A $250 solar panel will produce all the energy that you setup need, about 30KWHr (250W *4hr/days *30day/month).
if you store this 30kW in a battery you will only have a loss of less than 10% (5% from batter and another 5% from charge controller)
If you convert from solar to (1)motor to (2) kinetic moving water to (3)motor to (4) alternator to battery, lets not forget friction and also water loss due to wind/spills/seepage/etc.
I am sure that you will have lost 75% of the energy from the solar panel.
I dont see why you would rather store the electrical energy as kinetic/potential energy vs directly in a regular battery where you can recovery 4times more energy.
Let go with the idea that you got a
free $250/250W solar panel, and you already have free piping (1) and a free pond/pool(2) and a free "alternator" (3).
And you just dont have the fund to buy more batteries to add to your existing system. It would only cost about $140 to buy a battery to store all 1kWHr that the solar panel is producing per day.
I have this feeling that the battery system is a bit cheaper.
Now if you just have free time and you want to do something for fun or if you plan on getting a site in 5yrs that does have hydroelectric potential and you want to get your hand "wet".
Then by all means please do it and learn something cool and valuable, I almost always support doing something cool for learning purposes.