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Introduction to USEPA SWMM

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  1. Introduction to USEPA SWMM CE 572 - Analysis of Urban Water Systems Fall 2008

  2. Topics to Be Covered • SWMM’s Capabilities • Old SWMM v. New SWMM • SWMM’s Data Objects • SWMM’s Process Models • Additional Resources

  3. What Is SWMM? SWMM is a distributed, dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas.

  4. SWMM’s Process Models

  5. Hydrologic Modeling Features • Spatially and time varying rainfall • Evaporation of standing surface water • Snow accumulation and melting • Interception from depression storage • Infiltration into soil layers • Percolation into shallow groundwater • Interflow between groundwater & channels • Nonlinear routing of overland flow

  6. Hydraulic Modeling Features • Handles drainage networks of any size • Accommodates various conduit shapes as well as irregular natural channels • Models pumps, regulators, storage units • Allows external inflows from runoff, groundwater, RDII, sanitary, DWF, and user-supplied time series • Uses flexible rule-based controls for pumps and regulators • Models various flow regimes, such as backwater, surcharging, reverse flow, and surface ponding

  7. Water Quality Modeling Features • Pollutant buildup over different land uses • Pollutant washoff during runoff events • Reduction in buildup from street cleaning • Reduction in washoff from BMPs • Inflows from user-defined sources and sanitary DWF • WQ routing through the drainage network • User-defined treatment functions

  8. 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 wasteload allocation studies • Evaluating BMPs and LIDs for sustainability goals

  9. Limitations of SWMM • Not applicable to large-scale, non-urban watersheds • Not applicable to forested areas or irrigated cropland • Cannot be used with highly aggregated (e.g., daily) rainfall data • Its an analysis tool, not an automated design tool

  10. SWMM Chronology • 1971 - SWMM I (M&E, UF, WRE) • 1975 - SWMM II (UF) • 1981 - SWMM 3 (UF & CDM) • 1983 - SWMM 3.3 (PC Version) • 1988 - SWMM 4 (UF & CDM) • 2005 – SWMM 5 (EPA & CDM)

  11. Old SWMM Structure

  12. Structure of SWMM 5

  13. SWMM 5’s Visual Objects

  14. Flow Routing Algorithms in SWMM5 • Steady Flow • simple hydrograph translation • applicable only to branched networks • Kinematic Wave • gravity force balanced by friction force • attenuated & delayed outflow due to channel storage • applicable only to branched networks • Dynamic Wave • solves full St. Venant eqns. • accounts for channel storage, backwater effects, pressurized flow, and reverse flow • applicable to any network layout • requires smaller time step

  15. Flow Routing Algorithms in SWMM5 • Steady Flow Routing • Actually just sums instantaneous subcatchment runoff for all subcatchments upstream of the selected channel • Kinematic Wave • Uniform, unsteady flow • No backwater, no surcharge, tree branch systems only unless flow splits are input • Dynamic Wave • Non-uniform, unsteady flow • Backwater, surcharge, looped or parallel sewers, street routing of flooded sewer manholes

  16. General Conceptual ModelFor Dynamic Wave

  17. Link and Node Properties

  18. Conduit (N) JN JN+1 Hydraulic Boundary Conditionat Nodes Grelev(NN,1) Grelev(NN,2)

  19. Node Flooding Options

  20. Surface Gutter (NN) Zp(NN,1) Zp(NN,2) Conduit (N) JN JN+1 Surface Routing of Flood Flows

  21. Conceptual Representation of the Dynamic Routing Algorithm

  22. Basic Flow Equation

  23. Continuity Equation

  24. Flow Cases Covered in Dynamic Routing Algorithm

  25. Flow Cases Covered in Dynamic Routing Algorithm

  26. Flow Cases Covered in Dynamic Routing Algorithm

  27. Conceptual Representation of Storage in SWMM

  28. Orifices and Weirs

  29. Representation of Weirs

  30. Representation of Pump

  31. EPA SWMM Web Site http://www.epa.gov/ednnrmrl/swmm/

  32. The SWMM-USERS List Server List servers provide a means for subscribers to get quick answers to questions and participate in discussions relating to the list server topics. Subscription is free, and subscribers receive all the e-mail that is sent to the list and can in turn send e-mail to the list. The SWMM-USERS list server is a forum for users of the public-domain USEPA SWMM program to share ideas and ask questions on issues related to stormwater management modeling. A searchable archive of past questions and answers is available through our SWMM Q&A database. To subscribe to a list, send an email to listserv@listserv.uoguelph.ca. Do not put anything in the subject line and, in the body of the message, include the following line (with NO other text and no brackets): SUBSCRIBE SWMM-USERS [first name] [last name] For example, SUBSCRIBE SWMM-USERS JANE DOE

  33. SWMM Wrappers With GIS Interfaces • XP SWMM – XP Software(www.xpsoftware.com) • Mike SWMM – DHI (www.dhisoftware.com) • InfoSWMM - MWH Soft (www.mwhsoft.com) • PC SWMM – CHI (www.computationalhydraulics.com)

  34. Homework 1. Download SWMM5 from the EPA Website http://www.epa.gov/ednnrmrl/models/swmm/index.htm 2. Download the User’s Manual 3. Page through the Users Manual so you are familiar with it 4. Look at the tutorial and be prepared to run it in class on Thursday