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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/

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Information and uselful help (manuals, sourcecodes, updates) for downloading

New update