from the surface layer and loses water through ET and by percolation into the storage layer below it. The storage layer consists of coarse crushed stone or gravel. It receives percolation from the soil zone above it and loses water by either infiltration into the underlying natural soil or by outflow through a perforated pipe underdrain system.
New , the EPA's National Stormwater Calculator is a Windows desktop application that estimates the annual amount of rainwater and frequency of runoff from a specific site anywhere in the United States. Estimates are based on local soil conditions, land cover, and historic rainfall records. The Calculator accesses several national databases that provide soil, topography, rainfall, and
evaporation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
information for the chosen site. The user supplies information about the site's land cover and selects the types of low impact development (LID) controls they would like to use on-site. The LID Control features in SWMM 5.1.013 include the following among types of
Green infrastructure
Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
:
* StreetPlanter: Bioretention cells are depressions that contain vegetation grown in an engineered soil mixture placed above a gravel drainage bed. They provide storage, infiltration and evaporation of both direct rainfall and runoff captured from surrounding areas. Street planters consist of concrete boxes filled with an engineered soil that supports vegetative growth. Beneath the soil is a gravel bed that provides additional storage. The walls of a planter extend 3 to 12 inches above the soil bed to allow for ponding within the unit. The thickness of the soil growing medium ranges from 6 to 24 inches while gravel beds are 6 to 18 inches in depth. The planter's capture ratio is the ratio of its area to the impervious area whose runoff it captures.
* Raingarden: Rain gardens are a type of bio-retention cell consisting of just the engineered soil layer with no gravel bed below it. Rain Gardens are shallow depressions filled with an engineered soil mix that supports vegetative growth. They are usually used on individual home lots to capture roof runoff. Typical soil depths range from 6 to 18 inches. The capture ratio is the ratio of the rain garden's area to the impervious area that drains onto it.
* GreenRoof: Green roofs are another variation of a bio-retention cell that have a soil layer laying atop a special drainage mat material that conveys excess percolated rainfall off of the roof. Green Roofs (also known as Vegetated Roofs) are bio-retention systems placed on roof surfaces that capture and temporarily store rainwater in a soil growing medium. They consist of a layered system of roofing designed to support plant growth and retain water for plant uptake while preventing ponding on the roof surface. The thickness used for the growing medium typically ranges from 3 to 6 inches.
* InfilTrench: infiltration trenches are narrow ditches filled with gravel that intercept runoff from upslope impervious areas. They provide storage volume and additional time for captured runoff to infiltrate the native soil below.
* PermPave or Permeable Pavements: Continuous Permeable Pavement systems are excavated areas filled with gravel and paved over with a porous concrete or asphalt mix. Continuous Permeable Pavement systems are excavated areas filled with gravel and paved over with a porous concrete or asphalt mix. Modular Block systems are similar except that permeable block pavers are used instead. Normally all rainfall will immediately pass through the pavement into the gravel storage layer below it where it can infiltrate at natural rates into the site's native soil. Pavement layers are usually 4 to 6 inches in height while the gravel storage layer is typically 6 to 18 inches high. The Capture Ratio is the percent of the treated area (street or parking lot) that is replaced with permeable pavement.
*
Cistern
A cistern (Middle English ', from Latin ', from ', "box", from Greek ', "basket") is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by t ...
: Rain Barrels (or Cisterns) are containers that collect roof runoff during storm events and can either release or re-use the rainwater during dry periods. Rain harvesting systems collect runoff from rooftops and convey it to a cistern tank where it can be used for non-potable water uses and on-site infiltration. The harvesting system is assumed to consist of a given number of fixed-sized cisterns per 1000 square feet of rooftop area captured. The water from each cistern is withdrawn at a constant rate and is assumed to be consumed or infiltrated entirely on-site.
* VegSwale: Vegetative swales are channels or depressed areas with sloping sides covered with grass and other vegetation. They slow down the conveyance of collected runoff and allow it more time to infiltrate the native soil beneath it.
Infiltration basin
An infiltration basin (or recharge basin) is a form of engineered sump or percolation pond that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It i ...
s are shallow depressions filled with grass or other natural vegetation that capture runoff from adjoining areas and allow it to infiltrate into the soil.
* Wet ponds are frequently used for water quality improvement,
groundwater recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...
, flood protection, aesthetic improvement or any combination of these. Sometimes they act as a replacement for the natural absorption of a forest or other natural process that was lost when an area is developed. As such, these structures are designed to blend into neighborhoods and are viewed as an amenity.
* Dry ponds temporarily store water after a storm, but eventually empties out at a controlled rate to a downstream water body.
* Sand filters generally control runoff water quality, providing very limited flow rate control. A typical sand filter system consists of two or three chambers or basins. The first is the sedimentation chamber, which removes floatables and heavy sediments. The second is the filtration chamber, which removes additional pollutants by filtering the runoff through a sand bed. The third is the discharge chamber.
Infiltration trench
A percolation trench, also called an infiltration trench, is a type of best management practice (BMP) that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake ...
, is a type of best management practice (BMP) that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It is a shallow excavated trench filled with gravel or crushed stone that is designed to infiltrate stormwater though permeable soils into the groundwater aquifer.
* A Vegatated filter strip is a type of buffer strip that is an area of vegetation, generally narrow and long, that slows the rate of runoff, allowing sediments, organic matter, and other pollutants that are being conveyed by the water to be removed by settling out. Filter strips reduce erosion and the accompanying stream pollution, and can be a best management practice.
Other LID like concepts around the world include
seepage
Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids (usually air and wat ...
,
orifices
A body orifice is any opening in the body of an animal.
External
In a typical mammalian body such as the human body, the external body orifices are:
* The nostrils, for breathing and the associated sense of smell
* The mouth, for eating, bre ...
,
Weirs
A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...
, seepage and evaporation from natural channels):
constructed wetlands
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. ...
, wet ponds, dry ponds, infiltration basin, non-surface sand filters, vegetated filterstrips, vegetated filterstrip and infiltration basin. A WetPark would be a combination of wet and dry ponds and LID features. A WetPark is also considered a constructed wetland.
SWMM5 components
The SWMM 5.0.001 to 5.1.015 main components are rain gages, watersheds, LID controls or BMP features such as Wet and Dry Ponds, nodes, links, pollutants, landuses, time patterns, curves, time series, controls, transects, aquifers, unit hydrographs, snowmelt and shapes (Table 3). Other related objects are the types of Nodes and the Link Shapes. The purpose of the objects is to simulate the major components of the
hydrologic cycle
The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly const ...
, the hydraulic components of the drainage, sewer or stormwater network, and the buildup/washoff functions that allow the simulation of water quality constituents. A watershed simulation starts with a precipitation time history. SWMM 5 has many types of open and closed pipes and channels: dummy, circular, filled circular, rectangular closed, rectangular open, trapezoidal, triangular, parabolic, power function, rectangular triangle, rectangle round, modified baskethandle, horizontal ellipse, vertical ellipse, arch, eggshaped, horseshoe, gothic, catenary, semielliptical, baskethandle, semicircular, irregular, custom and force main.
The major objects or hydrology and hydraulic components in SWMM 5 are:
# GAGE rain gage
# SUBCATCH subcatchment
# NODE conveyance system node
# LINK conveyance system link
# POLLUT pollutant
# LANDUSE land use category
# TIMEPATTERN, dry weather flow time pattern
# CURVE generic table of values
# TSERIES generic time series of values
# CONTROL conveyance system control rules
# TRANSECT irregular channel cross-section
# AQUIFER groundwater aquifer
# UNITHYD RDII unit hydrograph
# SNOWMELT snowmelt parameter set
# SHAPE custom conduit shape
# LID LID treatment units
The major overall components are called in the SWMM 5 input file and C code of the simulation engine: gage, subcatch, node, link, pollute, landuse, timepattern, curve, tseries, control, transect, aquifer, unithyd, snowmelt, shape and lid. The subsets of possible nodes are: junction, outfall, storage and divider. Storage Nodes are either tabular with a depth/area table or a functional relationship between area and depth. Possible node inflows include: external_inflow, dry_weather_inflow, wet_weather_inflow, groundwater_inflow, rdii_inflow, flow_inflow, concen_inflow, and mass_inflow. The dry weather inflows can include the possible patterns: monthly_pattern, daily_pattern, hourly_pattern, and weekend_pattern.
The SWMM 5 component structure allows the user to choose which major hydrology and hydraulic components are using during the simulation:
# Rainfall/runoff with infiltration options: horton, modified horton, green ampt and curve number
# RDII
# Water Quality
# Groundwater
# Snowmelt
# Flow Routing with Routing Options: Steady State, Kinematic Wave and Dynamic Wave
SWMM 3 and 4 to 5 converter
The SWMM 3 and SWMM 4 converter can convert up to two files from the earlier SWMM 3 and 4 versions at one time to SWMM 5. Typically one would convert a Runoff and Transport file to SWMM 5 or a Runoff and Extran File to SWMM 5. If there is a combination of a SWMM 4 Runoff, Transport and Extran network then it will have to be converted in pieces and the two data sets will have to be copied and pasted together to make one SWMM 5 data set. The x,y coordinate file is only necessary if there are not existing x, y
coordinates
In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space. The order of the coordinates is sig ...
The_Storm_Water_Management_Model_Climate_change.html" ;"title="ini_file.html" ;"title="set. The command File=>Define Ini File can be used to define the location of the ini file">set. The command File=>Define Ini File can be used to define the location of the ini file. The ini file will save the conversion project input data files and directories.
The SWMMM3 and SWMM 3.5 files are fixed format. The SWMM 4 files are free format. The converter will detect which version of SWMM is being used. The converted files can be combined using a text editor to merge the created inp files.
SWMM-CAT Climate Change AddOn
The Storm Water Management Model Climate change">Climate Adjustment Tool (SWMM-CAT) is a new addition to SWMM5 (December 2014). It is a simple to use software utility that allows future climate change projections to be incorporated into the Storm Water Management Model (SWMM). SWMM was recently updated to accept a set of monthly adjustment factors for each of these time series that could represent the impact of future changes in climatic conditions. SWMM-CAT provides a set of location-specific adjustments that derived from global climate change models run as part of the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 3 (CMIP3) archive (Figure 4). SWMM-CAT is a utility that adds location-specific climate change adjustments to a Storm Water Management Model (SWMM) project file. Adjustments can be applied on a monthly basis to air temperature, evaporation rates, and precipitation, as well as to the 24-hour design storm at different recurrence intervals. The source of these adjustments are global climate change models run as part of the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 3 (CMIP3) archive. Downscaled results from this archive were generated and converted into changes with respect to historical values by USEPA's CREAT project.
The following steps are used to select a set of adjustments to apply to SWMM5:
1) Enter the latitude and longitude coordinates of the location if available or its 5-digit zip code. SWMM-CAT will display a range of climate change outcomes for the CMIP3 results closest to the location.
2) Select whether to use climate change projections based on either a near-term or far-term projection period. The displayed climate change outcomes will be updated to reflect the chosen choice.
3) Select a climate change outcome to save to SWMM. There are three choices that span the range of outcomes produced by the different global climate models used in the CMIP3 project. The Hot/Dry outcome represents a model whose average temperature change was on the high end and whose average rainfall change was on the lower end of all model projections. The Warm/Wet outcome represents a model whose average temperature change was on the lower end and whose average rainfall change was on the wetter end of the spectrum. The Median outcome is for a model whose temperature and rainfall changes were closest to the median of all models.
4) Click the Save Adjustments to SWMM link to bring up a dialog form that will allow the selection of an existing SWMM project file to save the adjustments to. The form will also allow the selection of which type of adjustments (monthly temperature, evaporation, rainfall, or 24-hour design storm) to save. Conversion of temperature and evaporation units is automatically handled depending on the unit system (US or SI) detected in the SWMM file.
EPA stormwater calculator based on SWMM5
Other external programs that aid in the generation of data for the EPA SWMM 5 model include: SUSTAIN, BASINS, SSOAP, and the EPA’s National Stormwater Calculator (SWC) which is a desktop application that estimates the annual amount of rainwater and frequency of runoff from a specific site anywhere in the United States (including Puerto Rico). The estimates are based on local soil conditions, land cover, and historic rainfall records (Figure 5).
SWMM platforms
The SWMM5 engine is used by a variety of software packages, including many commercial software packages. Some of these software packages include:
*EPA-SWMM from
EPA
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
*InfoWorks ICM SWMM, InfoDrainage, and InfoSWMM Developed by Innovyze An Autodesk Company by
Autodesk
Autodesk, Inc. is an American multinational software corporation that makes software products and services for the architecture, engineering, construction, manufacturing, media, education, and entertainment industries. Autodesk is headquartered ...
*InfoWorks ICM which has RDII, Water Quality, and Hydrology Components from SWMM5. Developed by Innovyze An Autodesk Company by
Autodesk
Autodesk, Inc. is an American multinational software corporation that makes software products and services for the architecture, engineering, construction, manufacturing, media, education, and entertainment industries. Autodesk is headquartered ...
*Autodesk Storm and Sanitary Analysis from
Autodesk
Autodesk, Inc. is an American multinational software corporation that makes software products and services for the architecture, engineering, construction, manufacturing, media, education, and entertainment industries. Autodesk is headquartered ...
*PCSWMM
*MIKE URBAN
*SewerGEMS and CivilStorm from Bentley Systems, Inc.
*Fluidit Sewer and Fluidit Storm
*Flood Modeller by
Jacobs
Jacobs may refer to:
Businesses and organisations
*Jacob's, a brand name for several lines of biscuits and crackers in Ireland and the UK
*Jacobs (coffee), a brand of coffee
* Jacobs Aircraft Engine Company, former American aircraft engine compan ...
*GeoSWMM
*Giswater
*GISpipe GIS-based EPANET and SWMM integration software.
*PySWMM by OpenWaterAnalyticsMcDonnell et al., (2020). PySWMM: The Python Interface to Stormwater Management Model (SWMM). Journal of Open Source Software, 5(52), 2292, https://doi.org/10.21105/joss.02292
See also
*
SWAT model SWAT (Soil & Water Assessment Tool) is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. SWAT is a public domain software enabled model actively supported by the USDA Agricultural R ...
*
Stochastic empirical loading and dilution model
Stochastic (, ) refers to the property of being well described by a random probability distribution. Although stochasticity and randomness are distinct in that the former refers to a modeling approach and the latter refers to phenomena themselve ...
Hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
*
Hydraulics
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
*
Surface runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when th ...
*
Precipitation (meteorology)
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...
*
Antecedent moisture {{Refimprove, date=November 2008
In hydrology and sewage collection and disposal, antecedent moisture is the relative wetness or dryness of a watershed or sanitary sewershed. Antecedent moisture conditions change continuously and can have a very si ...
*
Evapotranspiration
Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpi ...
*
EPANET
EPANET (Environmental Protection Agency Network Evaluation Tool) is a public domain, water distribution system modeling software package developed by the United States Environmental Protection Agency's (EPA) Water Supply and Water Resources Divisi ...
*
Rainfall
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
*
Hydrological transport model
An hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s a ...
*
Computer simulation
Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...
*
Water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...
*
Water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
*
Surface-water hydrology
Surface-water hydrology is the sub-field of hydrology concerned with above-earth water, in contrast to groundwater hydrology that deals with water below the surface of the Earth. Its applications include rainfall and runoff, the routes that surface ...