LULC code for Fallow.

[Joy Sanyal]

Hi,

What would be the most appropriate way to deal with fallow land. I am doing simulation for the rainy season in summer . Part of the area under agriculture remains fallow during that period which are primarily used for winter crops. Fallow is different in soil characteristics from barren land or bare rocks. Which should be the closest land use code available in the SWAT database? 

Any suggestions will be appreciated. 

Cheers, 

Joy 

[Vinay Manohar]

Use Agricultural Generic

[Joy Sanyal]

Thanks for your suggestion Vinay. However, if I assign the generic agriculture code for the area under kharif crop + the area under current fallow there is no way to spatially distinguish between them. However, I have a means to map them as separate categories during the kharif season. Any thought?

Cheers,

Joy

[Natalja C.]

Hi,

How about defining your management (mgt file) with rotations between growing crops and fallow years?

Natalja

[Joy Sanyal]

Hello,

Many thanks for replying. I am trying to create a situation where the area under standing crop and the area under fallow during kharif (June-October) season is fixed. If I do rotation between crops and fallow then for one period the entire place (crop+fallow) becomes under standing crop for some period and then it becomes entirely fallow (i.e. no crop) for the other period. This is not the scenario I am after. I have never created my customized land use class in SWAT. Is there any tutorial/manual available online that discuss this process? Or is there any built-in land use code in SWAT that resemble 'fallow'?

Cheers,

Joy

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[Jim Almendinger]

Joy -- What does "fallow" mean to you? 

a) Bare earth?

b) Killed and harvested crop, with residue left on field, but not tilled and replanted?

c) Planted with a cover crop (like grass or clover), between years with a grain crop?

In any case you should be able to find some crop type and management to simulate one of these.

You appear to want to run SWAT for just June-Oct each year, without including Nov-May.  SWAT generally works best after it has had a few years of "model warm up" to allow at least hydrologic components (e.g., soil moisture) to equilibrate. 

Whether whole areas become fallow or not depends on how you have subdivided your watershed into subbasins, and subbasins into HRUs. 

So far from your descriptions, it seems like simply writing the proper rotation, switching an HRU from crop to fallow (and back) over a seasonal sequence for several years will do what you want, yet you insist otherwise.  There is clearly something we (at least I) don't understand in what you want to do. 

-- Jim

--

James E. Almendinger, PhD

Director, St. Croix Watershed Research Station

Tel: 651-433-5953 x 11

Email: jalmen...@smm.org