Rainfall loosens grip of drought

Wednesday, June 12, 2002

By DAVID HENCH, Portland Press Herald Writer

The drought that gripped Maine for the past year has eased thanks to several weeks of healthy rainfall.

Maine's lakes, ponds and rivers are full. Fire danger warnings are at their lowest level possible across the state. Farmers have more than enough moisture to sustain crops.

The only lingering impact appears to be depleted groundwater levels, which will probably decline throughout the summer despite a succession of rainy days this spring. Some Mainers who rely on wells could run out of water again toward the end of the summer.

Climatologists call it a "green drought."

"Drought is different things to different people," said Al Wheeler, meteorologist in charge at the National Weather Service in Gray. "Two weeks without rain in the summertime may be drought to a farmer. It depends on what you use water for, what your definition of drought would be."

Tom Hawley, hydrologist with the National Weather Service, said conditions underground could become more important than what's above it.

"If we were in a state where we didn't rely so much on groundwater, it wouldn't be a really big deal," he said. "We'll continue to call it a drought until we see the groundwater come back to normal."

Climatologists use a device called the Palmer Drought Severity Index to track the extent of a drought's long-term impact. The index tracks precipitation for the previous 12 months and is adjusted for climate, the water capacity of different soils and other regional factors. The index helps analysts assess the adequacy of water supplies and the potential intensity of forest fires.

The index shows that Maine's below-normal precipitation for the past year produced the driest conditions in the state since the mid-1960s.

But the index also shows that a resumption of normal rainfall has improved conditions significantly.

Through the late winter and early spring, the state was in an extreme drought. Now, conditions in coastal and northern Maine fluctuate between mild and moderate drought. Those regions need 3 to 6 inches of rain in addition to the normal rainfall of about 3/4 of an inch a week to emerge from the drought altogether.

Central Maine, represented by a band running across the state parallel to the narrow coastal region, is rated as being in a mild drought. However, at times this spring, the index showed it as climbing briefly out of drought.

That region needs just 1 1/2 inches of rain, in addition to normal rainfall, to achieve normal conditions.

Little rainfall last summer and an abnormally light snowpack was capped off by a drier-than-normal early spring. That left the water table low, the ground parched and everyone from marina owners and boaters to farmers worried about the coming summer.

So far, those fears seem to be unfounded.

In fact, some farmers have been hurt by the late-spring rains, which have mired fields.

"We'd rather not have 3 or 4 inches of rain right now, because you're trying to plant crops and harvest hay and its difficult doing it when there's a lot of water on the ground," said Maine's Agriculture Commissioner Robert Spear. Still, the low water table could be a factor for the growing number of farms that rely on irrigation for a consistent water source, he said.

Most of the recent rain has either been drawn from the soil by vegetation or run off into streams. Little moisture actually has percolated down into the water table, and the aquifer is being depleted because groundwater is constantly leaking out to feed streams and brooks.

"Not all rain is as effective as it may seem on the surface," said Mark Svoboda, climatologist with the National Drought Mitigation Center at the University of Nebraska. "You need gentle soaking rains over sustained periods to bring well levels up." That, or some serious tropical storms.

"You need a sustained period of 150 to 200 percent above normal for a three-, four- or five-month period. Really, you're not going to see full recovery until we see what kind of winter we have."

The drought index also shows that, if conditions continue to improve, the drought was relatively short.

"You haven't had the duration you saw in the mid '60s and late '40s," Svoboda said. "While it has been dry, it's been a rather short and intense dryness but not something that's spread out over five years. Not yet."

Showers should end today, with partly sunny skies Thursday and Friday and another batch of rainstorms forecast for Saturday.

Staff Writer David Hench can be contacted at 791-6327 or at: dhench@pressherald.com

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