Cambridge’s drought status has been downgraded from significant to mild following recent rainfall, but the city’s primary storage reservoir remains at just 20% capacity, raising the possibility that Cambridge may have to purchase supplemental water this fall or winter for the first time in a decade.
The apparent disconnect between the improved drought designation and the depleted reservoir comes down to geography. The state determines drought levels using data from across its Northeast region, encompassing all of Middlesex, Essex and Suffolk counties, rather than assessing Cambridge’s water supply alone.
“It may be regionally a mild drought, but for us, it’s a little more significant,” said Mark Gallagher, managing director of the Cambridge Water Department.
Hobbs Brook, which can hold 2.9 billion gallons, is one of three reservoirs in Cambridge’s water system. Water flows from Hobbs Brook into Stony Brook Reservoir and then to Fresh Pond, where it enters the city’s treatment plant before being distributed to customers. Stony Brook and Fresh Pond are both close to full, Gallagher said, but the city has been drawing on Hobbs Brook to keep them replenished.
Typically, Cambridge closes the gates at Hobbs Brook Dam in October or early November, allowing the reservoir to refill over the winter and spring while the other two reservoirs meet the city’s water needs. The gates generally reopen in late June, when warmer weather drives up demand. This year, Hobbs Brook entered that high-demand season below normal levels and has continued to decline. Gallagher said its level is lower than it was at this time last year and is approaching the low reached during the 2016 drought, Cambridge’s worst since at least the 1960s.
Somewhat paradoxically, climate change is expected to increase the risk of both flooding and drought in Massachusetts, according to the state’s most recent drought management plan. Although the Commonwealth is projected to receive more precipitation overall, more will fall in intense storms that cause flooding but replenish groundwater less effectively than steady rainfall. Rising temperatures also increase evaporation, causing reservoirs and soils to lose more water during dry periods.
“From the 1960s to 2016, the Northeast region had three drought events,” Gallagher said. “Since 2016, this is our fifth.”
A possible need for purchase
If Hobbs Brook receives little to no additional recharge and water demand remains at its current level, Cambridge could need to begin purchasing supplemental water from the Massachusetts Water Resources Authority in late October, Gallagher said.
But he emphasized that scenario is a contingency, not a forecast. Demand typically falls as temperatures cool, and additional rainfall could allow the city to make it through the fall without buying water. Cambridge currently produces about 16 million gallons of water a day, Gallagher said. That figure typically falls to about 13 million gallons a day in October and 9 million gallons a day by January or February.
“I’m actually somewhat hopeful and think we might squeak by and get to winter,” Gallagher said.
The last time Cambridge purchased supplemental MWRA water because of drought was in 2016. The city sometimes buys it for other reasons, including construction that requires parts of its own system to be shut down. The supplemental water, which originates at the Quabbin Reservoir, would enter Cambridge’s distribution system directly rather than being used to replenish Hobbs Brook. MWRA water currently costs Cambridge about $5,000 per million gallons, Gallagher said.
Gallagher said the department would initially cover the cost using its water fund balance, which holds approximately $7.8 million in reserves and is replenished with money left over from the department’s annual budget, funded entirely by customers’ water bills.
“We have basically a piggy bank of reserve that we use for emergencies,” Gallagher said. “In this case, a dry day instead of a rainy day.”
If Cambridge had to purchase supplemental water throughout the winter, the cost could reach a couple million dollars, Gallagher estimated, though the total would depend on rainfall and demand. A prolonged need for supplemental water could eventually drain the water fund balance and affect the rates residents pay, he said, but that’s “not anywhere in the near future.”
Restrictions remain in place
The downgrade to a mild drought brings only one change to Cambridge’s restrictions on nonessential water use: Residents may now use sprinklers to water their lawns one day per week, before 9 a.m. or after 5 p.m. All other restrictions remain in place, and Gallagher urged residents to continue conserving water indoors by taking shorter showers and turning off taps when they are not needed.
The department produced approximately 157 million fewer gallons of water in fiscal 2026 than in fiscal 2025, a decline of about 3.5%. Gallagher said conservation efforts likely accounted for some of that reduction, although the department cannot determine precisely how much.
Despite the low level at Hobbs Brook, Gallagher said residents are far from facing drinking water interruptions because Cambridge has access to a full MWRA backup supply, an option not available to every Massachusetts municipality.
How quickly Hobbs Brook recovers will depend on the weather. Gallagher recalled that the reservoir fell to an even lower level during the 2016 drought but had refilled by the following June after a wet winter and spring. Another rainy stretch could replenish it; continued dry weather could leave Cambridge relying on supplemental water for longer.
“We’re still in a drought,” Gallagher said. “People need to be vigilant.”
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