Loveland Visitors Center
Heading east from this location in the Big Thompson Watershed the landscape becomes more rural, and farmers and ranchers rely on the river to irrigate crops and water livestock. The average annual precipitation along the Northern Colorado Front Range is 15 inches, hardly enough to grow crops. But look west and you will see the solution: snow.
In the Rocky Mountains, snow can accumulate up to 10 feet during the winter months. In the spring, the snow begins to melt and makes its way to the Big Thompson or Cache la Poudre Rivers. Some of this river water can then be diverted to lakes and reservoirs to be stored for future uses, such as irrigation.
Agriculture uses a large portion of the water in the Big Thompson River. In the 1920s, Larimer County farmers grew sugar beets, pinto beans, wheat, corn, barley, and alfalfa. They also cultivated fruit, such as apples, strawberries, and raspberries, and in the early 1900s Larimer County produced two-thirds of Colorado’s total cherry crop. Today, very few fruit crops are grown in Larimer County on a commercial basis. Instead, the emphasis is on corn, sugar beets, pinto beans, brewing barley, wheat, and alfalfa hay. Producers must have a source of high-quality water to grow these crops.
The Dam Store and the Colorado-Big Thompson Project
As you enter the Big Thompson Canyon near the Dam Store, you can’t miss the large green pipe that stretches across Highway 34. This is the Big Thompson Siphon, a transmountain water diversion project known as the Colorado-Big Thompson (CB-T) Project. The C-BT system 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 (in acres irrigated), second only to California’s Central Valley Project.
Construction of the CB-T began in 1938 and was completed in 1957. The project diverts water from Colorado’s western slope to the drier eastern slope and plains, delivering an annual average of 220,000 acre-feet of water to 30 cities and towns in northern Colorado to be 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 through Grand Lake. The 13-mile Alva B. Adams Tunnel transports the water under the Continental Divide to the eastern slope.
Once the water reaches the eastern slope, it is used to generate electricity as it drops nearly 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.
When touring this area, you can see the point above the canyon’s south wall where C-BT water in the Hansen Feeder Canal is diverted in one of three ways:
- Water in the canal continues north through the siphon and eventually makes its way to Horsetooth Reservoir.
- 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.
- Water for power generation is diverted into the Big Thompson Power Plant, a one-generator unit that is visible on the riverbank.
Detailed map of the Colorado – Big Thompson System
Viestenz-Smith Mountain Park
Note: Viestenz-Smith Mountain Park was destroyed in the 2013 Big Thompson flood. In 2018, the City of Loveland worked to restore the park, including the expansion of recreation opportunities on the north bank of the river, out of the floodway. The park re-opened on September 28, 2018.
Take a look around and you might spot a dipper on the river rocks or a deer drinking along the willows. Like humans, land animals need a dependable supply of clean drinking water. For fish and other aquatic animals, the quality of water in the Big Thompson is even more critical, as they live and breathe on its very essence.
The thin green line of life that we find where land meets water is called the riparian zone. This area is where the watershed works hard to clean the water and hold the river within its banks. The shape of the land and the communities of plants that live in the riparian zone work together to create an efficient system for filtering pollutants and debris from the water. The soil, rocks, and roots are able to withstand the power of running water and hold the river banks in place. With a properly functioning riparian zone, we can depend on a steady supply of clean water, even during dry periods.
The unique environment of the riparian zone supports a specialized wildlife community. You will find plants and animals—like the willow, the kingfisher, and the beaver—that have body parts and habits that help them thrive in the riparian area. Look for the willow’s thick mass of strong roots, the kingfisher’s strong beak and short wings, and the beaver’s webbed feet. You can also see cottonwood trees that only grow along the water, ducks dabbling in the shallows, and raccoons using their hands to feel under water for treats. Since all animals must drink water several times a day, this is also a good place to find upland animals—like rabbits, bighorn sheep, and great horned owls.
Where else can we go to experience such a concentrated ‘mixing pot’ of plants and animals? By protecting our riparian zones along the Big Thompson River, we are investing in both clean water and wildlife habitat.
Town of Drake
The beauty of the Big Thompson Canyon is evident in the Drake area, where the North Fork and Big Thompson rivers meet. This natural beauty, coupled with the canyon’s ease of access and close proximity to major urban areas, has resulted in land-use patterns similar to those found in many other areas of scenic Colorado.
During the past 100 years, many areas that were once rural and pristine have been developed for both residential and commercial ventures. Individual residences, motels, campgrounds, gift shops, and other commercial facilities dot the riverfront areas along major stretches of the Big Thompson River, offering living, recreational, and employment opportunities to thousands of people. The Drake area is a good example of a canyon watershed area being used for many different purposes.
In addition to offering spectacular visual settings, the Big Thompson River provides a variety of benefits to canyon residents and visitors. Shallow wells and springs are often directly impacted by actual river flows, and residents sometimes obtain irrigation rights to use river water for property and livestock watering. River recreation opportunities abound in the form of fishing, sightseeing, tubing, photography, and other activities.
Human activities in the canyon have a direct influence on water quality in the river. Soil erosion prevention, noxious weed control, proper trash disposal, and other sound environmental control practices are important considerations that should be implemented by all canyon residents. Sometimes, mother nature takes over—such as during the floods of 1976 and 2013.
After the 2013 Big Thompson flood, the river reverted to its natural course at its confluence with the North Fork near the town of Drake.
Lake Estes – Town of Estes Park
Lake Estes was created in 1948 when the Bureau of Reclamation completed construction of Olympus Dam, a feature of the C-BT Project. Located on the Big Thompson River, the primary purpose of Lake Estes is to store C-BT water diverted from the Colorado River headwaters on the western slope to the drier plains of northeastern Colorado. Lake Estes is also the after bay for the Estes Power Plant and provides significant recreational opportunities to residents and visitors in the Estes Valley.
Lake Estes and the surrounding property are owned by the United States. Through a cooperative agreement between the Bureau of Reclamation and the Estes Valley Recreation and Parks District, lands around the lake are managed for a variety of purposes, including recreation, wildlife viewing, wildlife habitat, and wetlands. There are 185 acres of water and 118 acres of land available for recreation and other purposes.
Recreational opportunities around and on Lake Estes include:
- Lake Estes Marina: Includes a marina store, boat docks, boat rentals, playground, fishing, picnicking, waterskiing, and lake touring.
- Cherokee Draw: Located on the south side of Lake Estes, this day-use area features picnicking, sightseeing, and fishing opportunities.
- Fisherman’s Nook: This day-use area is on the north side of Lake Estes and serves as a fishing and picnicking area with parking.
- Lake Estes Golf Course: An executive nine-hole golf course featuring four par-4 holes and five par-3 holes.
- Wapiti Meadows: Located below Olympus Dam, the Meadows provides areas for fishing and picnicking and includes many acres dedicated to wetlands, open space, and wildlife.
- Lake Estes Trail: A hard surface 3.75-mile trail encircles Lake Estes. The trail has spectacular mountain views and is used by hikers, bikers, rollerbladers, and joggers.
Rocky Mountain National Park
Rocky Mountain National Park not only provides visitors with beautiful scenery; it also contains the headwaters—or beginnings—of two large river systems important to Colorado. The Colorado River has its beginnings on the west side of the park, and the Cache la Poudre, Big Thompson, and St. Vrain rivers are headwaters of the South Platte River to the east.
Most water in the western United States originates as snow that falls on mountain ranges. In Rocky Mountain National Park, up to 80% of the annual moisture supply begins as snow during the winter and then melts in the spring to fill rivers, lakes, and reservoirs. Mountain snowfall provides water for recreation, irrigation, municipal, and industrial purposes. Rocky Mountain National Park protects the Big Thompson’s headwaters from development, preserving the river’s value as a source of clean water.