The North Fork is an open river. There are no dams to slow or control the flow, and there are no diversions for agriculture. The North Fork delivers 4 million acre-feet (MAF) in a year. The chart shows the variation in North Fork flow from one month to another.

The winter months tend to show average flows while the flows during the Spring runoff are much higher. Flows decline to a low in August and gradually return to average values by November. The North Fork joins the Main Fork in the northeast corner of the region where the combined flow enters American Lake.