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<br /> <br />- ,.. . ~ <br /> <br />;., v .. j~ <br /> <br />it will be needed, Storage of surplus water <br />underground has st'\'eral arJvantag:es. The re;- <br />ervoir i" already built, though some cost is in- <br />mind in preparin!1; it for recharge. And, the <br />wata is prOlencd to a comidcl"abk de~rc('" frnm <br />contamination and los." b} t'\'aporation, <br />Somt' aquift'J1, art' ft'charg-ed as a b~ product <br />of irrigation. When waler is eyaporalcd from <br />growin~ plants, tht. dis-..oh-ed ~all" an' kf! Jx.-hind <br />in the ~oi1. If they accumulate, tht" "Oil will be- <br />come unfit for cuhh'ation. for thi~ reason, it is <br />neCC!iSary 10 appl~ mort" water Ihan i.<' anualh' <br />needed for growin~ plant:;. TIll' nce:<;" irriga- <br />tion water '-eclX' dm\ll and adds 10 the ground- <br />walt'r supply, In the ShO!'hone Irri,E:::ation Project <br />in Wyoming-, a nonll;lll~ dry rtX"k formation hc- <br />came s..ltutatt'd and turned into a ~rollnd-water <br />reo;en'oir. The town of Powell. Wyo.. ha, been <br />prO\'ided a municipal ground-....ater supply as a <br />result of thi.s unplanned artificial rechar.ge. In <br />the Snake Rinr Plain of Idaho, 5'('epage from <br />irrigation of the land has incn-a$ed Ihe water <br />stored in Ihe g-round by s('wral million acre.feet <br />(3 acre-fC'et makes a million gallon,,), SeC'page <br />from irrigation mat cauS<' the water table to risc <br />100 hi~h. howen'r. If adequale drainage is not <br />al.so prO\'ided. the kind may bewlTle waterlo.gged <br />and unusabk f(or farmin_g. The drainag-e may <br />be achiewd b\ dit(h~ or e\l'n by pumpin~ from <br />wells. <br />Surfan~' rC$cT\'oirs may add water to the und('r. <br />,~round rf'Ser\oiN, in the ~lme \"a\ that "ome <br />nalural lake;; do. Tht. addition may hr accj. <br />dental. if Ihe rescTyoir hottom i~ leaky, But ~('p- <br />age through a permeahle bottom mat. aL"O be <br />deliberate. as in thl' ca_<.t' of thl' Sama Clara \"al- <br />ley Waler Con~en-ati()n Di~tricl in California. <br />A- we han said, thf'n' arc complication.s in <br />the artificial-rIThargr procr",s, .-\ rechar~e well <br />may become clo~~ed by ~t'dim('nt, t'hemical pre. <br />cipitatf"', or g-ro\\lh of baclt'ri.l or algae. If a <br />.....e]l become< cl~gt'd it mu_t be cleaned or <br />pumped periodically. or Ihe water treated Ixfore <br />it is injt'cled. Geolo~(' ("Ompliratiol1~ may pre- <br />\"em rt'charge by .....atf"r <'prTading- and make it <br />neces.-an to sink well" for rccharg-in,!::" <br />Water for artificial rfTh,lrl!:rof wells or aquifrn, <br />must be of l!:ood quality. If 't'wac:e l" u<,ed it <br />mu"t lx. thorou~hly treatrd, because once an <br />underg-round aquifer i~ contaminated hy or'~anic <br />or chemical pollution it may requirc \l'af" heforf' <br />the aquifer can Ix- purified by nature. The m(1re <br /> <br />22 <br /> <br />pf'mleable the rock., in the aquifer, the fast('r the <br />contamination will spread. In \'ery penneabJe <br />fO{ks, _,uch as some Iimc.stone or basalt. it may <br />mote mile;; in a few days or weeks. In s.1.nd or <br />sandslolle it will mo\'e more slowly. If recharge <br />is done by "preading tht. water over the land, the <br />wil will act as a filler. The deeper the .....ater <br />tahle. and the farther the water has to percolate, <br />the freer it will be of bacteria. Chemicals, in- <br />cluding ~~'nthetic detergents, are not screened out <br />in this \,'ay, howcHr. <br /> <br />The increasing u~e of ground waler. especially <br />in the We,st, ha..<, caused ground-wate-r le\els to <br />dt'dine in ~ome areas to the poinl whet(~ the watt"r <br />is actually being milled: that is, mure water is <br />hein,g removed from the ~round.water rcsen'oir <br />than is hcing put back in hy nature. To reduce <br />Ih<" amount of water pumped WQuId in many <br />cases serinu..ly dislocah' the economy. Artificial <br />fechargt'--wht're it l~ economicall~ fe3-sible--wiJl <br />he allt'lllpted Illflf(' and more as a remrdy for <br />dedinin,g \,'ater Icvels. To accompli_~h artificial <br />rechar~e sucn-s.sfully, certain data must be <br />known: tht' sour((' of natural recharge. the nat- <br />ur;.1 dirtctiun ,lI1d r,He of movcment of tht" <br />ground water, and the topog-raphy and gl":ology <br />of the art'a. The main difficulty is that each <br />rC'dlarge procedure is a separate probl~m, and <br />mll_st he tailonnade to each situation. <br /> <br />\L\:\,\GI:\G OCR GROU1\D-\\',\TER <br />RESOVRCES <br /> <br />Tht'ft" i~ water, m(1re or I('!;S of it, morC' or It'S!' <br />accc<.sibk. alrnoo;l e\'ef)'where under tht" earth. <br />,-\s u~C5' of water incrca<.e, thi!'; .c:Tound-walt"r rc- <br />s(Jur~t' i.. h('((1ming \-e~' important. We arc <br />u<,in~ more water than we ust"d to, partly bet-au~ <br />Ihl' population is con~tantly increasin~, But thi" <br />i.; not Iht, onh' r<"a'-On. Incrt"a~d U<.N by indus- <br />t~, for irri_g.llion. and for automatic wa~in~ <br />machinC", dishwa-ht'I"', garbag-e dL~post"rs. and <br />swimming pools arc all p1acin~ an extra burden <br />on the country.~ watrr resourcC"'. The ~upply of <br />surfact" \\'ater is so \'ariabl(' that people have <br />tended to u,e ground wattt a~ a more ",liable <br />source, \\hert' it has Ix'en available in needed <br />quantitie-, But no\\' (!Tound water is being in- <br />creasingly exploited a.s a principal wurce of <br />supply. <br />Ground-water r("-C'n'oit'$- in 1960 supplit"d a <br />little Ie;.... than a fifth of Ih(' ~ation'~ water with. <br /> <br />