Water Well Manual (USAID).pdf - The Water, Sanitation and Hygiene

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yield of the individual wells (Fig . 2.16). The drawdowrl at any point on tile composite cone of depression is equal to the sum of ihe drawdowns ai that point due to each of the wells being pumped separately. In particular, the drawdown for ;I specific disclltlrge ill Static water level I -_ a well affected by interference is greater fllA11 llit unaffected value b? the amount of drawdown ait that well contributed by the interfering wells. In other words, the discharge per unit of drawdown commonly called the specific capacit), of the well is reduced. This means that pumping must take place from a greater depth in the well, at a greater cost, to produce the same qaan:ity of water from the well if it were not Fig. 2.16 INTERFERENCE BETWEEN subject to interference. ADJACENT WELLS TAi’- PING THE SAME AQUIFER. Ideally, the solution would be to space the wells far enough apart to avoid the mutual interference of one ok the other. Very often this is not practic,tJ for economic reasons and the wells are spaced far enough apart. not to eliminate interference. but to reduce it to acceptable proportions. For wells use3 for water supply purposes, spacings of 115 to 50 feet between wells have bee11 found to be satisfactory. Spacings may be less in fine sand formations, in thin aquifers or when the drawdowrt is not likely to exceed 5 feet. Greater spacings may be used where the depth and thickness of the aquifer are such as to permit the use of screen lengths in excess of IO feet. There arc many patterns which may be used when grouping weils (Fig. 2.17). Where the aquifer extends considerable distances in all directions from the site of a proposed wetI field, the most desirable arrangement is one in which the wells are locaf!:d at equal distances on the circumference of a circle. This pattern equalizes the amount of interference suffered by each well. It should be obvious that a well placed in the center of such a ring of wells would suffer greater interference than any of the others when all are pumped simultaneously. Such centrally placed wells should be avoided in well field layouts. Where a known source of recharge exists near a proposed site the wells may be located m a semi-circle or along a line roughly parallel to the source. The latter arrangement is the one often used to induce recharge to an aquifer from an adjacent stream with which it is connected. This is a very useful technique in providing an adequate water supply to a small community long after the stream level becomes so low that only an inadequate quantity of poor quality water can be obtained directly from the stream. This is possible since the use of wells perrnirs the withdrawal of water from the permeable river bed and the quality is enhanced by the filtering action of the aquifer materials. ‘0
Fig. 2.17 LAI’OUT PATTERNS FOR MULTIPLE WELL SYSTEMS USED AS WATER SUPPLY SOURCES. CENTRALLY LOCATED PUhlP EQUAL.iZES SUCTION LIFT. I Well-point System Saturated sand A Sub-soil Water level while pumping Fig. 2.18 WELL-POINT DEWATERING SYSTEM. ‘I ID) \ ‘\ \
Page 1 and 2: A PRAGTICAL GUIDE FOR LOCATI CONSTR
Page 4 and 5: hmier Pwss Editorial Advisory Boani
Page 6 and 7: WATER EL1 MANUAL Covers Copyright @
Page 8 and 9: Page ACKNOWLEDGEMENTS ii FOREWORD 1
Page 10 and 11: S. PUMPING EQUIPMENT 114 CONSTANT D
Page 12 and 13: While man has always recognized ihe
Page 14 and 15: An understanding of the processes a
Page 16 and 17: Bsit of Soil Water tntermediate Bel
Page 18 and 19: and loess may be limited by both th
Page 20 and 21: deposition of large aprons of mater
Page 22 and 23: the pc>:ti,sity. This quautity is r
Page 24 and 25: permeability, P, we see from equati
Page 26 and 27: Flow Toward Wells Converging j&w: W
Page 28 and 29: expansion and deepening of the cone
Page 32 and 33: Multiple well or well-point systems
Page 34: 10 ppm of iron means that in every
Page 37 and 38: ground waters in some parts of Arge
Page 39 and 40: Geologic Maps Geologic maps, of whi
Page 41 and 42: depth. thickness. and description o
Page 43 and 44: CHAPTER 4 Generally, the aim of eng
Page 45 and 46: lodged in them and thus restrict fl
Page 47 and 48: Fig. 4.3 THE Y-SHAPED OPENINGS OFTH
Page 49 and 50: Fig. 45 CONTBNUOUSSLOT T Y P E OF W
Page 51 and 52: Manufacturers make well screens in
Page 53 and 54: The limiting size of material to be
Page 55 and 56: too 90 E 60 z t 50 : .L 40 2 30 E (
Page 57 and 58: prime concern in small we!ls. Gener
Page 59 and 60: otherwise unsatisfactory water into
Page 61 and 62: The object of formation stabilizati
Page 63 and 64: Pump unit Sanitary well seal I / ,R
Page 65 and 66: There are four basic operations inv
Page 67 and 68: Ham? driver ----k- Htle backfilled
Page 69 and 70: single wlley block : /Tripod Fig. 5
Page 71 and 72: Fig,..8 MAN ON SCAFFOLDING RAISES H
Page 74 and 75: Cutting edges Galvanized iron pipe
Page 76 and 77: inexperienced driller because of th
Page 78 and 79: string are usually joined together
Page 80 and 81:
.I Fig. 5.18 CAStbiG DRIVE SHOE. of
Page 82 and 83:
Fig. 5.22 A GRAVITY PLACEMENT METHO
Page 84 and 85:
Fig. 5.24 OUI’SIDE-TUBING METHOD
Page 86 and 87:
Pull-back Method The pull-back meth
Page 89 and 90:
Wash line- .Cemsnt grout ,’ Exoan
Page 91 and 92:
to the surface with the return flow
Page 93 and 94:
-Inner Carm~ Fig. 5.36 DOUBLE-CASIN
Page 95 and 96:
Lead packer Pulhg pipe Sand join1 S
Page 97 and 98:
saving that sbandunmcnt ot‘ the b
Page 99 and 100:
esult, tools lost in a hole do not
Page 101 and 102:
Tapered Tap Die Overshot Circulatin
Page 103:
If the hold is secure, continue lif
Page 106 and 107:
CHAPTER 6 WE11 C6MPLETION Well comp
Page 108 and 109:
‘N E L VI E L
Page 110 and 111:
Static water :evel -m----.-e Solid
Page 112 and 113:
The procedure is to lower the tool
Page 114 and 115:
wells. The thinner the gratlel pack
Page 116 and 117:
Wells, like all other engineering s
Page 118 and 119:
of the wells to determine whether s
Page 120 and 121:
Black iron or plastic pipe Well scr
Page 122 and 123:
,&ting technique is used to agitate
Page 124 and 125:
Drilling and completing a well form
Page 126 and 127:
container is termed the srrctiorl h
Page 128 and 129:
plunger on the tijrward stroke p~~s
Page 130 and 131:
or deep well type and are usually d
Page 132 and 133:
Fig. 8.9 VOLUTE-TYPE C’ENTRIFU- C
Page 134 and 135:
pre y.,,:~ 1; +-.b to, rourT the no
Page 136 and 137:
Check valve Radial bearing lmpetfer
Page 138 and 139:
To storage ha I 3 Power unit - Stat
Page 140 and 141:
Provision may also be made for pump
Page 142 and 143:
132
Page 144 and 145:
OF Too great stress can never be pl
Page 146 and 147:
feet before final disappearance at
Page 148 and 149:
REFERENCES Acme Fishing Tool Compan
Page 150 and 151:
T OF PE ICITY The coefficient of pe
Page 152 and 153:
Unit TABLE B.3 VOLUME Equivalents o
Page 154 and 155:
- B-8 PRESSURE 1 Atmosphere = 760 m
Page 156 and 157:
TABLE B-14 ESTIMATING DISCHARGE FRO
Page 158 and 159:
-z- TABLE B.16 DRILLING CABLE ROPE
Page 160 and 161:
A Abandoned well, I37 Acid. hydroch
Page 162 and 163:
Gelling, 64 Geologic cross-sections
Page 164 and 165:
s Sand, 7,9? 119, 126, 129, 137 --
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