This is a very big deal.
http://ktlo.com/wire/newsfri/01655_AGFC_SIGNS_HISTORIC_MINIMUM_FLOW_DOCUMENT_072944.php
Minimum flow ensures that there will be dissolved oxygen in the water, preventing fish kills in August, and it lowers the probability of stagnant conditions favoring algae blooms. In rivers like the Cumberland in Kentucky where they generate almost non-stop, the trout tend to be larger and stronger for their size to boot (because they fight the current at all times). Minimum flow also makes it possible to drift without a motor and know you’ll be able to float out. All around good news.