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__NOTOC__ Big Spring is one of the largest springs in the United States and the world.〔Vineyard and Federer, 1982, p. 12〕 An enormous first magnitude spring, it rises at the base of a bluff on the west side of the Current River valley in the Missouri Ozarks. Located about four miles downstream from Van Buren, it is within the boundaries of the Ozark National Scenic Riverways, and its visitor facilities are managed by the National Park Service. The average flow of of water per second 〔(USGS Surface Water data for US – Big Spring 1981-2009 )〕 from Big Spring constitutes the second largest tributary of the Current River. The spring is by far the largest spring in the Ozark Plateau region. The only two springs in the Ozark region that approach the size of Big Spring are Greer Spring and Mammoth Spring. Maximum discharge of Big Spring must be estimated because backwater from the Current River makes accurate high water measurements impossible. The spring issues from the base of a limestone bluff, churning out aqua-blue water with great force, creating white caps, then quickly calming to a crystal clear channel. The spring water travels about where it adds itself to the Current River. The water is about 58 degrees Fahrenheit (13.3°C), and the spring is surrounded by a well maintained park and a steep valley hillside covered in hardwood forest. Most of the known drainage basin encompasses northern areas of the Eleven Point River watershed. Big Spring is ever increasing in size, as the groundwater continues to dissolve limestone in a vast karst system, and continuation of stream capture in greater quantities. The spring is estimated to dissolve and remove 175 tons of limestone during an average day. The amounts of limestone dissolved and removed by the spring system in one year is estimated to equal a one mile (1.6 km) long cave high wide,〔Vineyard and Federer, 1982, p. 68〕 though that amount is dispersed among all parts of the karst system. ==See also== *List of Missouri rivers *List of Arkansas rivers *List of Ozark springs *Karst spring *Spring 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「Big Spring (Missouri)」の詳細全文を読む スポンサード リンク
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