Colorado Big Thompson Project
The Colorado Big Thompson Project is one of the largest and most complex natural resource management projects by the United States Bureau of Reclamation . It consists of more than 120 watercourses and 60 reservoirs, which are integrated into a water pipe system that annually stores, regulates and regulates approximately 320,000,000 m³ (260,000 acre-feet ) of water from the Colorado River on the west side of the continental divide and to the Big Thompson River , a tributary of the South Platte River that heads on the east side of the Rocky Mountains . Originally built as an irrigation system for agriculture, it now also supplies water to the fast-growing towns of Fort Collins , Loveland , Longmont , Boulder and Greeley on the east side of the Rocky Mountains. A total of eleven municipalities receive water for private and industrial consumption. It is also used to generate electricity , create new local recreation areas and for its actual purpose, the irrigation of approximately 291,600 ha (720,000 acres) of agricultural land.
history
In 1870, before the state of Colorado was founded, the Union Colony with 2,000 members was founded in Greeley. It marked the beginning of community irrigation in the South Platte River valley and the beginning of an era when irrigation was vital to the development of northeast Colorado. The Union Colony began building irrigation ditches that irrigated 4860 acres of land from the South Platte River. When the capacity of the rivers was exhausted around 1900, reservoirs began to be built in order to be able to absorb the annual spring floods. By 1910, reservoirs were built wherever they could be built inexpensively. The only way to expand the system was to divert water through the mountains, which was expensive.
During these years, due to the growing population, the demand for agricultural products increased. The trend to expand the irrigation system more and more, especially in years with high or normal water levels, led to problems in areas that were completely dependent on irrigation in years with low water levels.
The idea of diverting water from the west side of the Rocky Mountains to the east side had existed since 1889 when the Colorado legislature investigated the possibility of such a project. In 1922 the Colorado River Compact was signed, which regulated the distribution of the water between the riparian regions of the upper and lower reaches of the river. The Boulder Canyon Act later provided the funds to determine how much land in the Colorado Basin could be irrigated. A plan was made that water could be diverted from Colorado to northeast Colorado, where there was ample good farmland that could not be cultivated because of the lack of water. In 1948, the states on the upper reaches signed a treaty to divide up the water to which they were entitled under the 1922 treaty.
In November 1938, work began on the Green Mountain Dam, the first structure for the Colorado Big Thompson Project. The Green Mountain hydropower plant went online in May 1943 as the first power plant in the project. In the summer of 1940 construction work began on the Alva B. Adams Tunnel and in 1941 on the Granby Dam. During the Second World War, work on the project was severely restricted. They never stopped, however, and continued with great energy after the war. In 1956, the major structures of the Colorado Big Thompson Project were operational - except for the Big Thompson Power Plant, which was completed in 1959.
The system
Green Mountain Reservoir
The Green Mountain Reservoir was built to ensure irrigation and electricity generation despite older water rights on the Colorado. The Green Mountain Dam, a 94 m high earth dam, with a crown length of 350 m and a volume of 3.3 million m³, dams the Blue River, a tributary of the Colorado, 21 km southeast of Kremmling. The spring floods are stored here so that they can later be channeled into the Colorado and thus have water available for the project all year round. The reservoir has a total capacity of 189.5 million m³ (153,639 acre-feet).
Lake Granby
The main water reservoir on the west side is Lake Granby. The Granby Dam dams the Colorado River about 9 km northeast of Granby. The dam was built as a compacted earth dam with a height of 91 m, a crown length of 262 m and a total volume of around 2.3 million m³. Additional dikes with a total length of 3,878 m give the reservoir a capacity of 665.8 million m³.
Willow Creek Reservoir
The Willow Creek, a tributary of the Colorado, which lies below Lake Granby, is dammed by the Willow Creek Dam (39 m high, 335 m long) to the Willow Creek Reservoir with a capacity of 13 million m³. The water (approx. 49 million m³ / year) is led through a canal to the Willow Creek pumping station, which raises it by approx. 53 m. It then also flows into Lake Granby.
The Granby Pumping Station lifts the water from Lake Granby to the Granby Pump Canal, which transports it 3 km north to Shadow Mountain Lake. The pumping station has 3 centrifugal pumps with a total output of 17 m³ / s. at a pumping height of 56.5 m. The pumping height varies between 26 m and 56.5 m, depending on the water level of Lake Granby.
Shadow Mountain Lake
Shadow Mountain Lake is formed by the Shadow Mountain Dam, which dams the Colorado on the western border of Rocky Mountain National Park south of Grand Lake. The Shadow Mountain Dam is an earth dam that is 19 m high and 938 m long. The Shadow Mountain Lake has a capacity of 22.7 million m³ and is connected to the Grand Lake by a canal.
Alva B. Adams tunnel
From the east bank of Grand Lake, the Alva B. Adams Tunnel runs northeast under the national park through to the east side of the continental divide. It flows out about 7 km southwest of Estes Park. The tunnel has a diameter of 3 m, is 21 km long and has a capacity of 15.7 m³ / s. The water flows from the Alva B. Adams Tunnel into the East Portal Reservoir and then crosses the valley of Aspen Creek in a culvert. A tunnel leads it under Rams Horn Mountain through to a steel penstock, where it falls 62.5 m to the Marys Lake Power Station, which is on the west bank of Marys Lake.
Marys Lake
The original lake was enlarged by dikes in order to obtain sufficient storage capacity for an even flow. From Marys Lake, the water is transported through the Prospect Mountain Aqueduct and Prospect Mountain Tunnel pressure system to the power station on the shores of Lake Estes. It falls 147 m. The Estes hydropower plant with its 3 generator units generates an average output of 45,000 kW.
Lake Estes
Lake Estes (total capacity approx. 3.8 million m³) was created by the Olympus Dam (21 m high with a crest length of 595 m), which dams the Big Thompson River. The storage capacities in Marys Lake and Lake Estes enable the Estes hydropower plant to adapt its output to the changing energy consumption during the day.
Flatiron Reservoir
Water from Lake Estes and the occasional flood of the Big Thompson River is transported south through the Olympus culvert and tunnel and the Pole Hill tunnel and canal to a pressure pipe, which is 248 m to the Pole Hill power station (approx 33,250 kW average power). From the Pole Hill reservoir, the water flows through the Rattlesnake Tunnel into Pinewood Lake. The Bald Mountain pressure tunnel guides the water into 2 pressure pipes, through which it falls 321.5 m to the Flatiron power station and flows into the Flatiron reservoir. The power plant generates an average output of 71,500 kW. It has two main generators and a 13,000-horsepower reversible pump that lifts water from the Flatiron Reservoir to a height of 61 to 91.5 m (depending on the water level in Carter Lake) and transports it through a 2.25 km penstock and tunnel into Carter Lake. It has a maximum output of 10.5 m³ / s and is operated with excess energy from the main generators. The direction of flow is reversed during peak demand. The pump then works as a turbine generator and produces electrical energy (8,500 kW).
At the Flatiron power station, too, pre- and post-storage enable operation to be tailored to requirements.
Carter Lake
Carter Lake was created at a height of 1,750 m above sea level in a natural basin in the foothills by a 65 m high earth dam and two smaller dikes. It has a capacity of 138.4 million m³. At its deepest point it is about 55 m deep. The water collected in Carter Lake is used for irrigation. The St. Vrain supply tunnel leads south from Carter Lake to St. Vrain Creek near Lyons, to which it feeds approx. 16 m³ of water per second, the Little Thompson River receives 17.5 m³ / s. Shortly before the end of the St. Vrain supply tunnel, the Boulder Creek supply canal begins, which has an average water volume of 5.5 m³ / s. transported. It flows into Boulder Creek 25 km to the southeast near Boulder.
Boulder Reservoir
At the lower end of the canal, the city of Boulder built the Boulder Reservoir. It is used for storage and water regulation. The approximately 52 km long South Platte Supply Canal brings water from Boulder Creek northeast to the South Platte River.
Horsetooth Reservoir
The system divides at the Flatiron reservoir. In another branch, the water flows north through the Charles Hansen Feeder Canal with a natural gradient to the Horsetooth Reservoir and the Big Thompson River. The canal delivers 26 m³ / s. to the Big Thompson River and 15.5 m³ / s. to the Horsetooth Reservoir. The Big Thompson hydropower plant is located approximately 14.5 km west of Loveland on the Big Thompson River. It has an output of 4,500 kW. Water that exceeds the needs of the Big Thompson Valley is stored in the Horsetooth Reservoir. It is located west of Fort Collins between two ridges. With a capacity of around 187 million m³, it forms the main supply for the Poudre Valley, where 50% of the water of the Colorado-Big-Thompson project is used. The reservoir is 10.5 km long and is formed by large earth dams. The Horsetooth Dam closes the northern end of the valley. Soldier Canyon Dam, Dixon Canyon Dam, Spring Canyon Dam and Satanka Dam close the remaining gaps in the Hogback Ridge.
A drain at the Horsetooth Dam discharges its water into the Charles Hansen Canal, which has a maximum flow rate of 42.5 m³ / s and was built to transport water north to the Cache la Poudre River . The water in the Poudre Valley is distributed through a series of smaller channels. The municipal waterworks in Greeley is also supplied from here.
A drain on Soldier Canyon Dam supplies water to Colorado State University at Fort Collins, the Dixon Feeder Canal, which is used for land irrigation, to Fort Collins, and to rural areas.
Cache la Poudre, Big Thompson River, Little Thompson River, St. Vrain Creek, and Boulder Creek are tributaries of the South Platte River through which the water carried from the western slopes of the Rocky Mountains into the South Platte River system is fed in. This additional water is used to cultivate fertile land in the South Platte River Valley.
operator
The United States Bureau of Reclamation operates all facilities of the Colorado Big Thomson Project located on the west side of the Rocky Mountains and the facilities on the east side up to and including Carter Lake and Horsetooth Reservoir, including power generation, transportation and storage of the water. The portions of the project that lie below Carter Lake and Horsetooth Reservoir are maintained and operated by the Northern Colorado Water Conservancy District.
Services provided by the project
irrigation
The Colorado Big Thompson Project supports agriculture in northeast Colorado. For most years it is only used for irrigation towards the end of summer. However, in dry years it is vital to the economic survival of farmers. The main crops in this area are sugar beets, potatoes, beans, corn, alfalfa, fruits and vegetables. Other agricultural products include poultry, eggs and dairy products. In addition, lambs, pigs and cattle are fattened with the by-products of sugar beet processing.
Industry and municipal consumption
The supply of the municipalities is an important aspect in the distribution of water. Originally 9 municipalities received a total of 55.5 million m³ of water. Today 11 municipalities are partially or even completely supplied with water by the project. Due to the increasing consumption in cities, water intended for irrigation is now also being supplied to households. The constant availability of water makes this area attractive for a wide variety of industrial companies with their high consumption.
Recreation
Around 2 million people visit the artificial lakes every year. You can fish, motor boating, sailing, swimming, camping and hiking here. Trout, salmon, perch and pikeperch are some of the fish that live in these cold clear waters. In winter, ice fishing and snowmobiling are the most popular sports.
electricity
From the east exit of the Alva B. Adams tunnel to the foothills, the water falls by approx. 850 m. Almost every meter of it is used to generate electrical energy. A total of 760 million kWh are generated, of which 70 million kWh are used for the operation of the project (pumps etc.). The remaining 690 million kWh will go to consumers in northern Colorado, eastern Wyoming and western Nebraska. The electricity generated by the project will be marketed by the DOE.