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INTRODUCTION TOEPA SWMM 5.0
Rodrigo Concha JopiaFLUMEN Research Institute
Technical University ofCatalonia UPC
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Introduction:What is EPA SWMM 5.0?
EPA SWMMEnvironmentalProtection Agency
StormWaterManagementModel
SWMM is a distributed dynamic rainfall-runoff simulation model used forsingle event or long-term (continuous) simulation of runoff quantity and
quality from primarily urban areas
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SWMMs Process Models
Precipitation
Snowmelt
SurfaceRunoff
Evaporation/
Infiltration
Groundwater
Overland Flow
Channel, Pipe &Storage Routing
Washoff
SanitaryFlows
RDII
Treatment / Diversion
Buildup
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Key Hydrological Features
User-defined subcatchment areasSpatial Representation
Heat Balance/Degree Day ModelSnowmelt
Localized Two-Zone Flux ModelGroundwater Nonlinear ReservoirOverland Flow
Horton MethodGreen-Ampt Method
SCS Method
InfiltrationUser suppliedInterception/Evaporation
User suppliedRainfall
Process In SWMM 5
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Key Hydraulic Features
Overflow or PondingFlooding
Rule-Based ControlsModulated Controls (including PID)
Variable Speed Gate Opening
Controls
Steady FlowKinematic Wave (nonlinear form)
Dynamic Wave (semi-implicit)
Flow Routing
20 common shapes + irregular openchannels + custom closed conduits
Conduit Shapes
Nodes (Junction, Storage, Outfall)Links (Conduits, Pumps, Regulators)
Drainage Elements
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Key Water Quality Features
User-defined functionsDrainage System Treatment
CSTR modelDrainage System Routing
User-defined, Sanitary DWF,RDII inflow Non-Runoff Loads
User-assigned percent reductionBMP Removal
Rate proportional to runoff and
buildup or can use an EMC
Pollutant Washoff
Power, exponential or saturationfunction of timePollutant Buildup
Process In SWMM 5
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Typical Applications of SWMM Design and sizing of drainage system components
including detention facilities Flood plain mapping of natural channel systems Control of combined and sanitary sewer overflows Generating non-point source pollutant loadings for waste
load allocation studies Evaluating BMPs and LIDs for sustainability goals
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SWMM version timeline
1971 - SWMM 1 (M&E, UF, WRE)1975 - SWMM 2 (UF)
1981 - SWMM 3 (UF & CDM)1983 - SWMM 3.3 (PC Version)1988 - SWMM 4 (UF & CDM & OSU)2004 SWMM 5 (EPA & CDM)
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No sediment transport and erosion routines No pollutants routing in receiving waters and in the
sub-surface flow It is a hidrological-hydraulics analysis tool, not an
automatic design tool No direct linkage to GIS
SWMM 5.0 Limitations
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Program structure
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Example of .INP file
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SWMM 5 Objects
Visual Objects :elements thatconstitute thedrainage system
Non visualObjects : severaldata (tables,timeseries, etc.)neccesary inorder to peformsimulations
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Conceptual modeling scheme used bySWMM 5
Atmosferic compartmentPrecipitation falls on theLand Surface compartment Land SurfacecompartmentImportant hydrologicalprocess are modeled Rainfall lossesSurface runoff
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Conceptual modeling scheme used bySWMM 5.0
Groundwater compartmentReceives infiltration fromLand Surface compartment
Transport compartmentNetwork of conveyanceelements: channels, pipes,manholes, etc.
Use of Nodes and Links inorder to represent thisnetwork
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Key parameters for subcatchment objetcs
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Node Link network representation(fromRoesner et al.,1992)
Nodes
Links
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Non visual object categories
HydrologyClimatologyAquifersSnow packs
Hydraulic TransectsUnit HydrographsControl RulesExternal Inflows
Water QualityPollutantsLand UsesTreatments
GeneralCurvesTime SeriesTime Patterns
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Basic steps developing a new SWMM 5project from scratch
Specify a set of options and common objectproperties (Measurement units, offsets, etc.) Draw a scheme of your catchment (ornetwork) using Visual Objects Edit the properties of Visual Objetcs thatmake up your project
Select a set of simulation options Run a simulation View the results of the simulation
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Precipitation in SWMM 5.0:Rain Gage object
Using a user-defined external datafile ( Data File ) Using a time series ( Time Series ): entering by hand both the rainfall and time values importing data from an external file
Copying and pasting from a spreadsheet
Rainfall input data: two options
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Rain Gage: mininal data requiered
Rain Gage name Rain data format Time interval between each rain
data Way to feed Rain Gage with the
rain data: Timeseries or ExternalFile
20
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Rain data format in SWMM 5
21
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Rainfall losses in SWMM 5
Three types of rainfall losses can bemodeled: Evaporation
Depression storage Infiltration
All subcatchments contained in aproject use the same infiltration model
User should select these models accordingto his/her knowledge of the catchment(types of soils, land uses, measured data,etc.)
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Evaporation and Depression storage
Used at daily scale
modeling (it is a slowprocess)
Useful for continousmodeling studies
Not applied for a singlestorm event
It corresponds to a volumethat must be fill prior to theocurrence of any runoffIt represents initialabstractions such as surfaceponding, interceptation byvegetation and surfacewetting
Evaporation Depression storage
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Infiltration in SWMM 5
Process applied only onthe pervious area ofeach subcatchment
Three infiltrationmodels
User should select the
model according to thedegree of knowledge ofthe catchment
While better it is theknowledge of thecatchment, it is possibleto use models of greaternumber of parameters
Data input in eachSubcatchment editor
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Empirical method Model of 3 para meters Drying Time: number of days
for a fully saturated soil todry completely
Max Volume : Maximuminfiltration volume possible
Two last parameters are usedin continuos modeling
Horton infiltration method in SWMM 5
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Physically-based method 3 parameters although the
last one is the differencebetween soil porosity andinitial moisture content. So, 4parameters are necessary
G-A is not a popular methodused in urban hydrologystudies
GreenAmpt infiltration methodin SWMM 5.0
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Curve Number (CN) infiltration methodin SWMM 5
Derived from (but not the same as) the well-known SCSCurve Number method used in simplified runoffmethods
A derived equation from the classical SCS method isused:
where
P , precipitation; R, potential runoff ; S, maximum soilpotential moisture retention, and CN, Curve number Total infiltration (F) can be computed as
2P R
P S =
+
F P R=
100010S
CN =
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One parameter model: CN The parameter called
Conductivity is not used incomputations anymore User should use tables to get CN
values according to type of soil,
land uses, etc.
Curve Number (CN) infiltration methodin SWMM 5 (II)
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Surface runoff model in SWMM 5
I(t): Inflows
O(t): Outflows
S: Storage volume
Q: Surface runoff
W: Subcatchment width
d p : Depression storage
d: Water depth
So: Subcatchment slope
n: Surface roughness coefficient
5 03
( ) ( )
( ) p
dS I t O t dt
S Q W d d
n
=
=
Each Subcatchment istreated as a NonlinearReservoir
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Subcatchment width in SWMM 5
Subcatchment is conceptualized as arectangular surface that has a uniform slopeand a width W that drains to a single outletchannelInitial estimate is given by
where,A: Subcatchment areaLfp: length of the longest overland flow path
Maximum Lfp in rural areas: 150 mFor urban catchments Lfp could be thelength from the back of a representative lot tothe center of the streetIf the overland flow length varies greatlywithin the subcatchment, then an area-weighted average should be usedW is often used as a calibration parameterdue to it is not always easy to determineAnother way to determine W: subcatchmentcontribution width to the main closer conduit
=
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Subcatchment width in SWMM 5
DiGiano et al. (1976) Subbasin=subcatchment
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Hydraulic routing models used by SWMM 5
1. Steady Flow: instantaneous traslation ofa hydrograph from theupstream end of a conduitto the downstream endwith no time delay orchange in shape
2. Kinematic Wave: uniformunsteady flow, using thecontinuity equation and thenormal flow condition
3. Dynamic Wave : thismethod solves the complete
1D Saint Venant equationsfor the entire conveyancenetwork, allowing to theuser simulate allgradually-varied flowconditions (backwater,surcharged flow andflooding)
0
0
S S xQ
t A
f =
=+
0
0
2
=+++
+
=+
L f h AgS Ag x H
Ag x
AQ
t Q
xQ
t A
0S S f =
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Steady Flow model in SWMM 5
Estimation just for somecases
Steady Uniform flow Useful only to pre-design
the conveyance network,not to make the finaldesign of the network
Only applied to dentriticconveyance networks
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Kinematic Wave flow model in SWMM 5
Appropiate for steep slope conduits,where there are supercritical flows
It should not change the shape of the
hydrograph (if do, this is because ofnumerical reasons) It not take in account the
downstream boundary conditions From a numerical point of view, more
stable than Dynamic Wave method
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Dynamic Flow model in SWMM 5
SWMM 5.0 uses a explicit finite differencenumerical scheme in order to solve
the complete 1D the Saint Venant equations at each Conduit and
a continuity relationship at each Node
This model requires small time steps ( t between 30 and 1 second usually)
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Nodal flooding options in SWMM 5: PondingOff and Ponding On
All excess inflow to nodeis lost from the system
All excess inflow to node is pondingon it. When adjacent conduits recoverits conveyance capacity, then ponded
volumen will be reintroduce to them
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SWMM 5 web
http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/
http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/8/13/2019 IntroSWMM5_2013
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Information and uselful help (manuals, sourcecodes, updates) for downloading
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