G eBooks
eBooks di Titolo G di Anonymous editi da Ionlineshopping Com
Glen Canyon Dam. E-book. Formato PDF Anonymous - Ionlineshopping.Com, 2019 -
Glen Canyon Dam is a concrete arch-gravity dam on the Colorado River in northern Arizona, United States, near the town of Page. The 710-foot (220 m) high dam was built by the U.S. Bureau of Reclamation (USBR) from 1956 to 1966 and forms Lake Powell, one of the largest man-made reservoirs in the U.S. with a capacity of 27 million acre feet (33 km). The dam is named for Glen Canyon, a series of deep sandstone gorges now flooded by the reservoir; Lake Powell is named for John Wesley Powell, who in 1869 led the first expedition to traverse the Colorado's Grand Canyon by boat. A dam in Glen Canyon was studied as early as 1924, but these plans were initially dropped in favor of the Hoover Dam (completed in 1936) which was located in the Black Canyon. By the 1950s, due to rapid population growth in the seven U.S. and two Mexican states comprising the Colorado River Basin, the Bureau of Reclamation deemed the construction of additional reservoirs necessary. However, the USBR faced opposition when it proposed the Echo Park Dam in Utah's Dinosaur National Monument, which the nascent environmental movement saw as a legal threat to the status of protected lands. After a long fight, the USBR agreed not to build the dam in Dinosaur National Monument, but only if the environmentalists did not oppose the proposed dam in Glen Canyon. Since first filling to capacity in 1980, Lake Powell water levels have fluctuated greatly depending on water demand and annual runoff. Operation of Glen Canyon Dam helps ensure an equitable distribution of water between the states of the Upper Colorado River Basin (Colorado, Wyoming, and most of New Mexico and Utah) and the Lower Basin (California, Nevada and most of Arizona). During years of drought, Glen Canyon guarantees a water delivery to the Lower Basin states, without the need for rationing in the Upper Basin. In wet years, it captures extra runoff for future use. The dam is also a major source of hydroelectricity, averaging over 4 billion kilowatt hours per year. The long and winding Lake Powell, known for its scenic beauty and recreational opportunities including houseboating, fishing and water-skiing, attracts millions of tourists each year to the Glen Canyon National Recreation Area. In addition to its flooding of the scenic Glen Canyon, the dam's economic justification was questioned by some critics. It became "a catalyst for the modern environmental movement," and was one of the last dams of its size to be built in the United States. The dam has been criticized for the large evaporative losses from Lake Powell and its impact on the ecology of the Grand Canyon, which lies downstream; environmental groups continue to advocate for the dam's removal. Water managers and utilities state that the dam is a major source of renewable energy and provides a vital defense against severe droughts.
Grand Teton National Park, Wyoming (1952)(Illustrated Edition). E-book. Formato PDF Anonymous - Ionlineshopping.Com, 2019 -
Grand Teton National Park is an American national park in northwestern Wyoming. At approximately 310,000 acres (480 sq mi; 130,000 ha; 1,300 km), the park includes the major peaks of the 40-mile-long (64 km) Teton Range as well as most of the northern sections of the valley known as Jackson Hole. Grand Teton National Park is only 10 miles (16 km) south of Yellowstone National Park, to which it is connected by the National Park Service-managed John D. Rockefeller, Jr. Memorial Parkway. Along with surrounding national forests, these three protected areas constitute the almost 18,000,000-acre (7,300,000 ha) Greater Yellowstone Ecosystem, one of the world's largest intact mid-latitude temperate ecosystems. The human history of the Grand Teton region dates back at least 11,000 years, when the first nomadic hunter-gatherer Paleo-Indians began migrating into the region during warmer months pursuing food and supplies. In the early 19th century, the first white explorers encountered the eastern Shoshone natives. Between 1810 and 1840, the region attracted fur trading companies that vied for control of the lucrative beaver pelt trade. U.S. Government expeditions to the region commenced in the mid-19th century as an offshoot of exploration in Yellowstone, with the first permanent white settlers in Jackson Hole arriving in the 1880s. Efforts to preserve the region as a national park began in the late 19th century, and in 1929 Grand Teton National Park was established, protecting the Teton Range's major peaks. The valley of Jackson Hole remained in private ownership until the 1930s, when conservationists led by John D. Rockefeller, Jr. began purchasing land in Jackson Hole to be added to the existing national park. Against public opinion and with repeated Congressional efforts to repeal the measures, much of Jackson Hole was set aside for protection as Jackson Hole National Monument in 1943. The monument was abolished in 1950 and most of the monument land was added to Grand Teton National Park. Grand Teton National Park is named for Grand Teton, the tallest mountain in the Teton Range. The naming of the mountains is attributed to early 19th-century French-speaking trappers—les trois tétons (the three teats) was later anglicized and shortened to Tetons. At 13,775 feet (4,199 m), Grand Teton abruptly rises more than 7,000 feet (2,100 m) above Jackson Hole, almost 850 feet (260 m) higher than Mount Owen, the second-highest summit in the range. The park has numerous lakes, including 15-mile-long (24 km) Jackson Lake as well as streams of varying length and the upper main stem of the Snake River. Though in a state of recession, a dozen small glaciers persist at the higher elevations near the highest peaks in the range. Some of the rocks in the park are the oldest found in any American national park and have been dated at nearly 2.7 billion years.