The North Fork of the South Platte begins atop Kenosha Pass, making its way East along the HWY 285 corridor as trickling brook for several miles. The river grows several-fold when it encounters its first major tributary in the Roberts Tunnel: a 23-mile long underground diversion that transports water from the bottom of Silverthorne’s Lake Dillon, underneath the Continental Divide, and eventually into the North Fork of the South Platte. The Roberts Tunnel not only provides drinking water for millions of Denver area residents, but also provides the cold, clear water that makes the North Fork the spectacular fishery it is. Tunnel operation and flow varies based on Denver’s water needs, but generally runs through the Spring, Summer, and Fall seasons. Just downstream of the Roberts Tunnel in the town of Grant, the North Fork is joined by Geneva Creek, another major volume-adding tributary. Depending on the time of year, these two tributaries can attribute to anywhere from 20-600+ cubic feet per second (CFS) of streamflow.
Below Grant, the North Fork of the South Platte is a high-gradient, fast-flowing river. Riffles and runs are more common than pools, and slower holding water for fish is at a premium. This section of the North Fork is made up mostly of various ranches, many of which North Fork Ranch Guide Service operates on. These ranches have spent extraordinary amounts of time, effort, and money on stream restorations and improvements in order to handle the additional flows from the Roberts Tunnel and create ample holding water for trout. These ranches include North Fork Ranch, Shawnee Meadows, and Rawhide Fly Fishers.