This puzzle is part of the Monthly Topic Challenge #13: Variety Slitherlinks.
A watermill is going to be built next to a cozy town. You are the designer of the aforementioned mill/slitherlink, and you have been given some requirements for building.
When the mill is operational, every cell not inside the slitherlink will be filled with water. The water acts under the force of gravity: it will always attempt to move downwards. If it cannot move downwards, it may move randomly either left or right.
There are certain water reservoirs that the water must drain to, shown as cages.
Every water tile must uniquely drain to one reservoir. However, there is one special case where this does not apply.
In the bottom, two reservoirs have overlapping drainage areas. The purple tile of water intersects the reservoir 1 down, 2 left from it and the reservoir 4 down, 2 right from it.
Normal Slitherlink rules apply.
Solve on Penpa (answer checking not enabled because I legitimately can't figure out how).
Author note: there's a flaw with the Penpa link where apparently anyone can edit and it'll change the board.