The natural flow of the Colorado River runs through Shadow Mountain Dam, into Lake Granby and down to the western states and Mexico. At times, water flows in the other direction as well! Water from Lake Granby is pumped back to Shadow Mountain Reservoir and into Grand Lake, and then diverted through the Alva B. Adams Tunnel, under Rocky Mountain National Park and to the east slope. All part of the Colorado – Big Thompson Project, the diversion is designed to serve the people and agricultural lands on Colorado's Front Range.