The Colorado-Big Thompson Project is a major water diversion and storage system in Colorado, designed to supply water to the northern part of the state. Initiated in the 1930s, it transports water from the Colorado River basin to the South Platte River basin through a series of reservoirs, tunnels, and pipelines. The project includes several key components, such as the Granby Reservoir and the Alva B. Adams Tunnel, which is one of the longest tunnels in the United States. It plays a crucial role in providing irrigation water for agriculture and supporting municipal water needs in the region.