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<br />information,l.tMrt--hired a pri\'ate comultant to
<br />make dt'taikd pi am for water rlC\'dopmcnl.
<br />State ag:t'nd{'S and unin:n-ities, too. maintain
<br />h,'dro]o~.-j'b on their ~talls. and haw infomlation
<br />on loc!! (::round-waler condition.... \\'hercHf
<br />the~' afe, compt.trnt ,lUthoritic-:- ...hould lx, con-
<br />suhl'd. Ground water i~ not ju,t ll'ater under lhf
<br />,~round. It i_" watrr held in the rock~ by crrtain
<br />forces, fl"p]l"ni~hed b~' natun" accordin,~ to thl'
<br />climate and the local g('o]o~, and <'on"('quentl~
<br />.'ariable in both amount and quality. :\0 ma,g;c
<br />means are nrce,,"ary to locate it. just scientific
<br />knowlrdgc and plain common sense.
<br />Our purpo:<e in this booklet i... [(J tdl you tht'
<br />ha.,jc fan" alx>ut ground watn. and what is be-
<br />hind the lIecd for the sludies .\hifh enabled the
<br />Sur,ey to he helpful to lhe water St'ekefS.
<br />
<br />THE WATER \\'IZ,\RDS
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<br />Hm\ doe. the h~'drologist know where a well
<br />can be drilkd with ~uccbsfu] resuh...? How doe;
<br />he kno\. ..here to find water. a good, ~teady sup-
<br />ply of it? lie doesn'I use a forked Slid. like the
<br />dowscr'.s. His methods are more cmnplicated,
<br />hut at the same time mudl less lll~steJ'iuu... lie
<br />l!;rn."S out into the "field" or into a bi.~ eity-
<br />where"er there i.s a ll("('d to know ahout ground
<br />'\-aler-arrnrd with hi" gw]ogi..t'~ pick and nllll-
<br />pa,>s, a "terl tape for mra.~uring water !en:I", a
<br />current I1lrtrr for mea$uring flow of watrr, ami
<br />otht"r equipmrnt nerdrd for watn pru."pcCling.
<br />:\IO."t important. he lakes hi~ ..rielllific expnience
<br />and natiH curin~ity about th(" why'" and where-
<br />fore's of water. Before he ,tarb out, he arm~
<br />him~df with the be"t maps of Ih(' art'a hr can
<br />find-preferably onr of the Geolog-ical Survcy\
<br />own topographic map;;. Ht' reads carefully all
<br />Ihe puhlicatiom h(' can find thaI rdatr to the
<br />g-<'ology and hydrology of hi.. arra. In this way
<br />hecan check hi.~ own work again~1 pre,'iom work,
<br />and will not wa_~tt' time redoinl!; ..hat ha,; alr('ad~
<br />ocen done.
<br />Our h\'drol~i~t know... that Ihne i~ no "imp]('
<br />way of IcKatill,ll; ground water. But he kno..~
<br />"ornethin!! el"C that mosl people don't appreci-
<br />atc-Iocatinc: watrf is re;l]h- thl:' Iea~t of hi~ wor-
<br />rirs! Ther(' is some water undn the ('arth'~
<br /><urface a]mo..! c\cnwhrft-. This ~irnpJ(' fart i"
<br />hehind Ihc '<(.'emille: <\Irc~.. of '0 mam do\\"Cr....
<br />The hydf(lloc:i~t knO\\, that in nearh ;111 humid
<br />area". .lnd in most arid arl'a" .h ..dl. thcre i", at
<br />lea"'t a liuk !!round water in the rach \x']OW the
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<br />surface of the earth. The qu~tion is: How
<br />mllrh? How frl"(' is il to come into a \\ell? That
<br />is, can it come in fa.~t enough to he u-.efuP The
<br />hydrol~i."t ha" ]earned from his O\\n experience.
<br />and from that of hundreds of othen; \\ ho ha\"C
<br />~tudit'd ground h'atcr all mer the world. what
<br />kind~ of rocb water can lx, found in and whrr('
<br />10 look for thcm.
<br />Certain clul;'S art' helpful in Jo<:atin,t:;" ground-
<br />\\'ater supp]ie", For in"tance, ground water is
<br />likr]y to occur in larReT quantities under \'alleys
<br />than under hilk In arid regiom. certain types
<br />of water-lm'in.1! plants gin': the' rlue that there has
<br />to he l!;rollnd water at a ~haJlow dt'pth underneath
<br />to ftf'd them, Any area whrre water shows up
<br />al the <urfacc-in ~prin~, seep~. sv..amps, or
<br />lakes-has to ha\"C mmt ~'Tound water. though
<br />1I0t neccss<lri]y in large quamil\'. or of usablr
<br />quality.
<br />But Ihe most ,'aluable clues arc the rocks.
<br />Hydrologisl5 use the word TOd. 10 mean both
<br />hard, consolidatt'd fonnauons, such as sandstone,
<br />limestone, granite_ or la\'a rocks, and loose, un-
<br />consolidated sediments such :L~ g-ra\'Cl. sand. and
<br />day. They use the word aqllifn for a layer of
<br />rock that carries a usahle supply of water. Gr:t\'r1,
<br />s.lnd. S.lfl(t~tone. and limestone are the best \\'ater
<br />camen;. hut Ihey form only a fraction of the rock.~
<br />in Ihe earth'~ outer crust, and not all of them
<br />yield u_,,<,ful supplies of water. The hulk of the
<br />roek.~ consi."t of clay. ~hale, and crystallin(' rock~-
<br />the tenn lI<;l'd for thl' great ,'aril'lY of hard rocks
<br />thaI form mo~t of the earth's crml. Clay, shale,
<br />and fI)stalline rocks arc all poor '\'ater producer.;.
<br />but they may yidd rnough water for dome:>tic and
<br />slOck u~e; in area." "herr no Oruer aquifen; aft"
<br />prC"Cnl.
<br />The hydwlog-ist fiT"t of all prl'parrs, a g:t'olog-ic
<br />Illap and eros..... scctioll:- ..howifll!; wh('re the diller-
<br />elll rocb come to the land "'urfacr and how they
<br />ar(' arratll:~ed hencath the surface. lie will ob-
<br />ser\'e ho.. the rocks ha\"(' OCf'1l alTefl('d by earth
<br />prc<."lIres in the pa..t. Perhap" tht'y arc cracked
<br />and broken <0 as 10 form openings. Ihat will carry
<br />water (fig. 5). Or they may h<- folded or di.~-
<br />pJac('d, as shown in firzuft' 2. The rzl"ologic map
<br />and ,,<,nion.. ;md the acrompanyin!! rxp]anation.~
<br />will shO\\ jll<1 which rock." arc likely to earry
<br />'\atf'f. and whert' thn art' beneath the "'urface.
<br />:\cxt h(' will Ralhcr all thr information hr can
<br />on exis-ting ..ell~-{ht'ir location. depth, dt'pth to
<br />watt'r. and amount of watl'r pumped. and \\ hat
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