Water, water everywhere: groundwater

Typically, we don’t think of where our water comes from until something happens, such as a well pump failing, a broken pipe or a severe drought that mandates water use restrictions. Our uses for water are many. Where does it all come from, and what can happen to it?

Most households in the region that don’t have a municipal reservoir system have individual or community water well systems (and even some reservoirs are partially or wholly fed by groundwater.) These wells are drilled into underground aquifers, which may be a layer of sandstone or quartz embedded in shale or limestone. Even a seam in the rock can cause water to flow along it, yielding enough water for a usable well.

Another type of well is a gravel well. This type of well is usually found in areas of the river valley where gravel and sandy loam deposits can run several hundred feet deep. If a layer of suitable gravel is found, the well casing can be driven down to this layer and a metal screen installed at the tip of the casing. The gravel itself acts as a filter to help keep sand and other particles from ending up in the well water.

This underground water resource is not invincible from harm. Water recharge from any given aquifer can come anywhere from a few feet away to several miles away, depending on underground geology and type and depth of the well. Nitrates from fertilizers or wastewater, chemicals from spills or even dumping waste oil on the ground can all cause problems to our water supply. It behooves us to practice care, for water is one of our most important natural resources.

A groundwater fact sheet from the USGS can be found at pubs.usgs.gov/fs/OFR93-643/.