HARTFORD, Conn. — A summer drought in New England is unlikely despite a warm winter and little snow that sent far less water than usual tumbling into streams and rivers, U.S. scientists said in a recent study.
Summer rains play a bigger role than winter snowpack in feeding waterways, the study by the U.S. Geological Survey found.
The study also links stream flows to climate. Temperatures have been rising for half a century, causing snowpack to melt earlier, which in turn leads to most runoff early in the season, usually before April, it said.
Robert W. Dudley, an Augusta, Maine-based hydrologist for the Geological Survey and one of three authors of the study that was released last week, said he and others conducted the study after observing lower-than-usual streams.
“You look around, you see abnormally low stream flows in the spring,” he said. “People say it’s because of the warm winter. Or it’s a combination of the warm winter and little snow. Intuitively, they’re both right.”
In southern New England, stream flows were off 90 percent from typical flows in April.
The U.S. Geological Survey has collected stream flow data for decades at Maine’s Carrabassett River, New Hampshire’s Diamond River, Rhode Island’s Beaver River, Connecticut’s Mount Mope River and other waterways. Scientists analyzed April flows from 31 stream gauges in areas that are not strongly influenced by direct human changes to the watershed such as reservoir regulation or urbanization, the agency said.
Average temperatures in northern New England in March and April increased 1.3 degrees from 1953 to 2002. But the scientists avoided the charged debate over climate change. Climate projections are handled by other agencies such as the National Oceanic and Atmospheric Administration and university researchers, Dudley said.
A warm March contributed to early snowmelt runoff and to below-normal stream flows in southern New England in April, the study said.
“It is well-known that precipitation affects stream flows, but it has been less well-known that air temperature can affect flows, too,” said Glenn Hodgkins, the report’s lead author.
The study did not discount a lack of snow as a cause for low streams. Less snow results in reduced snowpack accumulation and less water in spring runoff.
Alfred R. Bettencourt Jr., executive director of the Rhode Island Farm Bureau, said turf growers irrigated last month because of dry conditions.
A state drought committee met recently and determined that three conditions have been met for a drought advisory: low stream flows and little rainfall and ground moisture, he said. However, a fourth condition, the level of reservoirs, has not been met. Reservoirs are a foot above capacity, he said.
The committee decided against issuing an advisory because it rained the day members met, and “it wouldn’t look good,” Bettencourt said.
Massachusetts officials are watching the weather closely to prepare for any possibility of a drought, said Jennifer Pederson, executive director of the Massachusetts Water Works Association. The Massachusetts Drought Task Force convened early this year after officials “had some concerns about not having a lot of snow pack,” she said.
Following a dry early spring, conditions improved in late April and May with rainfall, Pederson said.
In central Connecticut, the Metropolitan District, which provides water to eight municipalities including the capital of Hartford, was at 99.8 percent of capacity in its reservoirs at the end of April, said spokeswoman Kerry Martin.
“We’re not in the business of predicting rainfall. It’s been low, but we still maintain our supply,” she said.
Robert Lent, director of the Maine Water Science Center, said the study is not predicting that a warmer-than-usual winter will occur again.
“We’re not saying this is how things are going to be,” he said. “This is a real-world example.”