I have been digging to build water reservoirs by tunneling under existing water pockets, and diverting the flow to one central supply. While the animation for flowing water seems to be working correctly, the values for volume are lost in transit. This means that a considerable supply of water, which should flood a large area, does little more than add a few drops when it reaches its destination.
Dig a path for water to flow from one area to another. Watch water levels deplete into a trickle and vanish after any distance.