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<br />GLOSSARY <br /> <br />Aquifer,--A geologic formation, part of a formation, or group of formations <br />that contains sufficient saturated permeable material to yield signifi- <br />cant quantities of water to wells and springs. A confined aquifer is an <br />aquifer in which ground water is confined under pressure greater than <br />atmospheric by overlying, relatively impermeable strata. Water level in <br />a well penetrating a confined aquifer will be above the upper boundary of <br />the aquifer. An unconfined aquifer is an aquifer where the water table <br />is the upper surface of the saturated zone. <br />Chemical quality.--Concentration of solutes (any substance dissolved in water) <br />and certain properties or characteristics such as hardness, sodium- <br />adsorption ratio, percent sodium, and specific conductance. <br />Confining bed.--A rock unit above or below an aquifer that is much less <br />permeable than the aquifer and that restrains ground-water flow to and <br />from adjoining units. <br />National Geodetic vertical Datum of 1929 (NGVD of 1929).--A geodetic <br />derived from a general adjustment of the first-order level nets <br />the United States and Canada, formerly called "Mean Sea Level." <br />1929 is referred to as sea level in this report.) <br />Sodium-adsorption ratio (SAR).--The expression of relative activity of sodium <br />ions in exchange reactions with soil. The formula used for the computa- <br />tion of SAR is: <br /> <br />datum <br />of both <br />(NGVD of <br /> <br />SAR = <br /> <br />(Na+) <br /> <br />J (Ca+2) <br /> <br />+ (Mg+2) <br />2 <br /> <br />Where solute concentrations are expressed in milliequivalents per liter. <br /> <br />Specific capacity.--A measure of the productive capacity of a well: rate of <br />well discharge per unit of drawdown. <br />Transmissivity.--The rate at which water is transmitted through a unit width <br />of the aquifer under a unit hydraulic gradient. <br /> <br />iv <br />