Em4885 irrigation management practices to protect ground water

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4. Uncertainty - There is some uncertainty as to what is a genuine health risk due to certain
contaminants, especially for longterm exposures. Numerical limits are identified by State
and Federal Law and are based on a wide variety of health-related studies. An important
question is when do pollution prevention measures become required based on tests that only
approach the limit. There is also uncertainty about what efforts are required to prevent
pollution. Many factors governing pollution vary widely from area to area including soils,
crops, topography, climate, and aquifer depth and size. Efforts that may be successful in
one location may not be effective somewhere else.
5. Acceptable contamination - As stated, there are many uses and many users of ground water.
What is contamination for one class of users may not be contamination for another.
A continual concern for policymakers is putting too much of an economic burden on
one class of users to prevent contamination for another class. This is especially important
in areas of high agricultural activity where the economic viability of the region depends
on the economic health of the agricultural sector.
Water Quality Law
Although there had been several previous Federal laws regarding water quality, growing concern
about the degradation of the nation’s water supply quality led to the passage of the Federal Water
Pollution Control Act Amendments (Public Law 92-500) in 1972. This Act is more commonly known
as the Clean Water Act. It has subsequently been renewed and expanded several times. The 1972
Clean Water Act is important because it was the first Federal law to focus primarily on maintaining
in-stream water quality standards as the test for required reductions in polluting activities.
The primary Federal mandates for protecting water quality are contained in this Act.
The U.S. Environmental Protection Agency is responsible for administering and enforcing
these requirements. Most states, including Washington State, have been delegated some of these
responsibilities including the administration of waste discharge permits.
There are two categories of water pollution, point and nonpoint. Point source pollution occurs
when the source of the pollution is readily identifiable. Examples of point source pollution are a
discharge pipe from a factory or the outlet from a city’s sewage treatment plant.
Much State and Federal effort has been directed at controlling and reducing point source pollution
as a result of the 1972 Act’s passage. Most significant point sources now operate under discharge
permits that define the conditions of the discharge. These conditions are designed to control the
amount of contamination from the individual sources.
Because of the great strides in controlling point source pollution, the emphasis in recent years
has switched to nonpoint source pollution. Nonpoint source pollution is diffuse. Typically it is a
combination of many small, even insignificant, sources that have a significant cumulative effect on
water quality. However, a specific agricultural return flow site that is fed by a large area may also
be defined as nonpoint source pollution. Nonpoint source pollution is indicated by a general decline
in quality of surface or ground water.
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