Section 10.3: Large-Sample Hypothesis Tests for a Population Proportion.
Large Dia Well Tests
84
1 P T A – LARGE DIA P T A – LARGE DIA By A.V.S.S.Anand Scientist Central Ground Water Board Government Of India ([email protected]) ANALYSIS OF PUMPING TEST DATA LARGE DIAMETER WELLS
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Transcript of Large Dia Well Tests
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By
A.V.S.S.AnandScientist
Central Ground Water BoardGovernment Of India
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Types of Formations
Aquifer
Aquiclude
Aquitard
Aquifuge
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Types Of Formations
Homogeneous
Heterogeneous
Isotropic
Anisotropic
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Types Of Formations
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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State Of Flow
Steady State
Unsteady State
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Direction Of Flow
Fully Penetrated
Partially Penetrated
ANALYSIS OF PUMPING TEST DATA
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Types Of Aquifers
Confined
Semi Confined
Unconfined
Semi Unconfined
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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For Optimum Utilization Of Ground Water Resources
Understand fully The aquifer
If Large diameter wells are used
No Additional Cost Of Construction etc
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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It Is not Simple To Analyse This data Because
Effect Of Storage
Partial Penetration
Other Factors
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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DUG WELLS
Basically These are production Wells
Not Properly Designed For testing
Can Not Be Used Indiscriminately for
Aquifer Performance test
Can Be Used For Yield Characteristics
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Basic Objective Of a Test
Performance of a Well
Evaluation Of Hydraulic Parameters of
the Aquifer
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Large Diameter Well
Excavations in the Ground to Shallow
Depths having Significant Water Storage
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Types
Masonary Wells
Wells With Pervious Lining
Kutcha Wells
Wells In Hard Rocks
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Masonary Wells Have Masonary
Steining wall sunk in subsoil by applying static weight and simultaneously scooping out the earth from inside.
Entire water supply is drawn from from the pervious bottom
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Wells With Pervious Lining
Wells Are Lined with cylinders of intertwined brush wood or bricks laid dry.
In between dry masonary some bands of pucca masonary are provided for stability
The wells are plugged at the bottom by concrete
Constructed in areas where yield potential is less
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Kutcha Wells These are Unlined Wells Usually Dug in Hard Soils. They Stand Vertically
Without Lining Relatively wider pit is dug
upto just above water table. Below which normally
narrowed down usually lines with woven fabric of hemp stems or mattings etc. through which water oozes into the pit
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Wells In Hard Rock Areas
Usually Open Excavated Pits through top soil mantle and weathered rocks.
Generally Constructed in Large sizes to provide storage and also in order to tap more joints, cracks or water bearing weathered zones.
Top portion is normally lined.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Pumping Test
Is A Controlled Field Experiment To Find Out The Hydraulic Characteristics Of An Aquifer Or The Yield Characteristics Of
A Well
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Types of Pumping Tests
Aquifer TestsA Pumping Test Performed to Determine the Hydraulic characteristics of an Aquifer.
Yield TestsA Pumping Test which provides information about the yield and drawdown of a well.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Since the dug wells are not specifically designed to be used as test wells for evaluation of aquifer parameters, the selection of proper dug well needs utmost importance
It should be representative of the aquifer
Design Should be such that most of the limiting conditions should be fulfilled.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Procedure For The Test
Water is pumped from a dug well at a constant discharge for a certain time.
The effect of the pumping i.e drawdown is measured in the pumped dug well and in some piezometers if provided in the vicinity of the dug well.
Recovery is also recorded after cessation of the pumping.
Drawdown/ recovery data is analysed using applicable method.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Limitations Of Analysis
Definition of a Large Diameter Well By Sammel (1974)
A well in which storage is large enough to produce significant errors when aquifer tests are analysed by methods which neglect well storage.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Limitations Of Analysis
Basically Production Wells Discharge from the Formation is always less
than the Actual Discharge. Cone of Depression starts from the walls of
the well only after some time is elapsed. A Seepage face is formed I.e the drawdown in
the centre of the well is always more than the drawdown in the aquifer.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Limitations Of Analysis
Even After cessation of pumping it is often recorded that water levels in the Observation wells continue to show decline.
In hard rock areas these wells are normally fully penetrating where as in alluvial areas generally these wells are partially penetrating. The flow will be from lateral as well as from the bottom.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Preference
Preferably The analysis of pumping test data should be attempted for only those large diameter wells which can sustain long duration pumping and preferably provided with observation well/ wells.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Yield test
Main Objective is to have an idea of the maximum quantity of water which can be pumped out from a dug well either by continuous or intermittent pumping.
It also reflects upon the yield characteristics of the aquifer tapped.
Helps in selection of pumps.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Procedure For The Test
Water is pumped from a dug well for a sufficient time till either the well is emptied or the water level falls beyond the reach of the installed pumping device.
Drawdown and recovery data are recorded during pumping and after the cessation of pumping respectively.
Drawdown/ recovery data is analysed using applicable method for the evaluation of Yield characteristics.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Limitation
The yield characteristics of a dug well is dependent on the saturated thickness of the aquifer tapped which shows a wide variation in different seasons especially in hard rock areas.
Hence yield test should be conducted for both pre and post monsoon seasons.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Methods Available- Aquifer Tests Slichter(1906)
Muskat (1937)
Hvorslev (1951)
Raju & Raghava Rao (1967)
Papadopulos – Cooper (1967)
Adyalkar & Mani (1972)
Kumara swamy (1973)
Zdankus (1974)
Boulton & Streltsova (1976)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Methods Available- Aquifer Tests
Herbert – Kitching (1981)
Rushton and Holt (1981)
Rushton and Singh (1983)
Singh & Gupta (1986)
Roushton & Singh (1987)
Artificial Neural Networks
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Methods Available- Yield Tests
Karanjac (1975) Saleem Romani (1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Slichter’s Method(1906)Assumptions: Large Diameter Well Vertical Impervious Wall Flow is Only From The BottomProcedure: Well is Pumped For Some Time So That the
water level in the well is depressed to a level less than safe working head.
Recovery performance is recorded.
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Slichter’s Method(1906)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
ss
t
AC
2
1log30.2
Where,C= Specific CapacityA= Cross sectional AreaS1 = Drawdown when Pumping stoppedS2 = Residual draw down at time t’ after
pumping stops
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Slichter’s Method(1906)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Time Since Pumping Stopped is plotted on Arithmetic Scale and the Ratio between s1 and s2 is plotted on Logarithmic scale
Plot tends to fall on a straight line if the flow is only from the bottom
Take an arbitrary point on the line Obtain t’ and s1/s2 for that point Substitute in the equation and
calculate C.
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Limitations
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Slichter ‘s equation is merely an expression for volume change of water in the well.
It has no theoretical validity in terms of flow into the well.
This can not be used to compare with specific capacity determined by the methods of Theis etc
However this can be used to compare the performance of dug wells of similar types.
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Muskat’s Method(1937)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Muskat Extended the use of Slichter’s equation for estimation of Transmissivity by combining Theim’s Solution for steady state flow.
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Muskat’s Method(1937)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
ss
et
ACT
2
1log2
Where,
A = Cross Sectional Arear0 = Distance at which drawdown is negligible at the end of pumpingrw = Radius of the well
s1= Drawdown at the time pumping stops
s2= Residual Drawdown at time t’ after pumping stops.
we r
rC 0log
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Muskat’s Method(1937)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Validity Of Theim’s Equation Confined Aquifer Lateral Flow into the well Steady StateValidity Of Slichter’s Method Flow in the well is only from the
Bottom
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Muskat’s Method(1937)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Valid only for dug wells tapping confined aquifers with the well ending at the bottom of the confining Layer
Serious Limitation is to estimate the distance to a point of zero drawdown
Muskat & Slichter have assumed the value of r0 to be in between 500 to 600 ft for Alluvial Aquifers.
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Adyalkar & Mani’s Method(1972)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Assumed that the value of r0 to be in between 150 to 250 ft for Basaltic Aquifer when the Muskat equation is used for Unconfined Aquifers.
T=C’*580
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Hvorslev Method(1951)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Based On Recovery Data Takes Storage into Consideration Very Similar To Slichter Shape Factor is Introduced Shape factor Depends on the radius Of the
Well and the Nature of Intake Area.
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Hvorslev Method(1951)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,a = Well RadiusS = Shape factorK = Permeabilityh1 , h2 = Drawdowns at t1 and t2 Times
If water enters through base only the Shape Factor = 2* Diameter of the Well.
Shape Factor was derived based on the studies from Small Diameter Wells.
tthha
SK
12
21
2 lnln
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Raju & Raghav Rao Method(1967)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
This Method Describes a Procedure to Classify the Portion of the time – Drawdown Plot
that can be utilised for the analysis. Plot t versus Cumulative inflow Find a part of the graph in which the data
points fall nearly on a straight line Apply Cooper – Jacob (1946) Straight Line
method only for that particular data set.
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Felt That conventional methods for the estimation of T & S can not be applied in hard rock areas because of their anisotropy and occurrence of flow in the well through Fissure planes or conduits.
Hence Developed a mathematical equation defining the inflow into a well in hard rock areas.
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Assumptions Flow into the well is only through Very minute Fracture Conduits or
Fissure Planes opening through the inner surface of the well. The water travels from an outer feeder Surface limited to Short
extents from the well The flow in the planes is laminar The Operational depth of well is reckoned below the static water
level. No Flow Occurs above Static Water Level No flow is assumed to enter the well through the bottom of the well. The SWL outside Feeder Surface is not Declined.
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,W= Hard Rock Permeabilitya = Cross Sectional AreaD = Static Water Columnd1 = Water Column when pumping stopped.
d2 = Water Column at tR minutes
tR = Time Taken For Recouperation
Rt
DdDd
DdDd
D
aw
/1/1
ln/1/1
ln1
1
2
2
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,Qmax= Maximum inflow Capacity Of the well
w = Hard Rock PermeabilityD = Static Water Column
2max wDQ
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Kumaraswamy Method(1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,tR(max) = Time Taken For 99% Recovery
a = Area Of Cross SectionD = Static Water ColumnQmax= Maximum inflow
max
2645(max)
Q
aDtR
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Zdankus Method(1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Aquifer has an apparently infinite areal extent. In General Aquifer is Anisotropic Unsteady State Flow into the well of large diameter becomes
steady State Flow after some time due to its hydraulic parameters.
Aquifer is unconfined Fully Penetrated. Hydraulic Conductivity of the aquifer at the level of well is
constant. Well is pumped at a constant discharge. Specific Yield of the aquifer is to be assumed.
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Zdankus Method(1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Zdankus Method(1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Modified the Theis Unsteady Confined Radial Flow Equation
UrRQ wiK 2
/lnWhere,K =Hydraulic ConductivityU = Drawdown FunctionQi = Discharge of Ground Water inflow into the well
R = Conditional Radius of Influencerw = Radius of the Well
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Zdankus Method(1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
20
0
sHU s
Where,U = Drawdown FunctionH = Thickness Of The Saturated Zone
s0 = Drawdown in the aquifer recorded on the wall of the well or in the observation well.
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Inflow discharge during Pumping
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
t
srQQ w
i
02 *
Where,Qi = inflow discharge
Q = Discharge of Water Pumped
rw = Radius Of Well
s’0 = Decline in Water level in the well per t Time interval.
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Inflow discharge during Recovery
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
t
srQ wi
0
2 *
Where,Qi = inflow discharge
rw = Radius Of Well
s’0 = Rise in Water level in the well per t Time interval.
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Conditional Radius Of Influence
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
25.225.1
20 w
Y
rsH
S
KtR
Where,R = Conditional Radius Of InfluenceSY = Specific Yield
H = Thickness Of The Saturated Zone
s0 = Drawdown in the aquifer recorded on the wall of the well or in the observation well.
K = Hydraulic Conductivity
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Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Record drawdown in the well as well as in the aquifer for each time step
Compute decline/ increments of water levels for each time step
Calculate inflow discharge for each step Compute drawdown function for each time
interval. Compute mid time for each time interval. Determine the value of Qi /2U Assume SY and Compute values of K by trial
and error method.
UQ
w
i
rR
K2/ln
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Assumptions & Conditions
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Aquifer has an apparently infinite areal extent. Aquifer is homogeneous, isotropic and of uniform thickness over
the area of influence. Prior to pumping the phreatic/piezometric surface is horizontal. Discharge is constant. Pumped well penetrates entire aquifer – Horizontal Flow Storage can not be neglected. Aquifer is confined Flow is in unsteady state. Well losses are negligible.
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Papadopulos - Cooper Method(1967)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
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Papadopulos - Cooper Method(1967)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,
s = drawdown
Q= discharge
T= Transmissivity
),,(4
F
T
Qs
w
c
w
r
r
r
Sr
Sr
Tt
2
2
2
4
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Papadopulos - Cooper Method(1967)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,
sw = drawdown inside the well
Q= discharge
T= Transmissivity
WT
QF
T
Qsw
4
)1,,(4
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Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Get Or Plot Master Curve on Double Log F(, , ) Vs
Plot on Another Double Log s Vs t Superimpose – such that most of the points
match Choose an Arbitrary point Get values s, t, F(, , ), for the match point Substitute in the equation to get T Calculate S For reliable results sufficient part of data curve
should match with master curve.
Ws
QT
w4
2
2
2
4
w
c
r
rS
r
TtS
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Roushton and Singh Method(1982)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Papdopulos and Cooper Type Curves show a straight line behavour in the early part of the data curve corresponding to storage effect.
Due to the similarities of the curves for different storage coefficients, some times difficult to identify appropriate type curve.
Roushton & Singh gave an alternate approach to overcome this. Introduced well drawdown ratio
t
t
s
sratiodrawdown
4.0
64P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Roushton and Singh Method(1982)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Drawdown ratio normally varies from 2.5 to 1 Initially when water comes from the storage the ratio
will be 2.5 When in equillibrium conditions it approaches 1
t
t
s
sratiodrawdown
4.0
65P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Roushton and Singh Method(1982)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Drawdown ratio Vs Time Function
Data Plot Drawdown Vs t Data Plot need to be matched with the type curve. Get values for the match point
24.0
4
wt
t
r
TtVs
s
s
t
rT w
4
2
66P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Boulton and Streltsova Method(1976)
Assumptions & Conditions
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Aquifer is Compressible and Anisotropic Underlain by horizontal impermeable bed Pumped at Constant rate. Well losses are negligible.
67P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Boulton and Streltsova Method(1976)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
68P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Boulton and Streltsova Method(1976)
Assumptions & Conditions
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Q = Discharge
s = Drawdown
S= Storage Coefficient
T = Transmissivity
r = horizontal distance
rw = radius of the well
y = depth of any point below water table
y’ = y/h = r/h
w = rw/h
Sr
TtQ
TsW
WT
QSyllF
T
Qs
w
2
1
4
44
),,,,,,(4
l = Distance from water table to bottom of the unlined part of the abstraction well.
l1 = Distance from water table to the top of the unlined portion
l’ = l/h
l’1= l’/h
69P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Boulton and Streltsova Method(1976)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
If the values of l’,y’, and r/rw are near to those values given, this method can be applied.
If they are not matching trial and error method can be adopted W vs on double log paper for different values of r/rw s Vs t data curve Superimpose for a match Choose an arbitrary point Get values of W, , s,t and note down of the type curve. Substitute in the equation to Calculate T Calculate S by substituting r, , t and T. For Computing Specific Yield Type B Curves Should Be Used
Sr
TtQ
TsW
2
4
4
70P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Singh & Gupta Method (1986)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
A numerical Modeling Method Applicable even when abstraction rate is not constant Breaking the entire test into number of equal time
steps. Calculate the response of the aquifer from each of the
time step. Abstraction rate is assumed constant during each
step. Drawdown is small compared to saturated thickness
of the aquifer. Seepage face is neglected.
71P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Singh & Gupta Method (1986)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
)4
(4
)24
(4
)4
(4
)4
(4
22
21
21
2
21
1
tT
SrW
T
Q
tT
SrW
T
Q
tT
SrW
T
Qs
tT
SrW
T
Qs
T
SrY
TX
tj
YW
tj
YWQXs
n
jjnn
4
4
1)1(
2
1
0
72P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Singh & Gupta Method (1986)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Basically Iterative Process and Calculates the
Drawdowns with the assumed T & S Values. It Should be repeated till the error in between
measured and observed drawdown is within permissible limit.
73P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Artificial Neural Networks
74P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Yield Test
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Main Objective is to have an idea of the maximum quantity of water which can be pumped out from a dug well either by continuous or intermittent pumping.
It also reflects upon the yield characteristics of the aquifer tapped.
Helps in selection of pumps.
75P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Karanjac’s Method (1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
When a Large diameter well is pumped at a Constant Discharge ( Qp) for a known time (tp), the total volume of the water discharged from the well can be separated into two parts
Volume of water stored in the well between pre and post pumping levels.
Volume of water aquifer yields
76P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Karanjac’s Method (1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Where,
Qr= inflow rate during well recovery
tr = time taken for the recovery
Qp= Rate of pumping
tp = Time taken for pumping
rp
ppr
prrrpp
tt
tQQ
tQtQtQ
77P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Karanjac’s Method (1975)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Used the value of Qr to define the optimum yield of the well
If a well is pumped at this discharge, the well will never go dry.
78P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Karanjac’s Method (1975)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Pump the well till substantial drawdown is created
Measure the discharge(Qp) and pumping time(tp)
Stop the pump and record the time needed for recouperation (tr)
Calculate the Optimum yield.
79P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Karanjac’s Method (1975)
Comments
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Difficult to know the time of complete recouperation
Qr is always a fraction of the installed pump capacity
On low transmissivity areas it is very difficult to pump with Qr.
80P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Romani’s Method (1973)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Record Static Water Level
Pump the well with constant discharge.
Record Drawdown with time
Record the time at which the well is dry or the well reaches the optimum lifting capacity of the pump(t1)
Record recouperation with time after stopping the pump.
81P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
Romani’s Method (1973)
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
82P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Romani’s Method (1973)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Plot dd/rdd vs time on arithmetic paper
Draw a line of 50% recovery
Record time to empty 50% of the well (t2)
Record time for 50% recovery (t3)
Compute n
32
1720
tt
tn
83P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA Romani’s Method (1973)
Procedure
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
Compute Optimum Yield
)( 21 nttQY
84P T
A –
LA
RG
E D
IA
P T
A –
LA
RG
E D
IA
ANALYSIS OF PUMPING TEST DATA
LARGE DIAMETER WELLS
