<P> The Green River flows through Mammoth Cave National Park, located along river miles 190 to 205 . The river drains the cave and controls the master base level of the Mammoth Cave system: the construction of a 9 - foot (2.7 m) dam at Brownsville in 1906 has raised the water level in some parts of the cave system by as much as 6 feet (1.8 m) above its natural value . </P> <P> The 384 - mile - long (618 km) Green River, an important transportation artery for the coal industry, is open to traffic up to the closed Lock and Dam #3 (known as the Rochester Dam) at mile 108.5 . Muhlenberg County, once the largest coal - producing county in the nation, benefits greatly from access to the river, as does the aluminium industry in Henderson County . In 2002, more than 10 million short tons were shipped on the river, primarily sub-bituminous coal, petroleum coke, and aluminium ore . </P> <P> The river rises from Kings Mountain, Kentucky and follows a meandering path, collecting several smaller streams along its way to its impoundment by a dam at Green River Lake near Campbellsville . It then continues in a westerly direction and is joined by the Little Barren River before entering the Mammoth Cave National Park . After it exits the park, it receives the tributary of the Nolin River which exits Nolin Lake . Then continuing westward it is joined by the Barren River . It then takes a more northwesterly turn as it proceeds through western Kentucky . Near Sebree it provides coolant water for Robert Reed Power Station, a coal fired power plant, before it finally empties into the Ohio River at Evansville, Indiana . </P> <P> The Green River is home to more than 150 fish species and more than 70 mussel species . This includes some of Kentucky's largest fish and some of the world's rarest species of mussels . </P>

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