Word to the wise, deckle after the print, don't try to feed true watercolor paper into an inkjet.
1. You will get tons of trash in the printer from the raw edge
2. The print head will more than likely hit a deckle also.
3. You can't get a good print anyway as the deckled edge will not look right as the ink won't lay down evenly on the ragged edge.
The best bet is to print on good stock, matte paper like Arches from Canson, then deckle the edge afterwards. That is what I do. I provide a nice and different look for sure. You can do a much better job this way. There are nice tools out there to help make the deckle. Make sure you flip the print over to make the deckle.
Paul