Don’t you need lots of water for a whitewater park?

It all depends on what sort of feature/park you want. Parks can be functional with less than 100cfs of water or over 10,000cfs. For the Poudre the engineering company feels they can design features that will provide easy/beginner features at 1-200cfs, as well as at higher flows. One feature may be better at lower flows, and one at higher flows.