Dam/Reservoirs in SWAT modelling?

[majid...@gmail.com]

Hi everyone,

I have a watershed that I am trying to model the surface runoff for it, and I want to model the runoff for different land use maps of different years. In my watershed I have 2 dams, and I only have certain information for both dams, and I am not able to obtain other information for the dam operation. I have year the dams started operation, I have dam capacity, surface area, dam height, crest length, and I also have the amount of water each dams supplies to water treatment plants down stream. However I am not able to get dam discharge/release rates. And my gauging station is down stream below the dams.

So I wanted to know is there anyway I can still calibrate my SWAT model with the information I have? or any other method or software I can use to simulate the surface runoff, with the information I have?

I will really appreciate any help and advise, as I am currently stuck with this issue.

Thank You All,

Majid.

[Jim Almendinger]

Calibrating to a gauging station below the dams should be just fine -- that's very common.  If you don't have dam operation information, you could simply model the dams as impoundments with some storage that mitigates runoff events.  Try starting with IRESCO=2, set STARG1 to 12 = principal volume of the reservoir, and NDTARGR=2. 

-- Jim

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[majid...@gmail.com]

Dear Jim,

Thank you for the reply. What do I do for the RES_ESA, RES_PSA, RES_EVOL, RES_PVOL, and RES_VOL? do I use the surface area value i have for both the RES_ESA and RES_PSA? also do the same for the volume of water?

Also under the monthly data panel, under monthly parameters what should I be choosing ?

Regards,

Majid.

[Jim Almendinger]

Majid --

All I can tell you is that you have to make reasonable estimates of these values.  Your principal volume and area correspond to the elevation of the dam spillway and are likely very close to measured volume and area when the dam is spilling at typical baseflow conditions.  Your emergency volume and area MUST be larger than the principal values or SWAT will not allow any storage function of the reservoir -- all water in excess of EVOL is released the same day it is received.  If you have no other information, try setting the emergency volume and area at twice the principal volume and area, and see if that works well enough. 

I'm not sure I know what you mean by "monthly data panel."

-- Jim

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[majid...@gmail.com]

Dear Jim,

Thank you for the feedback.

I will try setting the volume and area twice the principal values. However currently I have another issue after I run the model and when i try to import file to database, if get a massage saying Not enough space on temporary disk. Do you know how I can resolve this issue? i still have about 80gb of free space.

As for the "Monthly data panel" I have attached a screen shot.

[Jim Almendinger]

I have no specific advice for disk-space issues, except to always keep >= 10% of your hard drive available, and rebooting your computer when you go get a cup of coffee.  There may be an ArcMap cache you can manually clear.  I've had to do that with other Arc tools in the past, but not ArcSWAT. 

-- Jim

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[majid...@gmail.com]

Dear Jim,

Thank you. I will try that.

Also did you see the screen shot I sent about the monthly data panel, when inputting reservoir info? It has the options Maximum monthly flow, minimum monthly flow, Monthly target storage, and Monthly consumptive use. So do i enter anything here?

Regards,

Majid.

[Jim Almendinger]

Majid --

I'm unfamiliar with the monthly data panel, I guess, because I always just enter my reservoir parameters directly into the res table in the project database.  I set up my reservoir parameters in an Excel spreadsheet, and then import the worksheet with my final values as a table in the project database -- and then I populate the values in the res table by using an update query in Access. 

For IRESCO=2, I think the only monthly data to enter would be the monthly target storages, which is optional.  I always set all 12 of them to the principal volume.  Otherwise the target volume is set to a value based on a soil-moisture, which I don't want for my lakes (my lakes are never managed to maximize water volume --- perhaps your reservoirs are). 

-- Jim

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[majid...@gmail.com]

Dear Jim,

Thank you for the reply.

I am still new to SWAT, so just wanted to make sure I Have go it right, is the res table in the MS Access file which has my project name and in the folder where I save my project? It's not the SWAT2012 access file right?.

Also is it ok to directly enter the reservoir values in the res table, without doing the excel sheet?

Regards,

Majid.

[Jim Almendinger]

Yes, the res table is in your project database, and you can enter values directly there, without the need to use an excel spreadsheet.  It's probably a good idea to make a copy of the table (and name it something like res_copy or res_orig) just in case you want to go back to it. 

The data in the tables in the project database are what ArcSWAT (actually, the SWAT-editor part of ArcSWAT, I think) uses to write the input text files in the txtinout folder, which are what the SWAT engine (the fortran executable) uses to actually run the model.  So every time you make a change in the database tables, you need to re-write the text files for that component (like reservoirs, or management, or soils, etc.) for SWAT to incorporate your changes. 

-- Jim

To view this discussion on the web visit https://groups.google.com/d/msgid/swatuser/d2a4c56a-3e58-4a34-a93b-76fb1bc1229dn%40googlegroups.com.

[majid...@gmail.com]

Dear Jim,

Thank you for the feedback and help.

I will try it and hopefully I am able to get some good outcomes.

Majid.

[majid...@gmail.com]

Dear Jim,

I entered the values in the res table and ran the model on monthly run. Then I did the swat error checker and for reservoir "it says At least one of your reservoirs ends the simulation with less than 20% volume that it begins with" I have attached a screen shots. What would you recommend I should change?

Also after running the model I checked the FLOW_OUT in the rch table and compared to the flow reading from my observation station, the model showing higher flow out. On some months its higher by like 10 to 20 m3/s and on some other months is more like by 60 m3/s. So I think one of the reservoirs is having high release and of curse I need to calibrate the other parameters of the model too.

Regards,

Majid.

On Sunday, 25 April 2021 at 20:08:18 UTC+8 almendi...@gmail.com wrote:

[Jim Almendinger]

I don't understand the output.  The initial/final volume ratios for both reservoirs are close to 1, so I don't see how the final volume for one of them is <20% of the initial.  Which is right?  You'll need to plot reservoir volume (or at least look at the output) against time to help interpret Swat-Check.

Also, your reservoirs appear to be generating sediment, which is unlikely. 

-- Jim

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[majid...@gmail.com]

Dear Jim,

I am not sure where the issue could be.

I have attached screen shots of the reservoir data I have entered and also the out put file of rsv and rch tables.

Can you check the screen shots and see if I have mad any mistake anywhere?

Also wanted to ask, my study area is in South East Asia and there is 2 monsoon and 2 inter-monsoon periods here, so it rains all year round. Should I be changing the IFLOD1R and IFLOD2R?

Also one more thing, when calibrating the calibration uses daily flow, is it still ok if my model run is in monthly time step?

Regards,

Majid.

[hermini...@gmail.com]

See the .res files

sometimes the reservoir settings are not saved

[majid...@gmail.com]

Hi Hermini,

Is the .res file in the Scenarios folder, in the Defaults folder and in the TxtInOut folder?