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Charles River with Longfellow Bridge crossing over it In the 19th century, the Charles River was one of the most industrialized areas in the United States and its hydropower soon fueled many mills and factories. By the century's end, 20 dams had been built across the river, mostly to generate power for industry. An 1875 government report listed 43 mills along the 9.5-mile (15 km) tidal estuary from Watertown Dam to Boston Harbor.   The Charles River Dam, built in 1978, controls the water level in the river basin. An earlier dam, the Charles River Dam Bridge, was completed in 1910 with the purpose of creating a fresh water river basin and riverfront park in Boston. The newly landscaped banks of the river became known as the Charles River Esplanade. The modern dam, has six pumps that provide flood control protection. The dam's lock system permits travel of recreational and commercial vessels from the river to the harbor year round. A fish ladder allows for passage of anadromous fishes, such as alewife, rainbow smelt, and shad during the migration season in late spring. The purpose of the new dam is to control the surface level of the river basin, as well its contributing surfaces upstream, such as The Back Bay Fens and Muddy River. It also prevents sea water from entering the Charles River freshwater basin during high tides. The previous dam's one lock is now kept open for navigation. The older dam could not keep sea water out and a layer of salt water accumulated at the bottom of the fresh water basin, contributing to pollution and fish migration problems. |
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