Soil erosion MUSLE equation

[erk]

Hello everyone, 

I have a question about USLE and MUSLE equations. Can I use MUSLE equation to calculate soil erosion for the subbasins? or MUSLE only calculates sediment yield?

Thanks in advance.

[Jim Almendinger]

SWAT uses the MUSLE equation to calculate soil loss (load) from each HRU (as mass/time).  The sum of all the HRU soil losses in a subbasin then gives the total soil loss for a subbasin.  Yields (mass/time/area) are determined by dividing the soil loss for an HRU or subbasin by the area of that HRU or subbasin. 

The USLE value given is for comparison purposes only.

I don't know what difference in meaning you give to "soil erosion" versus "sediment yield." 

-- Jim

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[erk]

Thank you for your answer Jim,

1- You said "  SWAT uses the MUSLE equation to calculate soil loss (load) from each HRU (as mass/time).  The sum of all the HRU soil losses in a subbasin then gives the total soil loss for a subbasin.". So, from the total soil loss of subbasins Can I calculate the Sediment Delivery Ratio for each subbasin?

2- The soil loss of each HRU is in the "output.hru" in the column USLE t/ha ?

Best.

[Jim Almendinger]

The Sediment Delivery Ratio (SDR) is ratio of net to gross erosion (or actual to theoretical erosion), where to my way of thinking, gross erosion is the erosion that takes place at a point on the landscape, and net erosion is the sediment that actually makes it out of an HRU, subbasin, or watershed (choose your scale) after some of the particles have been trapped along the flow path.  The longer the flow path, the more sediment traps are likely to be encountered, and hence net erosion (per unit area) and SDR get smaller as the area increases (from HRU -> subbasin -> watershed; there are some exceptions).  The MUSLE equation gives what it thinks is the actual erosion leaving an HRU, prior to any wetland sediment traps or channel processes (including reservoir sedimentation). 

The USLE t/ha value given in the output is not used in SWAT calculations but is given for comparative purposes.  It tends to be larger than the MUSLE t/ha.  I presume this is because the USLE was (I think) derived from plot-scale studies, and the MUSLE was derived with data from actual small watersheds, and so the MUSLE already takes into account some sediment trapping at the small watershed (subbasin?) scale, or at least at the field (HRU?) scale. 

I suppose you could calculate SDR as MUSLE t/ha divided by USLE t/ha, which would give you an SDR at the HRU scale (you could expand this to the subbasin and watershed scales as well).  I presume others have done this, though I haven't done a Google Scholar search on the subject.  If you're going to do that calculation, then you should do the literature search to see what others have done. 

Cheers,

-- Jim

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[Munei Naomi]

Hello erk...

As to what i just gained from doing a soil erosion modelling using MUSLE MODEL together with the SWAT model.

You can use SWAT to generate Surface runoff which you now integrate it in the MUSLE equation in the map algebra to make a soil loss map.

Thanks

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[June Cagampang]

Hi Erk, can you elaborate what you mean by swat using musle. I'm a bit confused how this two goes I already ran my model in arcWAT. Thank you

[Bhaswatee Baishya]

Hello Erk,

Have you got your answer? How do we calculate SDR from SWAT mode? Which data do we have to take from the output table? 
I have reviewed a few literatures, and no one has clearly written what value to take to calculate SDR for any scale. 

Please reply.