Natural Groundwater Characteristics

Understanding Groundwater

Well Water Program


As water moves down through layers of soil, disease-causing germs such as bacteria and viruses are filtered out. For this reason, groundwater often produces drinking water that does not need to have chlorine added to kill germs.

Wells close to streams or lakes, however, might not produce germ-free water. These wells are said to be under the direct influence of surface water. Water from these wells might not pass through very much soil as it moves from surface water to the well. Without soil filtration, germs from the surface water might be present in the well water.

Additionally, some wells are not constructed properly and allow germs to enter groundwater from the well itself. This is not a natural characteristic of groundwater and is discussed in more detail in the wells section under protecting groundwater.



Common Minerals in Oregon's Groundwater:

  • Iron. Water turns orange, stains laundry and bathroom fixtures, may make the water taste like metal.
  • Calcium & Magnesium. Cause "hard water" and leave chalky white deposits.

While iron, calcium, and magnesium are common in Oregon, minerals contained in groundwater vary greatly. These minerals are dissolved from the rocks of the aquifer. Generally, the longer water has been underground, the more natural minerals it contains. You can predict the type of rocks the groundwater flowed through during its time underground by the minerals in the water.

A small amount of minerals in water gives it a pleasant taste In excess, natural minerals can be a nuisance, but most are not a health concern in Oregon - one exception is arsenic.

In a few parts of Oregon, arsenic has been found in the groundwater above safe levels for drinking water. While arsenic can be a contaminant from human activity, the arsenic in Oregon appears to be naturally dissolved from rocks in the aquifers. If you have a private well and are concerned about arsenic, contact a local water testing lab:

Also, see the USGS report:

Arsenic in Groundwater in the Willamette Basin, Oregon

Water can be treated to remove germs and other materials that may pose a health risk or make the water unpleasant to drink. Contact the OSU Extension Service Well Water Program for more information.