Idaho is fortunate to have large quantities of groundwater. Groundwater is essential for almost 95 percent of Idaho's drinking water, more than 1.3 million acres of irrigated agriculture, and numerous industries.
Idaho's population is growing daily, and with more people comes an increased threat to groundwater. Groundwater is extremely difficult to clean up once it has been contaminated. Once depleted, aquifers often take decades or centuries to recharge. We must learn to use our groundwater efficiently and to protect it from contamination if we expect to continue to enjoy its benefits.
Groundwater is the underground water found in the cracks of bedrock and in the spaces between gravel and sand particles. It does not form an underground lake. Groundwater can occur just a few feet from the surface or may be buried several hundred feet down.
The hydrologic cycle explains the movement of water through its various phases from vapor in clouds to liquid water on the land surface, in the ground, and in the oceans. Groundwater originates as precipitation. When precipitation hits the ground it can evaporate, be taken up by plants, or move. If it flows across the top of the ground it becomes surface water such as in lakes and streams. If it moves downward through the soil and rock it becomes groundwater.
As groundwater moves downward, it passes through the spaces and cracks of the ground materials. Near the surface, where the spaces in the ground consist of both air and water, groundwater is referred to as soil water. Below this "unsaturated zone" is usually the top of the water table.
Like surface water, groundwater moves horizontally, but it moves at a much slower rate, usually only a few inches or feet per day. Its rate of movement depends upon the porosity and permeability of the soil, sand, gravel, and/or bedrock.
Porosity is the amount of pore space in the material and determines how much water the material can hold. Permeability is a measure of the ease with which water can move through the material. It depends on pore size and the path the water must take through the material. For example, water moves freely through the large pores between grains of sand but very slowly through the small pores in clay.
Surface permeability is important because it determines whether surface water will reach the groundwater and therefore determines the vulnerability of the groundwater to contamination.
POINT SOURCES OF WATER
Contamination sources are grouped as point or non-point sources. Point sources can be individually identified by point of release. Point source pollution of groundwater in Idaho is primarily from underground injection of waste, solid waste disposal sites (landfills), chemical spills, industrial chemicals, and underground fuel storage tanks.
Many groundwater contamination problems in Idaho are under investigation or cleanup. The relative importance of non-point sources and point sources of groundwater contamination within Idaho is unknown.
Injection wells -- Underground injection of waste has been a common practice for disposing of irrigation runoff and industrial waste. Injecting waste into the ground has the advantage of being generally inexpensive and of minimizing impacts on surface water. However, injection wells are often not deep or secure enough to avoid contamination of the local aquifer. Injection wells in parts of Idaho are being closely monitored by state and federal agencies. Because of potential groundwater contamination it is likely that injection wells will be out of use by the end of the decade.
Solid waste disposal sites -- When precipitation moves downward through solid waste it can dissolve some of the contents and carry them to the groundwater. Although modern solid waste disposal sites are lined to prevent leachate from entering the groundwater, sites that are at least 5 to 10 years old are generally not lined.
Underground storage tanks -- Underground storage tanks and their contents, whether at the local gas station or a major industrial complex, pose a widespread threat to groundwater. The major cause of leaking is corrosion of leaky pipe fittings. Many underground tanks are made of steel, which usually rusts and will eventually leak unless treated with special precautions.
Industrial chemicals -- Most hazardous wastes generated by large industrial facilities are currently regulated as point sources of pollution, but preregulation activities have caused groundwater contamination in many areas. In addition, users and disposers of small amounts of industrial chemicals may not have access to the best available disposal precedures or may not use them. This creates the potential for groundwater contamination.
It is the public's and the government's role to demand careful handling of materials and the use of Best Available Technology in pollution control, chemical storage, and waste disposal.
NITRATES IN DRINKING
Nearly 95 percent of Idahoans rely on groundwater as their source of drinking water. Thus, protection of groundwater from contamination by any substance that might cause health problems is a serious concern to many people.
One potential groundwater contaminant is nitrate (NO3). In general, recent surveys in Idaho have found that less than 4 percent of rural water wells have nitrate levels higher than the National Public Health Service drinking water standard.
Humans ingest nitrate in food and water. In older children and adults, nitrate is ingested, absorbed from the digestive tract, and excreted rapidly in the urine. Healthy human adults can consume fairly large amounts of nitrate with little if any known short-term adverse effects. The health effects of chronic, long-term consumption of high levels of nitrate are uncertain. They are the subject of several current research studies.
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. Death can occur when 70 percent of the hemoglobin has been converted to methemoglobin. Treatment must being quickly.
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.
Nitrate may also interact with organic compounds (secondary amines) to form N-nitrosamines, which are known to cause cancer. Many organic compounds could link with nitrate to form N-nitrosamines, including pesticides. This may be important because wells with high nitrate levels are often vulnerable to pesticide contamination. Neither the immediate nor the chronic health effect of N-nitrosamines in humans are well understood.
If nitrate is suspected in drinking water of humans, begin a routine water sampling and testing program to monitor nitrate levels. Nitrate is detectable in water only by chemical testing. It is colorless, odorless, and tasteless. In Idaho, the Department of Health and Welfare, the University of Idaho, and several private testing laboratories can test for nitrate.
Most laboratories usually report nitrate content in parts per million (ppm) of nitrate-nitrogen (NO3-N). Occasionally a lab will report results in ppm NO3. To interpret the results, you must know the form in which they are reported. To convert NO3-N to NO3, multiply by 4.4. For example, 10 ppm NO3-N equals 44 ppm NO3. Guidelines for use of water with known nitrate contents are as follows:
|0 to 10||0 to 44||Safe for humans and livestock.|
|11 to 20||45 to 88||Generally safe for human adults and livestock. Do not use for human infants.|
|21 to 40||89 to 176||Short-term use acceptable for human adults and all livestock unless food or feed sources are very high in nitrate. Long-term use could be risky. Do not use for human infants.|
|41 to 100||177 to 440||Moderate to high risk for human adults and young livestock. Probably acceptable for mature livestock if feed is low in nitrate. Do not use for human infants.|
|over 100||over 440||Do not use.|
LIABILITY ISSUES IN GROUNDWATER
While agricultural activities may contaminate groundwater, other sources of contamination have historically been the focus of most regulation and litigation concerning groundwater. Recently, however, attention has begun to shift to agriculture. While incidents in which agricultural activities have resulted in liability are not yet common, these incidents can be expected to increase as agriculture becomes more regulated and people become more aware of groundwater issues.
Persons responsible for groundwater contamination may be held liable -- and responsible persons frequently are a much larger group than just those whose agricultural activities directly caused the contamination. Anyone providing goods or services to those engaged in agriculture is potentially liable, even someone who unknowingly purchases contaminated land. Furthermore, even creating the potential for groundwater contamination may result in liability, even if actual contamination does not occur.
Who can impose liability?
Liability may be imposed through the action of a private party or a federal or state agency:
Federal and state agencies generally may seek all remedies available to private parties and, in addition, they can seek civil or criminal penalties. They may also take administrative (nonjudicial) action. Such actions give agencies broad latitude to impose civil monetary penalties and to require changes in the activities of those regulated.
Administrative actions are the route that governments most commonly use to impose liability. Such actions range from informal warnings for minor, first-time violations to formal administrative proceedings that resemble court actions.
Who is responsible for enforcement?
Enforcement of groundwater quality protection laws continues to be primarily a state and local responsibility. Nonetheless, federal regulation of groundwater has become increasingly important over the past two decades. As a result, interaction, overlaps, and even conflicts between federal and state regulation of groundwater have become increasingly important.
As a matter of policy, federal environmental legislation generally has
favored a major state role. The U.S. Environmental Protection Agency
(EPA) promotes this policy by delegating many responsibilities to
states. Congress also has assigned some responsibilities directly to
(Adapted from Groundwater and Public Policy, Series No. 11 by T. A. Feitshans)
RESEARCH UPDATE: INTEGRATED APPROACH
TO NON-POINT SOURCE POLLUTION IMPACTS
Over 30 water quality research projects are currently being conducted by University of Idaho College of Agriculture faculty. One of the most relevant projects involves developing an integrated approach to non-point source (NPS) pollution impacts. This project is under the direction of Dr. Dave Walker, and agricultural economist, and Dr. Merlyn Brusven, an entomologist. This research is supported in part by Idaho tax dollars and USDA-STEEP funds.
Non-point pollution sources originate from numerous land uses. These uses are usually individually insignificant but as they accumulate and occur in high densities, groundwater contamination results. On private lands, agriculture is responsible for contributing more NPS pollution than any other human activity. Nationally, about one-half of the sediment, total phosphorus, and total nitrogen discharged into U.S. waterways comes from agricultural sources. Non-point source pollution not only impairs water quality for municipal, industrial, and recreational uses, but may cause changes in the ecology, hydrology, and morphology of streams and rivers. Consequently, the erosion processes that deplete the topsoil and lead to watershed sedimentation reduce the productiviy of the land.
Up to this point there has been a lack of integrating both land and water resources as a tool for water quality planning. This research takes an integrated approach to combining soil, ecological, hydrological, and economic variables into a resource management planning process. The model utilizes a Geographic Information System (GIS) as its base. The ultimate goal of this research is to provide an integrated approach that acieves a balanced view of environmental wholeness as well as profitability in agricultural and forest systems.
The watershed being used as a case study to develop this integrated systems approach is the Tom Beall watershed in northern Idaho. This drainage system is composed of approximately 10,000 acres and is used primarily for dryland farming. Areas with soils too shallow to farm have been fenced and are used for grazing. No forest resource component is identified in this watershed. Best management practices (BMPs) are important in this watershed as they have an effect on the profitability of the farmers and ranchers as well as influencing downriver environmental concerns in the Clearwater, Snake, and Columbia rivers.
Using the systems approach, both land and water components are integrated through economical, biological, and ecological channels. The watershed is defined by its boundaries, components, attributes, and processes. These, in turn, are related to productivity, profitability, and environmental constraints. When considering management alternatives, the systems approach allows the consideration of impacts on one component and how changes in that component affect others.
For example, ground and surface waters are potentially impacted by land management practices. Groundwater contamination is a concern because of its importance to human consumption. Surface waters are susceptible to degradation from poor land use practices, especially on steep, erodible soils that occur on the Palouse. Stream habitat and water quality are initially impacted by land management practices as well as various biological components. Use of the integrated systems approach will allow optimum land management practices to maximize profits and minimize environmental damage.
Models are simulated by a computer program to answer important questions pertaining to the management of the Tom Beall watershed. These questions employ economic and environmental limits on the management systems simulated. The integrated systems model incorporates a geographic information system (GIS), watershed simulation model (AGNPS), climate generator, onsite erosion damage model (SOILOSS), and a farm management optimization model (MP MODEL). The integrated model traces the impact of changes in land use and farming practices at the field level on farm income, erosion damage, and water quality in an agricultural watershed.
Different combinations of crop rotations, tillage operations, and BMPs make up the resource management systems (RMS) for input. The 16 RMS combinations available include choices from four rotations, two tillage operations, and three BMPs.
At present, the basic model has been developed and the computer links between the different modules are being tested. Current work is focused on expanding the MP MODEL to include agricultural policy impacts. It will be another two years before the integrated model can be used as a tool for water quality planning.
By integrating the land and water resource components, a resource manager will be able to trace the impact of changes in land use on farm income and water quality in an agricultural watershed.
USING IPM TO PROTECT WATER
Agricultural pesticides are potential pollution threats to surface and groundwater quality. Integrated pest management (IPM) can help protect water quality by minimizing the amounts of pesticides that farmers use and by helping farmers to apply pesticides in ways that decrease the risk of chemicals washing off fields into lakes and rivers or leaching into groundwater.
The IPM philosophy uses the following five common sense priciples:
For additional information on IPM, obtain a copy of CIS 938, The Role of Integrated Pest Management, from your local Cooperative Extension System office.
N MANAGEMENT IN IDAHO
Lawns are an important part of our landscape. Besides being aesthetically pleasing, they cover erodible soils, produce oxygen, and fit nicely into our forested areas. However, lawns can be very expensive to care for if they are treated incorrectly. Incorrect nitrogen (N) fertilization can adversely impact water quality through leaching of applied nitrates into groundwater.
Nitrogen helps grass produce healthy, lush blades. Idaho lawns need 2 to 5 pounds of actual N per 1,000 square feet each year. The exact amount you apply depends on the length of growing season, soil type, and your choice of fertilizer. A gravelly soil will not hold N in the root zone as long as a loamy soil.
There are two kinds of N fertilizer: slow-release and quick-release. Slow-release fertilizers become available slowly. Use them in sandy soils, in other soils that drain rapidly, or when grass plants are not growing rapidly -- early spring and fall. Slow-release N fertilizers are often referred to as WIN (water insoluble nitrogen) materials.
Quick-release fertilizers provide readily available N to plants. Quick-release fertilizers are best to use when the grass is rapidly growing in early summer.
One N fertilization strategy is based on applying 0.5 pounds of N per 1,000 square feet of lawn for each month of active grass growth. (When daily temperatures average above 80 F, most grasses are not actively growing unless you water them. Many Idaho lawns start active growth in March or April and often continue to grow until late October.) If, for example, your lawn grows actively 8 months each year, you would apply 4 pounds of N per 1,000 square feet over the year (8 x 0.5 = 4).
Let's say you have a lawn that is actively growing 6 months each year.
You would calculate N fertilizer need for the year as follows:
0.5 lb N per 1,000 square feet per month x 6 months = 3.0 lb N per 1,000 square feet.
Apply the recommended amount of fertilizer in four applications: one-fourth in early spring (Easter), one-fourth in late spring (Memorial Day), one-fourth in late summer (Labor Day), and one-fourth in fall (Halloween).
For example, if you need 3 pounds of N per 1,000 square feet, you would
apply it as follows:
0.75 lb N around Easter
0.75 lb N around Memorial Day
0.75 lb N around Labor Day
0.75 lb N around Halloween
Do not apply more than 1 pound N per 1,000 square feet at one time.
For additional information on fertilizing lawns, fertilizer terminology, calculations, and application practices, obtain copies of the following publications from your local Cooperative Extension System office:
|CIS 792||Calibration and Safe Use of Lawn and Garden Pesticide and Fertilizer Applicators|
|CIS 846||Fertilizing Lawns in Southern Idaho|
|CIS 863||Fertilizer Primer: Terminology, Calculations, and Application|
|CIS 911||Northern Idaho Lawns -- Fertilizer Guide|
HOW CAN YOU PROTECT
There are many things we can do to protect Idaho's groundwater. First, we must realize that groundwater does not belong to anyone but is shared among individuals, municipalities, and industries. Second, we must realize that each one of us contributes to the threat of groundwater contamination. Finally, we must decide to change the way we conduct our daily activities. For example, we can:
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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