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SWMM-USERS Digest - 15 Mar 2012 to 16 Mar 2012 (#2012-28)

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Mar 17, 2012, 12:00:28 AM3/17/12

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There are 3 messages totaling 453 lines in this issue.

Topics of the day:

1. Evaporation rate and initial event time (3)

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Date: Fri, 16 Mar 2012 10:48:06 +0200
From: Gerald Krebs <gerald...@AALTO.FI>
Subject: Re: Evaporation rate and initial event time

I'm using SWMM 5.022 engine. One thing came to my mind still on the
evaporation issue:

When I have my evaporation set to "computed from temperatures in climate
file", every time I reopen the file I get the error message below and the
evaporation is set to "constant value". I always changed it back and it was
running fine (and computing what I assume to be correct evaporation rates).
Now I'm wondering, whether this error could have something to do with the
different output I get when using different methods for the evaporation
input. When evaporation is set to "directly from climate file", I don't get
any error when opening the file in SWMM.

Error Report for File C:\Users\gkrebs\TP_CAL.INP

Too few items at line 35:
[EVAPORATION]
TEMPERATURE

Thanks,
Gerald

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Pang,
Joseph
Sent: Friday, March 16, 2012 2:01
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Evaporation rate and initial event time

Which version of SWMM5 are you using? There have been updates on how
evaporation was handled since v19. If you are using SWMM5 v18 or older, you
would most likely get issues from evaporation depending on which methods you
use to input evaporation data into the model (calculated from temperature or
user input time series). Your AMC issue sounds like a v18 issue as well.
In v18, 0mm rainfall still equals raining. From information given in your
email, I would suggest that if you're not using SWMM5 v22 engine, try to use
v22 and see what you get.

Hope this helps.

Joseph Pang

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of
Gerald Krebs
Sent: Tuesday, March 13, 2012 8:40 AM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] Evaporation rate and initial event time

I'm in the process of calibrating an urban watershed (~95% impervious) in
SWMM for 6 independent storm events. The watershed is rather small 5.87ha,
but it is subdivided into 690 subcatchments (to allow for estimation of
on-site BMP effects). I'm planning to use multi-rainfall-event
multi-objective optimization for calibration. To minimize the model run time
(the events are from 2 different years) I want to rearrange (create a
continuous series) my calibration events to get them in an as short as
possible time span for one simulation. During this process two questions
were coming up:

1) I used SWMM's routine to compute evaporation based on daily
temperatures. When moving events (4 events stay at their correct date and 2
events move from July 2010 and 2009 to June 2010) the computed evaporation
rates change due to the difference in day length. My idea was to overcome
this issue by computing the evaporation rates first for the original event
dates and use the output as an input evaporation rate (mm/d) in my climate
file. However, my discharge curves differ (between 0.1 and 1 LPS) depending
whether I use SWMM to compute evaporation during simulation or use the
evaporation rates from the climate file. As my model setup is complicated I
used a very simple model (one 100% impervious catchment without any
depression storage and an outfall) to understand (or not ;-)) the issue.
Also this setup shows similar behavior. The water balance in the status
report is the same, losses for the subcatchment are the same, but the
discharge is slightly different (smaller though than in my complex model
setup). Any ideas where that comes from?

2) The second point concerns the initial time periods I need before the
events to maintain the same discharge behavior (initial catchment
condition). I will try to explain the issue using one event. The event dates
6/10/10-6/12/10 (~10mm precipitation). Before the event there was slight
precipitation (~1mm) on 6/10/10. The last rain before that was in the end of
May (~2mm). If I start the simulation on 6/10/10 (including the previous
rain), I get the same discharge as if I start the run 6/1/10. That's still
clear as there was no rain between 5/30/10 and 6/10/10. But when I still
include the rain from end May (simulation start at 5/29/10) I get a
different discharge for the event. The surface depression storage is empty
before the event with any initial run time. Besides surface depression
storage I have only the network and soil moisture to store water. I don't
believe a 2mm event can have an impact on soil moisture for 10 days in June
and affect the runoff (plus my pervious area allowing infiltration is very
small ~5%). I realized that the system storage is never getting empty after
a rain event (in fact it stays at 0.02m3 at the minimum). Also any ideas on
this subject are appreciated . Does somebody have experience with creating
a continuous sequence of independent events in SWMM?

Thanks, I hope I was able to explain somewhat understandable

Gerald

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

Date: Fri, 16 Mar 2012 09:55:39 -0700
From: "Pang, Joseph" <Josep...@SEATTLE.GOV>
Subject: Re: Evaporation rate and initial event time

This sounds strange. This might be issue with compatibility between your shell/GUI and the engine. Which GUI are you using - EPA SWMM, PCSWMM, XPSWMM? Open your .inp file in a text editor. Does your evaporation section look like this?

[EVAPORATION]
;;Type Parameters
;;---------- ----------
TEMPERATURE
DRY_ONLY NO <----this is line 35

Line 35 should indicate whether you want evaporation to happen during periods of no rain or not. If you're using EPA SWMM5 v22 GUI, your line 35 is automatically added and shouldn't have the error that you have, unless you're using a different shell.

If you are using any shell other than the EPA SWMM5 GUI, try to run it within the EPA SWMM GUI and see what you get.

Joseph

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Gerald Krebs
Sent: Friday, March 16, 2012 1:48 AM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Evaporation rate and initial event time

I'm using SWMM 5.022 engine. One thing came to my mind still on the evaporation issue:

When I have my evaporation set to "computed from temperatures in climate file", every time I reopen the file I get the error message below and the evaporation is set to "constant value". I always changed it back and it was running fine (and computing what I assume to be correct evaporation rates).
Now I'm wondering, whether this error could have something to do with the different output I get when using different methods for the evaporation input. When evaporation is set to "directly from climate file", I don't get any error when opening the file in SWMM.

Error Report for File C:\Users\gkrebs\TP_CAL.INP

Too few items at line 35:
[EVAPORATION]
TEMPERATURE

Thanks,
Gerald

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Pang, Joseph
Sent: Friday, March 16, 2012 2:01
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Evaporation rate and initial event time

Which version of SWMM5 are you using? There have been updates on how evaporation was handled since v19. If you are using SWMM5 v18 or older, you would most likely get issues from evaporation depending on which methods you use to input evaporation data into the model (calculated from temperature or user input time series). Your AMC issue sounds like a v18 issue as well.
In v18, 0mm rainfall still equals raining. From information given in your email, I would suggest that if you're not using SWMM5 v22 engine, try to use
v22 and see what you get.

Hope this helps.

Joseph Pang

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Gerald Krebs
Sent: Tuesday, March 13, 2012 8:40 AM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] Evaporation rate and initial event time

I'm in the process of calibrating an urban watershed (~95% impervious) in SWMM for 6 independent storm events. The watershed is rather small 5.87ha, but it is subdivided into 690 subcatchments (to allow for estimation of on-site BMP effects). I'm planning to use multi-rainfall-event multi-objective optimization for calibration. To minimize the model run time (the events are from 2 different years) I want to rearrange (create a continuous series) my calibration events to get them in an as short as possible time span for one simulation. During this process two questions were coming up:

1) I used SWMM's routine to compute evaporation based on daily
temperatures. When moving events (4 events stay at their correct date and 2 events move from July 2010 and 2009 to June 2010) the computed evaporation rates change due to the difference in day length. My idea was to overcome this issue by computing the evaporation rates first for the original event dates and use the output as an input evaporation rate (mm/d) in my climate file. However, my discharge curves differ (between 0.1 and 1 LPS) depending whether I use SWMM to compute evaporation during simulation or use the evaporation rates from the climate file. As my model setup is complicated I used a very simple model (one 100% impervious catchment without any depression storage and an outfall) to understand (or not ;-)) the issue.
Also this setup shows similar behavior. The water balance in the status report is the same, losses for the subcatchment are the same, but the discharge is slightly different (smaller though than in my complex model setup). Any ideas where that comes from?

2) The second point concerns the initial time periods I need before the
events to maintain the same discharge behavior (initial catchment condition). I will try to explain the issue using one event. The event dates
6/10/10-6/12/10 (~10mm precipitation). Before the event there was slight precipitation (~1mm) on 6/10/10. The last rain before that was in the end of May (~2mm). If I start the simulation on 6/10/10 (including the previous rain), I get the same discharge as if I start the run 6/1/10. That's still clear as there was no rain between 5/30/10 and 6/10/10. But when I still include the rain from end May (simulation start at 5/29/10) I get a different discharge for the event. The surface depression storage is empty before the event with any initial run time. Besides surface depression storage I have only the network and soil moisture to store water. I don't believe a 2mm event can have an impact on soil moisture for 10 days in June and affect the runoff (plus my pervious area allowing infiltration is very small ~5%). I realized that the system storage is never getting empty after a rain event (in fact it stays at 0.02m3 at the minimum). Also any ideas on this subject are appreciated . Does somebody have experience with creating a continuous sequence of independent events in SWMM?

Thanks, I hope I was able to explain somewhat understandable

Gerald

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

Date: Fri, 16 Mar 2012 21:12:43 +0200
From: Gerald Krebs <gerald...@AALTO.FI>
Subject: Re: Evaporation rate and initial event time

I'm using the EPA SWMM5 GUI. And my .inp file has the "DRY_ONLY NO"
entry in line 35 also, as your example. The change after the error message
from "computed with temperatures" to "constant value" happens only in the
GUI, the .inp file stays the same also after closing the GUI again (looking
like your example below).

According to Mitch Heineman, this error message is a user interface bug and
does not influence the computation.

Unfortunately I can't access my files at the moment to check, but I'm
wondering whether my varying discharge output depending on the evaporation
input method could origin from this line 35 entry. I have it set on NO, with
both input methods, and I can't check now which input method produces less
evaporation. Could the difference maybe come from evaporation happening only
in dry times when computing it during simulation because of some "wrong
reading" of line 35 (even though it's set to NO)? When getting to my files
I'll check whether I still have a difference if I set DRY_ONLY to yes when
feeding evaporation rates via the climate file.

What I mentioned in the first mail, that the water balance is the same
independent from the evaporation input method, and only the discharge curves
differ, concerned the simple test setup I made. In my actual model setup the
water balance also differs (more/less evaporation/runoff) depending on the
input method.

Thanks,
Gerald

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Pang,
Joseph
Sent: 16. maaliskuuta 2012 18:56
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Evaporation rate and initial event time

This sounds strange. This might be issue with compatibility between your
shell/GUI and the engine. Which GUI are you using - EPA SWMM, PCSWMM,
XPSWMM? Open your .inp file in a text editor. Does your evaporation
section look like this?

[EVAPORATION]
;;Type Parameters
;;---------- ----------
TEMPERATURE
DRY_ONLY NO <----this is line 35

Line 35 should indicate whether you want evaporation to happen during
periods of no rain or not. If you're using EPA SWMM5 v22 GUI, your line 35
is automatically added and shouldn't have the error that you have, unless
you're using a different shell.

If you are using any shell other than the EPA SWMM5 GUI, try to run it
within the EPA SWMM GUI and see what you get.

Joseph

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of
Gerald Krebs
Sent: Friday, March 16, 2012 1:48 AM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Evaporation rate and initial event time

I'm using SWMM 5.022 engine. One thing came to my mind still on the
evaporation issue:

Error Report for File C:\Users\gkrebs\TP_CAL.INP

Too few items at line 35:
[EVAPORATION]
TEMPERATURE

Thanks,
Gerald

Hope this helps.

Joseph Pang

2) The second point concerns the initial time periods I need before the
events to maintain the same discharge behavior (initial catchment
condition). I will try to explain the issue using one event. The event dates
6/10/10-6/12/10 (~10mm precipitation). Before the event there was slight
precipitation (~1mm) on 6/10/10. The last rain before that was in the end of
May (~2mm). If I start the simulation on 6/10/10 (including the previous
rain), I get the same discharge as if I start the run 6/1/10. That's still
clear as there was no rain between 5/30/10 and 6/10/10. But when I still
include the rain from end May (simulation start at 5/29/10) I get a
different discharge for the event. The surface depression storage is empty
before the event with any initial run time. Besides surface depression
storage I have only the network and soil moisture to store water. I don't
believe a 2mm event can have an impact on soil moisture for 10 days in June
and affect the runoff (plus my pervious area allowing infiltration is very
small ~5%). I realized that the system storage is never getting empty after
a rain event (in fact it stays at 0.02m3 at the minimum). Also any ideas on
this subject are appreciated
. Does somebody have experience with creating a continuous sequence of
independent events in SWMM?

Thanks, I hope I was able to explain somewhat understandable

Gerald

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

End of SWMM-USERS Digest - 15 Mar 2012 to 16 Mar 2012 (#2012-28)
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