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<br /> <br />or other materials upon which a pipe or conduit is supported. <br />Classifications are: impermissible, ordinary, ordinary projection, <br />first class. rim class projection and concrete-cradle bedding. <br />BEDROCK Any solid rock underlying soil, sand, clay, silt, <br />etc. <br />BENTONITE - The plastic residue from the weathering of ash <br />(volcanic). A soft, moisture absorbing rock, often of volcanic <br />origin, composed of any of the montmorillonite-beidellite grOup <br />of clay minerals. Some bentonites swell on contact with water <br />and are used for sealing leaks in canals, reser....oirs, etc., but they <br />have no apprcci3ble suuctural strength, hence must be used <br />together with concrete or soil to support a large head of water. <br />CALICHE - A hard deposit, consisting mostly of calcium car- <br />bonate, found in the subsoil in arid sections. The deposit may <br />range from several inches to several feet in thickness, and is <br />presumed to have been created by mineral-laden capillary water <br />evaporating and leaving a residue which served as a cementing <br />material. <br />CAPACITY, I\-10ISTURE, FIELD - The approximate quantity <br />of water which can be Jermanently retained in the soil in op- <br />position to the downwar pull of gravity. It may be expressed in <br />percent of dry weight or in inches deyrh for a given depth of <br />soil. The length of time required for a soil to reach field <br />moisture capacity varies considerably ....'ith various soils, being <br />approximately 24 to 48 hours for sandy soils, 5 to 10 days for <br />silt clay soils, and longer for clays. Also called capillary capacity, <br />field carrying capacity, maximum water holding capacity, moist. <br />ure holding 'capacity, and normal moisture capacity. See reten- <br />tion, specific; capacity, field. <br />CAPACITY, \VELL - The maximum rate at which a well will <br />yield water under a stipulated set of conditions, such as a given <br />drawdown, pump and motor or engine size. It may be ex- <br />pressed in terms of gallons per minute, cubic feet per second. or <br />other similar units. <br />CAPILLARITY - (I) The degree to which a material or ob. <br />ject containing minute openings or passages, when immersed in <br />a liguid. will draw the surface of the liquid above the hydrosta- <br />tic le\'el. Unless otherwise defined, the liquid is generally as. <br />sumed to be water. (2) The phenomenon by which water is <br />held in interstices above the normal hyclmstatic level, due to at- <br />traction of the molecules in the walls of an interstice for the <br />molecules of the water and the attraction of the molecules of <br />water for one another. <br />COMMISSIONER, \V ATER - (1) In western United States. <br />a person appointed under statutory or coun authority, whose <br />duties involve the administration of water rights or operations <br />related thereto or connected therewith. such as supervising di- <br />versions of water from a stream under a decree of adjudication, <br />. etc. (2) A Municipal or district official responsible for the ad- <br />ministration of a water supply system. <br />COMPACT, INTERSTATE - A compact between states; some <br />compacts cover the development and utilization of interstate <br />streams, abatement of pollution, and other purposes. <br />COURSE, SNOW - A line. laid out and permanently marked, <br />on a drainage area along which the snow is sampled at definite <br />distances or stations, and at appropriate times, to determine its <br />depth, water equivalent, and density, during a snow survey. <br />CUBIC FOOT PER SECOND - A unit of discha'ge fo, <br />measurement of flowing liquid, equal to a now of I cubic foot <br />per second past a given section. Also c::tIled second-foot or cusec. <br />CYCLE, HYDROLOGIC - The circuit of water movement from <br />the atmosphere to the earth and return to the atmosphere through <br />various stages or processes as precipitation, interception, runoff, <br />infiltration, percolation, storage, evaporation and transpiration. <br /> <br />4 <br /> <br />DAM, DETENTION - A dam whose ]?rincipal purpose is to <br />temporarily detain all or part of the runoff and for release of the <br />stored water at controlled rates through ungated outlets. <br />DAM, GROUND-\VATER - A geologic formation '\\'hic~ is im- <br />penneable or has a low permeability, and which occurs In such <br />a position that it impedes the horizontal movement of ground <br />.....ater and consequently causes a pronounced difference in the <br />levels of the water table on opposite sides of it. <br />DEFICIENCY, MOISTURE, FIELD - The quantity of wate, <br />which would be required to restore the soil moisture content to <br />field moisture capacity. <br />DEMINERALIZATION - The remo\'al from water of those <br />dissolved mineral constituents which cause it to be unsatisfactory <br />for domestic or industrial uses. <br />DEPLETION - (I) The continued withdrawal of water from <br />a surface or ground-water stream, reservoir. or basin ~t a rate <br />greater than the rate of replenishment. (2) In appralsa} work <br />the quantitative exhaustion of natural resources, usually III co~- <br />nection with commercial exploitation and usually recorded m <br />monetary terms. <br />DEPLETION STREAM-FLOW - The amount of water that <br />flows into a ~alley. or onto a particular land area, minus the <br />water that flows out of the valley or off from the particular land <br />area. <br />DETENTION, SURFACE - That part of the rain which re- <br />mains on the ground surface during rain and either runs off, or <br />infiltrates after the rain ends; surface detention does not include <br />depression storage. The detention depth increases until discharge <br />reaches equilibrium with rate of supply to surface runoff. <br />DISTRICT, DRAINAGE - (I) An organization, created and <br />operating under statutory enactment, for the purpose of financ- <br />ing. constructing, and lor operatin~ a drainage ~ystem. .(2) The <br />land or area within the boundanes of a dramage dlstnct, as <br />delimited in the organic statute. <br />DISTRICT, IRRIGATION - (1) An orgaOlzatlon, created and <br />operating under statutory enactment, for the purpose of fmanc- <br />ing, constructing, and/or operating an irrigation system. (2) <br />The land or area within the boundaries of an irrigation district <br />as delimited by the organic statute. <br />DISTRICT, SEWER - (1) An organization, created and op- <br />erating under statutory enactment, for the purpose of fjnancing, <br />constructing, and/or operating a sewerage system. (2) The land <br />or area within the boundaries of a sewer district, as delimited in <br />the organic law. It may embrace p:uts of one or more political <br />subdivisions. <br />DISTRICT, WATER - (1) An organization created and operat- <br />ing under statutory enactment, for the purpose of financing, <br />constructing. and lor operating a waler supply system. (2) The <br />land or area within the boundaries of a water district. as de- <br />limited in the organic statute. It may embrace parts of one or <br />more political subdivisions. <br />DITCH - An artificial open channel or waterway constructed <br />through eaIth or rock, for the I?urpose of carrying water. A ditch <br />is smaller than a caml, although the line of demarcation between <br />the two is indefinite. A ditch usually has sharper curvature in <br />its alinement, is not constructed to such refinement of unifonn- <br />ity of grade or cross section, and is seldom lined with impervi- <br />ous material to prevent seepage. <br />DIVIDE. GROUND-WATER A line on a water table on <br />either side of which the water table slopes downward. It is <br />analDgous to a drainage divide between two drainage basins on a <br />land surface. The boundary of the cone of pumping depression. <br />DRAINAGE - (I) A general term applied to the removal of <br />surface or ground water from a given area either by gravity or <br /> <br />5 <br />