Appendix A: Model Fact Sheets
SWMM: Storm Water Management Model
Contact Information
SWMM 4.4 and previous versions: Wayne C. Huber Oregon State
University Dept. of Civil, Construction, and Environmental
Engineering 202 Apperson Hall Corvallis, Oregon 97331-2302
(541) 737-4934
wayne.huber@orst.edu
SWMM version 5: Lewis Rossman
U.S Environmental Protection Agency Office of Research and
Development Water Supply and Water Resources Division 26 West
Martin Luther King Drive Cincinnati, OH 45268
(513) 569-7603
rossman.lewis@epa.gov
Download Information
Availability: Nonproprietary SWMM 4.4: http://ccee.oregonstate.edu/swmm
SWMM 5 (available for beta testing): http://www.epa.gov/ednnrmrl/swmm/index.htm
Cost: N/A
Model Overview/Abstract
SWMM is a dynamic rainfall-runoff simulation model developed
by EPA. It is applied primarily to urban areas and for single-event
or long-term (continuous) simulation using various timesteps (Huber
and Dickinson, 1988). It was developed for the analysis of surface
runoff and flow routing through complex urban sewer systems. The
latest official version of SWMM is 4.4h, which is recommended for
all users. EPA SWMM5 is a completely revised and updated release of
SWMM. The first beta test version SWMM5 was released in June 2003.
However, SWMM5 is still under development, with additional
functions being incorporated and released over time. In SWMM, flow
routing is performed for surface and sub-surface conveyance and
groundwater systems, including the options of nonlinear reservoir
channel routing and fully dynamic hydraulic flow routing. In the
fully dynamic hydraulic flow routing option, SWMM simulates
backwater, surcharging, pressure flow, and looped connections. SWMM
has a variety of options for quality simulation, including
traditional buildup and washoff formulation as well as rating
curves and regression techniques. Universal Soil Loss Equation
(USLE) is included to simulate soil erosion. SWMM incorporates
first order decay and particle settling mechanism in pollutant
transport simulations and includes an option of simple
scour-deposition routine. Storage, treatment, and other BMPs can
also be simulated.
Model Features
•
Watershed hydrology and water quality
•
Stream/conduit transport
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Appendix A: Model Fact Sheets
•
Urban stormwater and sewage systems
Model Areas Supported
Watershed High Receiving Water Medium Ecological None Air None
Groundwater Low
Model Capabilities
Conceptual Basis
The basic spatial unit for SWMM is the subcatchment into which
the modeled watershed is subdivided. Multiple small subwatersheds
and representative streams may be networked together to represent a
larger watershed drainage area.
Scientific Detail
Infiltration is calculated using the Horton or Green-Ampt
methods, at the user’s choice. A version of Manning’s equation is
used to estimate flow rate from the subcatchment area based on a
conceptual model of the subcatchment as a “nonlinear reservoir.”
The lumped storage scheme is applied for soil/groundwater modeling.
For impervious areas, a linear formulation is used to compute
daily/hourly increases in particle accumulation. For pervious
areas, a modified USLE determines sediment load. The concept of
potency factors is applied to simulate pollutants other than
sediment.
The Transport block has kinematic wave routing of flow and
quality, base flow generation, and infiltration capabilities and it
routes flow through user-defined system ranges from natural channel
to concrete pipes. The EXTRAN block carries out a numerical
solution of the complete St. Venant equations for urban
drainageways and conduits, by modeling the network as a link-node
system. SWMM can be directly interfaced with EPA’s WASP receiving
water quality model.
Model Framework
•
Subwatersheds and watershed
•
Channel/pipe network
•
One-dimensional flow and pollutant routing
Scale
Spatial Scale
• Subwatershed of flexible size
Temporal Scale
• User-defined timestep, typically minutes to hourly
Assumptions
•
The model performs best in urbanized areas with impervious
drainage, although it has been widely used elsewhere.
•
Model parameters for quantity and quality simulations are
developed such that the model will be calibrated to enhance its
capability.
•
Water table elevation is assumed to be fixed.
•
All the pollutants entering the waterbodies are sediment
adsorbed.
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Appendix A: Model Fact Sheets
Model Strengths
•
Fully dynamic hydraulic routing
•
Hydraulic structure (manhole, weir, orifice, etc.)
simulation
•
Overland flow routing between pervious and impervious areas
within a subcatchment (latest version)
•
Various options for quality simulation, including buildup and
washoff, rating curves, and regression techniques
Model Limitations
•
Only considers settling and first-order decay in in-stream
pollutant routing and transformation
•
Weak groundwater simulation capability
Application History
SWMM has been applied to urban hydrologic quantity/quality
problems in scores of U.S. cities as well as extensively in Canada,
Europe, and Australia (Donigian and Huber, 1991; Huber, 1992). The
model has been used for very complex hydraulic analysis for
combined sewer overflow mitigation, as well as for many stormwater
management planning studies and pollution abatement projects
(Huber, 1992). Warwick and Tadepalli (1991) describe calibration
and verification of SWMM on a 10-square-mile urbanized watershed in
Dallas, Texas. Tsihrintzis, et al., (1995) describe SWMM
applications to four watersheds in South Florida representing high-
and low-density residential, commercial, and highway land
uses.
Model Evaluation
The applications are primarily limited to urban areas.
Model Inputs
•
Data requirements for hydrologic simulation include area,
imperviousness, slope, roughness, width, depression storage, and
infiltration parameters. Land use data are used to determine ground
cover type for each model subarea.
•
Depending on what options are set for the loading
calculations, additional parameters are necessary (e.g., buildup
coefficients would be needed for the dry weather buildup
simulation).
•
Additional data are necessary if the user intends to model
subsurface drainage and interflow.
•
Depending on the stormwater system, dimensions, slope,
roughness coefficients, elevations, and storage are required.
•
Continuous records of evapotranspiration, temperature, and
solar intensity are required.
Users’ Guide
•
Huber, W.C. and R.E. Dickinson. 1988 Storm Water Management
Model User's Manual, Version 4. EPA/600/3-88/001a (NTIS
PB88-236641/AS). U.S. Environmental Protection Agency, Athens, GA,
pp.595
•
Roesner, L.A., J.A. Aldrich and R.E. Dickinson. 1988. Storm
Water Management Model User's Manual, Version 4: Addendum I,
EXTRAN. EPA/600/3-88/001b (NTIS PB88236658/AS). U.S. Environmental
Protection Agency, Athens, GA. pp.203
•
A revised and more readable User’s Guide from William James at
CHI can be purchased at
Cost: $85
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Appendix A: Model Fact Sheets
Technical Hardware/Software Requirements
Computer hardware:
• PC
Operating system:
• DOS and Windows
Programming language:
•
FORTRAN (v4.4 and previous versions)
•
C (v5)
Runtime estimates:
• Minutes
Linkages Supported
• SWMM can directly be interfaced with EPA’s WASP receiving
water quality model.
Related Systems
PCSWMM, XP-SWMM, MIKE-SWMM
Sensitivity/Uncertainty/Calibration
SWMM 4.4 includes a STATISTICS module, which performs simple
statistical analyses on both quantity and quality parameters.
Model Interface Capabilities
• SWMM 5 includes a Graphical User Interface for input data
preparation and output data display
References
Donigian, A.S., Jr., and W.C. Huber. 1991. Modeling of
Nonpoint Source Water Quality in Urban and Non-urban Areas.
EPA/600/3-91/039. U.S. Environmental Protection Agency,
Environmental Research Laboratory, Athens, GA.
Huber, W. C. 1992. Experience with the U.S. EPA SWMM Model for
Analysis and Solution of Urban Drainage Problems. In Proceedings,
Inundaciones Y Redes De Drenaje Urbano, ed. J. Dolz, M. Gomez, and
J. P. Martin, eds., Colegio de Ingenieros de Caminos, Canales Y
Puertos. Universitat Politecnica de Catalunya. Barcelona, Spain,
pp. 199-220.
Huber, W.C. 2001. New Options for Overland Flow Routing in
SWMM. American Society of Civil Engineers-Environmental and Water
Resources Institute, World Water and Environmental Congress,
Orlando, FL.
Huber, W.C., and R.E. Dickinson. 1988. Storm Water Management
Model Version 4, User’s Manual. EPA 600/ 388/
001a (NTIS PB88-236641/ AS). U.S. Environmental Protection
Agency, Athens, GA.
Irvine, K.N., B.G. Loganathan, E.J. Pratt and H.C. Sikka.
1993. Calibration of PCSWMM to estimate metals, PCBs and HCB in
CSOs from an industrial sewershed. In W. James, ed. New Techniques
for Modeling the Management of Stormwater Quality Impacts. Lewis
Publishers, Boca Raton, FL. pp. 215-242.
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Appendix A: Model Fact Sheets
James, W., W. C. Huber, R. E. Pitt, R. E. Dickinson, and R. C.
James. 2002. Water Systems Models [1]: Hydrology, User’s guide to
SWMM4 RUNOFF and Supporting Modules and to PCSWMM. Version 2.4.
Computational Hydraulics International, Guelph, Ontario, Canada.
pp. 311.
James, W., W. C. Huber, R. E. Pitt, R. E. Dickinson, L. A.
Roesner, J. A. Aldrich, and R. C. James. 2002 Water Systems Models
[2]: Hydraulics, User’s guide to SWMM4 TRANSPORT, EXTRAN and
STORAGE Modules and to PCSWMM. Version 2.4. Computational
Hydraulics International. Guelph, Ontario, Canada. pp. 359.
Tshihrintzis, V. A., R. Hamid, and H. R. Fuentes. 1995.
Calibration and verification of watershed quality model SWMM in
sub-tropical urban areas. In Proceedings of the First International
Conference - Water Resources Engineering. American Society of Civil
Engineers, San Antonio, TX. pp 373-377.
Tsihrintzis, V. and R. Hamid. 1998. Runoff Quality Prediction
from Small Urban Catchments using SWMM. Hydrological Processes, 12
(2):311-329.
Warwick, J. J., and P. Tadepalli. 1991. Efficacy of SWMM
application. Journal of Water Resources Planning and Management
117(3):352-366.
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