I am applying PLAPS rate on my SWAT model under climate scenarios, and I am applying a PLAPS rate of 2.1 mmH2O/km in the historical period (1981-2019) does not have big impact on the precipitation trend (i.e. the precipitation decadal averages from raw pcp files are very similar to pcp taken from std file which is expected).
However when the model start the future values (2020-2099) the decadal average of pcp from raw files start to look different from the pcp files obtained from SWAT std file (in other words the pcp obtained from SWAT showes a big jumps) while my understanding that they should remain with the same trend? any suggestion where the problem might be?
Note: when PLAPS is put back to 0, the historical and predicted pcp trend are identical.
Hi Yaser Kishawi
Is your precipitation properly calibrated according to the elevation of the recording weather station? Typically, if no elevation bands are defined, then the precipitation from the .pcp file is used for the subbasin with no adjustment. This could potentially introduce a systematic bias into your prediction model.
Hope this information is useful
Best regards,
Ebrahim
Thanks @Ibrahim Ghaderpour, for the clarification, yes I have defined elevation bands in the model, and used ELEVB_FR as 0.2 and PLAPS as 3.2. I have noticed after several trials that if I slightly increased ELEVB_FR from 0.2 to 0.24 and reduced PLAPS from 3.2 to less than 0.2 the problem is solved. But I still don't understand what is happening here. Does this mean reducing the PLAPS close to 0 reduce the possibility of systematic error as you mentioned?
Hi Yaser Kishawi
Yes, you should be consistent on how you calibrate your precipitation data (for all PLASP 0, 1, 2) using the elevation to avoid introducing undesired biases that can potentially alter your prediction!
Best regards,
Ebrahim
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