Modelling Irrigated Watershed Using SWAT

[Haddush Gidey]

Dear Friends,

I am having trouble with the Irrigation (Water management) Module of SWAT. I am using SWAT 2009, VER 488 to model a big Watershed characterized by different land uses, Agricultural (both Rain fed and Irrigated), Forest land Range land, Urban area and etc.

My question is, How can a simulated stream out flow at each reach that considers irrigation water abstraction be higher than a simulated stream out flow at each reach which do not consider irrigation water abstracted???.

My expectation was, the simulated stream flow at each reach that considers irrigation water abstraction would have been lesser than the one which don't consider irrigation water abstraction. However my result indicates the reverse!!! 

I need your help, Particularly about when irrigation water diverted from different junctions of the main channel of the study watershed???

           "when the source of irrigation is Reach"....

or How should I treat the General management and/or the management operations while editing my input data particularly diverted irrigated water to different sub basins

Kind regards...!!!  

[Willem Vervoort]

Haddush,

One possiblility is that the "return flows" from your irrigation are substantial. If the irrigation recharge leaks into your shallow groundwater reservoir then this can return water to the stream as baseflow.

The abstraction of irrigation water occurs from the reach that you specify.

You could check a few things:

- Are your crops growing? Are you getting biomass? If not that ET would be low and all your water just returns

- Is water being extracted from the reach?  (check your output) Or is there never enough water, as you specify some minimum value below which water cannot be extracted

I am not sure about different sub basins, I have never done that.

Willem

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[Haddush Gidey]

Dear Willem,

Thank you for your great information.

In my first message I asked that. "How can a simulated stream out flow at each reach that considers irrigation water abstraction be higher than a simulated stream out flow at each reach which do not consider irrigation water abstracted???. This result comes when I was editing only the second page of the management parameter "Auto Irrigation operation". I did not specify the irrigation SOURCE, SUB BASIN ID, FLOWMIN, DIVMAX, and FLOWFR. I know this is wrong even at that time, The reason was I could not fined any irrigation result if I edit both pages of the management parameter.

To make it clear, I have defined the irrigation source as well as its location, as the attached screen snap shot,

in both pages of the management parameter. After completing the other process required to Run my model, the model run was successful. However there is no result for Irrigation out put and water is not diverted at all. I am sure there is sufficient flow at each REACH specified as irrigation source

To verify this, I run the model for different irrigation sources, DEEP AQUIFER and for SHALLOW AQUIFER by editing both The management pages . in this case the auto irrigation provides me Irrigation out put results and possible schedule, Although the irrigation was not sufficient enough to produce sufficient biomass in for sugarcane.

my conclusion is the AUTO IRRIGATION is not working as long as the source of irrigation is REACH, or there is some thing which I couldn't understand with regard the auto irrigation when the source is diversion from REACH.

Finally; when I say "different sub basins" I have already specified earlier during the HRU definition the sub basins and the respected crop growing for example; out of the 16 sub basins in my study area, SEVEN,(7) of them are currently under irrigation. I specify not only the sub basin under irrigation but also the HRU in side that basin: for example, Sun basin number EIGHT,(8) has TWO HRUs under irrigation growing SUGARCANE in about 8000 ha of land. for this sub basin water is currently diverted from the main channel/river passing through this sub basin.

Why I am doing this, my scenarios are, determining return flow, optimizing irrigation as a result of improvement in irrigation efficiency, that is due to on farm and off farm management....and to determine the regional surface water balance....   

However due to this problem I didn't make any progress..., I hope you understand me. I need your kind support and recommendation in this regard brother!!!

Best regards

Haddush G.

[Ney Ríos]

I have the some problem. If you can solve the problem, please write me.
Regards,
Ney

[Haddush Gidey]

Dear Ney,

I didn't solved it yet...

However, I think it is better for you to start your irrigation by selecting an irrigation water source as " OUT SIDE SOURCE". After that you need to start editing the irrigation whose source is REACH. I tried in a similar way although the result was not satisfactory. I mean the irrigation out put results are not available in the HRU out put file..., on the other hand irrigation results can be seen from the General Watershed management file

 kind regards,

haddush G

[ashkan.f...@gmail.com]

Dear Haddush
As far as I know, currently auto-irrigation only work when the source of water set to groundwater (either shallow or deep). This problem still exist in 2012 version.
btw, I recommend you to use 2012, because the improvement is so much, specially in term of irrigation issues. 2009 version has a lot of bugs, specially rev 488.
You can edit general management parameters from "mgt1" table, in the project MDB file. You can edit all the model parameters on that file. But about management operations, I recommend to change them using arcswat interface, because manual setting of them is much harder from "mgt2" table.
Regards
Ashkan

[Haddush Gidey]

Dear Ashkan,

Thank you very much. I will try that option also...,

But my question is again, I tried to use the manual irrigation whose irrigation source is diversion from REACH. In the general management out put(watershed output). It shows me irrigation has occurred with a specifies amount and frequency for each HRUs scheduled for irrigation. However, this irrigation out put can not be seen in the management out put file, (IRRmm) under HRU. The IRRmm is zero for all the rotation years...why???

The other thing is, I tried so many options to find the best combination of the irrigation management parameters specified in mgt1, like FLOWMIN, DIVMAX, FLOWFR...., However the amount of irrigation diverted is very small as can be seen from the (Std output) in annual bases. I can see there is sufficient flow in the reach that could be diverted to the field, on the other side the area is semi arid with MAR of max 500mm and the crop is sugarcane...then why is that happening???

What is your comment with the manual irrigation scheduling diverted from REACH and with SWAT 2009 (rev 488), what about the Irrigation efficiency what does it account as flow parameter in the modelling because I don't understand where the water goes when modelling with less efficiency?

Best regards!

Haddush G. 

[sujan nepal]

Dear Haddush did you find any solution to this?