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<br />Milligrams per liter (mgIL)- A unit expressing the con-
<br />centration of chemical constituents in solution as
<br />weight (milligrams) of solute per unit volume (liter) of
<br />water; equivalent to one part per million in most stream-
<br />water and ground water. One thousand micrograms per
<br />liter equals I mg/L.
<br />Monitoring well- A well designed for measuring water
<br />levels and testing ground-water quality.
<br />Mouth- The place where a stream discharges to a larger
<br />stream, a lake, or the sea.
<br />Nitrate- An ion consisting of nitrogen and oxygen (N03 -).
<br />Nitrate is a plant nutrient and is very mobile in soils.
<br />Nonpoint source- A pollution source that cannot be
<br />defined as originating from discrete points such as pipe
<br />discharge. Areas of fertilizer and pesticide applications,
<br />atmospheric deposition, manure, and natural inputs
<br />from plants and trees are types of non point source pol-
<br />lution.
<br />Nutrient- Element or compound essential for animal and
<br />plant growth. Common nutrients in fertilizer include
<br />nitrogen, phosphorus, and potassium.
<br />Organochlorine pesticide- A class of organic insecticides
<br />containing a high percentage of chlorine. Includes
<br />dichlorodiphenylethanes (such as DOT), chlorinated
<br />cyclodienes (such as chlordane), and chlorinated ben-
<br />zenes (such as lindane). Most organochlorine insecti-
<br />cides were banned because of their carcinogenicity,
<br />tendency to bioaccumulate, and toxicity to wildlife.
<br />Pesticide- A chemical applied to crops, rights of way,
<br />lawns, or residences to control weeds, insects, fungi,
<br />nematodes, rodents or other "pests".
<br />Phosphorus- A nutrient essential for growth that can play
<br />a key role in stimulating aquatic growth in lakes and
<br />streams.
<br />Picocurie (pCi)- One trillionth (10-12) of the amount of
<br />radioactivity represented by a curie (Ci). A curie is the
<br />amount of radioactivity that yields 3.7 x 1010 radioac-
<br />tive disintegrations per second (dps). A picocurie yields
<br />2,22 disintegrations per minute (dpm) or 0.037 dps.
<br />Radon- A naturally occurring, colorless, odorless, radioac-
<br />tive gas formed by the disintegration of the element
<br />radium; damaging to human lungs when inhaled.
<br />Reference site- A NA WQA sampling site selected for its
<br />relatively undisturbed conditions.
<br />Sediment- Particles, derived from rocks or biological
<br />materials, that have been transported by a fluid or other
<br />natural process, suspended or settled in water.
<br />Species- Populations of organisms that may interbreed and
<br />produce fertile offspring having similar structure, hab-
<br />its, and functions.
<br />Streambed sediment- The material that temporarily is sta-
<br />tionary in the bottom of a stream or other watercourse.
<br />
<br />24 Water Quality in the Upper Colorado River Basin
<br />
<br />Study Unit- A major hydrologic system of the United
<br />States in which NA WQA studies are focused. Study
<br />Units are geographically defined by a combination of
<br />ground- and surface-water features and generally
<br />encompass more than 4,000 square miles of land area.
<br />
<br />Surface water- An open body of water, such as a lake,
<br />river, or stream.
<br />
<br />Suspended sediment-Particles of rock, sand, soil, and
<br />organic detritus carried in suspension in the water col-
<br />umn, in contrast to sediment that moves on or near the
<br />streambed.
<br />
<br />Synoptic sites- Sites sampled during a short-term investi-
<br />gation of specific water-quality conditions during
<br />selected seasonal or hydrologic conditions to provide
<br />improved spatial resolution for critical water-quality
<br />conditions.
<br />
<br />Trace element- An element found in only minor amounts
<br />(concentrations less than 1.0 milligram per liter) in
<br />water or sediment; includes arsenic, cadmium, chro-
<br />mium, copper, lead, mercury, nickel, zinc and selenium.
<br />
<br />Un-ionized ammonia- The neutral form of ammonia-
<br />nitrogen in water, usually occurring as NH40H. Un-
<br />ionized ammonia is the principal form of ammonia that
<br />is toxic to aquatic life. The relative proportion of un-
<br />ionized to ionized ammonia (NH4 +) is controlled by
<br />water temperature and pH. At temperatures and pH val-
<br />ues typical of most natural waters, the ionized form is
<br />dominant.
<br />
<br />Volatile organic compounds (VOCs)- Organic chemicals
<br />that have a high vapor pressure relative to their water
<br />solubility. VOCs include components of gasoline, fuel
<br />oils, and lubricants, as well as organic solvents, fumi-
<br />gants, some inert ingredients in pesticides, and some
<br />by-products of chlorine disinfection.
<br />
<br />Water-quality guidelines- Specific levels of water quality
<br />which, if reached, may adversely affect human health or
<br />aquatic life. These are nonenforceable guidelines issued
<br />by a governmental agency or other institution.
<br />
<br />Water-quality standards- State-adopted and U.S. Envi-
<br />ronmental Protection Agency-approved ambient stan-
<br />dards for water bodies. Standards include the use of the
<br />water body and the water-quality criteria that must be
<br />met to protect the designated use or uses.
<br />
<br />Water year- The continuous 12-month period, October I
<br />through September 30, in U.S. Geological Survey
<br />reports dealing with the surface-water supply. The
<br />water year is designated by the calendar year in which
<br />it ends and which includes 9 of the 12 months. Thus,
<br />the year ending September 30, 1980, is referred to as
<br />water year 1980.
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