Charles River Watershed Reenters Significant Drought
Low Flow in Newton, August 23, 2025
We're seeing low water levels across the watershed, and last week, Massachusetts Energy and Environmental Affairs Secretary Rebecca Tepper declared a Level 2 Significant Drought for parts of the Charles River watershed, and Level 1 Mild Drought for the remaining watershed area.
When we look at precipitation, we see that rainfall isn't far off the year-to-date average; in fact, statewide, 2025 has been rainier than average. In Boston, we are about 3 inches behind the cumulative average for this time of the year, but why are these typical variations from the average leaving us with completely dry riverbeds?
Let’s start by establishing that this time of year typically marks a period of lower water flow, as historically, precipitation is lower in the summer. August and September mark the end of the “water year”, characterized by a combination of dry, hot days and little rainfall, which leaves water to evaporate faster than it can be replenished. However, we cannot blame this on the rain; drought conditions are primarily due to water management issues. During the summer, especially when rain is scarce, residents increase water use to water lawns and fill pools. Outdoor water use is at its highest during the summer months, sometimes doubling or more, a community's typical winter water use. For many communities in the upper and middle Charles River watershed, this water is coming from the ground. This is the same groundwater that would serve as the river’s baseflow in a natural, undeveloped setting.
When it does rain during the summer, it’s typically intense storms, which bring large amounts of rainfall in a short period of time. These types of rain events aren’t conducive to water soaking into the ground to recharge groundwater and baseflow in rivers. We have paved over much of our landscaping, leaving little opportunity for the 30 inches of rain we have received to date to soak into the ground and replenish the groundwater that can supply the river with water during dry periods. (In contrast, Phoenix, AZ receives about 7 inches of rain a year.) This summer, we also observed a unique water management challenge with the state Department of Conservation and Recreation (DCR), which allowed a large portion of the Charles River flow to be diverted into the Neponset River in Dedham through the Mother Brook Diversion. This Diversion is a relic of the past, a time when water was moved from the Charles to power mills in the steeper terrain of the Lower Neponset. Like most of the dams along the Charles, though, this defunct infrastructure remains in place, and this summer DCR was very slow to adjust the Diversion to keep water flowing into the lower Charles; instead, considerable flow was diverted into the Neponset, allowing the lower Charles to completely dry up in areas between Dedham and Watertown. The situation was eventually addressed, but unfortunately, flows were already very low, so it will take time for the river to recover.
During times of drought, regardless of your water source, we must conserve water as much as possible by limiting outdoor water use, checking for leaky faucets and pipes, and advocating for the Massachusetts legislature to pass the Drought Bill, which will establish an effective drought management plan for regions across the state.
If you see low flow, please send an email to charles@crwa.org marking the date, location, and if possible, a photo. You can help us track the impacts of drought.
