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Officials say rain not absorbed into soil

September 16, 1999|By BRENDAN KIRBY

To explain how a drought can persist in the Tri-State area despite two tropical storms worth of rain, state environmental officials offer the analogy of a sponge.

Turn on a spigot over a bone-dry sponge and the water will bounce on the sponge and slide off before enough trickles down into the core.

But place an ice cube on a dry sponge and it will absorb all of the liquid as the ice slowly melts.

"You don't get into a drought overnight," said John Verrico, a spokesman for the Maryland Department of the Environment, which issued its first drought alert in December.

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While every bit of rain helps, Verrico said a lot of the rain that has fallen over the last few days will end up in the ocean before the ground can absorb it. As a result, groundwater levels remain below normal, even as rivers and reservoirs rise.

Michelle Margraf, a meteorologist for the National Weather Service, said the harder the rain, the less good it does for the underground water supply.

"A drizzle of four days would be best," she said.

Three U.S. Geological Service monitoring stations in Washington County tell the story.

The monitoring stations, at wells in Hancock, Big Pool and Smithsburg, measure the depth of groundwater.

A graph comparing the recorded levels with the average normal range over the last five years shows a dramatic drop in groundwater between winter 1998 and this summer.

The graph shows a normal range that peaks during the winter and drops off in summer.

For instance, at the monitoring station in Smithsburg, the groundwater reaches a high range of about 32 feet below the surface during winter and drops to a low point of about 48 feet below ground in summer.

In a normal cycle, Verrico said groundwater drops during the spring and summer because plants consume more of the surface water. Water tables recharge during the fall and winter because there are fewer plants using the water, he said.

But water tables did not recharge last winter because of below-average precipitation.

"The recharge that normally occurs wasn't very great," said John Grace, a division chief for the Department of the Environment's Water Supply Program.

The recent rain has stabilized underground water levels, but Verrico said the key will be what happens this fall and winter.

"Snow is better than rain," Verrico said.

Like the ice cube on the dry sponge, snow gradually melts and seeps into the ground.

It also helps when the precipitation is evenly spread out. Hagerstown has received 31.57 inches of precipitation this year, but 38 percent of that fell in just two months.

"There's only so much that the soil can absorb," Grace said.

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