Idaho Wellhead Nitrate Sampling
Sampling Program
GOODING COUNTY
OCTOBER 2000
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Idaho Wellhead Nitrate Sampling
GOODING COUNTY
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Water Quality
Water is the lifeblood of Idaho! Idaho ranks second in the United States in water
use, only to California. Our traditional industries such as agriculture,
forestry, and mining are all water dependent. And a large portion of tourist
revenues in Idaho are tied to attractions with water. In addition to the economy,
high quality water is essential to Idaho's recreational opportunities and
wildlands. We must protect water quality to maintain our high standard of
living and uniquely rich quality of life in Idaho.
Over 90 percent of Idahoans rely on groundwater for their drinking water. Surveys in Idaho have generally shown that groundwater quality is not a widespread problem.
The Program
The Idaho Private Wellhead Sampling Program was initiated and coordinated by the
Idaho Farm Bureau Federation (IFB). Charles Garner, Idaho Farm Bureau's Program Coordinator, in
conjunction with the Gooding Farm Bureau, collected 31 private wellhead
samples from farmers and rural residents on October 24, 2000.
This program was truly a cooperative effort as six different government agencies and the Idaho Farm Bureau Federation, a private membership-oriented organization, united to make the program a success. The Idaho Department of Agriculture (IDA) and the University of Idaho Cooperative Extension System (UI CES) assisted with program logistics, sample bottle distribution, and dissemination of information. The University of Idaho College of Agriculture's Analytical Laboratory (UI LAB) had major roles in planning and designing the quality assurance phase of the analytical part of the program and analyzed all samples for nitrates. The Idaho Division of Environmental Quality (DEQ) designed the quality assurance plan for the field effort, the questionnaire, and sampling procedures for the public. The United States Geological Survey (USGS) and the Natural Resource Conservation Service (NRCS) assisted with the collection of samples for quality assurance.
Why Conduct This Program in Gooding
County?
Groundwater monitoring surveys across the U.S. have shown that agrichemicals such
as nitrogen fertilizers are contaminating many sources of groundwater. Surveys in
Idaho show that nitrates are being found in several major aquifers. The Idaho Division of
Environmental Quality has identified the Snake River Plain aquifer in southern Idaho as a vulnerable
groundwater resource. This is a major concern since groundwater is the source of drinking water for
over 90 percent of Idahoans. Some of the factors contributing to this area being identified as
highly vulnerable include:
The Sampling
| Date: October 24, 2000 | |
| Samples collected: | |
| Rural residents | 31 |
| Blind/controls | 17 |
| Total | 48 |
Sampling Results
None of the 31 sampled wells in Gooding county contained nitrate-N levels greater than 10 ppm, which is
the National Public Health Service drinking water standard. Conversely,
48 percent of the sampled wells contained less than
2.0 ppm nitrate-N.
Compared to the EPA's National Survey for Nitrates conducted in 1988, a lower percentage of wells in Gooding county exceed the federal health standard for nitrates than the national average. In the EPA survey 2.4 percent of rural domestic wells contained nitrate levels exceeding federal health standards (10 ppm NO3-N). Another 40 percent of rural domestic wells contained detectable levels of nitrates. On a national level, EPA estimates that about 250,000 rural wells exceed U.S. Public Health Service standards for NO3-N.
What Do the Sampling Results Mean?
This study shows that:
The 52 percent of sampled wells that contained between 2 and 5 ppm NO3-N should be checked again in 2 to 3 years. Although these wells meet federal nitrate drinking water standards, it is probable that human activity has introduced nitrate into water in the vicinity of these wells since detected NO3-N levels are greater than normal, natural nitrate values in aquifers. Nitrogen fertilizer is a likely source of the elevated nitrogen levels in the groundwater; however, animal wastes, septic systems, and plant residues may also be responsible for the elevated nitrate-N values. Changes in the management of nitrogen fertilization may be warranted in certain situations.
Unlike other counties in the Magic Valley, no sampled wells in Gooding county exceeded the federal drinking water standard. This suggests that nitrate contamination of water in Gooding county is less of a problem than in surrounding areas of the valley.
The fact that depth to water table and the intensity of farming operations within Gooding county vary widely makes blanket statements about prescriptions for actions to protect groundwater unsuitable. It appears that the vast majority of landowners do not have a nitrate-N problem; however, nitrate-N values are most likely higher in areas where the water table is shallow. Here best management practices that ensure judicious use of N fertilizers should be used. Some of the more important N BMPs include:
Infants younger than 6 months are believed to be susceptible to nitrate poisoning. Bacteria present in their digestive systems at birth can change nitrate to toxic nitrite (NO2). Newborn infants have little acid in their digestive tracts, and they depend on these bacteria to help digest food. Generally, by the time infants reach 6 months, hydrochloric acid levels increase in their stomachs and kill most of the bacteria that convert nitrate to nitrite.
Once formed, the nitrite is absorbed and enters the bloodstream. There it reacts with the oxygen-carrying hemoglobin to form a new compound called "methemoglobin." This compound interferes with the blood's ability to carry oxygen. As oxygen levels decrease, babies may show signs of suffocation. This condition is called "methemoglobinemia." The major symptom of methemoglobinemia is bluish skin color, most noticeably around the eyes and mouth.
Infant deaths from methemoglobinemia, sometimes called "blue baby syndrome," are rare. Some documented deaths have been linked to high levels of nitrate in well water. Doctors now recommend using bottled water to make formula when nitrate levels exceed the U.S. Public Health Service drinking water standard of 10 parts per million (ppm) NO3-N.
Quality Assurance
Quality control in this sampling project was the top priority. Blind
spiked samples and blanks were randomly dispersed with farmer-provided
samples to assure top quality. In addition, in some cases, duplicate
farm wellhead samples were included. Thirty-seven quality control
samples were part of this study.
Nitrates were determined on water samples by the University of Idaho College of Agriculture's Analytical Laboratory in Moscow. After collection, a preservative was added to the sample before shipment to Moscow. Samples were run in the laboratory within 72 hours after collection. The most modern analytical techniques and equipment were used in this operation. A high degree of confidence should be placed on the numbers obtained from these samples.
The University of Idaho Cooperative Extension System has over 140 faculty strategically located throughout the state, including 84 agricultural educators stationed in 42 of 44 counties. In addition, faculty (specialists) are located on campus in Moscow and at research and extension centers in Aberdeen, Caldwell, Idaho Falls, Kimberly, Parma, Sandpoint, Tetonia, and Twin Falls.
This brochure, WQ-41, was prepared by R. L. Mahler, S. L. McGeehan, and K.
A. Loeffelman. Mahler and Loeffelman are in the Soil Science Division, University of
Idaho, Moscow, Idaho 83844. McGeehan is the Chief Chemist in the University of Idaho Analytical
Sciences Laboratory at Moscow.
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All contents copyright © 1997-2003. College of Agricultural and Life Sciences, University of Idaho. All rights reserved. Revised: January 3, 2003