Are you thinking that this will be a "perpetual motion" type of thing, or are you adding some supplemental power, and just hoping to conserve some energy by harvesting the power from the water overflow?
I understand your setup, and I wish it would work, but unfortunately nothing is 100% efficient. You pelton wheel would barely rotate with the head & flow you have to offer. The wheel itself would only be about 5% efficient with that sort of head. You'd be spending your money a lot more wisely with solar.
My 600 gallon system with 10 40 gallon barrel growbeds only needs 80 watts to run.
Well keep in mind everything i am using is recycled. I don't have any money tied up in my system, other than seeds and fish food. I'm only running a small water pump, I took it from my tiny water feature near my porch.
I have 20 V AC on one motor, I figure if I put a motor/alternator on both sides of the wheel, then I can get up to 40 V AC. Which I can power a battery or two with. Maybe even put a pump going towards the wheel to boost it up.
I think it is possible. Gravity is doing most of the work. All I need power for is pumping water back to the reserve tank. I will have to get a bigger pump, I have a dry pump that will work from DC already. From a small chemical prayer for the ATV that never is used.
My father owns a hydraulic shop and we do the county recycling. We fix motors, pumps, hoses, tractors, hydraulics, all kinds of things. So I have access to all kinds of neat things. People throw away amazing things also.
I just looked at that drawing again, I could also drain the GBs onto the pelton wheel. Give it a lil more boost. Have three or more water inputs going to it. When the bell siphon starts, there is a little pressure there.
Good luck with it. Make it work and you'll be a millionaire overnight. Loads of folks tried and failed.
Google pertetual motion. You'll see loads of people that offer it for $$$ and that is all that happens. They take your money.
I sure hate to tell someone that their idea will not work, but Badflash is right. This will not work. There is always energy loss. I honestly really hope that you make this work. If you do, I will invest most of my spare change into you!