Most of New Hampshire is now in a drought, following a dry and hot summer. But experts say it takes more than just one big downpour to end a drought.
Ted Diers, assistant director of the water division at New Hampshire’s Department of Environmental Services, said too much rain, too fast won’t be a cure.
“A really strong storm will tend to run off, just because that ground is so dry,” he said.
The drought is worst in the northern parts of the state. In the north, a foot of rainfall is needed to end the drought. Southern New Hampshire needs about five inches.
Climate change is making New Hampshire warmer and wetter overall but also increasing the risk of short term drought.
State climatologist Mary Stampone said that’s because a warmer atmosphere can retain more moisture, but also hold it in the air for a longer period of time, extending periods between precipitation events.
When rain finally does come, it can be more intense but less effective at hydrating soil and plants, even if people notice a superficial difference.
“You'll see a rise in streams and lakes right after the event, but that all washes away,” she said. “The grass will green up right away, but you don't get a lot of that moisture really infiltrating into the soils.”
A heavy storm with several inches of rain could move across New Hampshire over the course of an afternoon, and the state can still be in a drought.
Experts say a “soaking rain” spread out over a few days and a few separate events would be the most effective solution.
But Sarah Jamison, a senior service hydrologist at the National Weather Service Forecast Office in Gray, Maine, is nervous that won’t happen.
“Unfortunately, we are not seeing any rainmakers anytime soon that could come close to bridging that gap, so our deficits will only grow,” she wrote in an email to NHPR.
The criteria for ideal rainfall varies depending on the season.
Heading into fall and winter, Diers says local vegetation is starting to shut down and needs less water, so there will be less demand on the soils.
“At that point, more of the water can absorb deeper into the soil and then help to replenish groundwater,” he said.
The long-term effects of this summer’s drought depend on weather over the next few months.
If the different parts of the state get the amount of rain needed before the ground freezes, Diers said the lingering effects of the drought would be minimal.
But if that doesn’t happen, winter precipitation would fail to adequately hydrate soils.
This could worsen the extent of the drought’s damage and make soils next spring even more unhealthy than they are now. Other factors — like snowfall amounts and ice out on the state's bigger lakes — will also play into next year’s conditions.
According to Diers, surface water levels in lakes and rivers are low statewide, but the north is seeing particularly parched soils and low groundwater levels.
Diers says people underestimate how different weather conditions are across the state.
“For a very small state, we have a really diverse set of ecosystems and precipitation patterns,” he said.
Diers encouraged people to be “conservation minded" about their water use.
“While you might have water today in your well, if the drought deepens you might not tomorrow,” he said.
