how do i make a minuture river that can create electricity?

Question

how do i make a river it needs to be a circle and make it flow with a paddle that will spin and create electricity

Answer 1

Well, you've pretty much answered it yourself.

The only missing piece is a pump that will return the water to the higher elevation again. You can hide that inside the mountain or whatever you are using to create the height difference for the paddle wheel. Depending on the size of the model that you want to create, an aquarium pump may work well. If not, there are plenty of small fountain pumps that would work just fine. You'll need a valve or something to regulate the output of the pump so that it it neither lets the waterfall go dry, nor sucks your reservoir (or wherever your river leads to) dry.

Edit:
On second reading, it looks to me as if you want an undershot wheel instead of an overshot wheel. In that case, just put the pump inlet a little upstream of the pump outlet and have the river contain considerably more water than the pump is capable of pumping - again a valve will help control it. All the pump has to do, then, is suck out some water and pump it right back in to keep the flow going.

An overshot wheel will be more efficient, though.

Answer 2

Stores that sell decorative fish ponds (Home and Garden centers) have nice little 120VAC pumps and little reservoirs that would work nicely to lift up your water. They also sell plastic 'channels' that would work as your river. Maybe they'd donate some 'goodwill' hardware to you in turn for a promotional 'plug' on your project poster.

For your 'hydro generator', a bicycle light with a paddlewheel MIGHT just work enough to light up.