How do I sort out this mess of a lake?

Solution 1:

There's no practical way of fixing this ingame. The closest would be to fill in the area completely with sand, then systematically replacing each block with a water source from a bucket area, column by column (you can't do this layer by layer without having nasty downwards currents). If you don't want to use external programs, I suggest claiming this area entirely to your base. Make it a small and cozy underwater base or something (making a layer of water deep 1 is still a lot of work, but one level of magnitude less than clearing that mess.)

If you do want to use extenal editors, tools like Worldedit have what you need (/fixwater).

Solution 2:

What I would do is give myself ice blocks, fill up the lake, and then break the ice blocks. That's the easiest way, in my opinion.

Solution 3:

I've a technique that I've used to fill in some large lakes; as well as a deep and wide network of canals and moats. It requires some patience though. Here's the solution I use to fill in large bodies of water:

1. You will need:

   • A couple of buckets; At least two, but more if you don't have a convenient way to replenish them.
   • Lots of easy to destroy blocks. I usually use cloth because it can be broken quickly and stands out well against natural blocks, but dirt works just as well. Needless to say, you cannot use sand or gravel because it is affected by gravity.

2. Make sure the area to be filled is initially dry so that you can make sure you fill it completely with spring blocks.

3. Starting from the very lowest layer, place spring blocks until the bottom layer is fully flooded.
4. Fill the next layer with your cloth blocks*; Every empty space that must be filled with water needs a cloth block instead.
5. Starting from the center of the area to be filled, remove blocks one at a time and put a water spring block in its place by targeting the edge of the adjacent cloth block.
6. Once the current layer is completely replaced with water, go back to 4.

* You can actually optimize this a bit by placing the blocks in stripes spaced two apart. Filling first the spaces, and then going from one end of the stripe to the other, removing each block and replacing it with water.

Solution 4:

It looks like the section of lake here forms the corner of a rectangle, yes? Like so:

Assuming O is 'correct' water, and X is uneven water:
OOOOOOOOOOOOOOO  
XXOOOOOOOOOOOOO  
XXXXXOOOOOOOOOO  
XXXXXXOOOXOOOOO  
XXXXXXOOXXOOOOO  
XXXXXXOOXXXXOOO  
XXXXXXXOXXXXXOO  
XXXXXXXXXXXXXXO  
XXXXXXXXXXXXXXO  

In that case, this should be relatively easy: just cover the entire corner in dirt blocks, each placed one block beneath the surface of the water. Once the entire corner is covered, the water level will flatten, and you can destroy the dirt blocks to fill in the bottom of the lake. The only reason you should need a water bucket is if there's an entire horizontal or vertical row of blocks that's uneven.

Solution 5:

First, fill it up with sand or something up to the water level. Then pour water all on top. After this dig out the sand until you get the level you wanted.