|Glossary of Terms|
Alkalinity refers to the capability of
water to neutralize acids. The presence of carbonates, bicarbonates, and
hydroxides is the most common cause of alkalinity in natural waters.
Annual Runoff indicates the total quantity of water in runoff for a drainage area for the year. Data reports may use any of the following units of measurement in presenting annual runoff data:
Acruifer is a geologic formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
Artesian means confined and is used to describe a well in which the water level stands above the top of the aquifer tapped by the well. A flowing artesian well is one in which the water level is above the land surface.
Bacteria are microscopic unicellular organisms, typically spherical, rodlike, or spiral and threadlike in shape, often clumped into colonies. Some bacteria cause disease, others perform an essential role in nature on the recycling of materials; for example, by decomposing organic matter into a form available for reuse by plants.
Bed material is the unconsolidated material of which a streambed, lake, pond, reservoir, or estuary bottom is composed.
Bottom material: See Bed material.
Chlorophyll refers to the green pigments of plants. Chlorophyll a and b are the two most common green pigments in plants.
Contents is the volume of water in a reservoir or lake. Unless otherwise indicated, volume is computed on the basis of a level pool.
Control designates a feature downstream from the gage that determines the stage discharge relation at the gage. This feature may be a natural constriction of the channel, an artificial structure, or a uniform cross section over a long reach of the channel.
Control structure as used in this report is a structure on a stream or canal that is used to regulate the flow or stage of the stream.
Cubic foot per second (cfs) is the rate of discharge representing a volume of 1 cubic foot passing a given point during I second and is equivalent to 7.48 gallons per second or 448.8 gallons per minute or 0.02832 cubic meters per second.
Discharge is the volume of water (or more broadly, total fluids) that passes a given point within a given period of time.
Dissolved refers to that material in a representative water sample which passes through a 0.45-micrometer membrane filter. This is a convenient operational definition used by Federal agencies that collect water data. Determinations of dissolved, constituents are made on subsamples of the filtrate.
Diversity index is a numerical expression of evenness of distribution of aquatic organisms.
Drainacre area of a stream at a specific location is that area, measured in a horizontal plane, enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into the river above the specified point. Figures of drainage area given herein include all closed basins, or noncontributing areas, within the area unless otherwise noted.
Drainacre basin is a part of the surface of the earth that is occupied by a drainage system, which consists of a surface stream or body of impounded surface water, together with all tributary surface streams and bodies of impounded surface water.
Gage height (G.H.) is the water-surface elevation referred to some arbitrary gage datum. Gage height is often used interchangeably with the more general term 'stage,' although gage height is more appropriate when used with a reading on a gage.
Gaging station is a particular site on a stream, canal, lake, or reservoir where systematic observations of hydrologic data are obtained.
Hardness of water is a physical-chemical characteristic that is commonly recognized by the increased quantity of soap required to produce lather. It is attributable to the presence of alkaline earth's (principally calcium and magnesium) and is expressed as equivalent calcium carbonate (CaCO3).
Hydrologic unit is a geographic area representing part or all of a surface drainage basin or distinct hydrologic feature as delineated by the Office of Water Data Coordination on the State Hydrologic Unit Maps; each hydrologic unit is identified by an 8-digit number.
Micrograms per gram (UG/G, egg) is a unit expressing the concentration of a chemical element as the mass (micrograms) of the element sorbed per unit mass (gram) of sediment.
Micrograms per liter (UG/L, gg/L) is a unit expressing the concentration of chemical constituents in solution as mass (micrograms) of solute per unit volume (liter) of water. One thousand micrograms per liter is equivalent to one milligram per liter.
Milligrams per liter (MG/L, mg/L) is a unit for expressing the concentration of chemical constituents in solution. Milligrams per liter represents the mass of solute per unit volume (liter) of water. Concentration of suspended sediment also is expressed in mg/L, and is based on the mass of sediment per liter of water-sediment mixture.
National Geodetic Vertical Datum of 1929 (NGVD) is a geodetic datum derived from a general adjustment of the first order level nets of both the United States and Canada. It was formerly called 'Sea Level Datum of 1929, or mean sea level, in this series of reports. Although the datum was derived from the average sea level over a period of many years at 26 tide stations along the Atlantic, Gulf of Mexico, and Pacific coasts, it does not necessarily represent local mean sea level at any particular place.
Natural substrates refers to any naturally occurring emersed or submersed solid surface, such as a rock or tree, upon which an organism lives.
Organism is any living entity, such as an insect, phytoplankton, or zooplankton.
Partial-record station is a particular site where limited streamflow and/or waterquality data are collected systematically over a period of years for use in hydrologic analyses.
Particle size is the diameter, in millimeters (MM or mm), of suspended sediment or bed material determined either by sieve or sedimentation methods. Sedimentation methods (pipette, bottom-withdrawal tube, visual-accumulation tube) determine fall diameter of particles in either distilled water (chemically dispersed) or in native water (the river water at the time and point of sampling).
Pesticides are chemical compounds used to control undesirable plants and animals. major categories of pesticides include insecticides, miticides, fungicides, herbicides, and rodenticides. Insecticides and herbicides, which control insects and plants respectively, are the two categories reported.
Picocurie (PC, pCi) is one trillionth (1 x 1012) of the amount of radioactivity represented by a curie (Ci) . A curie is the amount of radioactivity that yields 3.7 x 10^10 radioactive disintegration's per second. A picocurie yields 2.22 dpm (disintegration's per minute).
Polychlorinated biphenyls (PCBs) are industrial chemicals that are mixtures of chlorinated biphenyl compounds having various percentages of chlorine. They are similar in structure to organochlorine insecticides.
Sea level, as used in this report, refers to the National Geodetic Vertical Datum of 1929 (NGVD Of 1929)--a geodetic datum derived from a general adjustment of the firstorder level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.
Sediment is solid material that originates mostly from disintegrated rocks and is transformed by, suspended in, or deposited from water; it includes chemical and biochemical precipitates and decomposed organic material such as humus. The quantity, characteristics, and cause of the occurrence of sediment in streams are influenced by environmental factors. Some major factors are degree of slope, length of slope, soil characteristics, land usage, and quantity and intensity of precipitation.
Sodium-adsorption-ratio (SAR) is the expression of relative activity of sodium ions in exchange reaction with soil and is an index of sodium or alkali hazard to the soil. This ratio should be known, especially for water used for irrigating farmland.
Solute is any substance derived from the atmosphere, vegetation, soil, or rocks that is dissolved in water.
Specific conductance is a measure of the ability of a water to conduct an electrical current. It is expressed in 5S/cm or US/CM (microsiemens per centimeter at 25'C) Specific conductance is related to the type and concentration of ions in solution and can be used for approximating the dissolved-solids concentration of the water. Commonly, the concentration of dissolved solids (in milligrams per liter) is about 65 percent of the specific conductance (in microsiemens per centimeter). This relation is not constant from stream to stream, and it may vary in the same source with changes in the composition of the water.
Stage-discharge relation is the relation between gage height (stage) and volume of water, per unit of time, flowing in a channel.
Streamflow is the discharge that occurs in a natural channel. Although the term ,discharge, can be applied to the flow of a canal, the word 'streamflow, uniquely describes the discharge in a surface stream course. The term 'streamflow' in more general than runoff, as streamflow may be applied to discharge whether or not it is affected by diversion or regulation.
Surface area of a lake is the area outlined on the latest USGS topographic map as the boundary of the lake and measured in acres by a planimeter. In localities not covered by topographic maps, the areas are computed from the best maps available at the time planimetered. All areas shown are those for the stage when the planimetered map was made.
Suspended (as used in tables of chemical analyses) refers to the amount (concentration) of the total concentration in a water-sediment mixture. The watersediment mixture is associated with (or sorbed on) that material retained on an 0.45micrometer filter.
Taxonomy is the division of biology concerned with the classification and naming of organisms. The classification of organisms is based upon a hierarchical scheme beginning with Kingdom and ending with Species at the base. The higher the classification level, the fewer features the organisms have in common.
Thermograph is an instrument that continuously records variations of temperature on a chart. The more general term 'temperature recorder' is used in the table headings and refers to any instrument that records temperature, whether on a chart, a tape, or any other medium.
Time-weighted average is computed by multiplying the number of days in the sampling period by the concentrations of individual constituents for the corresponding period and dividing the sum of the products by the total number of days. A time-weighted average represents the composition of water that would be contained in a vessel or reservoir that had received equal quantities of water from the stream each day for the water year.
Tons per acre-foot indicates the dry weight of dissolved solids in 1 acre-foot of water. It is computed by multiplying the concentration in milligrams per liter by 0 . 00136.
Tons per day is the quantity of a substance in solution or suspension that passes a stream section during a 24-hour day.
Water year in Geological Survey reports dealing with surface-water supply is the 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ending September 30, 1985, is called the '1985 water year.
Weighted average is used in this report to indicate discharge-weighted average. It is computed by multiplying the discharge for a sampling period by the concentrations of individual constituents for the corresponding period and dividing the sum of the products by the sum of the discharges. A discharge-weighted average approximates the composition of water that would be found in a reservoir containing all the water passing a given location during the water year after thorough mixing in the reservoir.
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Last Updated Thursday, 12-Aug-2004