With them being buried even with the ground, you're not concerned about silt ? Looks like they would fill up with silt after several rains.
Something I ran into and I will suggest here is adding a piece of hardware cloth or chicken-wire to the side. For some reason mice will swim around the edge of the tub and not to the center where they can reach the branch. If the water level is low they can't reach the branch at the edge. Maybe I just have stupid mice.....but my water hole turned into a water based mouse trap. As soon as I added the wire at the edge - problem solved. Otherwise it looks real good.
never thought about turtles - mine turned into pretty effective mouse traps! Since I added the screen/wire - no issues with that.So far I've found the remains of a box turtle in an old bathtub, and a mouse in a small plastic wading pool. Both had sticks in them. Now I pile rocks on the edge so that maybe critters can climb out easier. I'll post a pic as soon as my patent application gets filed...