My solution :
https://github.com/Ombridride/minetest- ... ods/spongeThis sponge mod created by Darvedevil, grant you the way to erase water source (a 3x3 area for the moment, but you can tweak this value)
This is part of my subgame Minetestforfun_game and of course it's activated in my server if you want to try it :)