GRICULTURE N SERVICE
OFFICIAL BUSINESS
•
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PENALTY FOR PRIVATE USE TO AVOID PAYMENT OF POSTAGE, S3o0
-a. -7 Li 7 (1 ) by uarT 7).chwer Introauction.
The ciunntit of water available from streams and
res:vvoirs in the aria reions of t?_e ,est is frequently not sufficient to supply the needs of the land suitable for irrigation. „here this condition exists, adaitional sources of water must _e sought. In many areas large quantities of water are stored beneath the surface of the ground in layers of saturated sand and grovel. Not all of this water can be recovered, nor is the water table in all areas close enough to th, surface to be within the economic limit of recovery, but TI-e-e conditi ,ns are favorable, the water stored in the soil may be used as the source of an additional supply for
(I) Pr,Jpa7ed under the ,firectioli of I.cLauchli, Chief of the ivision of irriation, :Aireau or _uxicultural nEineer-inc.. The writer wishes to acknowledce the assistance of • • •
Code of te 'olorr o- xneri int Jtation, Cr. D. W. Israelsen of the Utah ;xpe]1t tation, he ,lember- or the L-)''.ff of the division of Irri, LILL". an. various agencies 'hich supplied information for the r art. The drawings were prepared by Clorence iyler.
(2)
The .dost -eas_ by pumnin
meth d o r000veL'i:Ig t.i st C.: •Is
,or for this purpose ells c'_--)'ble of supplyin-• larg yu:'ntities or water at a reasonable cost are
require( . of differ 7rom those
ased for domestic -urfloos, and t or this roasun far.1:rs, the construction ▪ plants for i riation, sla'ald be Yz-Aaili ,ith all the factors necessary to obtain a satisfactory well.
▪ actors :Iffecting the Yeasibility of PumPinc, Plants' ce
The construction and operation of a pum7in,7 plant for irrigation using water frc,ra wells is an expeni\ic undertaking, and beA)re embarkin on a project of this sort a careful
investigation of the possibilities of success of the enterprise b C. CO A S e,ci should be made. The principal items v..;4-.4-eit—trt-t—t-tit
of-111%=-740,4446-444ts are the legal status of
pumping from wells for irrigation, the quantity of water required for the crops to be irrigated, the quantity and quality of
takci
=ter available from the underground source, the econ
pulqing lift k and the well conlrt'ct. In edition, the fact
-i-‘143 a zSdi.k5koc-k-ori weA1 c..evt-Irkrac.t o
Athat the lanC, must be prepared for irrition, That the soil
must be su:table Cor growing the prn'osej c ops under irricat ion, tha 4 the climate mu.- t be favorble, that accessible mtlri:ets
must be ,t hone a d that facilitius Cor the un:3ertikinF must be available, also h-ve an imro-tant bearina on the
possibilities of success. dome of thes,:', sift:;ecs a e ey')1ri_ red in detail in other pub]ications of the U. S. 'el.)::rtment of
2criculture,
to,
8, 9, 10, 11, 12, 1'6, 34, t7.1'bet the essential information /
‘7,
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3-7
(3)
is given here for those 7:ho io not hove access to these pub2ications.
Lnlv
Legal tatus of Pumping from -ells
str.to hfve a-1-y4tn-ty defined laws in re. ,i-nce to pul'ain from wells for irriFation (6), (A,
nevertheless the riht to pump water should be safe-byall the lef,a1 require _ens. The rJce,urc to be follow_d in orer to establish a ri,-ht to .1)24) from .21s should be aetermine by writing to the o'ricial in charge of irriation in the sta e and if thee are any restrictions in re:sard to sanitary measures or to
,o artesian formations t]-:en they should be co_ plied with. .herc, the aoctrine,of appropriation is in force, the well
own ,-; is•protected a,7ainst reauction IL the water suppl: of his 17'32_2 cuse,.1 by a tell or wells bein - arilled near him at a 1 ,-It dote. :he however, the Doctrine of correlative use hae been adopted, every land owner has a co _:ion ri:-ht to
use the .aiderground rater in proportion to the needs of his herethe latter doctrine is in force, the well cpner is constantly menaced by the possi-:- ility that wells drilled sul2sequentl- ill cause such a large draft on the :-round water that the water level will be permanently loered. his fact
-4-L
The 'at-Yer e-t r
The amount of 'ater reuird to irri7:ate (_1(27S derl-]Th on the crop, toe type ()f , to Cranky, the climate the L.(-20t11 In
=nrs the 7tcr rn , cLn dote7
from to, !local practice in. am ]y uev(;1Hped CO0. t"Le
the fe7t1i of -v:f-Iter ueec
un:er amm icr Ima. c-) on the infor'.atfon
11-_11icr.1 ion:3 of the Dor,,rti eqii. of q - 1- 0 13)- v7 on irric -',::;.on
art', . The
(#,
thc net irri fo]. the
7:incipc4 in to OSI 01,. .TisL O0Hrour.
of one 10 L.11 ,LIont -;.hich is u CO C1.C.LL 1,ionth. rjlee t.Co -j.es
AT:: that June and July us1.1.11:,' the nion hi 0J-1LxiLiu
and 1-;LitLr uHed ii. from thre to
nine inches or from 20 to 40 pe7.-.cent of the total sesol,a1 Er .:as hvin a ion season. 11. -ve the 7p_k delrlanc cml hose Imvine, a abort oro. ire
re-1C-for naxim= ,,oak o - no --iven ,..(2,,ter. If, ,a fam.,_L. - -_"Lt IL" In Li: 0
-5-uLL , or he may look in the bulletins referred to
in he preceJin part.rerEerh and find that the average secsoral
irrdation ree.uirement is 2.5 acre-feet, and the month of maximum
dethand is Ju2y e'urinE vhich 25 percent of the seasonal :11,3ply
....11] be required. Twenty-five Percent of 2.5 feet (30 inches) is 7.1s- inches, the depth of water required per Ecre in 'July. For ec, acres this amounts 'o 600 acre-inches or 50 acre-feet. Oince on e cubic foot ler'second equLles nea;.ly 450 Fea]lons
or minute, and since one cubic foot er second fJ.e in for
24 hours equals approximately 2 acre-feet, it nill require a lov. of one cubic foot per second or 450 gal2ons 'er
minute44
/
4-i, •7,
/
, '79,4/ .5-79a r /4 c--79
W\21 'ield 30 acre-feet 'ii 121 days of 24 hours 6ach or 25 days2 . _ of\12 hours each. A higher rete of flow will, of course, yield the\requireci amount in still less time.
b
e,..o re yvv,e.I.A•koK 4.8 poUlt c_ct LbS'
The values F)iv , n in the abodgigkare for averar‘e
coditions. If there are unusual features, such as groing only
one crop. on the farm, p:rov;inr two crops simultaneously on the same are. , or if the soil is very sandy, hen the n-,te of maximum demand 1,.ould probably ave to he increased.
Large pumping p]ants have the advantage that they have
to be operated a shorter tine in order to surply the required amount of . ater, and consequently the labor cost ror irrigating is smeller, but large pumping plants cost more to bui1d than
sma]] ones and also cost more to operate. It has been found that
Q. co c \-N CA con 8 iDc., ‘1 c\ \ el 4- shoold e qrt4
--y-\ cl IeN 0 e 010 +ED ,,•=\ co1 e ri it r rclutr e cl 0 r •th e----\•Y1 or+ k 4 \-r, c% A CI
_6_
the r_ost economical results are obtained, particularly for electric moor driven plants, when the sz,allest plant is inst&llei which will supply the reuired a'mount of water during the period of maximum demand even though the labor cost of aPpl::ing the water - lay be slightly higher. (4) -Pre= tc f-e-r-444511-44-e---44-ere-1-J-e-s-i-ern ti7a-t- the flow of
gal] on Ter- Minute, which is about the smallest amount that
• e. n, ....a.... • In{ .Nt 41. willreTutr- Tuanuity of water for the 80-acre
farm within thei _ 4rnih-, siTotzld "
0
. .
Pumping plan's are frequently built to provide a
supplement 1 su'Dp=y fm of water, and ,urin:: periods of drouth large numbers o plants of this type are constructe.. In case the plant is being uesicned to provi_e a supplemental supply, the quantity of water necessary will be the difference between the total requirement anc the amount vbich will be available from the other source.
In some sections the supply of -.round water is suCficielt to provide whatever quantity is needed for irrigation, but in many areas conditions are not so :avorable. In these rei;;_ons the ca -m city of the well will determine the size of the plant; the acrege irrigate,, and the kind of crows Ero, n sill hove to be adju tc-,,d to The water supply from the well. For general farm crops about 300 gallons 7,er minute is the smallest flow that can be economically han led, and where the yield of the well is loss than this amoult it is doubtful whether a pumping -at,nt will be successful except for small tracts such as orchards or gardens where the furrow or the sprinkler systom c'n be used
-7-to apply the
Ii
In some bections of :Jalifornia, Arirrona and Nevada, holiever, 300 v,allons per minute would be considered a Eood In cases where it is not possible to get a
sufficient sumpl: of v,ater from a sinrae it is o -ten possible to otain the desired amount by using a battery of wells, (See page""Jr) or several separate 1,7ells.
Except in areas where there are x many vells, it is,
w tnt,O,A,ey eAk ..-7-,cv\--1,44-csr-Itor or no-r im - ossible to predict Pat
tome, co•neot are mote, 40Yor4Ade. or loc,otinq 09
preoi,ion. The best wells are usually found where the water- 'cl6cy
bearing formaton is of considerLLle thickness and is made up P
of fair1y coarse material free from very fine san,J, clay or cementin•- material. The ground rater should be at a relatively shL;13o depth and shou1Z be fed from a dependable . source.
x The most,favornble locations for „c7ood wells are in the valleys
A
adjacent to streams and on the alluvial cones lzhere streams from mountain Lreas flow out on the plains. ..here irrir'ated areas are umlerlain by sand or Eravel, the conditions are generally favorable for c tting cood J1s.
Then th re is douLt as to the possibility of cet- in„-i, a good veil, test holes should be -Jut down to lo.;:te the water-bearin formatioL and the character of the 1,ter-water-bearing
(See- PcScle.s #pr- r,-,t 41n oat 04- dr,ntoci +e Lote,(150
material. .-, careful record should be kept of the deptl, to
A
watet ana the locL,tion and cness of the various m.teriEls pen-trated by the test hole. Samr)les of the ater-bearing mPterial should be saved. From the 1 - of the test hole and the samp]es or the 7,:ater-bearinP: mbterit 1, it is 2ossible to jete7..miLe Lithin reason ble whE,ther a satisfactory
-8--found to be unfavorable for a g-od 7e1l at the first test hole, a ne locaticl =IIL le he chosen and tested. Several test holes should be drilled before abandoning the hope of finding conditions suitable for locating a satisfactory well.
T-419--rac t -cti
Whe: other conditions are the same the well shoule be located so that the greatest area of the - arm can be irri,7ated with water fro Usually, however, the location of the
well is determined by the site where the prospects are best
for getting a rood well. A tor,ogranhic map of the farm wil3 be ver7- useful in la:.ine out the irrigation system.
r.),uality
The ground water in :Jost arieJ regons contains some
and in a few 71aces the concentration is so great that the 'eater is injurious to plants anh som• times to the soil also.
4
_pro • a
tqLlialer. done ground
f3 witer.
k.tr&ida-0,7d
water contains chemicals which corrode
metal casing, and some contain sufficient gas in solution to interfere with the operation of pumps. If there is doubt as
a
to the quality of the 'ter, sam le should be sent to the
Sta Agricultura uollege or other qualified agenc for testing. Pumping Lift m k
The limit of the lift against which water may be profitably numpoa for irriiation vories with the cost of pumping and the value of the crops grown. Is grectcr care
-9-efficiency of pumps is bein . constantly increases: au tbe cost o power re.uced, the cost of pumpinF, an acre-foot of water per foot of lift has been re6uce.; consequently, if otl!er conditions remain the same it vill be possible to
pump profitably against a higher lift than formerly. Higher lifts are also feasible, if the water pumpo, is to be used only as a supplemental supply in ase of shortaee. Low priced tgricultural products and small yields, however, re ,juce the econor-iical pumping lift.
\._„..fov.. trrLc‘oon ed c AA 0 + e. e 6-)
The average lift hr(Yuh 'which water was being pumT.:edA from all sources incudinr streams and lakes in c
is given in table I together i_th the estimated
economic limit of PUM in . lift fro;1 The area irrigated by pumping f4110010410mirs in each state, thia cos' of the pumping plant nor ixx acre irrir-oted end the cost of operation are ci_ven also. The-average lift shown is less than the estimated economic limit of lift, and althouh it is possible to
operate a pumpiIi lent successfully under favorable conditions against lifts e ual to the limiting values, anyone
contemplatin7 the installation or a numrini- plant should not plan to exceed the average lift given in the 'able nless he is f, vorbly located as to markets or can grow special
4-rom wre.
clops ilpo-n which the cash retuInOw hiher than from ,-eneral crops. 1_;specially fertile soil ana a favorable climate
ake i possible to numl , successfully againsT high lifts. lihe cost ol power for numpin - is al _ost directly proportional to the lift. For this reason the chances of financial success shouls be
-10-considered carefully before p,oing into any project where the
lift a_!ainst which the purr: must operate is C:ove the rv.rage
values given. 12-uFfP,-.4inf4._Xx \ • - 0$1• .t..0 1) ,JL-J-• \C1 -?, tl) StLte Irrig-ated by Pumping Invest- Cost of ment in operat-pumping ion per plant per aure (3) acre (2) Aver- Estimated age Economic lift(4) limit of lift (5) Acres Dollars
qir
T2-1,
Dollars :k 3'f Feet FeetArizona 104,637 58.70 10.76 46 40 California 1,453,272 146.04 10.05 53 50 Colorado 12,143 30.66 5.36 25 40 Idaho 3,546 19.64 2.30 32 35 Kansas 11,648 33.44 3.69 26 50 Nebraska 23,452 10.95 4.03 29 50 Nevada 2,137 20.19 4.82 31 30 New Mexico 30,425 38.75 6.44 40 40 OreFon 3,804 59.07 10.72 27 30 Texas 60,793 47.25 8.50 55 60 Utah 10,283 34.64 3.58 36 50 Washinton 19,456 82.24 15.43 59 JO (1) (2)
Data taken from S. Census
or
1930.Data irclude other investment besides that in well and Tura ing equi=dent.
Co,t of opel.ation covers cost of power, at'endance and repairs.
Data coveriallin,;I: 121-iethr from wells, streams, or reservoirs.
Estirwte, based on informationfrom members of the 2iViSiOL of Irrigation and other sources.
Under special conditions econellic limit of lift r:ay exceed 500 feet in Califorria.
-11-Where the pum-in,7 plant is being installed to supp1ement the supply of water for irrilion from some oticr s.:urce, the feasibiliy of the ',roject depends
primarily on finding a satisfactory supply of ,-.round water at a reasonable deth, because the is already in shape for applying %.ater, tbe suitability or the sil and the
climate .rol.inr crops under irrigation is knoym and the mark-e 4, for the crops is es ablishec. .,here, however, the pro-osed well and pumf are to he instelleJ in en area where irrigation has not been flretiued previously, each of thee must be consi ered.. It would be desirable also t, stud:- is b inp done in similar areas elsewhere
nd to fin out fro ri the count:: agricultural agent or state eerxent station whether thy consider the project feasible.
The bell Contract
If, aLter a thorouh 'investigation, it is found th:t con'i ions are favorable for the cons'ruction, financing and successful operation of a pumping plant for irrigation from wells, the next thing to be considered is the drilling of the well. ixcept under very favorable conditions the
land owner or rarricr nJ 1 not be able to do this work himself. ke should get in touch with a reliable well driller and should discuss with him what work is to be done pna that the cost
C• \-1 rA t;t, V;oe LA' S
is to be. kie agreement in regard to these matters should he - 1'4- in writing in the form of a well contract. Small --"7s, howeve- , are 'requent2y put down without entering
-12-into a forria2 contract, •
*,A) %.:0 9
cs...
he well contract should specify the work to be done, the time of startin' and completdng the work, the eguipment to be used ana the bid price for the various items. if the land cmner is to supply any of the equi:ment, materitA— or
each iter: should he jncluoed in the contract. If reconditionE,, casinE, is to be used in the well, this fact should be .esignated in the contract. The driller should be reqirou to furnish a bone to guarantee satisfactory completion df the rell and to carry liability insurance to nrote himself in case of property damage and should carry co inensa-lon insurance sufficient to cover his liidilitv un er the workman's colipensalion act. ',the Principal items cencerning the v.ell that should be included in the contract are, the length diameter and
1-lickness of the starter, if used; the type, material
and dimensions of the shoe; the 3er.i-th, cia-leter and tl- ick-ness of the casing; the material of which the ctJsi - is to be made, L':lether it is to be b - ack or Falvani-ed and whetr'r it is to be welded or riveted; the sire and nracin' of the roinforcin bands Ithel. large single thickness casn: is useu; the size En, number of the 1 erfortions and the Illethou of perforating; the thickness of the ,ravel envelop, if used; and the size of the ;1‘Elvel;. ana the method of oeveloping and testing the well. If concrete csin,=i; is to be Ygi;:0.:he* mix of the concrete should be L_esi nated. A guar; 1,teed minimum payment to the driller shou3a 'oe
contract in order to Protect the driller, and the maximum depth of el, or a provision authori in the owner to :etc -the or n he consiaers the well deep enough, should be
incu;iet in order to l'rotect the owner. iL clause ehoe2 be i- the contract 'o the effect that the bore o' the well TL1h enough so that the type an :lee of pulap 1ufl i. is planned to use can be inserte. in the well
nu operated successfully. If any chLnces in ;plans become neceseary after the work has sta tea, the oraer for the change should be in writing.
in some sections it is the custom for the well eriller to contract to arill a well of speclei,a c,,.-pecity. If Many wells have been drilled in the region and the water-bearing formation iS 'mown to be uniformly 'orouctive this pLn may
be feasible, but it is obvious that under these circumstances the driller takes all the A.sk
ct,(16
or)osi-44.uaal4=—Latztlicia btd enough higher to protect himself. The
ma; imum acceptable drawdown when T)umpin . the specified amount and the number of hours the v;e11 should be numpe'_: at this rote should be designated in the contract. If the drawdown is not x specified, the required quantity may be obtained by dr. wing own the well below the economical limit, and if the time is not specified the well may not hold this capacity when Pumped a longer tiltie. hese contrac s should also have a clau-e proviiiv a penalty if the well does not come up to the term: of the contract and u bonus if the well exceed -3 the terms. The penalty or bonus should be computed on the basis of a unit amount for a definite nJmber. of
-14--ce:7 07 • -riCiO. he penalty and bonus
clause -a: be inclucd in ';'ors of to because if an incert-fox
-to do batter ark.
'.Jhen the nell is completed, the driller should he requir -Jd tc furnish a complete lo-; of he 1-;e11 shoinc- the de .,th to water, 'he location, character and thickness of the different materials encountered in the ell,
location of the points vdhere the uiamee:' or te cLsinc was changed and the location of the perforations in the well. This information will be round to be invaluable i; -t come later date it bHc_mes desirable to raperforate
he '::e17 or lower the bowls of the pump.
In case any controversies a-ise the proceiuro to be folloled in settling the dis ute should be act forth in the
contract. Large wel3 drilling co ipanies have their own contract forms, and in case they are used the land olner should read over the provisions of the contract carefully before si“ninp. so that he will unerstand what the agreement is. Forms for well drillin contracts have been prepared
which protect both the driller and the lane owner. Information concerninc these contracts can be obtained bp writing to
the Division of Irriation, Bureau of 2,gricultural :iiineer-ing, Berkeley, dalifornia.
-15-Factors AffectinzILow of nround ater into eells
The source of supply for irrigation wells is the leater that accuriulates in the surface layers of the earth as the result of the eowne rc] percolation of water from rain and
snow, the percolation of water pplied for irriation or s.-:reel :t.,ground-water supply, and seepaFe or water from :-Creams,
canals and reservoirs. .-11 the water that sinks into the' soil froll these sources is not available for pumping; some of it is evaporated froei the surface of the ground while it is stil_ ,p; solde of it is brou:ht back to the Fround su:reace by capillary action and then evaporatee; some of it
ctf%
is hela in the soil as capillary oa" hygroscopic ,eater; ans. so e of it is taken up be7 the roots of erowin,e, pl:nte either to 'se stored in the z)lant or ev'porate, from the surface of the leeves. The remainiee water moves downward until it reaches e 7Orq of saturion or comes coetact with a
1 yer o2 =044-ortm=54:=4:0=6..r impervious materirel such as clay
or shale. this noint the water starto to spread leterally
I No \ CA A^ SCi
fill ing 1 ln the , orc s of tho !leterie] wes it ..434*8-escal-c-,-A,--, ,
These processes h. ve continue for lonr: nerioTh o° tie-e e have , as 2 resul t , built us a eupPl: of wat-r
hi ch un lerge of +he Tan-: surfece of he earth. This Later, .iLh ehe exee tion of tbat b ld in elosed basins, is 11 movin,.: tosar:1 points where it can escene in'o
snrin,e, strem. or e--e --. in elost areas additions to - he .aterI out equal the amount bein lost, ane as a r-eult e coneition of a:yeroximute e Luilibrium has been
11111111111111111
-16-reached. In so m ho-eve- the b,,;lance ha_ been artificially interfered with a s in the case of irrigated areas. Here the water level may still be risinc. on account of the application of irria'ion water or _1E17' be - oering on account of eTcessive pumping.
The water that e7ists in the zone of saturation is knon as ground 1.ater, an. the upper sur'aee of the zone of
att.17:,lion or the free water surfaeo is kno n as the hater tabl_. _hen the water in the zone of aiur-lion is confined between layers or impervious aterial the eater in contact with the to layer of impervious material is un.er pressure and eonseuently there is no eater table. when a zone c saturation of this type is tanped the .ater will rise above the level of the bottom of the confinine; layer.
condition t)rouces what are 'mown as artesien bnsins)( i&-ffe-4errr.7,-r-held;--T
prs&ure Le—s1.1=444-1- to raise v -of. the tog_aLe.t_he_wein'-'17,76-7-7.-S regarded ss an aret-e-, here the e.roun weter is not under press-ure, as in the case .:,here the zone of saturation is not
between layers of impervious _ tonal, the eater when tapped eill not rise above the le-el of the ester table. eegions e ere This coneition e-ists are known as non-artesian or normal Pressure areas. The conditions which 'ive rise t- t'e
,s o are shown in fieur -section of a brote, vol_ey.
-17-The amount of water in layer o etuTot.e erial eD atter depends on the thicnees anu exter_t o the 1ei' tl
porosity of the eceterial in the la::0]. _oroiI: is the measure of the emeunt of pore srLce. , it is the rtfo 0 -the oluo o he One ins or pores in the suteniel to the tole] v'leno or he ,bteribl Lnd is usu'lly express e as
';ercelt. e- . _orosity increases - ith .he finenes of the materiel and Lith the anuuleri -, of the partici_ an is greatest 'hen all the particles are of uniorm sloe. hen the particles are well grade in sloe, the smaller particles fill the spaces bet- :en the layger particles, an if the
sines of the eifferent articles are in the proper proportion, each smaller size jusl fill the spaces beeeen the
1 -1_:er particles. The porosity of soils varies widely, ranFin7 from as low as 20 percent for graded sand to as hi711 as 65 percent for very heavy clay. .ater-bearing formations suitable for providinr-, water for irrigation
wells usually have porosities ranging from 20 to 40 percent of the total volume of the material.
From the foregoing it is seen that clays have t' e largest percentae.e of 7)ore space although it is a well known fact that wells in clay yield very little water. The reasons that these wells are no satisfactory even
thouL the clay contains much more Later than sand or gravel is that the cla7 will not 7i170 117 the Later when the well is
pumped. (lay of extremely fine particles, and
as a result 1he pore spaces also are extreme2:
T
.At..c.,, r
to - -ar, 1 1 t: , A 4. I. k AA-A-4 b k 3.„..-I,
-1E-
Tr-• +A 7v- ,
by 04-p..1.1.1ax44-- e-. In addition a portion of the _s held by :Iolecul.r attraction. This portion is known as hygroscopic 'ater. Neither cani2lar:' 4Eite-,-' nor hyrosco- ic vater is ajvefl u -,T, when a well is pumped. The moisture
held in this mannermilci. the _7pecific retenti:n., is the ratio of tl-e amount of v:ater r tamed to the volume of the water-bearini- material expressed as a Percent0e,may
ffic,unt to from 5 to 35 percent (26 p 57-59) of the volume of the Water-bearin material depending on the distance from free water an: the nature of the - ater-bearing medium. The low act percent ges ace retained by sand and !ravel and the highest percentage5by clay an clay loagi. The percent-age of th moisture retained decreased in general as the distance from the free water surface increases. (-,5)
The amount of water tat a definite volume of v.- ter-bearng terial ill iela as distinuished from that uich it dli retain is called the specific yield. It is expressed as 8 percentage and is the ratio of the - ield from
a -iven volume of 7:-tr-bearin,. material to the volume of the .ite7ial. he sp'cific yield varies between 16 and
41 Percent p. 121-123) of the volume of the water-btaring medimi. it is gra test or sand and gravel and least for clay and clay loam. It has been estimated by Lee that frol:. 15 to -0 p,-celit 0- the volume of the uaterbeaning medium represent he ater that is available for umrinF although
1 teats _ )ve shun as lou as 12 percent (3 p. 82-87) 7' ,' could he obtained.
-19-e-eep, in closea basins vheri it has
a definite thou 'h slow velocity which oepends on the slope of the 'water surface, on the size, shape, uniformity and compactness of the particles in the medium thayow;h which t'b zater is moving and °nth° temperature of the water.
the ef'ec' of tomerature althour_th 2nlige is usually cisregarded .17 --v_,4.4;, because the teriperature of the ground water does not
r 4- e 0+ rv\ creme vi
r- th-pu'h 100,ride limits. The IPP-Mt-th,y of rater through o‘i kredkoc.,,0-‘'es erkk-mol the p' in sEltuzate6 sof-171 1s iaectly prorortional to the
A
slope of the water *ahle. This relation is known as _',arcy's law. :he effect of the other factors on the le_An of "low
is so calplicte; that i c not be expresser by a simple law, but it c n be determiner ex-eerimentlly.
The combined effect of these factors is epressed by wh:t is known as the transmission constant or the coefficient pf permeebility* which is the rate at which water will flow throuh a column of th- material of en11; section when the slope is unity, or, in other ieores, wh_n the head is equal to the length of the column of mieter11. The coefficient of r_'ermeability is given in _4a3.3ons per cloy, ana the trans-mission con -Itant is friven in cubic feet per minute. (1? p. 148) *The term specific water eoneuc'ivi:y (NP p. 200-203) is
also used to :lesienate the water transcijttino charac'eristics of a soil. It is defined as te we] rime of water that will flow in unit time throu_th a soil column of unit cross-section / area cue to the drivine-- force nor unit mass correspondinF, to unit potential era. ient. This term is not generally used by en7ineers, but it has the adlyE.ntage that the vaThe of the constant iJ1 the same rep.. rdless of the s:*stem of units
adopted.
formulas ave been erive- for coeeeutinp; these constants, 13 but the results obtainer have not been satisfactory.
(4e)
0
The connts com-1;ute_ from the a &,-,ses o: the materials have usually been too le . (11 p. lo) More satisfactory results are obtained 'hen these constants are deter -ined experimentally by observin,7 the rte at thich water
percolrtes through the material. she other factors required to comrute the luantity of flow are obtained by direct
observtion. he slope of the water table is found from observations on vells, and the denth and extent of the water-bearin- mec;i'lm are obtain" by pu-letin:- ,o,fn nest holes. The nroduct of the area o the water be'arinL. lyer at ri_11 an7le:; to direction flow, the slo!De of the ater surace an.i the -'rn7-1577n 4 nr r'o-- ient of permeability gives the 41Intit: of water flowin.o in the area in cubic feet per minu7e or in --allons per day.
The velocity of flow nay also be measure- by not_ng the tillie it Elk!--_,s a salt solution to move from one v,ell to another in the directions of flow of the grouno water.
p. 16-85) The salt is inro uced in the upper well, and the time or arrival of tha solution at the lower well is deterined I chemical. analyes or by electrical methods. ubserv-ti-ns have been made by this method on the velocity of flow of ground water in riany sections of the united
Ste Js. -h se 'rtu,ji-s show that the velocity varies from a fraction of a foot 'o nearly DOO feet per dL.v denendin
on the un,; the characteristics of the , ate -bearin he ordinar: range of velocities, however, is ],L
volft-u u: :r0t1.11u in stor...e in a gi-1.7e area be -v iri ru tb. e an of the sttit:,rL tad
zone (-)!: tbe Houever,
0
n•-••
be ,i_tha.-nan for -Lie for
ti e from a f.,iven
cIL in: _u:ium
-1;1L 7; (.2Y • '
firml: in 12:- 50'1 tht I annot out by
The 5 as ,j-i_u3t. ia en,
but the water ahieli t saf,* eab ear depends la the recro, t t re e tubich is bein • added to the .7one f :.;t:tu a ion by inon from other areas, by downard percolation of th ,: rileisLure from rain and snow falaing on the ar a, the uonetration of water applied for irrigation or sTlred. to increase
v.ater sapp2 - (icy- the zone or saAirL.tan, by a. e.,)t:e from stream, or by tho combination of an: of these -30uL.ees
in an _Liereilcy, such as a perio., o' 14zauer may be nihruwn at a faster rate than it
but in the long run the rate of viLh.lrawal can not exceed the rate of recharge or the water table will continue to lover. The disasterous effects of this practice have already been observed in some areas.
The rate at thich water may be safeJy with rawn from a P.iven ,1-, can be (ietermind ?-nproximate2, hut it is a
&T.,20 no rIaa
-22-run-off cen be measuree, but no one can say definitel how much of the water tat seeps int, the soil is going to be used by plants or loot by evaporatioh. The same may be said of the ater that is applied for irrigaion. Yurthe-ee,_e, in?low from other areas, which is
fre_uent:y an important source of suppl:, is di'ficu3t uu measure accurte]y on account o the ract that the velocity of the a_tier in the - ater-hearing:edim can not he measured occurotey nor can the Pore space through which the water is movina be determined vith certainty.
Aere puneine is bein . Practieed, the simplest method of nformation as to the rate at which water may bc ithdrawn from a ieiven area is to measure the lorJrin of' the v,ater table in the eel's _f the area from
time to time. if there is a , r(=e- uel lowering of the water table e, tendine over e period of y, ars, then the rate at thich the water is beinc pumpe- is exceedine• the rate of recharge, and the lowering of the r table will continue unless the rte of .ithdrawal is reduced or the r te of rec ar,ee atxxxxxxxxxxaxixxxxx is increased. Airime per ods of ,routh the rate of recharge decreases, and as pumping, is ueually h,e-ier because f the dreuth the
combination of causes ro uces a mar lowering of the water tab1e wwi ch mieht be inter -ereted as i.ndicatine a definite
ova draft on the are!-. , ore-er, a period of 1.et' years
inere-,s= rate or r c'-large and usu,e1]:: reduces the pUniing •raft. his eon ition again estaLlisi-.AS lhe 'calance beteeen
- th rewal and recharge un ess the area is being
017
ilyc,raulic3 of ,e1,1s
-LC V
“1-1(_,n :n in ion well is pu do1.1_ into a lEy of .hen utire , the water in the
ter fro- The
satuef col-Je
into the , 01T. -if 7,um'in - c.:ontinu tho T.nter in the well car Thu: to lane VVali_ the -,,c tor Canine the satu-ated mateci I ill inc,r..70 until it :1_] -2 just ejtal the heir: 77)umpd out. 'ille : V:
car
7:e2] has to -rass throu JV thc POT: in tho Cell,en te
CloSVn i nets to the V,1 V he 1:ator has to 'r.ocuse the area t1irouiTh TiP V tc tr -voi is cor,tiusly
e:- plaineL,, the velocity of Later floe in throu,:h a water-bearing medium is directly proportional
to the slope of the water surface. For this reason the slope increases as the eaten approaches the well, and the change in the slope is directly proportional to the change in the velocity. The water surface foriied, as the result of the continuously increasin . doLnl...rd slope toward the well is
an inverted bell -shaped depression which is 'alown as the cone of depression. The circle form, j 13:- the intersection of the
surfc ZOO* is called the ci- cle o2 fr1:2, usf-rice,
this circle is called he area of inf.:'ace. ha
inor-sction uf the surface of the water in tic cone a, _c5 -1Dr._, don with a vertical plane throuch the center of the well is
a curved line which is known as the dra'::do .L curve. The distLnce that the water level is iL the •,-.L..dovin. It is the distance between the v,ater level in the
well when bein„:, pumped an the static late:: level or water table. These Liffer:nt l'e.tureL,• of a well are shovJi in figure 2 which is a vertical cross-section or a typical well in a non-artesian formatioL.
The flow into a well depends on the dradcwn, the ckness and n'ture of the water-beaYin strLtum, tte
of the vell and the raoius of the circle of
inei nce. -Formulas (22e) have been developed shoe in the theLTe :'a(.Aors and the :7ischarge for
the 7'11
wel3s, but, o'J,inc to the ccr ,plexit- of ill -7 Thn n7 the ,_ifficulty of determininE
accuratel:: the values of some of the valiatles, dischares
COTi uted by these 1ormu1as have not been satisfactory. These
forumlas*, however, shov, certain funamentql relations vhich are of value in studyirw wells.
* For the tyT,e of well shorn in fic.ure 2 the aischrrp:e formulr is
(3g
p. 278-286)QA1K' 112 - h2
in u"H_ch dischar- in ,2,a3lorls poi' day
cluantity vhich depends on the character-istics of the water-bearing material.
TH,:. distance i-ft--•f-r*e..1-, of static water level above 1 ,ot1 ori of wnter-l- earinc
fornat
wv-h.,e+. •
-25-to te,k
h=distance ii,lit-NOss..t of water n well above bottom of voter-bearing formation while being pumped. R radius of circle of influence in feet.
r =radius of veil in feet.
an artesian well which penetrates the entire depth of a water-bearing formation the discharge formula is
t "7 -h :f*tit
in which t is the thickness of the water-bearing formation, and the other letters hove -the same sinificnnce as before.
If two wells of different ciameters are in the sane
formation and the 6rawdolm is kept the same, then the relaion of the dischares of the to nells nil be
_log R: Q,
log 7;
This relation holds for both types of wells.
H2- h2 log — r vi eik Aay be written kxxiaxxi&xxlli n (H+h)(H - h) log
if the drawdown is small, then H h is approximately equal to 27, then
(),7=2E." H(H - h) log jj;
This formula shows that in I:Jells of this t:Te the discharge is proportiona] to the quantity the . epth of water H, the drawdown H - h and
1
log R•
The formula for the artesian well shows that the discharge is proportional to the quatity the thickness or the artesian formti.n the draTdoTr and 1
t;)
-26-All the formulas show that the eischai.ge from a tell is directly proportional to the transmission constant of the mnteeiel in the water-bearin,cq stratum. „Ls previously exnlained, the value of the transmis ion constant increases as the
coarseness and porosity of the water-beErin :ceterial increase and decreases as the compactness increeees. It is also affeetei by the uniformi'y of the material. The transmission constant varies throwth wide rane!es, the 17a]ue for coarse sane beirip:
37
4C00 times as great as that for.fiee snna. (.444r. 257). An artesian water-bearing formation in Utah was found to be 1C0,000 times as nerNeable ovlyino clay. (2t p. 29 IL 0LLLcLL, therefore, that it i, imtortaet to have the water-bearing medium as coarse as Possibe and also free from fine material such as silt or clay 1:ecuse it is the fire
materiel that fills the pores teteren the largo -earticles an retards the flow of water.
It is fre:uently assumed that the water-berinc medium is satisfactory simply because it contains _juite a feo boul ers the size of baseballs or larger. If there were no fine
perticles, these boulders would be an indication of an excellent well, usually, hcreever, the spaces aroune these boulders are co=lete27: filled \ith gracted sand, alid the
result is that the boulders obs'ruct the flow, This is clearly shown in fimire 3, which is a section of such material taken at rilat n1es to the direction of flow of the ,ater. it is obvious that the atter cannot floo through the large rocks, and cens,.uently the water is retar:,=d rare 'han it would be
-27-ho
the laroe r t41-le 1:12,4ari
CI, uno ruc,ea 1pc,
In wells, ;'here the casing -penetrates the full devAh of the water-bearing strtum, the capacity of the well is directly pro7ortionl to the thickness of this stratum if the drawdown and other conditions remain the same. It may a2so be said that the deeper the well is driven into a
water-bearjna strtum the greater ill be the discharge for 7iven S:rawdewil. This fact is i'reluently lost sight of when are bein7 Tut down. 7!here the E-Iter-bearing for.ltions are quite thick there is a tencicr:cy to i:it he derth - wells on account of the cost. It is true that increE 17 the increases the cost of construction, but this a ditional cost is usually talanced by the saving in cost of operation resulting from the secreasec:i drawdown.
In wells :,7rlich penetrate 2,eem into ,ater-bearing forLLations of considerable thicnessi the capacity is
directly proportional to the drawdown so long, as the sraw-is small in comparsraw-ison with the depth of water in the
well. if he drawdown is large, then the tischarge of the well does not grow larger as rapily as the carawdon
increases.If the depth of water in, the well is small the yield per foot of drawdown will decrease as the drawdown
ta u e
increases. The decrease in yielC, is ci,o to tho fact that as the drawdon increses the deth of sand through which the 7::ter enters he well is decreased. in other words, the
3ft r, )4 3),
tn?
iLt
•
LLAI-U.) C-SLe•-■. Aok--0-k-k4-14
1,3•11
AAI `11
effeu, the increased -rawdun is euunterbeted by the effect the deci.ease6 de-nth f rater-hear inc sand thrcyl:-.
th ..ater can enter be well. In artc .,.)ian wells ielc is irutiv -:,roportioLal to the Orawdon as lon as the
, is lass th - the artesian :r,-surc.
The relation of the dischar e to the drawdown for the different conditions is shown in figure 4. The discharge from the well in the shallow water-bearing nectium increases 80
gallons per minute when the drawdown is increased from 2 feet to 3 feet, whereas, it increases only '10 gallons per minute when the drawdown is increased from 10 feet to 11 feet. it is apparent from these vlues that when the limit of the drawdown is being a.-- proached, the increase in yieli; is
being ob - ained at the cypense of a disproporti: nate increase in the dravdown. This fact should be kept in mini when
ieciling, b ow uch water to Pump from a well. For the same con'itions in the artesi-n \,e12 or the well drilled deep into a thick - rer-bearing, formation, the increase in discharge is er minute thether the drawdown is increased from 2 feet to 3 feet or Prom feet to 9 feet. in this case the :ielj may be incra .cd without ausin a ois-)roportionate
increase in he arav,down.
Considera-ion c -r the t]eore -!.ical re3aion or the various facto -,3 ,:-recting the .A.schare from yells leLds to the
conclusion that the discharge incrases as the diameter iLureases bat not in the same Troortion.* Theoretically, the .,ischare 11144,40.=i---47====mmiebtadrs from a 2-foot veil
s.) o tTh t'tn q,
-29-is only 10 ')ercent greater than that from a 1-foot well, eha the discharge fro: I a 4-foot well is only 21 percent
greater than that from a 1-foot well. ( 7 1.). 264). For other conditions the percentages would be a ferent. Experiments made on two wells in Colorado under rractical]y identical con itions s'powed, however, that the discharge from the
2-foot well was 25 rcent reater than that from the 1-foot well (5). If, while the L.iameter is increased the :ischaree is kept constant then the drawdovin will decrease in about the same ratio as the disciefrge increases when the :_traudo.n is
-4Vlsor CA.\ c <11
constant. The change in the drawdown caused by increasing A
the diameter of the well is shown graphically in figure 2 (le 24). ',;her, the oiametor of the well is increased from 2r to 2r', the level of the ater in the well ch. nges from EF to :17P% if the loss of head cause by the resistnce of the casing to the loie of the water through it is neglected. The
The'-e. v50mc,
drawdown is re ucc fro e - h to H - ho: ever, tvAcAeo,erthe drawdo n curve for the large well 4.e.€144.46i. coincidewith
the curve for the small well as shown in fi -Ire 2.
e " - gain:: uiscussion it is seen Vnet Loubling , iemeter of the _-foot well increases the discharge of the well somewhere between 20 and 25 rercent, whereas,
the depth of penetration of the well into the water-bearin meaium increases the (;ischere4e by a-pro imete]y
100 ,ercent. if the discharge were kept constant, the drawdown would be cut in half. This fact should he wiven careful consideration whew utting down a well.
Battery ells e
In .leny aieaz, the de..1 -1-_ of water-bearin6 material is small. It isS o inerease the capacity of the well by aee7- eninr because Tells in these regions are usually drilleI throuFh the v.ater-bearinr formction. adeiticnal capacity or El smaller dravAloun for a giveL cpacity is
desired battery of veils is installed. This is a group of ieells arrane:ed in a lino or in a circle and connected either by siphons to a central well in vhich the pumr is ins'allee suction hea er to the pumP wbich is
leop -ed , n a nit at a centra: -oint. hen the latter arranFe-ment is used, the drep pipe for each Tell is attached to tl,c suction but v -PeF siphons are used they discharge into the central Tell vhich has to be lare Thri.-,uh to accomodate the dro pipes of the siphons as well as the suction pipe of the
For this reason the central well is usually made larrIer in ,iamct-r than the other '.e21s. :11.en a suction heLder
is em,)1 yed t.13 the Ifells are usually made the same eiunieter. lhe .ells in bt,-iter:: systems are mT de smaller in aiamtter ti_an
when sinc.le wells are 11:3ea e:-cept,
or
course, the centrl in si-hoh systes.The be'tery sy tem de; pa ticul=ly adapte- to con, itions ,diere the uater ta.e.le is relF.tivc:y close to the ground
sur ,'oce 1.--cuse the suction h-eaer or the siphon nies have o -lo e the uater surfLce so thet
erau-C,ciuS 4-ta
UU\,:ii in .ells will not ec-,44.ed. the suction limi tts
the v,ator table is at a considerable :stf-mce beloT the f
-31-cround surr'aco, vi eep tremhes Hi.11 be necessar:
salatl-44R-1444.4*.* The construction cost -ner th, se conditions is likely to be prohibitive.
The practical limit of suction lift for Dumps is 22 feet at sea level, 17 feet Lt 5000 feet elevation and l feet at 10,000 feet elevr.tion. L-iiphons will operate if t'ese lifts are e:-:ceede, but they wi11 probably require frequent
7)riming on account uf the accumulation of air from the water or from small 2ea:a.; in the -nine.
The met od of loc atina the wells on the circumference of a circle is host suited to conditions where the water-becrinn medium cont4lins cla: or consierable fine s:-nd which does not r-i-ve un -nter re. dily. The effect of this crrange-ment is 3quivlent tho o hLvin one large yell. This is clea]2y s'J'_o_n in 5 'Mich is t, vertical section thr,:u h a tat'er - of IolTh. F is the position of the water surface if all the -ater is t'umped -rom a sini7Te
and AEFB is the rc.i.',don curve. E'F' is the level o u- -L2ter vher the same a:'1uull of aster is he ma Yumred from the battery of wells. The intersection of the line ,14,'10' with the crawdown curve ,ILFB at E"F" locates to points which dtermine the radius Re of the sin,:le well which is the equivalt of the batter: of wells with the r dius Ra because the arawdown of this well is the same as that of the battery of wells (17' p. 20).
Satisf. ctory re:',ults have been obtained by putting
()- n .1 small I.:ell in the bottom of L 10 feet in diameter, nn bE ter re - ults 1.111 be o tamed if the
riner of the c:ircTe is 1-.1,e .2.onT.16.cyr
fro .H to TOO 1:Jr-J ut riht
illOet conitions. 'f,Tom 4 to 7 i:€311=1, (-)r-t.li:]in.- on the dicimeer of he circl, are s11. tht tre noces:7,ary in the
they :-Th(faed closcr 1.1:1 be
considerable intecH (See lzr.7e
The Ileti-:oC, th battr-,- in a
line is satisfactory whether the ';:ater-bearin - is . 7-10e ss or Coc 'Tavel. This arrangement is used liost 'hen the Eround no or ht.-?.s a jui: Ito :.1(.)vet in ne
'irection, and in this case The -veils are -.16.ceci in a 11110
!_t- to Hi7etton of flow of te
7,7 tl-*7 ice ortion of the trou : t; a . 'Fyct -i.on "-any be int:ree-oter..-...
The 2.7, •_ ifl U: battery in
11.710 2.1 need thn .:Taffctcr end .e1.7)th (DV te (22', tan tf-,e of
cic,,unt of their cc t.
'he vJator-bearing
at' s:H_21ou relic, an in
ice hr
•ho Thouad 1:e from 30 to 73 fet (6). .oils viith each otLr ill be
.on the rc c is o but the co:.sH of ing v;111 be zre&tcr on cccouTh of 'AIH
-33-Interl'ere ce of
-The tmount of interference beteen wells in a battery depends on the dianOter, depth, spncin7 and nuelber of the wells, the drawdown and the nature of the 1,ater-bearing mnterial. This subject has been investi ated theoretically by Mchter (34), an: has been stu:ied eeeperieentally in
Kansas*, by pu:TeiTece a f7reup of four 7e]ls an- in €jicups.
* Unpubishee records of tests made in Uansas by vern 3tambuh under the direction of G. S. InepT).
The 1,ells were inches in diameter Eine dros .3 to 38 feet deep. The dietance bet'eeen the wells was p6, 73 and 92 feet. The depth to water was 11 feet. she eater-bearing mediem %;Ele fairly coerse'eand and the casing whieh as of concrete ass driven into the impervious layer below the sand. hen these wells were pumped as a group, the average
r e31 as 74 percent of the average yield of the
.':edls -1- en these wells were -umTed
ia ir a av - rf' -e ;i:ld per well compared to the average )f thu ells ellen DIIIMOCA se- . rately sho - ed the
fol oe* ,- e re,uctions:
be feet 73
92 148 221 tt
-e'ls Reduction in yield 14.2 percent
8.7 7.5 II
5.3 TT
None
The resu:ts irCicae that under the conditions of the test theme eas no 'fle:.ticulea or vantage in spncin
Use lelle rete-- a Lllan from 50 to 75 feet apart. It
than 2 wells in the b,:ltt , the interference would be greater EN:11_111P
Irrigation ',Tells and Their Construction
Tha. v:P 7 1 is the im .7ing
u ?ovi
t. 2-123=•e w.41,0ands to a _large extent "The success or
failure of -tc,-.1i944x.-ThiliT7s. , motors and engines have been perfected until they era hihly lependable and effici-nt, 'out in :'der to have a success?ul lyum plant it is essential that the el] be satisr ctory also, It is imrossible to
D..0 ,•-Ak
ot Eoo] ell 'Alen conditions aro not favorable, but even when conditions are iJel it is necessary to choose the proper type of ',ell and mst construction in order to get the :Jost satisfactory results.
The typos of' v;ells most commonly used to obtain water from unjerground sources are driven uells, dug, wells, bored
wells and drilled ells. This classification is on the
basis of the method or construction. there are other methods of classifying wells, but this arrangement is satisfactory and convenient. Of these different t:Tes the drilled wells are most in ortnt from the stanuPoint of irrigbtion ES the
number of wells constructed by this method exceeds all the others talcen toetter. There Ere, however, special
conditions where oter methods should be used and for this reason must be !iven consideration.
Driven Wells a
-g-Q-driven welt is one that consThts of a pipe and sand forced into the :;ate]7-bearin
--5-/,s the driving proceeds additiona3 lengths of pipe are adued until the desired depth is reached. i. drivin cap is used to protect the end of the pipe while it is being
and Qs_ --Vcsv-v\
ur1venL the pipe) with a wrench rake driving easier. In order to keep clay from cloinF, the screen of the sand point while beinF driven, it is frequently desirable to drill through formations of this sort with an L'ur,er. Jriven wells are usually from ll- to 3 inches in dia:leter, and slnuard weigh witer pipe, either black or 1.1valii fith throaed coup insused as cpsin -. The san:' Point, also called a drive -oint, consists of a forFey stee1 or c3t iron point which is at achel to a Piece of p.'rforate Pipe. The
perforated nine is 'r:app-d with c: layer of :Inc mesh
screen and then covered with a shcet of brass perforated vith
" 1 Y1 The perforat jacl:et protects
the fine mesh screen from injury while the sEgT:i point is r.--.+11 • Several ri Si. es suitable for 6iffHrent T_,E,s of _Iter-b:iLiLir, :'orations
Sand points may be cp - aiDed i a ,;ariety 01' lent-hs to stit
the thicres fermtion q=tity
of rioter required. nes type o nyc o . rit has recentl
been nerfected consistin7 noun•.. rass stri7)s nsich o that t orm a contincus slot of any riesire
..33o!;s in. ri the outside than on the
lni3le L. uunsu uenulf o flu s;lon easily with sand. These uri no: ii !),.3 also one mode in various :en;--2.ts. A typical
Driven hLve lJn - been used to eupp - y .e,er :or
dostimu:e 0806, uatterie , uhese wells connected
by a euction header eep a sinyle pump have recently been use, to lower the water table over consideraule areas in censuruotion work. The yield from a single well is rather small, the maximum *beim: between 20 and 50 gallons ner minute, but the ageregate yielo from a large number or these eells would be sufficient to provide water for irrigation. AlthouFh
there is no record ov the use of driven wells for irrigaion pur-oses, if is believed 'hat a battery of these wells would have suficien merit to warrant ;i trial where conditions are feLvorebIe.
This 0 - dnstallatien is best suited t conditions where the - -'er-berin orretion is free from iarge gravel and boulders which i .h inure the screen on the sand point, and 'ere the ,a-er ahle is no more then 10 or lb feet be-low the ground sur ace b -cause the _ipe connoc 4 i F, the wells has to be near ic eater level in order to et suficient drawdown in the wells to obtain the deeired quaLtity of water without exceedinr7 the uction limit. Althouh driven wells can be used in thickeater-bearing formations
other types are more effective, but in format ions of limite t ickness the driven ells probably eive the best results. The yield from thin layers of water-bearinc ,atLriL,1 is slight, and eonequently small eells are adapted to this condition. ?he cost of these wells is senlT, and they have the further aaeantae that. the con he put (H.ov:n by tho farmer
-37-Dug Wells
The fire irri7ation wells were large open its excavated by an and lined with wood, brick, :TeLeme or special types of curbs. these pits were usually shallow and from 6 to 10 feet in diameter althoue5. sometirdes larger. They seldom penetrated very ddeply into the
water-bearjns formtAien and were freuently failures for this reason. ians of these wells had to be abandoned beers they . ere completed because of the difficulties eecountered in sinking them to the desired depth.
Dug wells are sometimes made rectangular or square in shape, but the circu2a -e form is usually chosen, because it is stroner an it is also eesier to construct. When
the materite] wil2 stand without support while being excavated, the hole is dug down to the water table without eutting in a curb. The material is esca-osted with spades or shovels and after it is no longer possible to throw the excavated material out of the hole, a windlass or hoist sith a bucket and rope is used to remove it.
The curb is started in the we31 as soon as the water table is reached or the wlls of the pit begin to cave. Many different types of curbs have been used, but the
commonest dorms are the wood-stave and te ring typ • The latter type consists of rings of brick, flat stones, concrete blocks or cylindrical concrete sections which usually are laid on some form of shoe. The woodstave curbs are rade eith either loose or fixed staves and are either square, rectanFular or
rigid frmes are built which are ,,=:11 u h smaller than +*-- pit so that the staves mrly be placed in a vertical position on the outside 01 these froeos on still leave ,AC-flicint room to feed in gravel bete the stoves and 7tJ•le wail of tIe pit. The stoves should be 17,veld on the bottom from be inside placed clo JJ;he_i: :_ee) the and fr,D TL
ui cfreing a1iy. more obstruction -uo Lne passage o: the water than necessary.
The staves are made from 8 to 16 feet lorw depend in: on the depth to water and are usually 2 or 3 inches thick. As the excavating proceeds the stoves are driven down one by one with a sled7e or a wooen aul. The ri[7iJ frames hoL he ooves in niece, and the beveled edge forces out the ho tor of the st,vo as it is driven downward. The riid frames ore also ri.os own ccasiona717, so that the
alviays be near the 2o er end of the staves otherwise the vel_:,!.ht of the material ack of the staves will force them inward. The upper ends of the staves should be
chamfered and then iraT)p d with three turns of number 10
sot steel wire to mteel) them from s-„DlittinF7 while being driver. Uhen the excLip iou is about a foot below the water
table, it will be necessary to install a pump to Keep do the 'ater so that the men will not be hampered in
-39-excavating the material from the bottom of the pit. A turbine pumr) is best suited for the ork if electric power is nv' liable because it does not require nriming
ro not OOO of
its o7- n accord as the exc. va'il -r cer;ds.
re9ul's may also be obtained vib ertic I centric'Jg1 rump. s the::e )umr . are um boil thP ulie on the DIJ_H shaft wi71 have to r net M:0 - ucl't - y 05 t-re well 7ets Jeepe. split pulle7- houle be us -or t is purpose. A horizonatl centrifuuLT ao be u.e. TLZ
the water out of the well , but in t is ctIse the rn)11;co mount always be kert within 10 or 20 foe- of the nater s;rfce so as not to exceed the suction lift. ',. Fate 77:1ve is required on the ,ischarge of a horizontal 1= for the purpose of regulati. nba _lac arge so the it will not e ceed the flow into the ell. A foot valve in the suction
-Din A 12J ol o le desirfible as it )ill eliminate the
neces;ity for nriing each time the pump is shut off.
Ankino. num:)s ,:,hould be eq;linped with a substantial screen on the section I.-)e to keen coarse grave] and rocks out of the '.umn. his screen shoulo hae a large ff.reo of openiLos one should T,7-eferably be short so that the pumn will keep '}-)P -.fl 4- -; in the roil a low level. in oror to keen the
- At-T. in the well as low as nossible a surio should be dug for the rump suction, which shoul:i be kert a foot or two
deeper than the eel]. 116.10====6:63.e.3inkinr 711rMS are subjected to sevelteervice on account of the amount of sand.and -7ravel pumped, and for t' is reason new pumps „lhouLi not be used Cor
-40-• When the fire:t set of staves has been _riven dowl as far as pos-ihle, a second curb is built inside the first and in the e. me mane_er. This curb ill reduce the si e of the we :LT considerably, ar. 1:: a deep well is planned,
ke4 e)(.11,4
which list.51Ct require several curbs, the die Hoter of the Jell should: be n , de large enou=--11 in The beeinning to
install the necessary number of curb: without re ucing the well di-meter too mUch.
Considerable di:ficulty is frequently encountered in sinkina wells by thie:, metho because the pressure on the
\S GUC‘MeYA4- e-Ci
curb ±11.44-±44.Jes as the depth of the well increases, and when the water is rem ,1:ed from the 1,ell th pressure is
au reel.ted stil: more. This added pressure makes driving difficult. Ieurthermore, the weiht of the material back of the curb and the velocity of the eater under the ewes of the staves causes the sane and ,7,rav 1 to wash into the
well, if this washin continues, a hole will be formed which will ultim tely c ye-in and may either crush the curb or -iitort it. TO overcome this di ficulty gravel is
fea down en the outside of the curb from the tors to keen these cavities filled. If this prucaution is not token a 11.7e area around the well frequently begins to sink - cpe:n. sinking is very likely to happen if a layer of fine :alai is encounte -eea which is :ii'ficult to
keel-, from runnin . under the bottom of the staves. Sometimes as much as a. foot or more of sanl and t'inc gravel will
come into the el at one tore. This i :no' n as hefivinp; and usually usually occurs while the wall is beirr -eum-eed
-41-to sink the curb under these conditions, and the well
has to be ilbndoned. if it is possible to drive the staves down into the sJnd a c nsiderble distance ahad of the escavation, it m.y be pos-ible to keep the sand from commnc in, other ise a different method will have to be adopted for s2inking the well if it must be driven depper.
The fixed-stave type of curb, (See figure 7), wbich is freuently used in dug wells, consists of a cylindrical tube mace of vertical timbers securely attached to a s -:ries of rigid rr. me,' in the s'ia70 of rings which are built Up out of
sev 17ers of 2-inch lumber cut to form is circle. These rin:s ore m de vith lapping joints and are secure3y spiked ow o - to ether. his ty7e of curb is sunk in the
the loose 5.11w) type except hat the curb is ..Y1 rote blocks to f rce it own.
the water is removed lium the velIi b7 the necic mythos as previously explain,
is fed Firound the
ou._ he co c7-fl ce t-Ashed out.
, the ho tom of the curb
in at every point,
or thel- in n. - of la: :0 uLn's],itIn of
S tO) o in
vel
it is - n.if the curb is th shollTh be •c.:1---21,sa foot or tuo into t o: - 1 7.1 ho 0000 ili it of
_
tdc 3--H). if,
of c(y_rse .7.rt:Ivel to op the ccii rc comi.n7 in un or the curb. hen the 0 1 it -1Dckfille, 0 it should be IT:de
the '.7- •..CtiOL the .,1_11:1-p to the fror -.1
, ,ovAn to the li it.
ul oil •.LUO i h thie head cut out and hoe side;3 cucLci full of hobo k.*es a ,:L;uiable linin for thiLA
unde-2 condi jam:, this t, -7)e of curb has boon ,-'11.nk 30 feet in - o the .E-1 -ter-bef-±rin fc;rHation, 1:cut un(jer ordilnar: con it ions 25 feet is about the 3imit ihti uhu hole hoc to he uneetcref and thL: ai..7.1n is :iono by lant.
erect in sin'-jr, be elThinnted I ce r: on 1
itchou un eterLe tico c11. In thL.; is
•
_ ,
4:1; o is thiL, t•o6. b ,.cau:7,n flit
cc CO3 t'- C
those
ten 'ii --7e-ren:1
IT cc flee cc —
cc unto Cii b er edI er ten I leo A-2ep
-_L • 21' 1_
-cc rc , fIccc ed. u 1011.- .
•
T•'--monolithic concrete or 1,-:a-2,70 ieeici sd• •c acts as the strainer. to - :7! cho tide , , ‘. C • icuch h 000; -1 - tee I; • en
ri pie 11 _ r e •r;
-7er - four or flue .. -1
n c'ar.s
or :a l' .i..: L.,., - i /
IC Cli -- : ,, :: :cyln c 'HIT -.:
Ylli s c ,-_-: -...r-_____, .-..ill _r::
J
i.00t'f., curb fich cUT LCor o
ID( ca2,tin - rort c 1-inch
es or garden hose in the curb. The I I, tubes are plu god vith _fl070:q1XXplaci in conurete and are cleaned out after the forms ore
or
should be 4aced in each s:juare fcc u' a
The large metal curbs are generally made of use, m,terial. The bottom of the curb is stren--thened a sten1 ri onsi tinc or a healTy fl- t bar on an an -le, and if the curb is no v.ry rj4-4d additional Ii fniri 171 at ir.tervC ic treu hout the lenrht of the
:4
-i ,01.- C;-i[, Or "ifro 4E to
1/2 inc , 1 resiA]ts will be obaine_ if the per ore (rw s - -,..)urore the or L7..; laced in '
JYtoe curb :oeo not sLr reLdil, it may be loaCed on the in-bric, but in that c: so an an tc- , i7con should be iroet o a i'lat bEr for the otlifnin riro. at the
-hnttn Of tT.e curb
nncrt t7le tiers of brick.
I is ore .7cnerally e::cavatec': Lb hand vith spades :.:;hovels, but a and buc'7et or an orEnc-peel buct vith a po'- or hoist (see figure may be us
1,0
he no bcr7.1rjers, 1-7 rs on clay, har a- or other consolida'cd ra‘terils
Tricoun' • -Men a snolif ic is bein
., coarse cr vel should be used to :eep the sand 77ro corlinr. t-Lre17 -"- the perforations • hioh an usually ssde
in ties t The bottoms of the oils should the 1&ith n previ,_.us1: escribed. TTnr
or conoete blot c rb yells can .be 15 jo 20 feet intG 111
- _
or laa:E(.i
LtJre-diLeter sukc'li as v11.17, for pro-,-i,..ili;j; rater for i-rition, are to conitins eboae the i;:ater table is nar the ionS aid ne the t'
of the v.ater-bearinp formtion is no gat.
of staill'= rater to enter the eli 1::ith a
tunency
ZUf 1,hLE;a: u a;s ILO 1.Lb ali is 1/4.-uce(]. There is 1,11a -u ]are olis a a iduch LT(:Lter
capcity than aia] on b t'or he same drown, but actually the 6vantage of thu srge veils in this ,:,spct is not
newly as :1-eat as is 11:-)ual:: hal ii Theoretical2:. unuer ordinary conditions a mell 8 feet in diaeter has a ca,:acity
onl 3? percent -,ref.:ter than a well 1 foot in diL.meter
(2g
p. 264) Under actual con-itions the ielci from the F--foot well willprol.'bly be somewhat sre ter then this because the loss of head throth-sh the strainer will be less for the [-foot well than for the 1-foot well. Th se large 1.el1s are much
Iore expen.-'' to construct than • smaller wells, and it is
tb 1-,cr - t-l-c in I - 7;r1 4--'i'H-r.t o j to ' ble centr:.. which • • (..; • . 7 ey 4 ! and he water ha vu Lo L,..; us Al'—oupt rc :re , Luent]y installed in J area ad is, the practice is r, u one ow,nf . to the po: f-hat gasol inc Purses mic:ht accumulate in L a ana e7.D1ode Then conditions ';.ere favorable. is C,anger also frord carbon monoxide poisoning.
The la ,Te open Hell the thu o:ten r.,ttul.--)ts to . he ree(JH is 0.
- - 1
th7 C 1.1a . :1 7. r • ir one of I-,
: t t c oIls o con,- , r:n3 r (_, Cten 1_ in -july,...)7.C.•:;c out
or 1,73 oot of the
fruetier. he unual difricul tics er hat the ct.sin of r•lL1t or (.:-:-.11arcs, curie into the 7;c11 ur,.,-le-z the (7.. hf_In the:: cc.n be rLI:ivecTi
- Li curb rnfue',z. LE.J3 - • T chICI I.JJL to 1,o hireL
to in too Lad
con:iition sin-4 a sr:la:1..1u:-. to tTh -th iLside the r If, do • ever, the E.-',.rea :=,ruun, the ha sur177. to c coLlJe7.LLM eeth u the csir,c: is
:7-.Luch rn o7 -)11.1.171'L 07dufi coil 0c50 it be
ode to e1.1.. t f C 17C 71. _HJ
I
()oc an - n tote roll • 0'.r o t.e
---Ltri-‘e Fits
Ojj, , •.; 'to _ :ii no or
s 'd ao. to CUt p± Oh or
.,)C) t 250 feet lc;r1':, End
, the ut. 50 feet .
.1 or027 we. a , ossible
tLe
On enc7 -t- tonu ,o run in,o it o
-4
Iii tLC
lit ii 00 0
prosur-The m terial exo1 to
and the area reql
of
e - it to oJou
izr,1 c..):17 ban -:-...
_ •
up IIAAulble space. ho 1uu. li _6 6
it difficult ir foun ' U.: .
;11.en the water-bearin; 2; re
coupled tl , e c; t-.cdty
of the pit should make it o facto -l- y
suppi uli-er these conditions, but the r,--sults are usually poor because the small depth of water in tilu pit IilLkub l imposL,iole to ,-et sufficient drElL(J,11 to force a 1arr7,e '11.'ntity of water throuh the
•
rio trunc Cl
ur-lu ,istanuu below the wator table and tLen
Tith coarse :'ravel. -1thougn & of this :art little storage capacit it viould probably more watr than the large pit because it would_ be possible to draw the water in the v.ull don to a gre ter depth.
Bored
huc'ers are sometim s used to -ut don irria:a ion we] is to the point where unconsolidated t‘ter-bearing material is encountered. -hese wells are called bored wells, and the augers used to construct them are similar to ,_)ost-hule
rs (fli-u.re 20) but r,reqf much larEer an: are more su:stantially ma e, They consist of a cylindrical steel bUcT:et v.ith a cu'tin. ed7e alone a s2ot in the boltom. The bucket is fi2led hy turning ith a uower driven rotating mechanism. The turning motion is imparted to the auger through a square em which slides down tl- rougt a hole of
T,he rotatin[2: mechanism as the well gets deeper. hoist is rquireu to lower the auEer into the
:et is fillea. After has beeli brou, to the surface the material lirouh a door in the siee of the
in dirrerent si es, but reamer is us hen it is C,eired to LIEJke a hole 1
al, Lc 11' . ',Tc re '-t p( 1i
in --'_ a manner that the 1-1Eitial
i 7 C! - 7-1". -1._ '' 7• in - o Ia a bucke'
•-, t -1.'ino t,.7 . 7--'o=17.,
„
sometimes to ',..:,2 inches in dia,- ,._ uhu
