There is a really good reason a pump up-drain down system isn't used: transition losses. I used to have the actual current figures but just operating off memry the water ram system required four gallons of water through to pump one gallon up even on a well adjusted system. Using electric power to run a pump is something like only 25% efficient at best. And getting electricity back out through a turbine only 40%. So for every 100 watts you put in your getting ten out. (100w x .25 x .40 = 10w) Your losing 90% off your energy just in transitions. Ancillary losses, evaporation, friction and heat loss in transport, are going to a bit more after that.

Of course if you have a huge, and essentially free, initial energy source of an intermittent nature and no other way of storing energy to use on off times then over 90% loss could be quite acceptable.

A simple battery system, 12v to charger and battery bank to 12v use or inverter for AC loads, can get you much higher efficiencies.