------------------===~E== = t=====
TUBEWIVLL DESIGN C2ITS IIA
Northern Zone, West Pakistan
TIPTON AND KALDI~BACIH, INC.
March 12, 1966
TUBEWE.LL DESIGN CRITERIA
Northern Zone, West Pakistan
Many physical, technical and economic factors affect the
design of tubewells." Engineering considerations and construction
techniques restrict the rank.e of choice of components and physical
conditions affect performance. Still, within the restrictions
imposed by these factors, a wide range of design possibilities
exists. The best or optimum design is one which results in a
minimum total cost for the water pumped.
Screen dimensions, length and diameter, have the great-
est influence on optimum tubewell design, and of the two, length'
is the most important. Within certain minimum technical restric-
tions both dimensions are subject to wide variation depending on
several physical and economic factors. Characteristics of the
aquifer are the most important physical factor and the most
important economic factors are 1) life of the tubewell, 2) cost
of components and construction, 3) cost of power, 4) rate of
interest on investment, and 5) annual volume pumped or utilization.
In order for design criteria to be applicable, the
factors which are considered must be subject to evaluation or
estimation and the criteria must be in usable form. In this
report the most important design factors are discussed, certain
design parameters are chosen and an operational procedure is
derived for designing tubewells of optimum dimension during
- 2 -
Length and diameter of the screen are the most important
determinants of drawdown. Drawdown, in turn, has a major influence
on consumption of power. In the absence of other considerations,
minimum drawdown would result in minimum cost of water. But to
reduce drawdown, diameter of screen must be increased, or more
importantly, length of screen must increase. Both factors can be'
obtained only by increasing initial construction cost of the
tubewells. In order to determine optimum screen length a balance
between added construction cost and reduced power cost must be
Regardless of changes in screen length and diameter,
many components of construction do not change or are of minor
influence. Only those components whose cost changes with screen
size need to be considered in determining optimum screen dimensions.
The construction components which Vary with screen length or dia-
meter are 1) depth of well, 2) amount of gravel shrouding, 3) length
of housing as influenced by drawdown, 4) length of blank as influen-
ced by amount of impervious layers in the aquifer and total well
depth, and 5) cost of screen.- In general, the total amount of these
variable cost items can be stated as follows:-
C = P(D ) + P (L) + PD (B) + P gH ) + P,(G) (1)
It is convenient to express water volume and energy cost
on nn annual basis, so equation (1) must also be converted to this
1/ Borehole radius is considered constant (1 ft.) within the range
of screen radius examined.
2/ All symbols are defined at the end of the report
basis. The usual procedure is to make an interest charge on initial
cost and depreciate the initial cost over the life of tubewell.
Fifteen years has been accepted as the life of tubewells under
conditions in the Punjab. The West Pakistan Water and Power
Development Authority pays 4% percent interest on the loans granted
for tubewell construction. Combining power charges with deprecia-
tion and interest charges on half the initial investment (average
investment over the life of the tubewell), the average variable
cost for a given volume of water can be expressed as:
C = 0.09 C + C a CA + C (2)
v I E IA E
where CE = PE (), PE is the rate for electricity and E is annual
consumption in K','H,
Total pumping head
Power consumption is a function of total pumping head,
Ht, which is the sum of ultimate depth to static water level, Wt;
tubewell drawdown, s; height of discharge pipe above surface level;
friction head loss of column pipe and discharge pipe, h ; and
discharge velocity head, h That is
H = W + s + h + h + 5 = H + WV + 5 (3)
Ultimate depth to static water level is specified by considerations
not directly related to optimum screen length and will be prescri-
bed for purposes of optimiz.ation. Average height of discharge pipe
is approximately 5 feet above the surface level. The variable
components of head, or dynamic head, IHd, are therefore drawdown,
friction head and velocity head,
Tubewell drawdown can be divided into three parts in
general tubewell design:
s = 1 + s2 + s3 (4)
1. s1 is the part of drawdown due to aquifer loss which is
a function of tubewell discharge, screen length, screen radius,
radius of borehole and aquifer permeability. Theoretically, sI is
also a function of area recharge intensity, anisotropic condition
of the aquifer, degree of penetration, time of pumping, aquifer
boundary conditions, interference of well field and so on. Tasting
data show that the most suitable formula for computing aquifer loss
in the Punjab area, is to consider the well as partially penetrating
an aquifer of semi-infinite depth with essentially radial flow with-
in the influence radius of (TT/2)L at the end of the well-testing
period. That is
Q 2 7r L5s 0.20 )
s1 n7nK i, s.r.+ (5)
1 47r K LLs 2 r
Since the term 0.20 is usually negligible, the relation
can be simplified to:
= /./5 Q. /157Ls (6)
Tr K L5 ~
2. sa is the part of drawdown due to gravel pack loss
It is a function of tubewell discharge, screen length, screen
radius, borehole radius and gravel pack permeability.
3. s3 is the part of drawdown or head loss which is
caused by the flow passing through the screen slot and the
accummulative flow along the well screen axis,
,53 U2 Q
(c h c'- >-i )//
where C' = 11.31 C A /As, and C is the coefficient of contraction
c p c
and A /As is the ratio of slot opening to screen surface. With
properly designed screen slot, size, shape and distribution, if
L /2 rs > 15 the equation above can be simplified as follows:
The column pipe and discharge pipe friction lose is
computed by the following equation:
Zf ^ z y (9)
hf =J2r 2T rU4
and the velocity head is
h = (10)
Therefore the dynamic head can be computed by
n. -H^-LL ]r + qZ
7 L-- 07 (11)
For average Punjab aquifer conditions and general tubewell
design practices, the following values are recommended for use in
computing total dynamic head:
Aquifer permeability for water, K=1.5x10-3 ft/sec(excluding clay layers)
Gravel pack permeability for water, K = 100 K = 1.5 x 10 ft/sec
Bore hole radius, r = 1.0 ft
- 6 -
Pipe friction factor, f = 0.015
Acceleration of gravity, g = 32.2 ft/sec2
By substituting these values into equation (11), the
following equation can be derived:
S 2.44x / L.s 4.87 xo' 2.44 y/ 7
d L Ls zS Ls
.7/ X/O -2 c z
+/47 IX//O XjJ/xto5 L (12)
Following are workable equations for design purposes for
the case of depth to static water level nt 20 feet:
A. Screen radius, r = 3 in = 0.250 ft
d = 2.44 4 93 X0'7 q 4 (13)
B. Screen radius, r = 4 in = 0.333 ft
Ifd -Z. '44/oz-17 93" !--'^ "jQ ro30x,-'IQz (14)
C. Screen radius, r = 5 in = 0.417 ft
id s 4.87 X/o OX Q2 (15)
id =2.44 Ls + -- / + .o -]Qz (/S)
The theories, assumptions, analyses of testing data, and
other engineering and practical considerations upon which these
equations are based are beyond the scope of this report.
Under usual contract sporifications, the cost of drilling
is variable with depth. Present contracts specify Rs 32 per foot for
the first 300 feet of drilling, Di. Rs 36 per foot for drilling between
300 and 400 feet, D2w; Rs 45 per foot for drilling over 400 feet in
depth, D3w. The rate continues to increase with deeper drilling but
depths beyond 500 feet are seldom applicable for conditions found in
the Punjab and will be ignored in this report. Using the designations
above, total depth of well can be specified as:
D = Dw + D2w+ D3w (16)
Alternately, depth of well is also the sum of screen length, length
of housing pipe below the surface and length of blank pipe:
D = L + Hg + B 3 (17)
Length of housing pipe must exceed depth to static water table plus
drawdown and can be specified as follows for usual conditions
Hg = Wt + s + 8 (18)
This allows 5 feet of housing pipe below drawdown water level and a
3 foot extension above ground level for the pedestal.
Length of blank pipe varies with the number and thickness
of impervious layers in the aquifer. In the Punjab the length of
blank usually vari.-s between zero and 50 percent of the length of
screen and averages about 15 percent. For most calculations, length
of blank will be considered 15 percent of screen length:
B = 0.15 L (19)
Equation (17) can be restated using equations (18) and (19) as:
D = 1.15 L + Wt + s + 5 (20)
w s t
It will also be convenient to restate equation (16) as:
- 8 -
D = 1.15 L + + + + 5 D. D(
iw s t j j w
Present contract unit prices for non-drilling components
are Rs 60 per foot for 6 inch fiberdla:,. screen, Rs 75 per foot for
8 inch fiberglass screen and Rs 85 per foot for 10 inch fiberglass
screen, P ; Rs 44, Rs 58 and Rs 70 for 6, 8 and 10 inch blank pipe,
P1 ; Rs 55 per foot for housing pipe, PIg ; and Rs 11 per foot for
gravel shrouding, PG. From equation (19) the cost of blank pipe
can be stated as PB(0.15L ) or for 8 inch blank pipe, Rs 8.70 L .
Using this and the other stated prices, equation (1) becomes
C = 32 Dl + 36 D 2+45D +(8.70+75) L +11D +55(W +s+8) (22)
I 1w 2w 3w 8 w t
for 8 inch screen. On an annual basis, equation (22) becomes
C = 2.8D w+3.24D w+4.05Dw +7.53L +.99D +4.95(W +s+8) (23)
IA 1w 2w 3w s w t
Daily energy consumption is specified by:
2.03 QHt (24)
Usinp 60 percent combined wire to water efficiency, e,- the annual
electrical cost is:
CE = 1,235 UQHt(P ) = 86.45 U4Hf (25)
where U is average annual utilization and PE, the price of elec.tri-
city is Rs 0.07/KWH .
The Ranual cost of a volume of water specified by U and
Q is C the sum of .equations (23) and (25). For 8 inch screen it
1/ Performance test data for 225 SCARP I test wells show combined
efficiency to be 5,.6 + 2.0 percent. As efficiency is expected
to increase, a value of 60 percent is appropriate, Although
efficiency varies through the life of the tubewell it will be
considered for design purposes that the effect of this
variation is offset by a decline i.n the water table,
- 9 -
can be written
C = 3.87 Dw + 4.23 D2 + 5.04 Dw + 7.53 L + (4.95+86.45 UQ) s
v 1w 2w 3w s
+4.95(Wt+8)+86.45 UQ (Wt+hf+h +5) (26)
This equation is a continuous, concave function of L for any Di but
discontinuous over its full range. The minimum value of C with
respect to screen length can be found by differentiating in segments
because within anysegment two Di are constant. Furthernmor4, the
last two terms in equation (26) are-not functions of screen length
and also drop out. For D ', 300 feet, equation (26) becomes .
C 3.87(1.15 L +W is+5)+7.53 L + (4 98 +* 86,45 UQ', .
+ 4.95(W +8)+86.45 VU (W +H1 +h +5)
a. = 11. 9 8 + (8.82z 8:..-5 UQ)
- .s s :
9 9=7 896.4 (6.8.2 S.4 7 -0Q44
45 L .(27)
For = 4 cusecs and U = 60 percent, equation (27), when set eliual
to zero reduces to
L2 17,617 log L 4i128 (28)
S S -
which can be solved by successive approximitien.
.. The form of C and its components and the solution for
(18) are shown graphically in Figure 1.
Influence of various factors
Length..of blank pipe: The general case for equation (19)
can be written B = b L where b is the factor indicating blank pipe
;as a percent of screen length. Using the general case for: length
of blank pipe andcombining equation ('3) -and (25) with D 3 300;
C (10.62+9.Q9b) L.+(8.82+86.45 ,U() s +8,82(Wt)
V .s* ,.* t 1. */ ; *
86.45 UQ (IV +h +h +5)+58.95
for 8 inch screen. And
9Cv (/aBz O ( ^B. d52) s (30)
Thus the blank pipe factor, affects the constant term in equation.. (27).
The effect on optimum screnenength as b varies from zero to 100
percent is shown in Figure 2,
The larger the amount of impervious layers in the aquifel
the more costly the tubewell is to construct because depth must be
increased accordingly. As more blank pipe is required, initial
construction cost becomes relatively more important in determining
optimum screen length than cost of power consumption. As a result,
optimum screen length decreases when the amount of blank pipe
Price of screen: Again combining equation (23) and (25),
C can be written
C = (5.22+.09P )L +(8.82+86.45UQ)s+8.82(Wt)
V a t
+86.45 U'l(l +h +h +5)+58.95 (31)
for 8 inch screen and D1 .300 feet, Thus, like the proportion of
blank pipe, screen price affects the *constant term in. equation (27).
An increase in screen price, as would be expected, decreases optimum ,:
screen length (Figure 3).
S. .. . .., ,'." .iti. ..
Static Water Level: From inspection of equations (26) 4o
(28) it is obvious that static water level, Wt has no direct
influence on optimum screen length. However static water level
does affect total depth of well which affects the location of the
discontinuities in equation (26). Because of this Wt has a snall
effect on optimum screen length but calculations 3how the effect
to be no mo,-e than 5 feet for the usual rano:e of W't, and there-
fore, ne 'liibleo
Annual Utilization: Higher annual utilization allows
initial construction cost to be distributed over a larger volume
of water, reducing the relative importance of this component of
annual variable cost. The effect is an increase in optimum screen
length if greater utilization is anticipated (Figure 4). It .is
evident from inspection of equation (27) that proposed utilization
is a significant determinant of optimum screen length
Cost of Power: Variation in cost of power has a marked
influence on optimum screen length figure e 5). The relatively high
price of electricity in West Pakistan puts a premium on low total
head causing greater optimum screen lengths than expected in areas
of lower power cost9
Rate of interest and tubelell life: These factors
influence optimum screen length because they affect annual charges
on initial construction cost, CI, in equation (2). The constant
(0.09) in equation (2) is comprised of (i/2+1/L) where i is rate of
interest .znfl L is tubewoll life in years. Thus, a decrease in i
or an increase in L reduce the initial construction component(CIA)
of the cost of water. If annual charges on initial construction cost
are smaller, the use of greater screen length-to reduce power cost
is justified even though it increases initial cost. The effect from
varying interest rate is shown in Figure 6 and the effect from vary-
ing estimated life is shown in Figure 7.
Di.cuqsion and Conclusions
The values of many variables affecting screen dimension
including prices of components, cost of power and rate of interest
on initial investment are known for any given time and location.
Tubewell life is estimated on the basis of type of components used
and conditions prevailing in the area and must be resolved before
hand. For a given project area, therefore, these factors are given.
Aquifer permeability varies from site to site and in
large projects it is usually not possible to determine specific
vliluir for each site. However an appropriate design value for a
project area can be selected. Blank pipe also varies from tubewell
to tubewell but its length is determined at each location during
Within a project area, variables such as tubewell
capacity and anticipated utilization vary from site to site. In
order for an optimization process to be useful all combinations
of these factors neeil to be considered seprately,
Although radius of screen is an important variable in
tubewell design, sufficient parameters, are available to predetermine
this dimension for tubewells of different capacities prior to
installation. Length of screen, the most important consideration
in tubewell design, should and can be determined individually at
e:ch site at time of drilling.
Selection of Design Value for Aquifer permeability: Refer-
ing to equations (5) and (11), the most critical single factor
affecting optimum screen length is the inherent property of the
aquifer, permeability. Aquifer permeability varies from place to
place :-nd is extremely difficulty to predict accurately regardless
how colaplete have been the investigation and testing programs.
Figure 8 shows the influence of aquifer permeability on
cost per acre foot of water. Three heavy dots represent optimum
design for each permeability value. The curves radiating from
these points show the effect on water cost when actual permeabil.4y
conditions differ from the assumed value. When an incorrect per-
mehbility valuc is assumed, the cost of water is higher than when
the correct value is used. However, as can be seen in Figure 8,
the magnitude of deviation from optiimum varies with the choice of
assumed 'permeability. Thus, even though actual permeability at
each site is unknown, a value for use in desii'n can be selected
which results in minimum cost of water over a broad area if
distribution of permeability for the area is known
i'ortun;t:ely the variation of aquifer permeability in
the water yielding formations of the Punjab is rather small from
the geological point of view (Figure 9). Nevertheless, such a
variation, as well as practical considerations, defy the possibi-
lity of site by site estimation and establishing a precise per-
meability for design of every tubewelle
Figure 9 shows the distribution of aquifer permeability in.;:
Chaj Doab based on samples from installed tubewells, The mean value,
is (1.65 + 0.06) x 10-fps at the 95 percent probability level.
Considering this distribution and the effect on water cost shown
in Figure 8, a permeability value of K = 1.5 10 -fps has been chosen
for tubewell design purposes for this area.- There is evidence that
a.similar distribution occurs over the Punjab as a whole. If so, a
design permeability value of 1.5 x 10-3fps can be used over Ihe
entire region. However, if adequate test data are available to
determine permeability distributions for specific project or scheme
areas, savings can result from estimating individual design per-
meability values for each area.
Screen radius: Given an optimum design value for -'
permeability, the cost of components and other considerations,
optimum screen radius can be chosen. The primary choice criterion
17 T eoretl celermination o? an optimum design value For pesa
lity from known water cost and permeability frequency relations
can be demonstrated. Let
C =#1(Kd, K,. Qd
F =b2 (K)
where C is unit water cost, K is design permeability, K is
permeability at the site, Qd as design discharge, and F is the
frequency function of permeability in a project area. The
weighted average unit water cost is
Ave. 2 (K dk
where K and K2 are the upper and lower limits of aquifer
The optimum design value for permeability (Kd opt) can.be
obtained by solving
From examination of Figures 8 and 9, it is obvious that
the optimum design value for permeability for this area is
near, but smaller than, the mean K value .
.5 + . .-''
is.cost of water including consideration of both initial construction ... ,
cost and power cost.
Figure 10 shows the cost of water from a 2 cusec tubewell
with three screen radii, screen length being optimum in each case:.
Over all ranges of utilization, the cost of water from a 6 inch
screen (3 inch radius) exceeds the cost from 8 or 10 inch screen
There is no significant difference in cost between the latter. On the
basis of water cost, it appears that a 6 inch screen can be eliminated.
but thore is no means to choose between 8 and 10 inch screen. From
Figure 11, showing initial construction cost, the slight advantage
of the 8 inch screen is apparent. If capital for project construction
is scarce (perhaps more scarce than the 4% percent rate of interest
indicates) then this factor should be considered as the criterion in
choosing between screen of 4 and 5 inch radius. Alternately, if
power is relatively more scarce than capital (though the Rs 0.07/KWII
is quite high) the choice would have to be 5 inch radius (Figure 12).
For a 3 cusec tubewell the cost of water criterion alone
favors 10 inch screen though by only a small margin (Figure 13). The
initial construction cost and power cost criteria produce the same
conflicting; choices as for the 2 cusec tubewell.
The choice of screen radius for 4 and 5 cusec tubewells is
more cle.ir cut based only on the cost of water criterion. In those
two cases the savings in water cost definitely favor the larger
screen (Figures 14 and 15).
One further consideration can aid in choosing between 8
and 10 inch screen for the smaller capacity tubewells. Cost of
shipment of the screen is based on yardage rather than weight.
Eight inch screen can be inserted in 10 inch screen for shipment,
making an important savings in overall cost. In the absence oi
another definite choice indicator, this consideration favors the
use of 8 inch screen for the smaller capacity tubewells.
Optimum screen radius, therefore, is taken to be 4 inch
for 2 and 3 cusee tubewells and 5 inch for 4 and 5 cusec tubewells.
Tubewell capacity: Occasionally situations arise when a
choice can be made between tubewells of different capacities, e.g.
two tubewells of 2 cusecs capacity could be installed or one 4
cusec tubewell serving two closely situated watercourses could be
substituted. The cost of water criterion favors larger tubewells
in such situations (Figure 16). This results primarily from the
greater construction cost associated with two tubewells versus one
tubewell. However, if limited power generating capacity is an
overriding consideration, the larger number of small tubewells
would be chosen (Figure 17),
Screen Length: As shown previously, length of screen is
a function of a large nunb-r of variables. It has been shown that
screen length varies with such factors as tubewell life, rate of
interest, cost of screen, cost of power, length of blank pipe and
annual utilization. In the past it has been a practice to consider
screen length primarily as a function of tubewell capacity, ie.
L = AQ. This practice provides an easy means for determining
screen length in the field and, when A is properly chosen, results
in tube;wlls of relatively high economic efficiency. However,
because many other factors affect screen length the initial cost of
some tubewells thus designedl is higher than necessary and in other
cases a greater pumpini7 head than necessary is produced. Figure
18 shows the relationship between screen length per cusec of tubewell
discharge and utilization. Also shown for comparison are screen
lengths resulting from the practice of considering screen length
only as a function of tubewell discharge. The difference in the
magnitude and shape of the curves is an indication of the error
which can occur by an overly simplified method of screen length
Length of screen is the most important controllable
factor in tubowell design. After values for the fixed factors have
been established and capacity and utilization factors for a specific
tubewell have been determined, optimum screen length can be calculated
by a simple process on site at time of drilling.
Figure 19 is designed to be used in conjunction with the
weil log to determine optimum screen length and concomittant lengths
of housing and blank pipe as well as total depth of well. Based on
equations and values of parameters developed previously, graphs such
as Figure 19 can be constructed for various combinations of water
tahle and utilization factor anticipated. As drilling proceeds,
the inspector would lo- length of blank pipe required as shown by
the dashed line. When the log intercepts the curve in the upper
right hand quadrant corresponding to the capacity of woll being
drilled, approximate well depth would have been reached. A horizon-
tal line drawn to the left from the point of intersection to the
appropriate curve in the upper left quadrant specifies optimum
lergth of screen and a vertical line from this point to the appropriate
curve in the lower left quadrant specifies proper length of housing
*' ; ., .. . ( .8 ,, ,'., -:,
pipe. Rounded values of blank pipe, screen ani, housing: wiou-ld be'
entered in the lor,'r right corner and thtkir sum would giv? actual
Thus, embodied in Figure 19 are all the components of
tubowell design which can be measured and specified at time of
tubewell con-truction. The use of this figure provides a simple
process by which tubewells of optimum dimensions can be constructed
throughout a project area. Becau e of the ease of incorporating
this process, it can be substituted for other methods of tubwwell
design which result in non-optimum dimensions for many wells in a
Definition of Symbols
D Length of blank pipe (feet)
b A factor indicating blank pipe as a percent of screen length
C, Annual cost of electricity (rupees)
CI Initial Tubewell construction cost in rupees (including
only those items which vary with screen dimensions)
CIA Annual cost of tubewe.ll construction (rupees)
C Annual variable cost of water (rupees)
JS -iffPect 0f a 4taurr C70ei
D. Amount of drilling at various depths (feet). When D) -300'
i = 1; 5 0') < ) ) 400', i= 2; 400' < D 500' i = 3.
D Depth of well (feet)
f Pipe friction factor
G, Depth of gravel shroudin,; (feet)
g Acceleration of gravity (feet per second per second)
IId Total dynamic head (feet)
II Length of pump housing pipe (feet)
Ht Total pumping head (feet)
hf Friction loss in column pipe and discharge pipe (feet)
h Discharge velocity head (feet)
K Aquifer permeability for water (feet per second)
Kg Gravel pack permeability (fert per second)
L equivalent length of column pipe and discharge pipe (feet)
L Length of screen (feet)
Pb Unit price of blank pipe (rupees per foot)
1' Unit cost of drilling (rupees per foot)
PG Unit price of gravel shrouding (rupees per foot)
PtG Unit price of pump housing (rupees per foot)
' Unit price of screen (rupees per foot)
Q Tubewell discharge in cubic feet per second (cusecs)
rs Radius of screen (feet)
r Borehole radius (feet)
s Total tubewell drawdown (feet.)
U Annual utilization expressed as percent
Vt Ultimate depth to static water level (feet)
COST PER ACRE FOOT OF WAT Vs
S TUBtWELL CPAL\PLTY = 4 cUSt$CS
5CREE(N RAN1US = 4 N .
EPTHR TO STATIC, WATtR. LEAVE L= 20 FT .
LIFE OF TUBtWELL = 15 Y'EAV5
-UTILtZATION FPLTO. 60 %o
N-TEREST RATE = -43 'o
too 200 300 AOO
- I I I i IN .., 1I I -
TUBEWELL SCREENN LENGTH ,r.
__ _ __ __
.t _.I.' C-
5 rUiiM - TOT L Co ST
:: 2: : - i
~;~ : r
";; :': r
5lANK P!P As EC4~C~r EQW5 CREET L~N~iVH Y. OPTriii4Uh~ Lthc~H sFi
3' '3 3
vu174zkf0i'$ r-CArfr 3-60
f- .S -ELP4 4 irN
TO _iTA11I C. 'WTtz EML: 2 OF-t
OprrmUM 5CRE.EN LE.NC-H -Pr.
3 4 3 3 .
4;r. 3 ~ i
300. * .
~ -~- -~- -~ m
S C.P e N
,- I..- r
i 1-- :
PRICE. OF SCAECN Vs. OPTIMUM SCREEN LE1I'TH
50 loo 150 200 250 300
UTILZAOto t r-c-TOR GO
1LojUS oF Sc 14 w .
M4 TO ST-TIC. watlc. .EEV= 2OFt.
LL) 170:) 701
50 10. 0o.
OMMTIUM SCREEN LENMT~H.
TILlZ4 TOR Viw.1 OPTIMUM
OPTIMUM: C' E.E LENGTH, FT.
o 100 "
DEPTI TO STATIC WATER LEYTL= 20~.,
SCLE RDlU5 = 40
- ` 1 -- ---~--~---'--
POWER COST Vs. OPTIMUM SCREEN LLECGTH
- too. --- T
/ RADIUS OF SCREEN 4 N4
SOTEP TO STl I c-A WkErLt.EL 20 FT.
UTIUZATIOoN FACTOR = 0%
OPTIMUM SCRLED LESJCTH, F-.
RATE OF INTEREST YV. OPTIMUM SCREEN LEJN4G
50 100 150 200 250 300
-20 DEPT o -IQ SAI.IC WAs. LevrL- =2O v. 20 -
SRMDU5 OF SCREEN = 4 .
\ UTILIZATION FACTOR f%
5 \ \
50 too 200 250 300
15 I \ 15
\ +3 *
S\ \ \
90 rO0 MSO 200 2.5 300
.,I1 I I _1__ 1 ____t ,_I _
OPTIMUM SCREEN LENGTH, Fr.
LIFE OF TUSEWELL Vs. OPTIMUM SCRS.Er .LENG I i
-~ r rr
h-40 -. I I
; ; i.: i/
soL .. 200
O..Pu.Ai .SCREE.N IENGTHi, FT.
M CAGL. kE
RWW~j OF SCREWi .
EPIH *TO S~IIC. "MTE Wjv 20-v,.
250. s oba
:- * : ;
' .i.*: i' ^ '-. fl '1'- ':
^* "/ : ^ i. .*:: -p
4 :- ~
, ; rl. -- .P '?~
"; - -: ~ " : --.:
~ - .-
I i. I' 2I I
n 1.0 2.0 2.5
TUMWALL, CAPACITY =4 CUSCES .
52.tEN A'US A 1N.
D\ PTH TO STATIC 'WTEi. LEV EL 2o0r.
TnlLZ.ATMoN VTorv 60.
3Pon'Um DEmIq W/mt. CoeUixrLT
ASuaJ1ss AWJ'FeR PBMEASiLrFY
ppljrMUM dAt L"JW&Gthe DESlGNLD
ON THE 54IS 'O A ,iQre PERMM.,ILTy "
- .= 9"74 BSI' O .6..'"a L
ON T.. As AAut5o 1E:,U-TY
K J.50 tolI FT/E. . -
----OPTIMUM 6tCAEeI LQT14 DESrtIGND On
TE SAas ov AQUIVEIR 9U 1ssLWBY
K .--2 .o. m Fi.irsec. O
AQUIFER. PtRME8BluTY, IO FTr/sc.
COST OF WATER Vs RPADIS OF SCR.Et
A e 0 d
TU BWELL CAPK'TY 2
DEPTH TO 5TATIC WATER LEVEL
40 60 80
CUSEC5 I _
A... DEPTL ~ UAEL
-= Z F'r.
UTILiZATION FACrD PE.CCEPt I
C T R-.
*NITAL CIOH$TVRUCTON CO$ VJ-i RADi&)S. OVF 5CIIUJ~
~ 1 :..
-1 ..~. .
[. :,. ,''
POWER COST Vs R.ADIUS OF SCREEN
TuBEw utL CAPAcATY = 2 CU5ECS
DEPTH TO STATIC WATER LEVEL = 20 FT.
UTILIZATION FACTOR PE cE.NT
COST OF WATER Vs RADIUS OF SCREEN
06 60 SO
DEPTH TO STATIC WATER LLVEL 20 Ft.
in -87 7-
COST OF WATER Vs RAtDIUS OF SCR tEE
UTIL\2ATION FACTOR PERCLi
COST OF" WATER Vs. QADIUS OF SCRaiX
40 60 b
TUSEWYALL CAPACITY= S CusECS,
S DEPTH TO STATIC WATER LEVEL 20 Ft.
-14 I : 14
SI UTILIZATI ACTO PE
UTILIZATION -FACTOR. P-.CENT .
GU CE 15 .
COST OF WATER Vs TUBEWELL CAPACITY
(OPTIMUM SCREEN DIMENSION)
UTILIZATION FACTOR, PERCENT
POWER COST Vs TUBOWELL CAPACITY
(OPTIMUM SCREEN DIMEN51ONS)
EPTH TO STAC WATER LEVEL 20
DEPTH "TO STATIC WATER LEVEL = ZO Fr.
40 GO 80
U II I A ,
UTILIZATION FACTOR PERCENT.
-SCR.EN LEN.CTH PER CUSEC Vs. TUBEWEUL CA.Pb~\TY
LI/Q = 50 ; Q 34,5 CUSECS
BASED ON SIMPLIFIED
Ls/Q= 40; Q=2 CUSECS
NOTE'. DEPTH TO STATIC. vATER LEVEL= 2.0 FT.
SCRCLEN RADIUS Fo. 2&3 CUSEC TUBEWELL= IN.
SCR-.EEN RADIUS FDo 4 & 5 CUSEC TUBIEELL= 5 IN
i 35 8 O
S A 60
UTI LtZATION -ACTOR PERCENT.
C/ s- ___
to0 t5o 200 250
DEPTH OF WELL, r-
TO STATIC WJVTEP. LEVEL 20PT-