There are a number of companies that offer small hydropower systems. They usually offer system design help to determine your hydropower potential. As I get the time, I’ll list some of them on this site. If you have recommendations I’d like to hear them.
Note: Water height is more important than water volume; it is easier and less expensive to convert water under high pressure (from height) into useable energy.
It makes huge economic sense to size power systems to meet your average needs and provide a means to store excess power for times when you need more power than your system is designed to handle. It costs about ten times less to design a power system this way. AND in most cases this is the way that the power system would need to be designed anyway, because most water supplies are low flow or low drop and simply could not provide enough water to make an instaintanious demand of, let’s say 20 KW.
Hydropower can simply store water in a reservoir behind a dam for use as desired. Usually wind and solar are best advised to store their power in batteries, but there are times when batteries are not the best or only solution.
Example, using a windmill water pump to pump water up into a reservoir, which then drains down through a water turbine as the power is required. In addition to not having to maintain a battery bank, the reservoir can be useful for a fresh water supply, raising fish, a thermal heat storage, etc.
Another way to store excess hydropower is to use the ‘Reverse your Electric Meter’ technology. Assume for example that you get times of the year that you have a lot of water flowing and no practical way to build a large reservoir or battery bank. You can ‘store’ your excess power in your local utilities power grid by turning your electric meter backwards. An arrangement with your utility will allow you to use your stored credit at a later time when your water flow slows down.