Moving waterblocks make funky shorelines?

In my game, the water level of my various lakes and water holes must change over time. I am doing this by setting the transform of the water blocks. It looks fine as the water level drops, but then when I raise it back up again, the "deep" water texture does not expand to fill the space, and my shoreline texture (the semi transparent part) is wider than the original. Anyone have any ideas on how to solve this?

My sissy elephants are awfully picky about their water holes...

Thanks in advance,
Andy