This is the most awesome water feature I have seen yet!
The leaf castings are made of concrete . . . there is no tutorial to go with this photo, but it should not be too difficult to figure out how the water feature part of it could work.
Use the photo as inspiration, as well as some of the websites listed below. These concrete leaves are used for stepping stones in the garden, bird bath, decorations and water features. You can also do a search on Pinterest for leaf castings for additional inspiration.
Here are some articles and tutorials on making concrete leaves . . .
Concrete Leaves for Garden or Fountain
How to Make a Concrete Leaf Casting
Casting Nature
Concrete Casting How To
Make A Concrete Leaf
How to Make Concrete Garden Fountain with Rhubarb Leaves