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SWMM-CAT accepts monthly adjustment factors for climate-related variables that could represent the potential impact of future climate changes.

SWMM allows engineers and planners to represent combinations of green infrastructure practices as low impact development LID controls to determine their effectiveness in managing runoff.

Although some of these practices can also provide significant pollutant reduction benefits, at this time, SWMM only models the reduction in runoff mass load resulting from the reduction in runoff flow volume. Download Drains The most popular versions of the Drains are This tool was originally designed by Watercom.

The most frequent installer filenames for the program are: Drains. It provides a much enhanced successor to the ILSAX program which has been widely used for urban stormwater system design and analysis in Australia and New Zealand. It is co-developed by Watercom and Dr. Helps predict runoff quantity and quality from drainage systems Disclaimer: Any mention of trade names, manufacturers, or products does not imply an endorsement by EPA. EPA and its employees do not endorse commercial products, services, or enterprises.

Rain Gardens Rain gardens are depressed areas, planted with grasses, flowers, and other plants, that collect rain water from a roof, driveway, or street and allow it to infiltrate into the ground. More complex rain gardens are often referred to as bioretention cells.

Bioretention Cells or Bioswales Bioretention cells are depressions containing vegetation grown in an engineered soil mixture placed above a gravel drainage bed that provide storage, infiltration, and evaporation of both direct rainfall and runoff captured from surrounding areas.

Vegetative Swales Vegetative swales are channels or depressed areas with sloping sides covered with grass and other vegetation that slow down the conveyance of collected runoff and allow it more time to infiltrate the native soil beneath it.

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About Us. Linkedin Twitter Youtube. New to Smart City Water? What is Smart City? Why Smart City Water? Our Software Platform Product Pricing. About Smart City Water. The procedure for finding the surface area of a storage unit given its volume was corrected for the case where the storage curve has a section of decreasing area with depth.

The procedure for finding a cross-section area given a section factor value was corrected for the case where the section factor table does not have its highest value as the last entry in the table. An error in computing the hydraulic radius of the Rectangular- Triangular conduit shape as a function of flow depth was corrected. Released: April 21, It is now defined as the saturated hydraulic conductivity of the native soil below the layer instead of the conductivity of the layer itself. One should still enter a non-zero conductivity for the layer if infiltration into native soil is allowed.

If the top width of the overland flow surface for an LID is zero then any excess water above the surface storage depth simply spills out instantaneously. The calculation of infiltration in a Vegetative Swale was corrected so that a swale with vertical sides will produce the same results as a fully pervious subcatchment with the same dimensions, roughness, and slope.

Error messages are now generated if the surface layer vegetation volume fraction is less than 1, if the area of all LIDs in a subcatchment is greater than the total area or if the total capture area of all LIDs is greater than the subcatchment's total impervious area. Missing values for accumulation periods within an NWS rain file are now processed correctly. See rain. A new error message is now generated if a user-prepared rainfall file has its dates out of sequence.

Evaporation during wet time periods was including rainfall and run-on as moisture available for evaporation when it should only be the current ponded depth.

See subcatch. Curve Number infiltration was modified to use only direct precipitation, not including runon or internally routed flow, to compute an infiltration rate. See infil. A new error message is now generated if the ground elevation of a subcatchment is less than the initial water table elevation of its groundwater aquifer.

See gwater. A check was added to the tailwater term of the groundwater flow equation to insure that the term is zero when no tailwater depth exists. Checks were added to the solution of the governing groundwater mass balance equations to catch conditions where the lower zone depth is greater than the total depth or when the upper zone moisture content is greater than the porosity.

A divide by zero error no longer occurs when computing the hydraulic radius of an empty Filled Circular pipe whose filled depth is zero. A similar error for the hydraulic radius of an empty trapezoidal channel whose bottom width was zero was also eliminated. See xsect. The critical or normal depth adjustment made for a conduit is no longer allowed to set the depth to zero -- some small depth level is always maintained. See dynwave. The Pump Summary Report was expanded to include number of start- ups, minimum flow, and time off both the low and high ends of the pump curve.

See objects. When the setting of an orifice or weir was changed to 0 to completely block flow the flow depth in the element wasn't being set to 0.

This was only a reporting error and had no effect on the flow routing calculations. See link. See stats. Released: November 18, Double counting the final stored volume when finding the nodes with the highest mass balance errors has been eliminated.

A warning message was added for when a Rain Gage's recording interval is less than the smallest time interval appearing in its associated rainfall time series. An error message is issued if the recording interval is greater than the smallest time series interval.

See gage. Hot Start interface files now contain the final state of each subcatchment's groundwater zone in addition to the node and link information they have always had.

See routing. To avoid confusion, the actual conduit slope is now listed in the Link Summary table of the Status Report rather than the adjusted slope that results from any conduit lengthening. The Status Report now displays only those summary tables for which results have been obtained e. See massbal. Some code re-factoring was done to place rain gage validation and initialization in separate functions.

See project. The engine version number was updated to this update had been overlooked since release 5. See consts. Released: October 07, Engine Updates The Ponding routine for dynamic wave flow routing was once again modified, this time to account for the special case where a node transitions between surcharged and ponded conditions within a single time step. This should correct the large continuity errors experienced with ponding under release 5.

Error a conduit's elevation drop exceeds its length is now treated as a Warning condition and not a fatal error. Inflow interface files no longer have to contain data for all of the same pollutants defined in the current project e. See iface. Instead of using the rain gage's recording interval as the time step for processing a set of RDII unit hydrographs, the smaller of the wet runoff time step and the time to peak of the shortest unit hydrograph in the set is now used.

As a result, it is now permissible to use hydrographs whose time to peak is shorter than the rain gage recording interval. See rdii. The small tolerance used to determine how much ponded depth in excess of depression storage is needed to initiate runoff was removed. This produces a smoother runoff response for some data sets.

A default concentration for dry weather flow has been added to the Pollutant object. It can be overriden for any specific node by editing the node's Inflows property. See landuse. For water quality routing, the simplified analytical solution to the CSTR mixing equation was replaced with a more robust finite difference approximation. This seems to avoid numerical problems with high decay rates. See qualrout.

First order decay was not being applied to pollutants transported through conduits under Steady Flow routing. To do this correctly required writing a special water quality routine just for Steady Flow routing. A small minimum depth tolerance was introduced for treatment to occur at nodes and to have non-zero concentrations in conduits. Large water quality mass balance errors in systems that provide treatment at nodes were eliminated by correctly accounting for both the inflow mass and mass in storage when computing the mass lost to treatment.

See treatmnt. Released: June 22, Engine Updates A new option was added to compute daily evaporation from the daily temperature values contained in a climate file using Hargreaves' method.

See climate. When the Ponding option is turned on, nodes that can pond are no longer always treated like storage nodes that never surcharge. Now they are only treated this way after ponding occurs. Otherwise they behave like a normal node. The small tolerance used to decide when a storage node was full or not has been removed since for very small time steps it could cause a currently full storage unit to remain full even if there was some small net outflow from it.

See node. When the water level at a storage node exceeds the highest level supplied in its Storage Curve, an extrapolated surface area from the curve is now used only if the curve is sloping outward i. If instead it slopes inward then the last surface area entry in the curve is used.

See table. Space delimited NCDC rainfall files with empty spaces in the condition code fields can now be read correctly. A bug created in release 5. A new error check was added to detect if the time base of an RDII unit hydrograph is less than its rain gage recording interval.

Released: April 10, Engine Updates Storage unit nodes have a new optional property named Infiltration that can store Green-Ampt infiltration parameters for the unit and thus allow it to serve as an infiltration basin. The Green-Ampt infiltration model was modified to explicitly include the effect of ponded water depth on infiltration rate. Different sets of Initial Abstraction parameters maximum depth, initial depth, and recovery rate can now be specified for each of the three unit hydrographs short term, medium term, and long term that comprise an RDII Unit Hydrograph group see keywords.

A Meander Modifier was added to a Transect's parameters. It is the ratio of the length of a meandering main channel to the length of the overbank area that surrounds it.

This modifier is applied to all conduits that use this particular transect for their cross section. It assumes that the length supplied for these conduits is that of the longer main channel.

SWMM will use the shorter overbank length in its calculations while internally increasing the main channel roughness to account for its longer length. NWS files in space delimited TD or format that include a station name field have been added to the types of rainfall files that are automatically recognized by SWMM see rain. The 2 GB binary output file size limit for runs made under the GUI that was inadvertently added into release 5.

Any backflow that flows into an outfall node due to the head condition at the node is now correctly reported as part of the node's Total Inflow result see node. A fatal error is now generated if the smallest time interval between values in a rainfall time series does not match the recording time interval specified for the associated rain gage object instead of internally adjusting the gage interval and issuing a warning message see error.

The normal flow limitation for dynamic wave flow routing based on the Froude number now requires that the latter be greater or equal to 1.

An reporting error for the overflow rate into the ponded volume for a node that floods under dynamic wave flow routing was corrected see dynwave. Released: January 21, Engine Updates Rain Gages gage. When two or more rain gages reference the same time series data, a fatal error message is now generated if the Rainfall Formats intensity, volume, or cumulative volume for the gages are not all the same.

Infiltration infil. The saturated hydraulic conductivity is no longer needed by the Curve Number method to compute a regeneration rate for infiltration capacity. The latter is now set simply to the reciprocal of the user supplied drying time. Thus the CN method now requires only two param- eters the CN and the drying time. An optional monthly adjustment pattern can now be used to modify the recovery rate of infiltration capacity by month of year. The name of this pattern is specified as part of the Evaporation data.

See the Help file or the Users Manual for details. This also affects files climate. Flow Routing flowrout. When this option is non- zero a computed conduit slope is not allowed to be below this value. The default is 0. Note: the slope of a conduit whose elevation difference is below 0. The following files were also changed for this feature: keywords.

An optional Baseline Time Pattern was added for external inflows at nodes. It can be used to apply a periodic adjustment to the baseline inflow value by month of year, day of week, etc. See the Help file or the Users Manual for more details. Specific conduits can now be designated as Culverts and have Inlet Control flow computed for them under Dynamic Wave flow routing.

The rating curve used to determine flow through an Outlet can now be based on either the freeboard depth above the outlet bottom as before or on the head difference between the upstream and downstream nodes.

The calculation of the maximum outflow that a node can release over a time step should be based on the initial volume, not the final volume, at the node. A problem with the program not accepting an ideal pump when the connecting upstream conduit had an adverse slope was fixed. A problem with the program crashing when the No Routing option was selected in combination with the Save Outflows Interface File option was fixed see output.

Under Steady Flow and Kinematic Wave routing one can now use a Dummy conduit that connects to a node at higher elevation without having to specify an inlet offset. Dynamic Wave Flow Routing dynwave. When ponding is allowed, ponded volume is now computed from the computed nodal depth rather than adjusting the depth to accommodate the ponded volume based on the excess of inflow versus outflow.

This is a return to the original method that was used up until Release 5. The volume at the inlet node of Type I pumps where an implicit wet well is assumed to occur is now determined on the basis of computed depth, just as with storage nodes, rather than computing depth from the change in volume.

The possible closing of tide gates on outfalls directly connected to orifice, weir, or outlet links is now correctly accounted for. Conduit Cross-Sections xsect. It thus becomes an upside down version of the Rectangular-Round shape. The section geometry functions for both shapes received extensive revision.

Control Rules controls. The way that concentrations in runoff are combined with those from runon and direct rainfall was modified so as to produce more consistent results, especially when a BMP removal value is appled. Water Quality Routing qualrout.

An inflow rate adjustment was added when routing quality through conduits under Dynamic Wave flow routing to help lower the mass continuity error. The formula for updating the hydraulic residence time HRT in a storage node was revised.

Quality routing under Steady Flow routing is now treated as a special case where the concentration within a conduit simply equals that of the upstream node. Any reverse flow into the system that occurs at an Outfall node is now treated as an external inflow with respect to water quality and will therefore contain whatever pollutant concentration was specified for external inflows at the node even if no external flow inflow was defined.

This feature can be used to model saltwater or contaminant intrusion in tidally influenced channels. Groundwater gwater. The flow equation was re-expressed in terms of distances above the aquifer bottom instead of absolute elevations. The equation for computing the maximum infiltration rate that the upper zone can accept was corrected. Snowmelt snow. The fraction of this amount that remains on the surface is whatever is left over after all of the redistribution options are satisfied.

The "Depth at which removal begins" value is now correctly converted to internal units of feet. RDII rdii. Time Series table. See the Users Manual or the Help file for details. Status Report statsrpt. The widths for the various types of flow volume fields e. Binary Output File output. Output Report command line version report. Released: March 11, Engine Updates The check on acceptable values for site latitude was corrected see climate.

The definition and implementation of the PID controller was changed. See the Help file or the Users Manual for details see controls. The following changes were made to the dynamic wave flow routing routine in dynwave. A code re-factoring error that crept into the inertial term of the momentum equation was corrected. The flow in a fully flowing open channel can no longer be greater than the full normal flow. The Normal Flow Limit based on both slope and Froude number was modified to simply implement the two criteria together in the same fashion as they are done individually.

A check was added that prevents any flow out of a node that is dry. The ponding computation was reverted back to that of 5. Using the maximum allowable change in depth at a node as a criterion for selecting a variable time step was restored.