Actually it doesn't. The bélier hydraulique uses water flow to create a water geyser. It leaves more of the water at a lower level.

One of the essential parts of the water storage tanks is that it reuses all of the water. It cannot have what wikipedia calls the "free flow at waste valve".

In the two tank system, the pump and the turbine will probably never be used at the same time. It is a storage of kinetic energy for future use. In this particular example, to pump water to the top tank between 10am - 3pm, and then use the water, mostly between 3pm and 8pm, with a small trickle all night (however, there are many other power plants that NEED to supply electricity at night.)

I will edit my post to make it more clear sometime soon.