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As you look west up the Big Thompson Canyon, you can't miss seeing the large
green pipe that stretches across the highway. This is the Big
Thompson Siphon,
part of the largest transmountain water diversion project in Colorado,
referred to as the Colorado-Big Thompson Project, or C-BT. The C-BT spans 150 miles from
east to west, and 65 miles from north to south. It is one of the largest water
diversion projects of its kind, second only to California's Central Valley Project in acres irrigated.
Built between 1938 and 1957, the C-BT brings water through the mountains from
the western slope of Colorado to the drier eastern slope and plains. It delivers an
annual average of 220,000 acre feet of water to 30 cities and towns in a seven county
district in northern Colorado. The water is used for agricultural, municipal, and industrial
needs. Water supplied to reservoir and ditch companies helps irrigate more than 600,000
acres of farmland and augments drinking water supplies for more than half a million people.
West of the Continental Divide, Willow Creek Reservoir and Lake Granby collect
and store the water of the upper Colorado River. It is then pumped into Shadow
Mountain Reservoir where it flows by gravity through Grand Lake. The 13.1 mile Alva B.
Adams Tunnel transports the water under the continental divide to the eastern slope.
Once the water reaches the East Slope, it is used to generate electricity as it falls
almost half a mile through five power plants on its way to Colorado's Front Range.
Carter Lake, Horsetooth Reservoir, and Boulder Reservoir store the water until it is
released for irrigation in the South Platte River Basin or for cities and industries in
northeastern Colorado.
From this display, looking up and turning to your left, you can see the point above
the canyon's south wall where C-BT water in the Hansen Feeder Canal is diverted one
of three ways:
1. Water in the canal continues north
through the siphon and eventually makes
its way to Horsetooth Reservoir, nine and a half miles away.
2. Water for irrigation is delivered directly into the Big Thompson
River through a buried concrete waterway, part of which is exposed
right before it runs under Highway 34.
3. Water for power generation is diverted into the Big Thompson
Power Plant, a one generator unit which you can see directly
below you on the riverbank. |
