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Utah Lake is a freshwater lake in the U.S. state of Utah. It lies in Utah Valley, surrounded by the Provo-Orem metropolitan area. The lake's only river outlet, the Jordan River, is a tributary of the Great Salt Lake. Evaporation accounts for 42% of the outflow of the lake, which leaves the lake slightly saline. The elevation of the lake is legally at above sea level. If the lake elevation goes any higher, the pumps and gates on the Jordan River are left open. The first European to see Utah Lake was Father Silvestre Vélez de Escalante in 1776. He stayed with the Timpanogots band of Ute Tribe for three days. The Timpanogots were later moved out or integrated with the Mormon settlers between the 1850s and 1870s. The fish of the lake were overharvested by the settlers and restocked with non-native species. Although thirteen species of fish are native to the lake, only the Utah sucker and the critically endangered June sucker remain. The dominant species in the lake is the common carp, introduced in 1883 as an alternative to the over harvested native fish. The carp is now estimated at 90% of the biomass of the lake and is contributing to a decline in native fish populations by severely altering the ecosystem. Pollution has also caused problems with the lake's ecosystem. Raw sewage was dumped into the lake as late as 1967. Pollution problems still remain; the lake's phosphorus and mineral salt levels are in violation of the Clean Water Act. ==Geography== Utah Lake is within Utah Valley, in north-central Utah. Mountains surround Utah Valley on three sides: The Wasatch Range to the east, Traverse Mountains to the north, and Lake Mountain to the west. Mount Nebo reaches an altitude of , and Mount Timpanogos reaches an altitude of , nearly above the valley floor. Jutting into the south portion of the lake is West Mountain, which divides Goshen Bay and Lincoln Beach. Utah Lake is situated on the western edge of the valley and covers more than 25% of Utah Valley's floor. Because of its location on the western side of the valley, the eastern shore has a gentle slope and the western shore rises abruptly against Lake Mountain. Connected to the main body of the lake are two large, shallow bays: the aforementioned Goshen Bay (north Goshen Valley), to the south and Provo Bay to the east. Major cities such as Provo and Orem are located between the lake's eastern shore and the Wasatch Mountains. Utah Lake is a remnant of a much larger pleistocene lake called Lake Bonneville, which existed from 75,000 to 8,000 years ago. At its peak 30,000 years ago, Lake Bonneville reached an elevation of above sea level and had a surface area of , which was nearly as large as Lake Michigan. The weight of the lake depressed sections of the lake bottom by as much as before the surface rebounded when the lake dried up. About 12,000 years ago, the climate of the region became warmer and drier. As evaporation rates exceeded inflow rates, the lake began to dry up, leaving Utah Lake, the Great Salt Lake, Sevier Lake, and Rush Lake as remnants. Over the roughly 65,000 years that Lake Bonneville existed, sediments built up, creating a lacustrine plain over Utah Valley. As a result, the valley floor and lake bed are relatively flat, which causes the lake to be shallow. The lake has a maximum depth of just under and an average depth of about . This shallowness allows winds to easily stir up sediments from the lake's bottom, contributing to the turbidity or the impression of pollution seen in Utah Lake's water. Three faults run under Utah Lake. One of the faults, the Bird Island fault, runs under the eastern edge of the lake and helps give rise to hot springs near Lincoln Beach. The other major hot spring is on the northern shore and is called Saratoga Springs. The hot springs mostly result from the development of hydraulic pressure as the ground water slopes toward the middle of the lake. The lake contains a small island called Bird Island, about north of the Lincoln Beach boat ramp, near its south end. The island has a few trees and is somewhat visible from Lincoln Beach. During high-water years, the island may be completely submerged, the trees being the only indication it is there. It is a fairly popular destination among fishermen seeking walleye, white bass, and channel catfish. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Utah Lake」の詳細全文を読む スポンサード リンク
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