It creates the Barkhamsted Reservoir which has a volume of 36.8 billion US gallons (139,000,000 m3) and is the primary water source for Hartford, Connecticut.

In 1927, the Metropolitan District Commission began to purchase land in the present-day footprint of the dam and reservoir.

The foundations for "Bill's Brook Dam" and the diversion tunnel for the East Branch of the Farmington River were completed in August 1934.

Subsequently, the East Branch was diverted into the concrete conduit at the bottom of the Bill's Brook Dam site.

The Farmington River East Branch is impounded for nearly 8 miles (13 km) behind the dam, with the northernmost open waters of Barkhamsted Reservoir terminating in Hartland, Connecticut just south of the Massachusetts border.