rather than field returning normal at 6th turn, how about making it a permanent that goes like this
first turn, nothing
second turn, at the cost of 3 water quanta (give it a "flood" active ability, so it's not passive)), flood the field like
X------X
-------
X------X
third, at the cost of another 3 water quanta (active ability)
XX----XX
-------
XX----XX
fourth, at the cost of 3 water quanta... and so on, when the whole field is flooded (in the pattern of the post above), field reset, and start from the beginning again
no other effect changes