The lower nine mile portion of the watershed known as the "Charles River Basin" was created in 1910 with the construction of a dam across the mouth of the river. There was no dependable means of discharging river flood flows into Boston Harbor, since the dam relied on gravity flow with the sluice gates operating only at low tide. In addition, the dam effectively eliminates salt water intrusion into the Charles. The congested cities of Boston and Cambridge and upstream communities of Watertown, Waltham, Brookline and Newton were often exposed to the threat of serious flood damages.

In 1968, congress authorized the Corps to build a new dam at the mouth of the Charles in Boston. The $61 million structure was completed in 1978. Six massive pumps at the dam maintain a safe Basin level by discharging river flows into the harbor. Each 3,000 horsepower diesel engine pump is cable of discharging 630,000 gallons of water per minute. The structure includes navigation locks to handle ever-increasing boat traffic. The dam is now operated and maintained by the Metropolitan District Commission of Massachusetts.

Studies by the Corps of Engineers revealed that the communities above Newton had a history of only minimal flooding. Extensive marshes, swamps and wet meadows scattered around the upper watershed were holding floodwaters and then only slowly letting them go.

In 1974 Congress authorized the "Charles River Natural Valley Storage Area," allowing for the acquision and permanent protection of 17 scattered wetlands in the middle and upper watershed. final acquisition totaled 8,103 acres, with 3,221 acres of land acquired in fee and 4,882 acres in flood easement, at ta project cost of $8,300,000. The Massachusetts Division of Fisheries and Wildlife manages the fish and wildlife resources in some of the Corps' fee - owned land.

Thanks to the foresight of the Corps' planners of the 1960's increasingly valuable wetlands now provide both flood protection and open space to be enjoyed by future generations.