Thursday, December 24, 2009

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

Saturday, December 12, 2009

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

Sunday, December 6, 2009

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

Saturday, November 28, 2009

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

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 ( 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

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

Sunday, August 16, 2009

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 ๐Ÿ“˜SWMM5 ๐ŸŒŠInfoSWMM ๐Ÿ”„ICM SWMM ๐ŸŒช️Emoji Illustration ๐ŸŽจ
Proposed DWF Scale Factor ๐ŸŽš️Addition 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)๐ŸŽš️๐Ÿ‘ฅ๐Ÿ’ง
Usage Ease ๐Ÿค—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)๐Ÿค—➡️๐Ÿ’ป
Future Conditions Modeling ๐ŸŒ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)๐ŸŒ๐Ÿ‘ฅ๐Ÿ”„

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.

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Friday, August 14, 2009

New Warning Messages in SWMM 5.0.014 to 5.0.016

These warning and error messages were added in SWMM to 5.0.016 to trap questionable raingage, link and node data. Correcting these errors does make a better model . The list shown below has the major new warnings and errors and help on interpreting the messages.

WARNING 01: wet weather time step reduced to recording interval for Rain Gage
Explanation: The user selected hydrology time step is automatically reduced by the engine to match the rain gage interval. The smallest rainfall interval among all of the gages will be used during the simulation.
WARNING 02: maximum depth increased for Node
Explanation: The rim elevation of a node has to be at least equal to the crown elevation of the highest connecting link to the node. The maximum depth of the node is increased to match the highest crown elevation.
WARNING 03: negative offset ignored for Link
Explanation: Negative Offsets are set to offsets of 0.0
WARNING 04: minimum elevation drop used for Conduit
Explanation: If the elevation across the link length is less than 0.001 feet then the elevation drop is set to 0.001 feet (internal units).
WARNING 05: minimum slope used for Conduit
Explanation: If the link slope is less than the user defined minimum slope then the engine will set the slope of the link to the minimum slope.
WARNING 06: dry weather time step increased to the wet weather time step
Explanation: The Dry hydrology time step cannot be less than the wet weather hydrology time step.
WARNING 07: routing time step reduced to the wet weather time step
Explanation: Routing step set to the wet hydrology time step.
ERROR 112: elevation drop exceeds length for Conduit
Explanation: The drop across the conduit cannot exceed the conduit length. It indicates short conduits that likely have improper offset elevations or incorrectly estimated lengths based on the large offsets of the conduit.
ERROR 134: Node has illegal DUMMY link connections.
Explanation: This means either the model has more than one Ideal Pump connecting the same upstream and downstream nodes or a dummy link with more than one link exiting its upstream node.
ERROR 151: a Unit Hydrograph in set has invalid time base.
Explanation: The value of T*K or the Time Base for a RDII Unit Hydrograph has a value less than the rain gage interval. The fundamental time unit for Unit Hydrographs is the rain gage time interval.
ERROR 157: inconsistent rainfall format for Rain Gage
Explanation: Two or more gages using the same time series have different rainfall types in the rain gage definition. For example, intensity and volume.
ERROR 159: inconsistent time interval for Rain Gage
Explanation: The rain gage user defined rainfall interval does not match the actual rainfall time series.
ERROR 173: Time Series has its data out of sequence
Explanation: A time series has either the same time value for consecutive intervals or the time values are out of numerical order.

Saturday, July 18, 2009

Peeling Back Pavement to Expose Watery Havens


Hi Seoul' 2008. Spring.
Image via Wikipedia

Peeling Back Pavement to Expose Watery Havens
SEOUL, South Korea — For half a century, a dark tunnel of crumbling concrete encased more than three miles of a placid stream bisecting this bustling city.

The waterway had been a centerpiece of Seoul since a king of the Choson Dynasty selected the new capital 600 years ago, enticed by the graceful meandering of the stream and its 23 tributaries. But in the industrial era after the Korean War, the stream, by then a rank open sewer, was entombed by pavement and forgotten beneath a lacework of elevated expressways as the city’s population swelled toward 10 million.

Today, after a $384 million recovery project, the stream, called Cheonggyecheon, is liberated from its dank sheath and burbles between reedy banks. Picnickers cool their bare feet in its filtered water, and carp swim in its tranquil pools.

The restoration of the Cheonggyecheon is part of an expanding environmental effort in cities around the world to “daylight” rivers and streams by peeling back pavement that was built to bolster commerce and serve automobile traffic decades ago.

In New York State, a long-stalled revival effort for Yonkers’s ailing downtown core that could break ground this fall includes a plan to re-expose 1,900 feet of the Saw Mill River, which currently runs through a giant flume that was laid beneath city streets in the 1920s.

Cities from Singapore to San Antonio have been resuscitating rivers and turning storm drains into streams. In Los Angeles, residents’ groups and some elected officials are looking anew at buried or concrete-lined creeks as assets instead of inconveniences, inspired partly by Seoul’s example.

By building green corridors around the exposed waters, cities hope to attract affluent and educated workers and residents who appreciate the feel of a natural environment in an urban setting.

Environmentalists point out other benefits. Open watercourses handle flooding rains better than buried sewers do, a big consideration as global warming leads to heavier downpours. The streams also tend to cool areas overheated by sun-baked asphalt and to nourish greenery that lures wildlife as well as pedestrians.

Some political opponents have derided Seoul’s remade stream as a costly folly, given that nearly all of the water flowing between its banks on a typical day is pumped there artificially from the Han River through seven miles of pipe.

But four years after the stream was uncovered, city officials say, the environmental benefits can now be quantified. Data show that the ecosystem along the Cheonggyecheon (pronounced chung-gye-chun) has been greatly enriched, with the number of fish species increasing to 25 from 4. Bird species have multiplied to 36 from 6, and insect species to 192 from 15.

The recovery project, which removed three miles of elevated highway as well, also substantially cut air pollution from cars along the corridor and reduced air temperatures. Small-particle air pollution along the corridor dropped to 48 micrograms per cubic meter from 74, and summer temperatures are now often five degrees cooler than those of nearby areas, according to data cited by city officials.

And even with the loss of some vehicle lanes, traffic speeds have picked up because of related transportation changes like expanded bus service, restrictions on cars and higher parking fees.

“We’ve basically gone from a car-oriented city to a human-oriented city,” said Lee In-keun, Seoul’s assistant mayor for infrastructure, who has been invited to places as distant as Los Angeles to describe the project to other urban planners.

Some 90,000 pedestrians visit the stream banks on an average day.

What is more, a new analysis by researchers at the University of California, Berkeley, found that replacing a highway in Seoul with a walkable greenway caused nearby homes to sell at a premium after years of going for bargain prices by comparison with outlying properties.

Efforts to recover urban waterways are nonetheless fraught with challenges, like convincing local business owners wedded to existing streetscapes that economic benefits can come from a green makeover.

Yet today the visitors to the Cheonggyecheon’s banks include merchants from some of the thousands of nearby shops who were among the project’s biggest opponents early on.

On a recent evening, picnickers along the waterway included Yeon Yeong-san, 63, who runs a sporting apparel shop with his wife, Lee Geum-hwa, 56, in the adjacent Pyeonghwa Market.

Mr. Yeon said his family moved to downtown Seoul in the late 1940s, and he has been running the business for four decades. He said parking was now harder for his customers. But “because of less traffic, we have better air and nature,” he said.

He and his wife walk along the stream every day, he added. “We did not think about exercising here when the stream was buried underground,” Mr. Yeon said.

The project has yielded political dividends for Lee Myung-bak, a former leader of construction companies at the giant Hyundai Corporation. He was elected Seoul’s mayor in 2002 largely around his push to remove old roads — some of which he had helped build — and to revive the stream. Today he is South Korea’s president.

Even strong critics of the president tend to laud his approach to the Cheonggyecheon revival, which involved hundreds of meetings with businesses and residents over two years.

A recent newspaper column that criticized the president over a police raid on squatters ended with the words “Please come back, Cheonggyecheon Lee Myung-bak!” — a reference to the nickname he earned during the campaign to revive the stream.

The role of Seoul’s environmental renewal in Mr. Lee’s political ascent is not lost on Mayor Philip A. Amicone of Yonkers, a city of 200,000 where entrenched poverty had slowed a revival project. Once the river restoration was added to the plan, he said, he found new support for redevelopment.

Yonkers has gained $34 million from New York State and enthusiastic support from environmental groups for the river restoration, which is part of a proposed $1.5 billion development that includes a minor-league ballpark. The river portion is expected to cost $42 million over all.

A longtime supporter was George E. Pataki, who helped line up state money in his last year as governor, Mayor Amicone said. “Every time he’d visit, he’d say, ‘You’ve got to open up that river,’ ” he added.

Part of the plan would expose an arc of the river and line it with paths and restaurant patios that would wrap around a shopping complex and the ballpark. Another open stretch would become a “wetland park” on what is now a parking lot.

Mr. Amicone, who has a background as a civil engineer, said the example of Seoul’s success had helped build support in Yonkers. In an interview, he recalled the enthusiasm with which Mr. Lee, then Seoul’s mayor, toured Yonkers in 2006 and discussed the cities’ parallel river projects with him.

“Whether it’s a city of millions or 200,000, the concept is identical,” Mr. Amicone said. “These are no longer sewers, but aesthetically pleasing assets that enhance development.”

Jean Chung contributed reporting.

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Thursday, April 2, 2009

Surcharge Level in SWMM 5

How does the surcharge depth work in SWMM 5?

The surcharge depth from the node attribute table is added to the maximum full depth in the routine dynwave.c as an upper bound check for the new iteration depth of yNew.

    // --- determine max. non-flooded depth
    yMax = Node[i].fullDepth;
    if ( canPond == FALSE ) yMax += Node[i].surDepth;

If the new depth yNew is greater then yMax then the program will calculate either the amount of flooding from the node or the ponded depth and volume.  If the node cannot pond (canPond is False) then the amount of overflow is the excess flow in the node and the new depth yNew is set to yMax.

    if ( canPond == FALSE )
    {  Node[i].overflow = (Node[i].oldVolume + dV - Node[i].fullVolume) / dt;
        Node[i].newVolume = Node[i].fullVolume;
        yNew = yMax;    }
    else    {
        Node[i].newVolume = Node[i].fullVolume + (yNew-yMax)*Node[i].pondedArea;
        Node[i].overflow = (Node[i].newVolume - Node[i].fullVolume) / dt;    }
        if ( Node[i].overflow < FUDGE ) Node[i].overflow = 0.0;
    return yNew;
As an example, if the node floods then the depth will go above the manhole rim elevation as the following image shows.

If the ponded area of the node is zero then any excess flow is lost as overflow and the depth only stays at the rim elevation.

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Friday, March 27, 2009

Q full vs Q dynamic vs Q normal in SWMM5

Introduction – the reason for these series of blogs are as an expanded view of the input, engine and output of #SWMM5 It is a companion to the EPA Documentation which I describe here:

I have noticed based on email questions and postings to the SWMM List Sever (a great resource hosted by CHI, Inc.) that many SWMM 5 users do not know about the really outstanding documentation on SWMM 5 posted on the EPA Website It consists of two now and in the near future three volumes on Hydrology, Water Quality, LID’s and SuDS and Hydraulics. The documentation is fantastically complete with detailed background on the theory, process parameters and completely worked out examples for all of the processes in SWMM5. It is truly an outstanding aid to modelers and modellers worldwide. It would benefit you to read them (if you have not already downloaded the PDF files)
1. It gets more flow than qFull because the water in the pipe has more than just the bed slope to push it - it also has the water surface slope.
There is about a 5 meter head pushing the water out if you the bed slope to the water surface slope - see the HGL Plot.

2. The Q dynamic or St. Venant flow uses ALL of the information you have about the condition in the link (see the next image) so the flow is greater than Qfull and Q normal flow. The information includes the hydraulic radius and cross sectional areas for upstream, midpoint and the downstream ends of the links.

Normal Flow, Q and St Venant Flow.   Fraction Normal Flow Limited is the fraction of time SWMM5 uses Normal Flow for the Conduit.

Sunday, March 22, 2009

Future Rainfall

Outlook: Extreme
As the planet warms, look for more floods where it’s already wet and deeper drought where water is scarce.
By Elizabth Kolbert

The world's first empire, known as Akkad, was founded some 4,300 years ago, between the Tigris and the Euphrates Rivers. The empire was ruled from a city—also known as Akkad—that is believed to have lain just south of modern-day Baghdad, and its influence extended north into what is now Syria, west into Anatolia, and east into Iran. The Akkadians were well organized and well armed and, as a result, also wealthy: Texts from the time testify to the riches, from rare woods to precious metals, that poured into the capital from faraway lands.

Then, about a century after it was founded, the Akkad empire suddenly collapsed. During one three-year period four men in succession briefly claimed to be emperor. "Who was king? Who was not king?" a register known as the Sumerian King List asks.

For many years, scholars blamed the empire's fall on politics. But about a decade ago, climate scientists examining records from lake bottoms and the ocean floor discovered that right around the time that the empire disintegrated, rainfall in the region dropped dramatically. It is now believed that Akkad's collapse was caused by a devastating drought. Other civilizations whose demise has recently been linked to shifts in rainfall include the Old Kingdom of Egypt, which fell right around the same time as Akkad; the Tiwanacu civilization, which thrived near Lake Titicaca, in the Andes, for more than a millennium before its fields were abandoned around A.D. 1100; and the Classic Maya civilization, which collapsed at the height of its development, around A.D. 800.

The rainfall changes that devastated these early civilizations long predate industrialization; they were triggered by naturally occurring climate shifts whose causes remain uncertain. By contrast, climate change brought about by increasing greenhouse gas concentrations is our own doing. It, too, will influence precipitation patterns, in ways that, though not always easy to predict, could prove equally damaging.

Warm air holds more water vapor—itself a greenhouse gas—so a hotter world is a world where the atmosphere contains more moisture. (For every degree Celsius that air temperatures increase, a given amount of air near the surface holds roughly 7 percent more water vapor.) This will not necessarily translate into more rain—in fact, most scientists believe that total precipitation will increase only modestly—but it is likely to translate into changes in where the rain falls. It will amplify the basic dynamics that govern rainfall: In certain parts of the world, moist air tends to rise, and in others, the moisture tends to drop out as rain and snow.

"The basic argument would be that the transfers of water are going to get bigger," explains Isaac Held, a scientist at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory at Princeton University. Climate models generally agree that over the coming century, the polar and subpolar regions will receive more precipitation, and the subtropics—the area between the tropical and temperate zones—will receive less. On a regional scale, the models disagree about some trends. But there is a consensus that the Mediterranean Basin will become more arid. So, too, will Mexico, the southwestern United States, South Africa, and southern Australia. Canada and northern Europe, for their part, will grow damper.

A good general rule of thumb, Held says, is that "wet areas are going to get wetter, and dry areas drier." Since higher temperatures lead to increased evaporation, even areas that continue to receive the same amount of overall precipitation will become more prone to drought. This poses a particular risk for regions that already subsist on minimal rainfall or that depend on rain-fed agriculture.

"If you look at Africa, only about 6 percent of its cropland is irrigated," notes Sandra Postel, an expert on freshwater resources and director of the Global Water Policy Project. "So it's a very vulnerable region."

Meanwhile, when rain does come, it will likely arrive in more intense bursts, increasing the risk of flooding—even in areas that are drying out. A recent report by the United Nations' Intergovernmental Panel on Climate Change (IPCC) notes that "heavy precipitation events are projected to become more frequent" and that an increase in such events is probably already contributing to disaster. In the single dec­ade between 1996 and 2005 there were twice as many inland flood catastrophes as in the three decades between 1950 and 1980.

"It happens not just spatially, but also in time," says Brian Soden, a professor of marine and atmospheric science at the University of Miami. "And so the dry periods become drier, and the wet periods become wetter."

Quantifying the effects of global warming on rainfall patterns is challenging. Rain is what scientists call a "noisy" phenomenon, meaning that there is a great deal of natural variability from year to year. Experts say that it may not be until the middle of this century that some long-term changes in precipitation emerge from the background clatter of year-to-year fluctuations. But others are already discernible. Between 1925 and 1999, the area between 40 and 70 degrees north latitude grew rainier, while the area between zero and 30 degrees north grew drier. In keeping with this broad trend, northern Europe seems to be growing wetter, while the southern part of the continent grows more arid. The Spanish Environment Ministry has estimated that, owing to the combined effects of climate change and poor land-use practices, fully a third of the country is at risk of desertification. Meanwhile, the island of Cyprus has become so parched that in the summer of 2008, with its reservoir levels at just 7 percent, it was forced to start shipping in water from Greece.

"I worry," says Cyprus's environment commissioner, Charalambos Theopemptou. "The IPCC is talking about a 20 or 30 percent reduction of rainfall in this area, which means that the problem is here to stay. And this combined with higher temperatures—I think it is going to make life very hard in the whole of the Mediterranean."

Other problems could follow from changes not so much in the amount of precipitation as in the type. It is estimated that more than a billion people—about a sixth of the world's population—live in regions whose water supply depends, at least in part, on runoff from glaciers or seasonal snowmelt. As the world warms, more precipitation will fall as rain and less as snow, so this storage system may break down. The Peruvian city of Cusco, for instance, relies in part on runoff from the glaciers of the Quelccaya ice cap to provide water in summer. In recent years, as the glaciers have receded owing to rising temperatures, Cusco has periodically had to resort to water rationing.

Several recent reports, including a National Intelligence Assessment prepared for American policymakers in 2008, predict that over the next few decades, climate change will emerge as a significant source of political instability. (It was no coincidence, perhaps, that the drought-parched Akkad empire was governed in the end by a flurry of teetering monarchies.) Water shortages in particular are likely to create or exacerbate international tensions. "In some areas of the Middle East, tensions over water already exist," notes a study prepared by a panel of retired U.S. military officials. Rising temperatures may already be swelling the ranks of international refugees—"Climate change is today one of the main drivers of forced displacement," the United Nations High Commissioner for Refugees, Antรณnio Guterres, has said—and contributing to armed clashes. Some experts see a connection between the fighting in Darfur, which has claimed an estimated 300,000 lives, and changes in rainfall in the region, bringing nomadic herders into conflict with farmers.

Will the rainfall changes of the future affect societies as severely as some of the changes of the past? The American Southwest, to look at one example, has historically been prone to droughts severe enough to wipe out—or at least disperse—local populations. (It is believed that one such megadrought at the end of the 13th century contributed to the demise of the Anasazi civilization, centered in what currently is the Four Corners.) Nowadays, of course, water-management techniques are a good deal more sophisticated than they once were, and the Southwest is supported by what Richard Seager, an expert on the climatic history of the region, calls "plumbing on a continental scale." Just how vulnerable is it to the aridity likely to result from global warming?

"We do not know, because we have not been at this point before," Seager observes. "But as man changes the climate, we may be about to find out." 

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Saturday, March 21, 2009

Additional SWMM 3,4 Converter Information

Step 1: Open up or run the converter
Step 2: Define your text editor if you want to use the Edit Button
Step 3: Define the programs ini file if you want to use it multiple times
Step 4: Click on Select to convert either a Runoff, Runoff and Transport or Runoff and Extran
Step 5: Click on Convert to convert the two selected files
Step 6: File Converted Message will tell you that the file9s) were converted correctly.
Step 7: Please make sure to check the log file to confirm that everything was converted successfully.
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Saturday, January 3, 2009

๐Ÿ“Š SWMM 5 Complexity Index ๐Ÿ“Š

๐Ÿ“Š SWMM 5 Complexity Index ๐Ÿ“Š

The SWMM 5 Complexity Index offers a way to measure a model's intricacy against a benchmark: the first Extran example in Extran 3, now referred to as network #1 in this broader SWMM 5 context. The foundational network showcases 22 objects and runs simulations over 8 hours. ๐Ÿ•— Notably, it took 5 minutes to process this network on an IBM AT back in 1988. ๐Ÿ–ฅ️⏳

The core aim of this complexity index? To provide a comparative tool for contemporary models. ๐Ÿ“ˆ๐Ÿ”„ The complexity formula evaluates the object count in the new model versus the baseline, while also accounting for any extensions in simulation time. ๐Ÿ”„๐Ÿ”๐Ÿ“

๐Ÿ“Š Complexity Index Breakdown ๐Ÿ“Š

The complexity index consolidates the count of various elements: raingages, subcatchments, junctions, outfalls, dividers, storages, conduits, pumps, orifices, weirs, outlets, control curves, and many more, right up to snowpack objects. ๐ŸŒง️๐ŸŒ๐Ÿšฐ๐Ÿ”€๐ŸŒŠ

For a more nuanced understanding, this index is then amplified by tallying pollutants across various elements like subcatchments, junctions, or weirs. Additionally, the multiplication of the number of land uses by the count of subcatchment objects is considered. ๐Ÿงช๐Ÿ”„๐ŸŒณ๐Ÿ˜️

To gauge its relative complexity, this index is juxtaposed against network #1. This involves dividing the freshly computed complexity index by the foundational 22 objects and contrasting the new network's duration against the 8-hour benchmark of the base network. ๐Ÿ•—๐Ÿ“ The exemplified network flaunts a complexity rating of 5.2 and, impressively, executes in under a second on an Intel Dual Core Processor. ๐Ÿ–ฅ️⚡

๐Ÿ” Understanding the Complexity Index

The complexity index is a comprehensive metric that sums up various components of a given hydrologic model. Specifically, it aggregates:

  • Rain gauges, subcatchments, junctions, outfalls, dividers, storages, conduits, pumps, orifices, weirs, outlets, and several curve types (control, diversion, pump, rating, shape, storage, tidal), as well as time series, patterns, transects, hydrographs, aquifers, controls, climate objects, and snowpacks. ๐ŸŒฆ️๐ŸŒ๐Ÿšฐ

  • The index is then adjusted by taking into account the number of pollutants for multiple components like subcatchments, junctions, outfalls, and so forth. ๐Ÿงช

  • Additionally, it factors in the number of land uses multiplied by the count of subcatchment objects. ๐ŸŒฒ๐Ÿ™️

๐Ÿ“ Comparing the Complexity Index:

To gauge the relative complexity of a network:

  1. The computed complexity index is divided by a baseline value of 22 objects. ๐Ÿ“Š
  2. The duration of the new network is normalized against an 8-hour duration of a reference network. ๐Ÿ•—

For example, a showcased network had a complexity index of 5.2 and executed in under a second on an Intel Dual Core Processor. ๐Ÿ’จ๐Ÿ–ฅ️

๐Ÿ“‚ Complexity Indices from Sample Models:

Using the EPA SWMM 5 QA/QC suite of files, the complexity indices for different models in the DATA.ZIP file are:

  • USER4.INP: 88.5 ๐Ÿ“ˆ
  • USER1.INP: 7.4 ๐Ÿ“‰
  • USER2.INP: 55 ๐Ÿ“Š
  • USER3.INP: 20.1 ๐Ÿ“‰
  • USER5.INP: 18.5 ๐Ÿ“‰

In essence, the complexity index provides a quantitative measure of a hydrologic model's intricacy, enabling modelers to benchmark and optimize performance efficiently. ๐Ÿ‘ฉ‍๐Ÿ’ผ๐Ÿ”ง๐Ÿ“Š

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