“Great tidal river.” That is what the Massachusett, Nipmuc, and Pawtucket tribes called the Mystic River. We are standing at the Mystic Dam. It plays a vital role in the story of this great river.
This dam, along with its gatehouse, is a historic landmark. The Mystic Dam sits between the Lower and Upper Mystic Lakes. It is located north of Boston.
The Charlestown Water Commission built it in 1864 and 1865. At that time, Charlestown was separate from Boston. The dam was part of a new water supply system. The dam spans a narrow point between the two lakes. Its west end is in Arlington. The east end is in Medford.
The Mystic Dam became part of a larger system. It eventually merged into the Metropolitan District Commission or MDC. The MDC was the predecessor to today’s MWRA and DCR. That is the Massachusetts Water Resources Authority and the Department of Conservation and Recreation.
Originally, the Mystic Dam was quite large. It stretched over 1,500 feet long. It stood 16 feet high. Most of its length was earthen embankments. These were lined with riprap and puddle clay.
Near the center, you can see a spillway area. It features square columns made of granite blocks. These columns have grooves. Workers could install stop logs to control the water flow. A wooden walkway once ran across the top.
The Mystic Dam also included a wooden fish ladder. This helped fish migrate. The ladder was later removed. On the Medford side, the gatehouse connected the upper lake to an aqueduct. This aqueduct carried water to Charlestown. The lake area impounded by the dam covers 186 acres.
Both the dam and gatehouse are on the National Register of Historic Places. They were added in 1990. By the early 2000s, the Mystic Dam was showing its age. The spillway masonry was failing. Erosion and other damage marked the stonework.
A major storm in 2006 caused flooding. It showed that the dam might not handle significant high water. This could lead to catastrophic flooding downstream.
From 2010 to 2012, major work was done to improve the Mystic Dam. A new spillway was built east of the old one. The old spillway got a new apron. Workers repaired the embankments and shores. A new fish ladder and bridge were added. The historic gatehouse was also updated. Modern controls now allow better management of water levels.
The Mystic River has changed over time. It was once a tidal river with extensive salt marshes. Dams like this one altered the landscape. They also impacted the native fish populations.
In 2012, a fish ladder was installed at the new Mystic Lakes Dam. This helped river herring reach the Upper Mystic Lakes. This increased their spawning ground. Before that, volunteers used buckets to move herring.
The Mystic River Watershed Association works to protect and restore this area. They honor the indigenous communities who call this area home. The name “Mystic” comes from their word “Missi-Tuk”. It means “great tidal river”.
The Mystic Dam stands as a testament. It highlights the ongoing efforts to balance human needs and environmental stewardship. It is a landmark of engineering, adaptation, and respect for the natural world.