Help needed with pebble pool please :)

Hi all, I would like to turn this and this into a pebble pool..... Am I right in thinking after cementing the circle I dig a hole in the centre put in a bowl to collect the water... Put in a pump ... Cover with heavy duty grid... Run a bit of pipe up through the ball and hey presto? If that is correct how much water would you need (I.e what size bowl or how deep a hole ) and what size pump? I just want it to trickle down the sides of the ball not shoot up or anything and would that be safe for my dog to drink? I know you top the water up but that ball is pretty heavy and not much chance of me moving it once it's in place to change the water all together! Please help!

 

If you Google pondless waterfalls there's loads of info about them. I think you'd need a pond liner under the stones too. They seem to please themselves and run without maintenance bar topping up the water now and again