Question: Milner Dam impounds a river that is how long?
Context: Milner Dam is a rockfill dam near Burley in south central Idaho.  It impounds the Snake River in a reservoir named Milner Lake.  The dam spans the river across two islands, with three embankments. Chatuge Dam is a flood control and hydroelectric dam on the Hiwassee River in Clay County, in the U.S. state of North Carolina.  The dam is the uppermost of three dams on the river owned and operated by the Tennessee Valley Authority, which built the dam in the early 1940s for flood storage and to provide flow regulation at Hiwassee Dam further downstream.  The dam impounds the 7000 acre Chatuge Lake, which straddles the North Carolina-Georgia state line.  While originally built solely for flood storage, a generator installed at Chatuge in the 1950s gives the dam a small hydroelectric output. Fort Patrick Henry Dam is a hydroelectric dam on the South Fork Holston River within the city of Kingsport, in Sullivan County in the U.S. state of Tennessee.  It is the lowermost of three dams on the South Fork Holston owned and operated by the Tennessee Valley Authority, which built the dam in the early 1950s to take advantage of the hydroelectric potential created by the regulation of river flow with the completion of Watauga Dam, South Holston Dam, and Boone Dam (which were primarily flood control structures) further upstream in preceding years.  The dam impounds the 872 acre Fort Patrick Henry Lake.  While originally built for hydroelectric generation, the dam now plays an important role in the regulation of water flow and water temperature for the John Sevier Fossil Plant and other industrial plants downstream. The Snake River is a major river of the greater Pacific Northwest in the United States.  At 1078 mi long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean.  Rising in western Wyoming, the river flows through the Snake River Plain of southern Idaho, then through the rugged Hells Canyon area via northeastern Oregon and the rolling Palouse Hills, to reach its mouth near the Washington Tri-Cities area, where it enters the Columbia.  Its drainage basin encompasses parts of six U.S. states, and its average discharge is over 54000 cuft/s . Crystal Dam is a 323 ft double curvature, concrete thin arch dam located six miles downstream from Morrow Point Dam on the Gunnison River in Colorado, United States.  Crystal Dam is the newest of the three dams in Curecanti National Recreation Area; construction on the dam was finished in 1976.  The dam impounds Crystal Reservoir.  Crystal Dam and reservoir are part of the Bureau of Reclamation's Wayne N. Aspinall Unit of the Colorado River Storage Project, which retains the waters of the Gunnison River and its tributaries for agricultural and municipal use in the American Southwest.  The dam's primary purpose is hydroelectric power generation. The New Croton Dam (also known as Cornell Dam), part of the New York City water supply system, stretches across the Croton River near Croton-on-Hudson, New York, about 22 mi north of New York City.  Construction began in 1892 and was completed in 1906.  Designed by Alphonse Fteley (1837–1903), this masonry dam is 266 ft broad at its base and 297 ft high from base to crest.  Its foundation extends 130 ft below the bed of the river, and the dam contains 850000 yd3 of masonry.  The engineers' tablet mounted on the headhouse nearest the spillway lists the spillway length as 1000 ft and the total length of the dam and spillway combined as 2188 ft .  At the time of its completion, it was the tallest dam in the world.  New Croton Dam impounds up to 19 e9USgal of water, a small fraction of the New York City water system's total storage capacity of 580 e9USgal . Ocoee Dam Number 2 is a hydroelectric dam on the Ocoee River in Polk County in the U.S. state of Tennessee.  The dam impounds the Ocoee No. 2 Reservoir and is one of four dams on the Toccoa/Ocoee River owned and operated by the Tennessee Valley Authority.  Ocoee Dam No. 2— which was completed in 1913— is perhaps most notable for its design, which utilizes a wooden flume that carries water from the reservoir down the side of the Ocoee Gorge to the dam's powerhouse 5 mi downstream.  Ocoee No. 2 is also situated at the center of one of the nation's top whitewater rafting locations, and the dam's releases help to maintain consistent rapids on the river during warmer months. Wilbur Dam is a hydroelectric dam on the Watauga River in Carter County, in the U.S. state of Tennessee.  It is one of two dams on the river owned and operated by the Tennessee Valley Authority.  The dam impounds Wilbur Lake, which extends for about 3 mi up the Watauga to the base of Watauga Dam.  Completed by 1912 the Ocoee Dam No. 1 is the only Hydroelectric dam that is older, Wilbur Dam was one of the first major hydroelectric projects in Tennessee, and remains one of the oldest dams in the TVA system. Fontenelle Dam was built between 1961 and 1964 on the Green River in southwestern Wyoming.  The 139 ft high zoned earthfill dam impounds the 345360 acre.ft Fontenelle Reservoir.  The dam and reservoir are the central features of the Seedskadee Project of the U.S. Bureau of Reclamation, which manages the Fontenelle impoundment primarily as a storage reservoir for the Colorado River Storage Project.  The dam suffered a significant failure in 1965, when the dam's right abutment developed a leak.  Emergency releases from the dam flooded downstream properties, but repairs to the dam were successful.  However, in 1983 the dam was rated "poor" under Safety Evaluation of Existing Dams (SEED) criteria, due to continuing seepage, leading to an emergency drawdown.  A concrete diaphragm wall was built through the core of the dam to stop leakage. Fort Loudoun Dam is a hydroelectric dam on the Tennessee River in Loudon County, Tennessee, in the southeastern United States.  The dam is operated by the Tennessee Valley Authority (TVA), which built the dam in the early 1940s as part of a unified plan to provide electricity and flood control in the Tennessee Valley and create a continuous 652 mi navigable river channel from Knoxville, Tennessee to Paducah, Kentucky.  It is the uppermost of nine TVA dams on the Tennessee River.  The dam impounds the 14600 acre Fort Loudoun Lake and its tailwaters are part of Watts Bar Lake.  The generating capacity of Fort Loudoun Dam is enhanced by the Tellico Reservoir, from which water is diverted via canal to Fort Loudoun Lake.
Answer: 1078 mi