We have been told repeatedly since last summer that we are in a drought. So why is the grass on my not-yet-mowed lawn so tall and lush — isn’t it supposed to be dry and crunchy?
Sarah Jamison, a hydrologist with the National Ocean and Atmospheric Administration, has a concise explanation: “Don’t judge a book by its cover.”
“It’s true our surface level conditions are rebounded nicely, we’ve had some nice recharge events of late. Soil moistures have improved; lake levels have mostly returned where we want them to be; wetland areas are wetter than we have seen them in a while,” Jamison said. “The question remains: How much is going to make it down into the aquifer to start to recharge our groundwater.”
According to National Weather Service data, through June 4, the Concord area has seen almost 2 inches more rain than normal over the previous 30 days. That’s why my lawn is going bonkers.
But since Jan. 1, we have seen almost 2 inches less rain that normal for that period. More importantly, since the start of June last year we’ve had 11 inches less rain than normal, thanks to last year’s rain-free summer followed by a fall and winter than were a little below average.
A shortfall of 11 inches is a lot — close to a third of the normal total. It’s worse on the Seacoast: They’re nearly 18 inches below normal over the past year.
For more details, check the Drought Information Statement from the Gray, Maine, office of the National Weather Service, at www.weather.gov/gyx/droughtinformationstatement.
I queried Jamison about this because she’ll be one of three knowledgeable folks discussing drought on June 16 during the annual meeting of the New Hampshire Rivers Council. She’ll be telling people who know that rivers and ponds look OK right now why we need to stay concerned about drought.
The key point, Jamison said, is that there are basically two kinds of drought: short-term and long-term. Or, as I like to think of it, above-ground and below-ground.
Short term and above ground, we’re doing OK. Long term and below ground, not so much.
Below ground, of course, is where water collects in aquifers that we depend on for most of our drinking water. If it runs low, we’ve got a lot more problems than just crunchy lawns.
Importantly, Jamison said we can’t always correlate aquifer health with recent precipitation levels since it takes months or years to recharge underground supplies.
“The term is ‘effective precipitation.’ Are we are actually recharging our system with the precipitation? … If we have 7 inches (of rain) in an hour, most of that becomes runoff, it doesn’t soak in. On paper for the month it might show we had 8 inches of rain, but no, you had one day of torrential rain,” she said.
Due to good old climate change (by which I mean, of course, not good at all), we’re an increase in both sudden flood events and flash droughts.
“Our net water budget is shifting. Whereas we’re seeing more of these heavy torrential rain/flash flood events, that precipitation is not the effect that our climate is used to,” Jamison said. Big snowpacks used to recharge through melting and carry us through a warm, dry summer, but our winter snow accumulation is shrinking.
What this means is that even though New England is lucky enough to be a pretty wet area by global standards, we need to be vigilant. Habits built up over decades of predictable effective precipitation may need to change in an era of weather whiplash.
Jamison will be accompanied at the talk by Ted Diers of the New Hampshire Department of Environmental Services and Mary Stampone of the University of New Hampshire, the state climatologist. There will be time for questions.
The annual meeting starts at 6 p.m. at the Conservation Center, 54 Portsmouth St. in Concord, with the discussion session starting at 6:30. For more information, go to NHrivers.org.
