<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 />
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<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
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