<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 />
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