CHOICE OF STATIONS TO CONSTRUCT THE FILE PCP1.PCP

[KAUEM SIMOES]

In the case where there are two or more rain stations within a sub-basin, which station does SWAT choose to create the pcp1.pcp file? What is the SWAT criterion used? How is this choice made? Is it based on some geometric criterion? Is it based on the distance between the station and the sub-basin's centroid? Do you have any reference or article that talks about this? Can someone help me please?

[Roland Yonaba]

Hi Kauem,

I do not think there is any issue with having multiple raingages. Actually, you just have to edityour raingage stations file where you specify all the locations of all available rainagges within your watershed. Then edit all relevant pcp files.When running the simulation, actually, each subbasin will receive the same amount of rainfall than the nearest rain gage(subbasin centroid).

You will find more details on how it works reading this discussion:

https://groups.google.com/forum/#!topic/swatuser/me1IbzCw56Q

Regards,

Roland.

[KAUEM SIMOES]

Dear Roland

Thank you for your response. So in my case my project has 9 rainfall stations outside my basin, Indaia basin, Minas Gerais, Brazil. I do not have rainfall stations inside the basin. Ten sub-basins were delineated for this basin.

If I put the 9 stations I have in the pcp.txt file and run the swat, it generates a PC1.PCP with only 2 stations.How does he make this choice? What is the criterion? Is it by the centroid method?

Is it worth using the Thiessen method and generating 10 virtual stations in these 10 sub-basins? Will I have better results?

Will a PC1.PCP file with 10 stations be created?

Thank you for your support.

Regards

Kauem

[Roland Yonaba]

I cannot say for sure, since I am no expert in SWAT. but I do believe if only two stations were included in the final generated pcp file, then it means they were the two stations closest in distance from the centroids of all your subbasins.

From that perspective, you can try out two things and compare the results. First, keep going with the actual pcp you had, and run the model. Then after that, you can also try calculating average precipitations using Thiessen polygons outside SWAT (using say ArcGIS for example) and then feed it back to your model and run another simulation and see for yourself if there are huge differences in the output. This is, if and only if spatial variability of precipitation does not account that much four your study.

Hopefully, there are some details worth of interest in this old thread :

https://groups.google.com/forum/#!topic/arcswat/41MJtfRGNg8

The alleged program pcpSWAT mentionned can still be found here: https://swat.tamu.edu/software/links/

Best,

Roland.