SWMM-USERS Digest - 5 Feb 2012 to 6 Feb 2012 (#2012-11)

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Feb 7, 2012, 12:00:19 AM2/7/12

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There are 7 messages totaling 1036 lines in this issue.

Topics of the day:

1. Pumping in SWMM - timeseries reporting (4)
2. how to get "automatically" time series output
3. FW: Water Quality EMC- Calgary (2)

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Date: Mon, 6 Feb 2012 06:49:20 -0500
From: Rob James <r...@CHIWATER.COM>
Subject: Re: Pumping in SWMM - timeseries reporting

Hi Nick,

Not sure if this is a typo, but startup depth should be greater than the shutoff depth.

Sincerely,

Rob James
Computational Hydraulics Int.
www.chiwater.com
Tel: 519-767-0197 x1002

On 2012-02-05, at 6:46 PM, "Nick Andrewes" <Nick.A...@GHD.COM> wrote:

> Hi there,
>
> I am after some advice on the use of pumps in EPA SWMM.
>
> I have been using EPA SWMM to model a storm water scenario that includes
> pumping between two open storages. Modelling has been undertaken on a 6
> min timestep over 3 years.
>
> I have two variable speed drive 'type 2' pumps operating based on start up
> and shutoff depths at the 'source' storage as follows:
>
> Pump 1
>
> Initial status: OFF
> Startup Depth: 1
> Shutoff Depth: 1.3
>
> Depth (m) Flow (CMS)
> 0 0
> 0.999 0
> 1 0.015
> 1.2 0.015
> 1.201 0.03
> 1.3 0.03
>
> Pump 2
>
> Initial status: OFF
> Startup Depth: 1.301
> Shutoff Depth: 3
>
> Depth (m) Flow (CMS)
> 0 0
> 1.3 0
> 1.301 0.23
> 1.4 0.23
> 1.401 0.43
> 3 0.43
>
> I am concerned the pumps are not operating correctly based on a time
> series comparison of depths at the 'source' storage and pump flow rate.
>
> The pump flow time series shows that pumping generally occurs at the
> intended rates when the depth of the 'source' storage is appropriate.
> However in some cases the time series indicates no pumping occurs when the
> depth time series indicates there should be pumping.
>
> Additionally, when there is zero flow in the pumping time series in some
> cases the depth of the 'source' storage appears to reduce at a rate
> similar to what would be expected if pumping was occurring. However in
> other cases where pump flow is zero and the depth is within pumping range,
> the depth of the 'source' storage does not reduce.
>
> Pump 1 and pump 2 are reported in the 'highest flow instability indexes'
> table with values of 31 and 1 respectively. I have tried other pump
> setups including using a single pump and a force main pipe instead of a
> direct pump connection between storages but have not been able to achieve
> a more stable setup.
>
> Neither the storages being pumped from or two are reported as having high
> continuity errors.
>
> At this stage I am unsure if this is a reporting or modelling issue (or
> both) and would appreciate any feedback from people who may have
> encountered this before or could suggest anything I might try.
>
> Some additional information is included below:
>
> 1. Model numerical precision is 4 decimal places for depth and flow
> 2. Flow routing continuity error is 0.025 %
> 3. Pumps are directly connected between storages
> 4. A control rule is in operation for another pump in the model. The
> control rule specifies pump operation based on month of the year. This
> does not correlate to when pump 1 and pump 2 appear to be malfunctioning
> as per the time series.
> 5. Other than pumping losses occur through monthly evaporation @ a peak of
> approximately 7 mm/day.
>
> Thanks for your help.
>
> Regards
>
> Nick Andrewes
> Environmental Engineer | Waterways & Stormwater Service Group
>
> GHD Accomplish More Together
> T: 61 3 8687 8000 | V: 318626 | nick.a...@ghd.com
> 180 Lonsdale St Melbourne VIC 3000 Australia | http://www.ghd.com/
> Water | Energy & Resources | Environment | Property & Buildings |
> Transportation
>
> Please consider the environment before printing this email
>
> _____________________
> This email and all attachments are confidential. For further important information about emails sent to or from GHD or if you have received this email in error, please refer to http://www.ghd.com/emaildisclaimer.html .
> _____________________
> This e-mail has been scanned for viruses by MessageLabs.
>
> **********************************************************
> * To sign off, email to: list...@listserv.uoguelph.ca *
> * In the body of the message type: signoff swmm-users *
> **********************************************************

------------------------------

Date: Mon, 6 Feb 2012 13:10:48 +0100
From: Roberto Perin <robert...@UNIUD.IT>
Subject: how to get "automatically" time series output

Dear Sirs,
I'm trying to use the report options to get flow time series output in
the "rpt" text only for some links (or node).
Is there a way to get "automatically" the time series output (for
example in .txt format) only for selected nodes or links without the use
of the GUI ("Edit - Copy To" then in the "Copy Chart" box select
"Clipboard" or "File" etc.).
Thank you very much,

Best regards,

Roberto Perin

------------------------------

Date: Tue, 7 Feb 2012 08:13:45 +1000
From: Nick Andrewes <Nick.A...@GHD.COM>
Subject: Re: Pumping in SWMM - timeseries reporting

Thanks for your comments Jonathan,

I plan to run a couple more tests with the existing setup, including
running a series of fixed flow pumps (thanks for the suggestion!). My
next step after that is to break the model up also as you suggested. I'll
keep you posted.

Cheers

Nick

Nick Andrewes
Environmental Engineer | Waterways & Stormwater Service Group

Please consider the environment before printing this email

From:
Jonathan Welke <jwe...@KAMLOOPS.CA>
To:
SWMM-...@LISTSERV.UOGUELPH.CA
Date:
06/02/2012 02:10 PM
Subject:
Re: Pumping in SWMM - timeseries reporting
Sent by:
SWMM-USERS <SWMM-...@LISTSERV.UOGUELPH.CA>

Nick,

I've always had issues with pumps and storage in SWMM. The larger the
storage the more issues. Here are some tips that have worked for me in
the past.

Instead of using a variable pumping set up series of fix flow pumps
varying start/stop levels to achieve the same thing.Superficially lower
you storage so that water levels do not back water any incoming
elements.Run the model for the upstream elements to develop the incoming
hydrograph to the storage node. Then use this in a separate model of the
storage and pumps.
These may work for you, or may not. I'm not sure why they have worked in
the past, but suspect backwatering over multiple elements complicated
things (even though this should not be an issue with dynamic wave). I'm
more of a practical user rather than knowing the intricacies of the
engine. So when I find something that works just run with it.

Definitely test it out with some shorter runs as Robert suggested to proof
things out.

Good luck!

Jonathan Welke, P.Eng.
Water and Sewer Engineer
City of Kamloops
Direct Line: 250-828-3467

>>> Nick Andrewes 02/05/12 4:42 PM >>>
Hi Robert,

Thanks for your very fast response!

In response to your comments:

1. The pump summary table indicates that the percent utilised for Pump 1
(low flow pump) is 11.04 % with a total of 221 ML pumped. Pump 2 (high
flow pump) is 0.55% utilised with 180 ML pumped.
The % time off the high curve for Pump 1 is 17.1% and 0% off the low
curve. The % time off the high and low curve for Pump 2 is 0% and 0 %
respectively.

The latter seems consistent with the modelled pump curves (as per my
previous post).

2. The model is reporting on a 6 min time step.
3. The model also includes a pipe network upstream of the storages. It is

setup to run using dynamic wave routing at a 0.5 second timestep.
4. Based on the number of start-ups for pump 1 (17326472) and
considering the time series lengths, this equates to one start up every
5.46 seconds!

I fully agree that care must be taken to understand how the output time
step may portray the modelling results. However in this case my thoughts
were that the reporting time step should be sufficient to capture the
change in the 'source' storage depth and therefore the pumping rate, which

is being used as the pump control based on depth.

Thanks again for your comments/suggestions, based on my response would
you alter anything else with regards to the model setup?

Regards

Nick Andrewes
Environmental Engineer | Waterways & Stormwater Service Group

Please consider the environment before printing this email

From:
Robert Dickinson
To:
SWMM-...@LISTSERV.UOGUELPH.CA
Date:
06/02/2012 10:59 AM
Subject:
Re: Pumping in SWMM - timeseries reporting
Sent by:
SWMM-USERS

Hi Nick,

A few comments:

1. Have you looked at the Pump Summary Table to see how many times the
pumps turn on and what percent of the time the pumps are high or low off
the pump curve - you can find this table at the very end of the RPT file,
2. You mention using a 3 year simulation which sort of implies you are
saving information every 15 minutes or longer and thereby missing most of
what happens in your model visually in the graphs.
3. Is your hydraulic time step 6 minutes for the dynamic wave solution?
4. How long do your pumps turn on for the average pump start - this might
be a better time step to use.

I would lower your time step, run the model for a few weeks at a very
small report time step and then do some node vs pump graphs to satisfy
yourself the pumps and node depths are in sync at small report time steps.

Once you understand visually how matters stand for a short period
simulation you can go back to a 3 year model but realize the report time
step is important in understanding your model.

Robert Dickinson
Product Sector Leader
Innovyze Inc.
9340 Pontiac Drive Tel: 813-712-0664
Tampa, Florida USA 33626
robert.d...@innovyze.com
www.innovyze.com

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of
Nick Andrewes
Sent: Sunday, February 05, 2012 6:36 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] Pumping in SWMM - timeseries reporting

Hi there,

I am after some advice on the use of pumps in EPA SWMM.

I have been using EPA SWMM to model a storm water scenario that includes
pumping between two open storages. Modelling has been undertaken on a 6
min timestep over 3 years.

I have two variable speed drive 'type 2' pumps operating based on start up

and shutoff depths at the 'source' storage as follows:

Pump 1

Initial status: OFF
Startup Depth: 1
Shutoff Depth: 1.3

Depth (m) Flow (CMS)
0 0
0.999 0
1 0.015
1.2 0.015
1.201 0.03
1.3 0.03

Pump 2

Initial status: OFF
Startup Depth: 1.301
Shutoff Depth: 3

Depth (m) Flow (CMS)
0 0
1.3 0
1.301 0.23
1.4 0.23
1.401 0.43
3 0.43

I am concerned the pumps are not operating correctly based on a time
series comparison of depths at the 'source' storage and pump flow rate.

The pump flow time series shows that pumping generally occurs at the
intended rates when the depth of the 'source' storage is appropriate.
However in some cases the time series indicates no pumping occurs when the

depth time series indicates there should be pumping.

Additionally, when there is zero flow in the pumping time series in some
cases the depth of the 'source' storage appears to reduce at a rate
similar to what would be expected if pumping was occurring. However in
other cases where pump flow is zero and the depth is within pumping range,

the depth of the 'source' storage does not reduce.

Pump 1 and pump 2 are reported in the 'highest flow instability indexes'
table with values of 31 and 1 respectively. I have tried other pump
setups including using a single pump and a force main pipe instead of a
direct pump connection between storages but have not been able to achieve
a more stable setup.

Neither the storages being pumped from or two are reported as having high
continuity errors.

At this stage I am unsure if this is a reporting or modelling issue (or
both) and would appreciate any feedback from people who may have
encountered this before or could suggest anything I might try.

Some additional information is included below:

1. Model numerical precision is 4 decimal places for depth and flow
2. Flow routing continuity error is 0.025 %
3. Pumps are directly connected between storages
4. A control rule is in operation for another pump in the model. The
control rule specifies pump operation based on month of the year. This
does not correlate to when pump 1 and pump 2 appear to be malfunctioning
as per the time series.
5. Other than pumping losses occur through monthly evaporation @ a peak of

approximately 7 mm/day.

Thanks for your help.

Regards

Nick Andrewes
Environmental Engineer | Waterways & Stormwater Service Group

Please consider the environment before printing this email

_____________________
This email and all attachments are confidential. For further important
information about emails sent to or from GHD or if you have received this
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Our corporate mission is...
MAKING KAMLOOPS SHINE

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------------------------------

Date: Tue, 7 Feb 2012 08:19:51 +1000
From: Nick Andrewes <Nick.A...@GHD.COM>
Subject: Re: Pumping in SWMM - timeseries reporting

Hi Rob,

That could be a major problem! I was under the impression that if I
wanted to pump between say 1m depth and 1.5 m depth the start up depth was
the lower of the two numbers. However I guess I was thinking about it
from the perspective of the incoming hydrograph entering the storage and
raising the water levels.

I'll certainly give it a go but what baffles me is that the pumps seem to
be working correctly with the existing startup depth/ shutoff depth setup
for most of the time series.

Thanks

Nick

Nick Andrewes
Environmental Engineer | Waterways & Stormwater Service Group

Please consider the environment before printing this email

From:
Rob James <r...@CHIWATER.COM>
To:
SWMM-...@LISTSERV.UOGUELPH.CA
Date:
06/02/2012 10:49 PM
Subject:
Re: Pumping in SWMM - timeseries reporting
Sent by:
SWMM-USERS <SWMM-...@LISTSERV.UOGUELPH.CA>

Hi Nick,

Not sure if this is a typo, but startup depth should be greater than the
shutoff depth.

Sincerely,

Rob James
Computational Hydraulics Int.
www.chiwater.com
Tel: 519-767-0197 x1002

On 2012-02-05, at 6:46 PM, "Nick Andrewes" <Nick.A...@GHD.COM> wrote:

> Hi there,
>
> I am after some advice on the use of pumps in EPA SWMM.
>
> I have been using EPA SWMM to model a storm water scenario that includes

> pumping between two open storages. Modelling has been undertaken on a 6

> min timestep over 3 years.
>
> I have two variable speed drive 'type 2' pumps operating based on start
up
> and shutoff depths at the 'source' storage as follows:
>
> Pump 1
>
> Initial status: OFF
> Startup Depth: 1
> Shutoff Depth: 1.3
>
> Depth (m) Flow (CMS)
> 0 0
> 0.999 0
> 1 0.015
> 1.2 0.015
> 1.201 0.03
> 1.3 0.03
>
> Pump 2
>
> Initial status: OFF
> Startup Depth: 1.301
> Shutoff Depth: 3
>
> Depth (m) Flow (CMS)
> 0 0
> 1.3 0
> 1.301 0.23
> 1.4 0.23
> 1.401 0.43
> 3 0.43
>
> I am concerned the pumps are not operating correctly based on a time
> series comparison of depths at the 'source' storage and pump flow rate.
>
> The pump flow time series shows that pumping generally occurs at the
> intended rates when the depth of the 'source' storage is appropriate.
> However in some cases the time series indicates no pumping occurs when
the
> depth time series indicates there should be pumping.
>
> Additionally, when there is zero flow in the pumping time series in some

> cases the depth of the 'source' storage appears to reduce at a rate
> similar to what would be expected if pumping was occurring. However in
> other cases where pump flow is zero and the depth is within pumping
range,
> the depth of the 'source' storage does not reduce.
>
> Pump 1 and pump 2 are reported in the 'highest flow instability indexes'

> table with values of 31 and 1 respectively. I have tried other pump
> setups including using a single pump and a force main pipe instead of a
> direct pump connection between storages but have not been able to
achieve
> a more stable setup.
>
> Neither the storages being pumped from or two are reported as having
high
> continuity errors.
>
> At this stage I am unsure if this is a reporting or modelling issue (or
> both) and would appreciate any feedback from people who may have
> encountered this before or could suggest anything I might try.
>
> Some additional information is included below:
>
> 1. Model numerical precision is 4 decimal places for depth and flow
> 2. Flow routing continuity error is 0.025 %
> 3. Pumps are directly connected between storages
> 4. A control rule is in operation for another pump in the model. The
> control rule specifies pump operation based on month of the year. This
> does not correlate to when pump 1 and pump 2 appear to be malfunctioning

> as per the time series.
> 5. Other than pumping losses occur through monthly evaporation @ a peak
of
> approximately 7 mm/day.
>
> Thanks for your help.
>
> Regards
>
> Nick Andrewes
> Environmental Engineer | Waterways & Stormwater Service Group
>
> GHD Accomplish More Together
> T: 61 3 8687 8000 | V: 318626 | nick.a...@ghd.com
> 180 Lonsdale St Melbourne VIC 3000 Australia | http://www.ghd.com/
> Water | Energy & Resources | Environment | Property & Buildings |
> Transportation
>
> Please consider the environment before printing this email
>
> _____________________
> This email and all attachments are confidential. For further important
information about emails sent to or from GHD or if you have received this
email in error, please refer to http://www.ghd.com/emaildisclaimer.html .
> _____________________
> This e-mail has been scanned for viruses by MessageLabs.
>
> **********************************************************
> * To sign off, email to: list...@listserv.uoguelph.ca *
> * In the body of the message type: signoff swmm-users *
> **********************************************************

_____________________
This e-mail has been scanned for viruses by MessageLabs.

_____________________
This email and all attachments are confidential. For further important information about emails sent to or from GHD or if you have received this email in error, please refer to http://www.ghd.com/emaildisclaimer.html .
_____________________
This e-mail has been scanned for viruses by MessageLabs.

------------------------------

Date: Mon, 6 Feb 2012 15:23:48 -0800
From: "Pang, Joseph" <Josep...@SEATTLE.GOV>
Subject: Re: Pumping in SWMM - timeseries reporting

See code in link_setTargetSetting(int j) and this should help you to figure out what's going on...

if ( Pump[k].yOff > 0.0 && //(5.0.010 - LR)
Link[j].setting > 0.0 && //(5.0.010 - LR)
Node[n1].newDepth < Pump[k].yOff ) Link[j].targetSetting = 0.0; //(5.0.010 - LR)
if ( Pump[k].yOn > 0.0 && //(5.0.010 - LR)
Link[j].setting == 0.0 && //(5.0.010 - LR)
Node[n1].newDepth > Pump[k].yOn ) Link[j].targetSetting = 1.0; //(5.0.010 - LR)

link_setTargetSetting(int j) is the only place where I can find reference of Pump[].yOn and Pump[].yOff. If I understand the code correctly and haven't missed anything in the code, I think this is what it does..

Condition 1: If Shut-off Depth > 0 and Pump is on and wet-well level < shut-off depth, then pump is shut off.
Condition 2: If Start-up depth > 0 and Pump is off and wet-well level > start-up depth, then pump is turned on.

So if you've a shut-off depth greater than start-up depth and your wet well is empty initially, your pump is turned on once the wet-well level is above start-up depth (Condition 1), but then it will be shut off probably in the next time step because it will have satisfied Condition 2 in the next time step.

I think the shut-off depth is used to model operation of pump station with the shut-off depth being lower than the start-up depth which is usually the case for setting pump station on/off level under normal operation.

If you find your wet-well level reduces while your pump is not pumping, check whether your wet-well storage node is flooding or not. If you use storage node to model wet-well, ponded area function is not applicable to storage node and thus all water that floods a storage node is lost from the system.

Joseph P.

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Nick Andrewes
Sent: Monday, February 06, 2012 2:20 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Pumping in SWMM - timeseries reporting

Hi Rob,

That could be a major problem! I was under the impression that if I wanted to pump between say 1m depth and 1.5 m depth the start up depth was the lower of the two numbers. However I guess I was thinking about it from the perspective of the incoming hydrograph entering the storage and raising the water levels.

I'll certainly give it a go but what baffles me is that the pumps seem to be working correctly with the existing startup depth/ shutoff depth setup for most of the time series.

Thanks

Nick

Nick Andrewes
Environmental Engineer | Waterways & Stormwater Service Group

Please consider the environment before printing this email

From:
Rob James <r...@CHIWATER.COM>
To:
SWMM-...@LISTSERV.UOGUELPH.CA
Date:
06/02/2012 10:49 PM
Subject:
Re: Pumping in SWMM - timeseries reporting Sent by:
SWMM-USERS <SWMM-...@LISTSERV.UOGUELPH.CA>

Hi Nick,

Not sure if this is a typo, but startup depth should be greater than the shutoff depth.

Sincerely,

Rob James
Computational Hydraulics Int.
www.chiwater.com
Tel: 519-767-0197 x1002

On 2012-02-05, at 6:46 PM, "Nick Andrewes" <Nick.A...@GHD.COM> wrote:

> Hi there,
>
> I am after some advice on the use of pumps in EPA SWMM.
>
> I have been using EPA SWMM to model a storm water scenario that
> includes

> pumping between two open storages. Modelling has been undertaken on a
> 6

> min timestep over 3 years.
>
> I have two variable speed drive 'type 2' pumps operating based on
> start
up
> and shutoff depths at the 'source' storage as follows:
>
> Pump 1
>
> Initial status: OFF
> Startup Depth: 1
> Shutoff Depth: 1.3
>
> Depth (m) Flow (CMS)
> 0 0
> 0.999 0
> 1 0.015
> 1.2 0.015
> 1.201 0.03
> 1.3 0.03
>
> Pump 2
>
> Initial status: OFF
> Startup Depth: 1.301
> Shutoff Depth: 3
>
> Depth (m) Flow (CMS)
> 0 0
> 1.3 0
> 1.301 0.23
> 1.4 0.23
> 1.401 0.43
> 3 0.43
>
> I am concerned the pumps are not operating correctly based on a time
> series comparison of depths at the 'source' storage and pump flow rate.
>
> The pump flow time series shows that pumping generally occurs at the
> intended rates when the depth of the 'source' storage is appropriate.
> However in some cases the time series indicates no pumping occurs when
the
> depth time series indicates there should be pumping.
>
> Additionally, when there is zero flow in the pumping time series in
> some

> cases the depth of the 'source' storage appears to reduce at a rate
> similar to what would be expected if pumping was occurring. However
> in other cases where pump flow is zero and the depth is within pumping
range,
> the depth of the 'source' storage does not reduce.
>
> Pump 1 and pump 2 are reported in the 'highest flow instability indexes'

> table with values of 31 and 1 respectively. I have tried other pump
> setups including using a single pump and a force main pipe instead of
> a direct pump connection between storages but have not been able to
achieve
> a more stable setup.
>
> Neither the storages being pumped from or two are reported as having
high
> continuity errors.
>
> At this stage I am unsure if this is a reporting or modelling issue
> (or
> both) and would appreciate any feedback from people who may have
> encountered this before or could suggest anything I might try.
>
> Some additional information is included below:
>
> 1. Model numerical precision is 4 decimal places for depth and flow 2.
> Flow routing continuity error is 0.025 % 3. Pumps are directly
> connected between storages 4. A control rule is in operation for
> another pump in the model. The control rule specifies pump operation
> based on month of the year. This does not correlate to when pump 1
> and pump 2 appear to be malfunctioning

> as per the time series.
> 5. Other than pumping losses occur through monthly evaporation @ a
> peak
of
> approximately 7 mm/day.
>
> Thanks for your help.
>
> Regards
>
> Nick Andrewes
> Environmental Engineer | Waterways & Stormwater Service Group
>
> GHD Accomplish More Together
> T: 61 3 8687 8000 | V: 318626 | nick.a...@ghd.com
> 180 Lonsdale St Melbourne VIC 3000 Australia | http://www.ghd.com/
> Water | Energy & Resources | Environment | Property & Buildings |
> Transportation
>
> Please consider the environment before printing this email
>
> _____________________
> This email and all attachments are confidential. For further important
information about emails sent to or from GHD or if you have received this email in error, please refer to http://www.ghd.com/emaildisclaimer.html .
> _____________________
> This e-mail has been scanned for viruses by MessageLabs.
>
> **********************************************************
> * To sign off, email to: list...@listserv.uoguelph.ca *
> * In the body of the message type: signoff swmm-users *
> **********************************************************

_____________________
This e-mail has been scanned for viruses by MessageLabs.

_____________________
This email and all attachments are confidential. For further important information about emails sent to or from GHD or if you have received this email in error, please refer to http://www.ghd.com/emaildisclaimer.html .
_____________________
This e-mail has been scanned for viruses by MessageLabs.

------------------------------

Date: Mon, 6 Feb 2012 19:12:22 -0500
From: Bill <bi...@CHIWATER.COM>
Subject: FW: Water Quality EMC- Calgary

Hello swmm-users:

A consultant working for the City of Calgary has been asked to size and
design a rain garden and is considering using SWMM to carry out the water
quality and long term simulation analyses. However the City has never used
SWMM for such analyses and therefore has not yet developed an EMC
coefficient to model TSS. Can anyone commend EMC coefficients for
Calgary/Alberta or a way to find appropriate EMC coefficients? If these
criteria are not available then we would appreciate knowing that too.

Regards, Bill James

------------------------------

Date: Mon, 6 Feb 2012 20:03:50 -0500
From: Bill Lucas <wlu...@INTEGRATEDLAND.COM>
Subject: Re: FW: Water Quality EMC- Calgary

Hello Bill,

That is because there are no coefficients. Unlike ponds that use good old
Stokes Law, LID practices are primarily infiltrative, with essentially no
discharge until they cannot handle any more runoff. Then they discharge
with essentially minimal attenuation, or even export stressors, as is often
the case of pathogens.

However, if underdrain flows are somehow segregated, most stressors in those
flows are greatly attenuated, so one could use an irreducible concentration
approach. For instance, bioretention systems will typically discharge TSS in
the range of 2-10 mg/l. Dissolved P will vary depending upon load, media
and age of the system, so no good answer there. Dissolved N will vary even
more, depending upon retention time. I am hoping that Lew will put together
a module to compute that one of these days.

So the issue comes down to segregating the annual surface flows from
underdrain flows. While SWMM-LID does not do this explicitly in terms of
routing, you can set up the LID file to be queried so as to obtain this
data. You can then apply the "appropriate" EMCs to the volumes filtered and
those bypassed to get the effective mass loads delivered via each pathway.
You can go to the literature for the appropriate EMC values. I strongly
recommend this approach.

Frankly, if you want to model a rain garden by its lonesome, I think the
RECARGA or SPAW models do as good a job as any model in the public domain.
Their unsaturated flow and ET algorithms are quite realistic. SWMM is a tool
better used for routing.

If you need to segregate underdrain flows from bypass flows in the routing
model, as is often needed for CSO modeling, then you have to get a little
sneaky. I do it using a dummy storage node, with an underdrain formulated
to match the SWMM parameters (this takes a little doing), and a bypass weir
to allow overflows to stay in the conventional drainage system. Pretty
simple, but now you have added a node and two links to each catchment, so
kind of cumbersome.

At the end of the current day, we still have a quite primitive understanding
of how LID works in terms of biogeochemistry of stressor transformations and
removals. However, we are getting there in terms of the hydrology. But we
still have a ways to go there, so there is still plenty of work for Lew :)

Bill L.

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Bill
Sent: Monday, February 06, 2012 7:12 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] FW: Water Quality EMC- Calgary

Hello swmm-users:

Regards, Bill James

------------------------------

End of SWMM-USERS Digest - 5 Feb 2012 to 6 Feb 2012 (#2012-11)
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