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〕 | mouth_name = Sandy River | mouth_location = Dodge Park | mouth_district = | mouth_region = Clackamas County | mouth_state = Oregon | mouth_country = | mouth_note = | mouth_lat_d = 45 | mouth_lat_m = 26 | mouth_lat_s = 46 | mouth_lat_NS = N | mouth_long_d = 122 | mouth_long_m = 14 | mouth_long_s = 48 | mouth_long_EW = W | mouth_coordinates_note = 〔 | mouth_elevation_imperial = 243 | mouth_elevation_note = 〔 | length_imperial = 21.9 | length_round = 1 | length_note = 〔 | watershed_imperial = 140 | watershed_round = 0 | watershed_note = | discharge_location = Mount Hood National Forest, from the mouth | discharge_round = 0 | discharge_imperial = 404 | discharge_note = | discharge_min_imperial = 30 | discharge_max_imperial = 15800 | discharge1_location = City of Portland water intake | discharge1_imperial = 770 | discharge1_note = 〔 | map = Bull run river oregon watershed map.png | map_size = 300 | map_caption = Bull Run River watershed |map_alt = The Bull Run River watershed forms part of the western border of Hood River County, Oregon, on the east. The watershed tapers to the river's confluence with the Sandy River, on the west. The watershed is almost evenly divided between Clackamas County, on the south, and Multnomah County, on the north. | map1 = Oregon Locator Map.PNG | map1_size = 300 | map1_caption = Location of the mouth of the Bull Run River in Oregon | map1_alt = The mouth of the Bull Run River is in northwestern Oregon near its border with Washington. | map1_locator = Oregon | commons = Bull Run River (Oregon) }} The Bull Run River is a tributary of the Sandy River in the U.S. state of Oregon. Beginning at the lower end of Bull Run Lake in the Cascade Range, it flows generally west through the Bull Run Watershed Management Unit (BRWMU), a restricted area meant to protect the river and its tributaries from contamination. The river, impounded by two artificial storage reservoirs as well as the lake, is the primary source of drinking water for the city of Portland, Oregon. It is likely that Native Americans living along the Columbia River as early as 10,000 years ago visited the Bull Run watershed in search of food. Within the past few thousand years they created trails over the Cascade Range and around Mount Hood, near the upper part of the Bull Run watershed. By the mid-19th century, pioneers used these trails to cross the mountains from east to west to reach the fertile Willamette Valley. In the 1890s, the City of Portland, searching for sources of clean drinking water, chose the Bull Run River. Dam-building, road construction, and legal action to protect the watershed began shortly thereafter, and Bull Run water began to flow through a large pipe to the city in 1895. Erosion-resistant basalt underlies much of the watershed, and streams passing over it are relatively free of sediments. However, turbidity increases when unstable soils sandwiched between layers of basalt and other volcanic rocks are disturbed and wash into the river during rainstorms. Despite legal protections, about 22 percent of the protected zone was logged during the second half of the 20th century, and erosion increased. For a time in 1996, Portland had to shut down the Bull Run supply because of turbidity and switch to water from wells. A law passed later that year prohibited most logging in or near the watershed, and since then the Portland Water Bureau and the United States Forest Service have closed many of the logging roads and removed culverts and other infrastructure contributing to erosion. Mature trees, most of them more than 500 years old and more than 21 inches (53 cm) in diameter, cover about half of the watershed, and the rest of the watershed is also heavily forested. Annual precipitation ranges from 80 inches (2,000 mm) near the water supply intake to as much as 170 inches (4,300 mm) near the headwaters. More than 250 wildlife species, including the protected northern spotted owl, inhabit this forest. Downstream of the BRWMU, the watershed is far less restricted. In the late 19th century, an unincorporated community, Bull Run, became established near the river in conjunction with a hydroelectric project and a related railroad line. About of the lower river is open to fishing and boating, and the land at the confluence of the Bull Run and Sandy rivers has been a public park since the early 20th century. ==Course== The Bull Run River begins at Bull Run Lake, a natural body of water modified slightly by the Portland Water Bureau, near Hiyo Mountain in the Mount Hood Wilderness. Originating in Clackamas County north of Forest Road 18 (Lolo Pass Road), its unnamed headwater tributaries enter the lake. Flowing northwest from the lake, the river immediately enters Multnomah County and continues generally northwest for about . Along this stretch, the river flows by a United States Geological Survey (USGS) stream gauge at river mile (RM) 20.9 or river kilometer (RK) 30.6, passes under Forest Road 1025 and Forest Road 10 and receives Blazed Alder Creek from the left and Log Creek and Falls Creek, both from the right. Then the river turns southwest and passes another stream gauge just before entering Bull Run River Reservoir 1 at RM 15 (RK 24). Also entering the reservoir are Fir Creek from the left, North Fork Bull Run River from the right, then Deer, Cougar, and Bear creeks, all from the right. The Bull Run River exits the reservoir via a spillway from the river mouth. Forest Road 10 runs roughly parallel to the right bank of the river from near the headwaters to Southwest Bull Run Road, near the mouth.〔 The maps, which include river mile (RM) markers for the lower of the river, cover the following quadrangles from mouth to source: Bull Run, Brightwood, Multnomah Falls, Tanner Butte, Hickman Butte, Bull Run Lake.〕 Entering Bull Run River Reservoir 2, the river receives Camp Creek from the left, re-enters Clackamas County, and receives South Fork Bull Run River from the left. The river exits the reservoir via a spillway at about RM 6 (RK 10). Below Reservoir 2, Forest Road 10 (Waterworks Road) is on the river's right bank, and Forest Road 14 is on the left. The river flows by a stream gauge at RM 4.7 (RK 7.6) and passes under Forest Road 14 before receiving the Little Sandy River from the left at about RM 2 (RK 3). The river then turns northwest, passes under an unnamed road and then under Southeast Bull Run Road near the unincorporated community of Bull Run, which is on the river's right, and the defunct powerhouse of the Bull Run Hydroelectric Project, which is on the left. Southeast Camp Namanu Road runs roughly parallel to the river along its right bank from here to the mouth. Along this stretch, the river receives Laughing Water Creek from the right and enters the Sandy River at Dodge Park, about miles from the larger river's confluence with the Columbia River.〔〔 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「Bull Run River (Oregon)」の詳細全文を読む スポンサード リンク
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