A Watery Slitherlink

Question

_{This puzzle is part of the Monthly Topic Challenge #13: Variety Slitherlinks.}

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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.

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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.

Answer 1

Some opening deductions:

Here, I've used only basic Slitherlink deductions, and also blocked off the bottom of each reservoir.

Continuing,

I use the 3 in the lower left - it can only open up or right, and it can't open upwards or it would create a "pit" that water couldn't escape.

Now the reservoir in R7C2 can't continue right - if it did, it would spill downwards due to the 0. So we can continue the coloring arguments...

Now, noting the condition of the purple tile,

we can say that the 0 in the bottom right must have water.

More coloring along with the Slitherlink clues gets us this far. (This seems to contradict the rules for the purple tile - surely the water in it can go down so it can't go left. But the phrasing there is somewhat unclear.)

In the top left, we can use an interesting fact about 2 clues:

specifically, that the four cells around them must be split 50/50 between inside and outside the loop, regardless of the actual color of the clue itself. This lets us color several more cells...

...and then connectivity of the green section resolves some ambiguities.

Now, all that's left is the top-left corner.

The 1 in the top left must have an edge either above it or to the right.


Now consider the 2 in R2C2; it must either take both of the top and right edges, or neither of them. Either way, it connects to the dot in its lower right, so we can resolve the 3s...

...and from that, the rest of the solution falls into place:

(Thanks to fljx and quarague for correcting a mistake in the first version of this answer.)