I will try to answer you questions as completely as possible
Yes, I own both sides of the stream ( Approx. 42 Ft wide at spot video was taken)
No I cannot damn the stream.. used by kayaks, canoes etc during summer months
My energy needs are modest at best. Small LCD TVs at night, 12 V waterpumps and lights in trailers and cabins, radios during day. No appliance power needed as fridges are propane. The biggest gain I would like to make is to be able to run more lights etc at night without the constant worry that the batteries will run too low . Although the 30 W solar panels I have keep them reasonably charged up, it doesn't take too long for a pump or light to run them down.
The budget is not a huge concern as I consider myself above average in the handyman category. I have a good understanding of basic electricity and plumbing etc. and also have a well stocked garage ( welder, drill press, table saw, compressor etc).
The level of the creek changes quite often as it drains into a lake which is part of a major canal system here controlled by government run locks (up to 1 ft in dry summer mos) but the current always remains strong. I have seen the formula on here for measuring flow and will try to post the results from my creek ASAP
I was looking at a PM alternator that allows you to run smaller 3phase AC wire to your battery location, then rectify it there.