Water splits into two source blocks when placed above a piston that is then activated, leaving the second created water source block surrounding the extended piston.

I was trying to make obtaining obsidian in an easier fashion, and was playing with lava and water. I was trying to let the lava run under the water, and allow a piston to start and stop the water above the lava. The lava turned into cobblestone, as could be expected, but the water split into TWO water source blocks! I've been able to continuously double my water supply this way, and I thought you would want to know. 

Thank you