Drain the water into an aqueduct aquifer tile.
FTFY. Also, option 3 is pretty much the same as option 2.
There is technically another method, though it may be prone to errors - drain it into a reservoir containing a large drawbridge that periodically raises and lowers, atomsmashing the excess water before it can accumulate.
With a note for those who aren't aware (or haven't tried this), a draw bridge only atomsmashes water when it raises, and only the tiles in it's raised position (i.e. it's anchor edge) is smashed, the big long bridge slamming down, does nothing except allows the water to flow into the tiles which had been raised bridge.
This is different to how a bridge atomsmashes items, in which case it atom smashes with the boom when lowering, and with the edge when raising.
This can be compared with a door, when a door closes it
effectively turns into a wall and atomsmashes all the water in the tile. When a bridge raises, the part which turns into a wall atomsmashes water.
Doors open and close extremely quickly, so if attached to a suitable repeater (i.e. a lever set to repeat) will smash water very quickly. Bridges open and close at a truly ponderous rate in comparison, so slow to be nearly useless, if you want to maximize water smashing rate with a bridge, make "bridge walls" (i.e. one tile "long", maximum width). Doors are much more efficient per-tile than bridges, and may be more efficient per mechanism too, depending on your repeater rate. For a slow repeater, bridge walls will give better value-per-mechanism.
The other thing is that doors can be jammed, bridges cannot, this really just means if you're going to use a door, remove all stones and other debris first.
I hardly ever have found occasion to use a water-smasher, but occasionally if only a small amount of water needs to be disposed of, in an inconvenient location (like enclosed in the magma sea) then a door linked to a lever can be a quick, cheap, tidy solution that performs admirably (I did once set up a waterfall on a repeater so it only let dribbles of water through, if you set up the inlet on a repeater like that, you could also easily install a water smasher in the outlet)