Nitrate in Groundwater: A hidden concern

Author: Melissa Fery

Publish Date: Winter 2008

One of the most important responsibilities that come with rural living, is that of protecting the groundwater. Whether you operate a commercial farm, have a small acreage or enjoy a rural lifestyle, basic management practices will help provide good quality water for your family and animals.

All Oregonians should work towards protecting groundwater resources. There are three areas in Oregon, where nitrate contamination of the groundwater has been identified as a drinking water concern. The Southern Willamette Valley, Lower Umatilla Basin and Northern Malheur County have established Groundwater Management Areas to work to address nitrate contamination issues. The La Pine area of southern Deschutes County is also considered an area at risk for nitrate contamination.

Nitrate is a form of nitrogen that moves easily with water through the soil and therefore has potential to reach the water table. Areas most vulnerable to contamination are those with shallow or sandy soils, area of high rainfall or are under irrigation. There is health risks associated with elevated nitrate in drinking water. The EPA has set the maximum level of 10mg/l or 10 ppm of nitrate for public drinking water supplies, because higher amounts of nitrate in drinking water have been associated with a type of blue baby syndrome. Water containing less than 10 mg/l nitrate is considered safe for people of all ages to consume. If the nitrate level in water is approaching or above 10 mg/l, infants and nursing and pregnant women should not drink the water.

Nitrate screening during an OSU Extension Service workshop. Photo provided by Melissa Fery

Nitrate contamination in groundwater is the result of non-point source pollution from fertilizers and human and animal waste. Excess fertilization of gardens, lawns or fields, overstocked livestock on pastures, improperly managed animal feeding or holding areas or improperly maintained septic systems may be possible sources of contamination.

Nitrogen is necessary for optimum plant production; however, when fertilizers are applied in excess, it can be a cause for nitrate contamination in groundwater. All fertilizers should be applied at an appropriate rate, time and application method for the crop, garden or lawn to utilize all of the nutrients in the root zone.

Manure from livestock and horses may impact groundwater quality. Animal manure contains nitrogen and bacteria that may contaminate drinking water, if not managed properly. Animal manure should be applied to crops or pasture as a plant nutrient source. Manure that is stockpiled should always be covered, especially in the winter to avoid run-off and leaching of nutrients.

Failing and improperly managed septic systems may also lead to contamination of drinking water. Pumping the septic tank regularly, depending on household and tank size, using water saving devices in the house and protecting the drainfield area from damage by heavy animals, vehicles and construction activities will reduce potential impact.

Inspecting the well, removing all hazardous materials from the well house, installing backflow protection and ensure there is never standing water around the top of the well are simple practices to safe guard the well from risk. A recommended practice is to test drinking water wells every 1 to 3 years for nitrate and bacteria.

Every rural resident should take a good look at their property and management practices and do all they can help keep drinking water clean for their families, neighbors and animals.

For more information about well water quality, nitrate in groundwater, and testing water go to Oregon State University’s well water website.