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The San Juan River is a significant tributary of the Colorado River in the southwestern United States, about long.〔U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. (The National Map ), accessed March 21, 2011〕 The river drains an area of about in southwestern Colorado, northwestern New Mexico, southeastern Utah, and a small part of northeastern Arizona. The average flow of the San Juan River at Bluff is about and the highest discharge ever measured was about on September 10, 1927. The San Juan River joins the Colorado River at Lake Powell, a huge reservoir, and in fact the westmost (and lowest) miles of the San Juan River are impounded by Lake Powell and the Glen Canyon Dam. Most of the San Juan River lies in San Juan County, New Mexico and San Juan County, Utah, which share a boundary of one point at the Four Corners. The San Juan River lies just a few miles northeast of the Four Corners point. ==Geography== The San Juan River has its source in southwestern Colorado, along the southern slopes of the San Juan Mountains and to the west of the Continental Divide. The San Juan River flows southwesterly into the state of New Mexico, then westerly across New Mexico, and then northwesterly from New Mexico, and for a short distance across the very southwestern corner of Colorado, and then continues in its northwesterly course for an appreciable distance into Utah. The largest tributary of the San Juan is the Animas River (severely affected by the EPA's accidental August 2015 Gold King Mine waste water spill), followed by the Piedra and Los Pinos rivers. The tributaries of the San Juan River that are located in Colorado also flow from the San Juan Mountains, including the Animas River, the La Plata River, the Los Pinos River, the Navajo River and the Piedra River. The San Juan drains an arid region of North America, and along its length it is very often the only significant source of fresh water. The San Juan River is the only significant stream in the parts of the Navajo Indian Reservation that lie in New Mexico, Colorado, and Utah. Aside from Lake Powell, the only large impoundment of water along the San Juan River is at Navajo Lake, formed by the Navajo Dam in eastern San Juan County, New Mexico. Significant towns located along the San Juan River are Pagosa Springs, Colorado, the head waters of the San Juan and Farmington, New Mexico. The San Juan River meanders through many horseshoe bends and other windings, sometimes meandering as much as within a one-mile distance "as the crow flies" (straight line, point to point), such as in Utah's Goosenecks State Park. The San Juan River flows into the Colorado River at the center of Lake Powell. 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「San Juan River (Colorado River)」の詳細全文を読む スポンサード リンク
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