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A Short Primer on Maine Ground Water

December 26, 2007 - While we view the wildfires driven by the Santa Anna winds of southern California, we should appreciate the 43 inches of rainfall Maine receives each year in comparison to the 9 - 10 inches that San Diego receives. This rainfall keeps our soil moist and replenishes our surface water and groundwater supplies, so let's take this opportunity to review some of the facts and myths surrounding groundwater.

Groundwater. or ground water (even the experts don't agree on the spelling), is water that is stored in the ground. It is stored in the spaces between the grains of rock material (the sand, gravel, and silt); above the rock; and in fractures (cracks) in the rock. An aquifer is the rock, and rock material, that stores water for our use.

Groundwater is not only stored in these spaces and cracks, it flows through them as well. It flows as slowly as centimeters per year in fine-grained silts and clays; and faster in sand, gravel, and rock. The term "underground river" that you may have heard is inaccurate because (1) flow is not in channels as are streams and rivers on the surface of the earth, and (2) we can find water nearly anywhere we dig or drill into the land surface (at least in Maine).

In general, the water table (measured as the depth to the water surface in a well) is found deeper in the ground on hilltops, and shallower in the ground in the valleys. It is also a misconception that all groundwater in Maine comes from the White Mountains, and Mt. Washington in particular. Instead, groundwater is pretty local.

All over Maine, rainwater seeps into the ground to replenish the local aquifers in watersheds. Once the watershed is "filled up," streams and rivers within that watershed carry the excess water downstream to a river, lake or the ocean, not to an adjacent watershed.

How do we care for our water resources? We should always conserve as much water as possible to protect the long-term capacity of our ground water resources. Using less water per person will help slow down the "drain" on this natural resource, but remember that here in Maine we have a high level of groundwater "recharge" due to the amount of rainfall we receive.

If you are in an area where the groundwater resource is limited, you can supplement water supplies by carrying water from a public source, designing storage capacity (holding tanks), or using cisterns to collect rainwater. When the quantity of water is lacking, water quality may also be compromised.

Water quality does change with time and conditions, so it is wise to have a drinking water test taken periodically to determine if any treatment is necessary. Since arsenic is common in Maine's groundwater, we all should be testing for arsenic in addition to the basic water safety test. For more information on groundwater and drinking water wells, see the Safe Homes Program website by going to MaineDEP.com and clicking on "Safe Homes."

This column was submitted by Pat Seaward, an Environmental Hydrogeologist with the Maine Department of Environmental Protection's (DEP) Bureau of Remediation and Waste Management.


SOURCE: LINCOLN COUNTY NEWS

DATE: 12-13-2007


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