Steady State Option in SWMM 5

The skip steady state periods uses the last computed flows in the conveyance system instead of computing new flows. In the sample graphs you can see where the change in lateral flow is below 0.05 cfs (the blue arrow in the second image). The network solution used the steady flows about 27 percent of the time. The time step summary in the text output file tells you how often the model was in steady state.

Skip Steady State Periods
Checking this option will make the simulation use the most recently computed conveyance system flows during a steady state period instead of computing a new flow routing solution. A time step is considered to be in steady state if the change in external inflow at each node is below 0.5 cfs and the relative difference between total system inflow and outflow is below 5%.

Lead and Lag Pump Options in SWMM 5

Introduction: If you have a lead and lag pump connecting the same upstream and downstream nodes the normal behavior for the two pumps is to have the the lead pump turn on first followed by the lag pump. The turn on and turn off depths for the pumps determine when the pumps turn of. The pump will work as a simple lead and lag pump based on a wet well elevation without any real time controls.

If you want to add real time controls (RTC) to the lead and lag pumps you can add more sophisticated controls. For example, if you wanted to turn on and off the lead pump at successive time steps then you can add these RTC rules

; New Real Time Control (RTC) Rules

RULE RULE-1

IF PUMP LEAD_PUMP STATUS = ON

AND PUMP LAG_PUMP STATUS = ON

THEN PUMP LEAD_PUMP STATUS = OFF

PRIORITY 1.000000

RULE RULE-2

IF PUMP LEAD_PUMP STATUS = OFF

AND PUMP LAG_PUMP STATUS = ON

THEN PUMP LEAD_PUMP STATUS = ON

PRIORITY 1.000000

RULE RULE-3

IF PUMP LEAD_PUMP STATUS = OFF

AND PUMP LAG_PUMP STATUS = ON

THEN PUMP LEAD_PUMP STATUS = ON

PRIORITY 1.000000

If you want to add a pattern of 2 time steps and 1 time step off for both pumps then you can add this RTC new rule to control the lag pump:

RULE RULE-4

IF PUMP LEAD_PUMP STATUS = OFF

AND PUMP LAG_PUMP STATUS = ON

THEN PUMP LAG_PUMP STATUS = OFF

PRIORITY 1.000000

SWMM 5 Link Iterations

These three graphs show how the number of iterations to solve the St. Venant equation in SWMM 5 changes during the course of the simulation based on rapidly changing inflow, steady inflow and decreasing inflow. This example allows up to ten iterations and a tighter head tolerance to better illustrate how the number of iterations increase at the beginning of the simulation and during rapid inflow. Normally, in SWMM 5 the number of iterations will be between a minimum of 2 and a maximum of 4 iterations.

In the first graph the outflow is in blue and the number of iterations at each time step is shown in red. In the second graph the bubble size is based on the number of iterations and the y axis is outflow of the network. The third graph shows the number of iterations used at each link in the model at a particular time step. The more the flow changes the more iterations are needed to keep the flow in balance.

SWMM5 Bubble Plot of Continuity Error

The overall continuity error at any time during the simulation is simply the total inflow minus the total outflow. The total inflow is the dry weather, wet weather, groundwater, I&I inflow, external inflow and the initial network storage. The total outflow is the amount of surface flooding, outfall flow, reacted flow and the final storage.

Continuity error = Total Inflow - Total Outflow

The continuity error can be variable over time as this graph of the total inflow, total outflow and continuity error over time shows for the classic extran example from SWMM 3 and SWMM 4. The continuity error can be negative or positive at each saved time step and it tends to balance out over time. As you can imagine depending on how long the simulation lasts the continuity error may be much greater than zero. If you can the simulation to dry weather flow is reached in the sanitary network or the stormwater network has drained the continuity error will be better. You can see that the CE increases at the beginning of the simulation, continues on and then goes to zero CE when the system drains.

If we look at a bubble chart of the continuity error over time (with the bubble size the continuity error) and the y axis the Total Inflow to the network you can see how continuity error increases and then decreases over time. The white bubbles are negative continuity error points.

SWMM 5 Conduit Lengthening

If you use the conduit lengthening option under the dynamic tab the shorter lengths will be lengthened internally during the simulation and the results will be a smoother.

Vertical Migration of SWMM 5 Calibration Files

Note: It is often important to compare the results for your link flows, node heads and system variables between SWMM 5 versions to help you calibrate the new version based on the old version results. If you run a SWMM 5 model in an older version, save the .rpt and .out file and then open up the SWMM 5 input file in a newer version of SWMM 5 you should see a active graph symbol. The active symbol means that you can plot the results of the old model in the newer SWMM 5 GUI.

For example, you can plot one of the system variables and then save ALL of the system variables to either a clipboard or a system calibration file. You can then use the Calibration dialog of SWMM 5 to compare the older results with the simulation results of a new version of SWMM 5.

Water Analogies for Divergence, Curl and Gradient

Comment: A really nice water analogy for the field properties Divergence, Curl and Gradient from the Blog Starts With a Bang

....it's pretty mathematically intensive, but what's missing from most textbooks and E&M courses are physical explanations of what the mathematics means. For instance, I've started teaching about fields, and pretty much every textbook out there goes on and on about the properties of fields. They say you can do three things to fields, take the gradient, divergence, or curl of them.

(Are you asleep yet? I'm sorry!)

What do these things mean? An easy way to picture it is in terms of water. If you placed a drop of water anywhere on, say,Earth, the magnitude and direction of how it rolls down is the gradient of the Earth's elevation.

If you let that drop of water flow, as it goes downhill, it can either spread out or converge to a narrower stream. When we quantify that, that's what the divergence of the field is.

And finally, when that water is flowing, sometimes it gets an internal rotational motion, like an eddy. A measure of that rotational motion is called thecurl of the field.

Well, one math geek statement is as follows: the curl of the gradient of a scalar field is always zero. What does this mean, in terms of our water? It means that I can take any topography I can find, invent, or even dream up.

I can drop a tiny droplet of water on it anywhere I like, and while the water may roll downhill (depending on the gradient), and while the water may spread out or narrow (depending on the divergence of the gradient), it will not start to rotate. For rotation to happen, you need something more than just a drop starting out on a hill, no matter how your hill is shaped! That's what it means when someone says, "The curl of the gradient is zero."

This passage uses the metaphor of water flowing over terrain to help explain some concepts from vector calculus and electromagnetic fields. Let's dig a little deeper into each of these mathematical operations and their physical implications.

Gradient

The gradient is a vector operation that acts on a scalar field. It tells you the direction and rate at which the field changes most rapidly. In the water analogy, the gradient of the Earth's elevation is the direction and magnitude of the steepest downhill slope at a given point. It's the direction the water would naturally roll down.

Divergence

Divergence measures the degree to which a vector field sources or sinks at a given point. In the context of water flow, the divergence of the field describes whether the water is spreading out or converging to a narrower stream as it moves downhill. A positive divergence indicates that the water is spreading out, like a water source, while a negative divergence implies it is converging, like a sink or drain.

Curl

The curl of a field measures its rotation or twisting. In the water flow example, the curl would represent the rotational motion of the water as it flows, such as the swirling of an eddy in a river.

The statement "the curl of the gradient of a scalar field is always zero" can be understood with our water analogy. When a droplet of water is placed on a landscape (which represents our scalar field), it can roll downhill (gradient) and it can spread out or converge (divergence), but it will not spontaneously start to rotate (curl). Any rotation (curl) in the water's motion requires an additional influence beyond just the shape of the landscape. It could be introduced by an external force like wind, or by irregularities in the terrain, but it's not a natural outcome of a droplet simply being placed on a slope. This is the physical interpretation of the mathematical statement "The curl of the gradient is zero."

This explanation aids in visualizing these abstract mathematical concepts, making them more tangible and understandable, especially for those who are new to these ideas or find them difficult to grasp. It also provides a more intuitive understanding of the mathematical operations involved in vector calculus and their significance in the study of fields, of both in physics and engineering.

Water Hits and Sticks: Findings Challenge a Century of Assumptions About Soil Hydrology

From Science Daily

ScienceDaily (Jan. 23, 2010) — Researchers have discovered that some of the most fundamental assumptions about how water moves through soil in a seasonally dry climate such as the Pacific Northwest are incorrect -- and that a century of research based on those assumptions will have to be reconsidered.

A new study by scientists from Oregon State University and the Environmental Protection Agency showed -- much to the surprise of the researchers -- that soil clings tenaciously to the first precipitation after a dry summer, and holds it so tightly that it almost never mixes with other water.

The finding is so significant, researchers said, that they aren't even sure yet what it may mean. But it could affect our understanding of how pollutants move through soils, how nutrients get transported from soils to streams, how streams function and even how vegetation might respond to climate change.

The research was just published online in Nature Geoscience, a professional journal.

"Water in mountains such as the Cascade Range of Oregon and Washington basically exists in two separate worlds," said Jeff McDonnell, an OSU distinguished professor and holder of the Richardson Chair in Watershed Science in the OSU College of Forestry. "We used to believe that when new precipitation entered the soil, it mixed well with other water and eventually moved to streams. We just found out that isn't true."

"This could have enormous implications for our understanding of watershed function," he said. "It challenges about 100 years of conventional thinking."

What actually happens, the study showed, is that the small pores around plant roots fill with water that gets held there until it's eventually used up in plant transpiration back to the atmosphere. Then new water becomes available with the return of fall rains, replenishes these small localized reservoirs near the plants and repeats the process. But all the other water moving through larger pores is essentially separate and almost never intermingles with that used by plants during the dry summer.

The study found in one test, for instance, that after the first large rainstorm in October, only 4 percent of the precipitation entering the soil ended up in the stream -- 96 percent was taken up and held tightly by soil around plants to recharge soil moisture. A month later when soil moisture was fully recharged, 55 percent of precipitation went directly into streams. And as winter rains continue to pour moisture into the ground, almost all of the water that originally recharged the soil around plants remains held tightly in the soil -- it never moves or mixes.

"This tells us that we have a less complete understanding of how water moves through soils, and is affected by them, than we thought we did," said Renee Brooks, a research plant physiologist with the EPA and courtesy faculty in the OSU Department of Forest Ecosystems and Society.

"Our mathematical models of ecosystem function are based on certain assumptions about biological processes," Brooks said. "This changes some of those assumptions. Among the implications is that we may have to reconsider how other things move through soils that we are interested in, such as nutrients or pollutants."

The new findings were made possible by advances in the speed and efficiency of stable isotope analyses of water, which allowed scientists to essentially "fingerprint" water and tell where it came from and where it moved to. Never before was it possible to make so many isotopic measurements and get a better view of water origin and movement, the researchers said.

The study also points out the incredible ability of plants to take up water that is so tightly bound to the soil, with forces nothing else in nature can match.

The research was conducted in the H.J. Andrews Experimental Forest near Blue River, Ore., a part of the nation's Long Term Ecological Research, or LTER Program. It was supported by the EPA.

Much to the surprise of the researchers, soil clings tenaciously to the first precipitation after a dry summer, and holds it so tightly that it almost never mixes with other water. (Credit: iStockphoto/Mats Lund)

Oregon State University (2010, January 23). Water hits and sticks: Findings challenge a century of assumptions about soil hydrology.ScienceDaily. Retrieved January 23, 2010, from http://www.sciencedaily.com/releases/2010/01/100121173452.htm

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• Water hits and sticks: Findings challenge a century of assumptions about soil hydrology (scienceblog.com)

Runoff Example Files for SWMM 4

These are 48 Runoff Example Files that I created based on PC-SWMM 3, SWMM 3 and new SWMM 4 features at UF between 1985 and 1981..

These files will work with any SWMM 4 version. If you look at page http://www.swmm2000.com/SWMM4/swmm-3-4-dos-engines

we have a variety of SWMM 3 and SWMM 4 engine.

The File Runoff45.DOC is the text documentation for the SWMM 4 Runoff File.

Link http://www.swmm2000.com/group/swmm4inputfiles

SWMM 5 Water Quality Example with Groundwater

A SWMM 5 water quality example based on the USGS BROWARD COUNTY Multi FAMILY SITE, this was Runoff example # 47 in SWMM 4.



usgs_runoff.inp

15 GPM

From the South Florida Watershed Journal

Fifteen gallons per minute
Alternative measurement units:

0.03 cubic feet per second
508 barrels per day (using 42.5 gallon barrels)
24 acre feet per year
7.9 million gallons per year
12 Olympic swimming pools per year

Weather Underground Data and SWMM 5

Weather Underground is a site that provides excellent local weather information in the form of graphs, tables and csv files. You can use the data very easily in SWMM 5 by copying from Excel to a time series in SWMM 5.

The data imported from the csv file to Excel and after the text to columns tool is used looks like this in Excel. The data is now ready to be imported into SWMM 5 after the time column is adjusted to fall on even 5 minute intervals. In Excel you can use the formula @ROUND((B2)/"0:05:00",0)*"0:05:00" to round all of the time values to 5 minutes. If you do not do this step then you will have problems in SWMM 5 due to the rainfall interval not being equal to the defined raingage interval.

Open up and make a new time series in SWMM 5 and then copy and paste the date, rounded time column and rainfall column into the SWMM 5 time series.

InfoSWMM and H2oMAP SWMM Release Notes

InfoSWMM and H2oMAP SWMM Release Notes

Sediment Modeling

SCS Rainfall Distributions

InfoSWMM Version 1.0

InfoSWMM Version 2.0

InfoSWMM Version 3.0

InfoSWMM Version 4.0

InfoSWMM Version 5.0

InfoSWMM Version 6.0

InfoSWMM Version 7.0

InfoSWMM Version 8.0

InfoSWMM Version 8.5

Node Convergence in SWMM 5

The solution is iterative but each iteration is dependent on the CFL or explicit time step. The time step we select is based on the CFL condition but instead of just using the explicit solution we iterate until the node depths are converged or a maximum of 4 iterations is reached.

The solution of node depths and link flows in SWMM 5 is an iterative process but the number of iterations for the flows and links depends on how fast the node depth converges. The node continuity equation is ALWAYS solved at each iteration for each node but depending on whether both the link upstream and downstream node depths have converged the the number of iterations for a link may be between 2 and 4. The minimum number of iterations for a link is 2.

Figure 1. Iterations in SWMM 5

Heavier Rainstorms Ahead in the Future

Heavier Rainstorms Ahead Due To Global Climate Change, Study Predicts
ScienceDaily (Sep. 27, 2009) — Heavier rainstorms lie in our future. That's the clear conclusion of a new MIT and Caltech study on the impact that global climate change will have on precipitation patterns.

But the increase in extreme downpours is not uniformly spread around the world, the analysis shows. While the pattern is clear and consistent outside of the tropics, climate models give conflicting results within the tropics and more research will be needed to determine the likely outcomes in tropical regions.
Overall, previous studies have shown that average annual precipitation will increase in both the deep tropics and in temperate zones, but will decrease in the subtropics. However, it's important to know how the frequency and magnitude of extreme precipitation events will be affected, as these heavy downpours can lead to increased flooding and soil erosion.
It is the frequency of these extreme events that was the subject of this new research, which will appear online in theProceedings of the National Academy of Sciences during the week of Aug. 17. The report was written by Paul O'Gorman, assistant professor in the Department of Earth, Atmospheric and Planetary Sciences at MIT, and Tapio Schneider, professor of environmental science and engineering at Caltech.
Model simulations used in the study suggest that precipitation in extreme events will go up by about 6 percent for every one degree Celsius increase in temperature. Separate projections published earlier this year by MIT's Joint Program on the Science and Policy of Global Change indicate that without rapid and massive policy changes, there is a median probability of global surface warming of 5.2 degrees Celsius by 2100, with a 90 percent probability range of 3.5 to 7.4 degrees.
Specialists in the field called the new report by O'Gorman and Schneider a significant advance. Richard Allan, a senior research fellow at the Environmental Systems Science Centre at Reading University in Britain, says, "O'Gorman's analysis is an important step in understanding the physical basis for future increases in the most intense rainfall projected by climate models." He adds, however, that "more work is required in reconciling these simulations with observed changes in extreme rainfall events." The basic underlying reason for the projected increase in precipitation is that warmer air can hold more water vapor. So as the climate heats up, "there will be more vapor in the atmosphere, which will lead to an increase in precipitation extremes," O'Gorman says.
However, contrary to what might be expected, extremes events do not increase at the same rate as the moisture capacity of the atmosphere. The extremes do go up, but not by as much as the total water vapor, he says. That is because water condenses out as rising air cools, but the rate of cooling for the rising air is less in a warmer climate, and this moderates the increase in precipitation, he says.
The reason the climate models are less consistent about what will happen to precipitation extremes in the tropics, O'Gorman explains, is that typical weather systems there fall below the size limitations of the models. While high and low pressure areas in temperate zones may span 1,000 kilometers, typical storm circulations in the tropics are too small for models to account for directly. To address that problem, O'Gorman and others are trying to run much smaller-scale, higher-resolution models for tropical areas.
Massachusetts Institute of Technology (2009, September 27). Heavier Rainstorms Ahead Due To Global Climate Change, Study Predicts.ScienceDaily. Retrieved September 27, 2009, from http://www.sciencedaily.com/releases/2009/08/090817190638.htm

InfoSWMM and H2OMAP SWMM Version 8.5

MWH Soft Releases InfoSWMM and H2OMAP SWMM Version 8.5,
Leveraging the Latest EPA SWMM5 Functionality

Newest Iteration of Industry-Leading Geospatial Urban Drainage Modeling and Design Software
Delivers Expanded Engineering Simulation Value

Broomfield, Colorado USA, November 11, 2009 — MWH Soft, the leading global provider of environmental and water resources applications software, today announced the immediate release of Generation V8.5 of H2OMAP SWMM and InfoSWMM for ArcGIS (ESRI, Redlands, CA). The new version adds powerful features and leverages engine enhancements included in the latest release of EPA SWMM5 (5.0.017). It also improves the breadth and performance by extending MWH Soft tradition of including new enhancements specifically requested by customers. Version 8.5 marks a significant evolution of the company’s SWMM-based urban drainage modeling and design products, which continue to be top choices for the effective evaluation, design, management, rehabilitation and operation of wastewater and stormwater collection systems.
Underlining MWH Soft’s leadership in the wastewater industry, InfoSWMM and H2OMAP SWMM reflect the company’s ongoing commitment to delivering pioneering technology that raises the bar for urban drainage network modeling and simulation, helping to shape the future of this critical sector. The full-featured InfoSWMM urban drainage network analysis and design program is the only urban drainage modeling solution certified by the National Association of GIS-Centric Software (www.nagcs.com). It addresses all operations of a typical sewer system — from analysis and design to management functions such as water quality assessment, pollution prediction, sediment transport, urban flooding, real-time control and record keeping — in a single, fully integrated geoengineering environment whose powerful hydraulic computational engine is endorsed by the USEPA and certified by FEMA.

SWMM 5.0.018

------------------------
Build 5.0.018 (11/18/09)
------------------------
Engine Updates

1. Reporting of the total infiltration + evaporation loss for each
Storage Unit (as a percent of total inflow to the unit) was added
to the Storage Volume Summary table in the Status Report. See
objects.h, node.c, stats.c, and statsrpt.c.

2. Double counting the final stored volume when finding the nodes with
the highest mass balance errors has been eliminated. See stats.c.

3. 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.c and text.h.

4. 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.c.

5. 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. See link.c and
dynwave.c.

6. The Status Report now displays only those summary tables for
which results have been obtained (e.g., if the Flow Routing
option is turned off, then no node or link tables are displayed).
See massbal.c and statsrpt.c.

7. Some code re-factoring was done to place rain gage validation
and initialization in separate functions. See project.c, gage.c,
and funcs.h.

8. The engine version number was updated to 50018 (this update had
been overlooked since release 5.0.010). See consts.h.

GUI Updates

1. A bug that prevented Status Report files from being deleted from
a users TEMP folder when they were no longer in use was corrected.
Users should check their TEMP folders (usually in
c:\Documents and Settings\\Local Settings\Temp)
for old files that begin with "swm". These can safely be deleted.

2. The project input file created for use by SWMM's Add-On Tools now
contains all project data, including map coordinates and element
tags.

Suggestion for Entering Population DWF Data at a Node

I (and a few others) think a welcome change to the DWF dialog in SWMM 5 would be the addition of another scale factor to modify the average flow field. The purpose of the scale factor would be to allow the users to enter the DWF contributing population * the various DWF patterns * the scale factor (in units of cfs/person or l/s/person) in the Inflows dialog. Some users of SWMM 5 prefer to use population directly in the GUI rather than doing this calculation externally and entering either the flow in cfs or l/s. An example of why this would be useful is a future conditions model in which the population either increases or decreases in the catchment.

Here's a revised emoji-laden table reflecting your suggestion for a welcome change in the Dry Weather Flow (DWF) dialog in SWMM 5, along with its implementation in InfoSWMM and ICM SWMM:

Topic 📘	SWMM5 🌊	InfoSWMM 🔄	ICM SWMM 🌪️	Emoji Illustration 🎨
Proposed DWF Scale Factor 🎚️	Addition of a scale factor to modify the average flow field, allowing users to input DWF contributing population, DWF patterns, and scale factor (in units of cfs/person or l/s/person) directly in the Inflows dialog.	(Potential implementation or extension in InfoSWMM based on user preference)	(Potential implementation or extension in ICM SWMM based on user preference)	🎚️👥💧
Usage Ease 🤗	Enabling direct population input in the GUI, eliminating the need for external calculations, thereby facilitating more straightforward flow entries in cfs or l/s.	(Assumed similar ease of use enhancement in InfoSWMM if implemented)	(Assumed similar ease of use enhancement in ICM SWMM if implemented)	🤗➡️💻
Future Conditions Modeling 🌐	Catering to models depicting population increase or decrease in a catchment, aiding in more accurate future condition analyses.	(Potential facilitation of future conditions modeling in InfoSWMM if implemented)	(Potential facilitation of future conditions modeling in ICM SWMM if implemented)	🌐👥🔄

This table encapsulates the proposed change in SWMM 5 concerning the Dry Weather Flow (DWF) dialog, allowing for a new scale factor to alter the average flow field. The table also leaves room for similar implementations or extensions in InfoSWMM and ICM SWMM, provided that these platforms decide to adopt this user-friendly feature, making it easier to handle population-based flow calculations directly within the software's GUI.