Putting New England’s drought in perspective
AMHERST, Mass. – The current severe drought in parts of New England is notable, says University of Massachusetts Amherst hydrologist David Boutt, but not extreme in historical terms and nowhere near the depth of dry conditions observed in the acute five-year drought years experienced in 1962-1967, when the water level in the Quabbin Reservoir was 20 feet lower than it is today.
“This drought is bad, but it’s not the worst,” says Boutt. “It’s probably not yet in the top five drought periods in New England historically, so we need to keep things in perspective. Drought is a normal part of the water cycle.” Boutt, who tracks natural chemical signatures in groundwater to research the hydrology of Massachusetts watersheds, says a series of drought years also occurred in the 1980s and a lesser dry period was noted in the early 2000s.
One reason this year’s drought is so noticeable is that it has come largely in the growing season, so everyone from farmers to homeowners and gardeners has felt its effects. It also follows an almost 15-year period of higher-than-normal precipitation, Boutt adds. “As a region we were blessed with abundant rainfall in particular from about 2005 to 2010, a bonus situation. Since then, conditions leading to this current drought started to be felt as early as 2013.”
Contrary to popular perception, he points out, droughts are seldom one-year events. “Droughts are multi-year events; they take some years to develop. And like the others, this one will be felt for longer than one season. When soils are so dry, even with the nice rainfall of this week, it will take time for the hydrologic system to recover.”
Also, there is a lag time in how groundwater responds to precipitation, a concept known as groundwater residence time, which is how long water remains in the groundwater portion of the hydrologic cycle. Groundwater residence time can be extremely variable, from two weeks to thousands of years, though surface water is usually resident for shorter periods.
Boutt says, “If you ever wondered how your local stream is still flowing even though it hasn’t rained for three months, the answer is that the stream is fed by a slow, slow draining of groundwater through the system. This can take five to 25 years in Massachusetts. Most rivers’ discharge is groundwater that may have been there for months or years coming to the surface through natural processes.”
His team recently received nearly $50,000 from the U.S. Geological Survey to establish a high-resolution map and database of natural chemical signatures – hydrogen and oxygen isotopes found in surface water, precipitation and groundwater – to better understand the isotopic composition of waters in the state and how groundwater is changing as a result of human activities. They are now actively seeking water samples from interested citizens.
Boutt explains, “Water that we see moving through the system now is a relic of the past. With isotopes we can develop a map to understand water’s residence time in ground- and surface waters. Using isotopes, we can track the source of moisture coming into New England.”
“When water evaporates into the atmosphere it picks up a signature,” he adds. “Using isotopes, we can clearly tell if our rain is from the Pacific, the Gulf of Mexico, the Atlantic or the Arctic by measuring these isotopes. We can use all of this to help us understand where all the water is coming from.”
With the isotope project, the researchers will create a public baseline and online tool where regulators, homeowners, watershed associations and researchers can get information on a range of isotopic concentrations that tell them the residence time for each aquifer.
“At the state level, such a database can tell us how responsive a particular watershed is to natural climate variability. Right now decisions are being made with not enough data and we hope to improve that situation,” Boutt says. “If we better understand the sources of moisture and how isotopes are moving through our local water systems we can better understand how water is being affected in a changing climate.”
Boutt and his team of researchers invite residents of western Massachusetts to contribute water samples to the project from wells or nearby streams by contacting Boutt at 413/545-2724 or email firstname.lastname@example.org