|
<br />distribution of ruck formatIOns, struclUral datil, attitude and posi.
<br />tion of geologic formatIOns underlymg the iirea, outcropping of
<br />ore bodies and ('rebearing fonnallons, location of mines, quarries.
<br />etc.
<br />
<br />1\.lAP. ISOHYET AL - A map .....hich shows the \'.J.Tiation and
<br />distributIOn of precipitation occurring o\'er an an~a during a
<br />given period through the use of isoh)'ets.
<br />
<br />i\lAP, \VATER TABLE A contour map (If the upper surface
<br />of the zone saturation.
<br />
<br />i\lEASUREi\IENT, DISCHARGE - (I) The determination of
<br />the quantity of Water fJowing per unit of tIme in a stream chan-
<br />nel, c')nduit,. or orifice at ,] given pomt by means of current
<br />meters. rod floats, weIrs. Pi rot tubes. or orher measuring devices
<br />or methods. The operation includes not only tbe measurement
<br />of velocity (>f water and the area of the cross section of the
<br />stream of \,:ater, but also tbe necessary subsequent computations.
<br />See gaging, stream. (2) The numencal results of a measure-
<br />ment of discharge, expressed in appropriate units.
<br />METHOD. ELECTRICAL.ANALOGY , A method by wh;,h
<br />the phenomena pertaining to (>ne physical system, such as flow
<br />of waler through porous media, are studied by experiments in
<br />another physical system, namely the flow of electricity through
<br />conductors. It is employed for the solution of problems in dif-
<br />ferent fields such as stress an81ysis of dams or machine parts bv
<br />the photoelastic method, estimation of water le\'e!s in tidal net-
<br />works, piping and uplift in the design of structures on permeable
<br />foundations, torsion of shafts, cavitation around streamlined
<br />bodies as airships, torpedos, heat transfer in the design of fur'
<br />naces and internal combustion engines, etc.
<br />l'\'tOU,ND, GROUND-WATER - A mound or ridge-shaped fea-
<br />ture in a water table, usually produced by percolation of surface
<br />water to the water table. Such features are often found under
<br />irrigated. a.reas where excessive application of irrigation water
<br />~)Ver a limited area has resulted in heavy seepage and the build-
<br />Ing up of the water table. Also called grollnd-water hill.
<br />OVER-DEVELOPMENT - In ground water; when the eco-
<br />nomic yield of an aquifer is exceeded, that aquifer is said to be
<br />oveTde\'eloped. If the trammissibllity of an dquifer is limited,
<br />excessive withdrawals in a restricted <lre;l mOly cause sufficient
<br />drawdown locally as to make it uneconomIc to continu~ to
<br />.....ithdrilw ......ater at that r3te, ~\"en though the physical yield
<br />limit for the enrire aquifer ha!> nnt be~n reached. That conditIOn
<br />is called local ol'er-del'elopme'lt.
<br />PARTS PER l\IILLION - Pans by weight of a substanc~ in a
<br />million parts of wHer.
<br />PERMEABIUTY - The property of :::I m8tenal whIch permits
<br />appreciable mO\'ement of water through It when saturated and
<br />actuated by hydrostatic pressure of the magnitude normally en-
<br />:ountereJ in natural subsurface water. The r<lte of penneabiJity
<br />]s measured by the quantity of W8ter passing through a unit
<br />cross section, in a unit time when the gradient of the energy
<br />head is unity. Prt?riousness is sometimes used in the same sense
<br />as permeability. See coefficient. pt?rll1eability.
<br />PHREATOPHYTE A plant that habitually obtains ib W<lter
<br />supply from the zone of saturation. either directly or through the
<br />capillary f[lnge.
<br />POINT, \NIL TING - The minimum quanlitv of water in a
<br />given soil necessary 10 maintain plant growth. \Vhcn the quanti-
<br />ty of moisture falls below this, the leaves begin to droop and
<br />shtl\'d up. In any given sod the quantity is practically constant
<br />for all plants, but it Increases with a decrease in the size of soil
<br />panicles. The moisture conte]~t of ~ given soil at whIch the
<br />tOree ha!dmg wdter to the SOlI pamcles equah the maximum
<br />water-absorbing force of the plant roots.
<br />
<br />8
<br />
<br />'-=:>
<br />a
<br />N
<br />a
<br />Co.)
<br />o
<br />
<br />'I
<br />"
<br />
<br />POROSITY - (I) The state of being porous or containing in-
<br />terstices, (2) An index of the \'oid characteristics of a sailor
<br />stratum as perraining to percolation: degree of perviousness, (3)
<br />The ratio, usuodly e,'(pressed as a percentage, of (a) the volume
<br />of the interstices in a gi\'en quantity of materi3l, to (b) the
<br />total \'olume of soil or rock.
<br />
<br />PRECIPITATION - (1) The total measurable supply of wilter
<br />of all forms of falling moisture, including dew, rain, mist, snow,
<br />hail. and sleet; usually expressed as depth of liquid water on a
<br />horizontal surface in a da\". month, or year, and designated as
<br />daily, momhh', or annual precipitation. (2) The process by
<br />which atmospheric moisture in liquid or solid state is discharged
<br />(Joto a land or water surf3ce. (3) The phenomenon which oc-
<br />curs when a subsl2nce held "in solution in a liquid passes out
<br />of solution mtO solid form.
<br />
<br />PUi\lP, DEEF-\VELL - A pump used for lifting water from
<br />deep wells, the pumping mechanism usually being installed
<br />within the well at a considerable distance below the surface.
<br />The pump m8Y be of the reciprocating or rotating type.
<br />
<br />REQlIIREl-.'IENT, LEACHING - The t"raction of the water
<br />(irrigation) entering the soil that must pass through the root
<br />zone In order to prevent ';;Oil salinity hum exceeding 'J. specified
<br />value.
<br />
<br />REOUJREl\IENT, WATER - The total qU;lntity of water, re-
<br />gardless of its source, required by crops for their normal growth
<br />under field conditions. It ma)' include water applied in irriga-
<br />tion, precipitallOn, and ground \\'ater available to the crops.
<br />
<br />RESERVOIR, GROUND-\~lATER - (1) A reservoir in which
<br />ground-water is stored for future eXlIaction and use. The water
<br />may be placed in the resen'oir by artificial means (spreading,
<br />etc.) or. by natural means (seepage, infiltration, etc.). (2) See
<br />acquifer.
<br />
<br />RESERVOIR, IVIUL TIPLE.USE - A reservoir cunstructed and
<br />equipped to I;>ro\'lde storage and release of water for tWO or more
<br />purposes, such as flood control, power development. navigation,
<br />irrigation, pollution abatement, and domestic water supply.
<br />
<br />RESERVOIR, REREGULATING - A reservoir used for the
<br />purpose of regulating the outflow received from another reser-
<br />\'oir or hydroelectric plant.
<br />
<br />RIGHT(S), \VATER The right(s), acquired under the law,
<br />to use the water occurring in surface or ground waters, for a
<br />specified purpose and in a given numncr and usually wilhin the
<br />limits of a given period. While slIch right(s) may include the
<br />use of a body (,f water for navigation, fishing, and hunting, and
<br />other recreational purposes, etc., the term is usually applied to
<br />the right to di\'en or store water for some beneficial purpose or
<br />use, such as irrigation, generarion of hydroelectric po.....er, domes-
<br />tic or municipal water supply. In some states, a water right by
<br />law becomes appurtenant to the panicular tract of land to which
<br />the water is applied.
<br />
<br />RIGHTS, WATER, ADJUDICATION OF (I) The legal
<br />procedure followed in determining the quantities of water to
<br />which persons claiming water rights in a stream or other body of
<br />water are entitled. 8nd in the case of rights by appropriation, the
<br />[elative ptlority of each such right. (2) The tenn is also applied
<br />to a court decree or other 8greement which sets forth such rights
<br />and priorities.
<br />
<br />RIGHTS, WATER. ADMINISTRATION OF. The pwee'
<br />dure involved in the creatIOn of ell1 orderly manner of handling
<br />the water rights existing in a slream or other bod\' of water to
<br />insure justice and equity in the utilization of such' water. Three
<br />steps in the procedure are generally im'olved: (a) Creation by
<br />statute of legal procedure for initi3ting watet rights and' estab-
<br />lishing their amount and priority, (b) adjudication of exisring
<br />rights which were initiated prior to the time when orderly pro.
<br />cedure was established, and (c) supen'ision of the distribution of
<br />
<br />9
<br />
|