Arlington’s second-largest body of water, the Arlington Reservoir, is a little different from the others. It was made by people instead of dug out by glaciers. According to the Arlington Reservoir Committee website, Arlington created it in 1871 by damming Munroe Brook. Arlington used the reservoir for drinking water until it joined Massachusetts Water Resources Authority in 1899. This is especially confusing because Arlington’s water tower, which is still active today, is also called the Arlington Reservoir.

The park around the Arlington Reservoir is open year-round, with a trail that leads around the entire body of water. In 2010 the town added a wildlife habitat garden on the spillway, filled with native plants. They’re also fighting an undesirable population of invasive water chestnuts.

Part of the reservoir is swimmable. The town forbids swimming in Hill’s Pond at Menotomy Rocks Park, and Spy Pond’s water quality makes it dangerous to swim in. But the Reservoir Beach, a sandy beach built off the Reservoir’s main body, has filtered water and, during the months it’s open for use, lifeguards.

The Res, as it’s commonly known, lies alongside Lowell Street in Arlington Heights, crossing over the Lexington border. The beach is open from mid-June to late August. The town charges admission, and beachgoers can buy season passes if they desire. There are changing rooms, a snack bar, a playground, and a ramp for wheelchair users to roll into the water.

Recently, at the end of the beach season, the town begun opening the beach for a single ‘Dog Day at the Res’ with Arlington Dog Owners Group. On this day, dog owners from Arlington and beyond can bring their dogs to the beach and into the water. This past Saturday was 2019’s Dog Day.

More information about the Arlington Reservoir may be found on its website here.