The Nepaug Reservoir was created by the Nepaug Dam which is located at the northwest corner of the reservoir and is approximately one mile (1.6 km) from the Farmington River. The final section of the Nepaug River carries the overflow from the Nepaug Dam east to the Farmington River at Collinsville (near Cherry Brook, Connecticut). The Reservoir is managed by the Metropolitan District Commission.

The Nepaug Reservoir is approximately two miles (3.2 km) long from north to south and approximately one mile (1.6 km) wide from east to west.

The AllTrails website has a map and description of a hike at Nepaug Reservoir.