Colorado Piedmont

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The Colorado Piedmont is an area along the base of the foothills of the Front Range in north central Colorado in the United States. The region consists of a broad hilly valley, just under 5000 ft (1500 m) in elevation, stretching north and northeast from Denver in the valley of the South Platte River, as well as along the Arkansas River valley southward from Colorado Springs. The name Colorado Piedmont also refers to the physiographic section of the Great Plains province.[ citation needed ]

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Description

The Colorado Piedmont elevation is lower than the foothills, but is also slightly lower elevation than the High Plains to the east. According to current geologic theory, the Piedmont was formed approximately 28 million years ago, during the broad bowing of the North American Plate that lifted the continent between present-day Kansas and Utah to its present elevation of approximately 5000 ft (1500 m). This uplift resulted in increased streamflow and rapid erosion on the eastern side of the Rocky Mountains. The erosion scraped away the top layer of Upper Cretaceous sandstone (which still exists as the top layer on the High Plains), exposing the underlying layer of Pierre Shale, which had been formed during the Cretaceous, when a shallow sea covered present-day Colorado. It was during this time that the South Platte River, which had previously flowed eastward across the Plains, rerouted northward along the mountains to join the Cache la Poudre River. In some areas of the Piedmont, a loose veneer of Pleistocene gravel overlays older shale and which accumulated during glaciation in the mountains, when streams descending onto the Piedmont became overburdened with sediment.[ citation needed ]

The drop off from the Plains to the Piedmont is noticeable to motorists driving southward from Cheyenne, Wyoming on Interstate 25. At approximately Mile 293 northeast of Wellington, Colorado, near the Larimer-Weld county line, the road drops noticeably from the Upper Cretaceous sandstone of the Plains to the lower shale of the Piedmont. The transition from High Plains to Piedmont is likewise accompanied by a change in agriculture, from pasture lands on the Plains to cultivated fields in the Piedmont.[ citation needed ]

In the 19th century, the Piedmont region was inhabited primarily by the Southern Arapaho and Cheyenne tribes. From the earliest time of white settlement in the middle 19th century, the issue of water has been a controlling force in the economy of the region.[ citation needed ] The region was not widely settled in the early Colorado Territory, when mining was the basis of the economy.[ citation needed ] The use of irrigation in the Piedmont starting in the 1860s led to widespread homesteading and cultivation of wheat and sugar beets, as well as cattle and sheep ranching. Much of the irrigation water in the Piedmont comes from shallow wells that tap the layers of Pleistocene gravel. Water diversion projects, locally from the Cache la Poudre and other rivers, as well as the Colorado-Big Thompson Project, also supply needed water to the region.[ citation needed ]

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The Laramie-Poudre Tunnel is an early transmountain tunnel in the U.S. state of Colorado. The tunnel transfers water from the west side of the Laramie River basin, which drains to the North Platte River, to the east side Cache la Poudre River basin that drains to the South Platte River. The tunnel is about 11,500 feet (3,500 m) long with variable diameters with a minimum diameter of about 5.3 feet (1.6 m). The diameter varied due to the different material mined through and the erosion of almost 90 years of water flow. It is located at about 8,400 feet (2,600 m) elevation with about a 1.7 degree down slope. The Laramie River lies about 225 feet (69 m) higher than the Cache La Poudre River at this location separated only by a mountain ridge. The Laramie-Poudre Tunnel is located about 45 miles (72 km) west-northwest of Fort Collins, Colorado, about 20 miles (32 km) south of the Wyoming border and about 25 miles (40 km) north of Rocky Mountain National Park. It was built between 1909 and 1911 for the Laramie-Poudre Reservoirs & Irrigation Co. to convey water from the Laramie River to the Poudre River for Front Range irrigation. The tunnel was driven for the purpose of conveying through the divide 800 cu.ft of water per second.

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