Algodoo

Grabs the bucket by the edge, lifts, carries, dumps. Rather complicated controls, sorry. Move with arrow keys, brake is on toggle so you don`t have to hold it while you`re trying to dump it on the slope.
A and D to control the grabbing part of the arm. A is on toggle to grip the edge of the bucket without being held. Use D to open the gripper further if necessary.
W and S to raise and lower the arm. These controls will not tilt the bucket.
Q and E to rotate the arm. These controls do rotate the bucket.

To dump the water, park it by the edge of the pit and a combination of W and E should have the right affect.

Credits to Lucidliquid for his rotation-damping Lucid device. Without it the bucket would get a rougher ride and the arm would swing back into place very quickly after being rotated, flinging any water all over the place.