Lab 7: Well hydraulic analyses using Macpump program
This lab introduces MACPUMP, an aquifer-test-analysis package for use with
Macintosh computers. Aquifer tests are used to make field measurements of
hydraulic properties (transmissivity T and storativity S) of groundwater
systems. Aquifer tests typically involve imposing a change in stress (pumping)
and monitoring responses in the system (change in hydraulic head or drawdown
of water table over time in observation wells). The data may be analyzed
using nonequilibrium theories such as Theis theory and Jacob method.
Practical implementation of the theory includes a comparison or overlaying
of plots of observed data with "type-curve" (theoretical curve)
solutions. When a best-fit is obtained between the data and the type curve,
the coordinates at an arbitrary "match point" are use to solve
the appropriate equations for calculating the hydraulic properties of the
aquifer. The traditional manual exercise can be very time consuming (as
we suffer from the last lab). This lab we use an interactive graphic computer
packages to do the job.
Tutorial 1 - Theis Method
1. Enter the application by double clicking the "Macpump" icon.
Next a "output" window appears, this window will disappear after
about 5 second. Choose whether to run the program without help windows by
selecting the appropriate radio button. Next click on the push-button corresponding
to your monitor screen size (13 inches). At this point, a Macpump logo window
appears, providing information about the program, this window will disappear
after a few second.
2. Read in the example data file "Lohman p19.pump" by selecting
the Open item under the File menu. The standard system window for opening
files will appear. Move to the 'Macpump' directory and double-click on the
file. The data will be display on the screen (careful examine the parameters
entered in this file). Click on the 'more' button to see the whole file.
Click on the OK button to move on to the next screen.
3. Now plot the data to the screen by choosing the Plot Data under the Plot
Options menu, which will produces the plot in window.
4. Choose a solution: select Theis, 1935 under the Solutions menu. The program
calculates points along the curve. It then overlays the type curve on the
data with scaling factors on both.
5. Observe that more of the Theis curve than necessary is plotted and, consequently,
the data are clustered in only a small area of the plot. To change the 1/m
interval over which the curve is plotted, select Curve Range under Plot
Options. The program will display the present minimum and maximum 1/m values
and prompt the user to enter the new range by specifying the integer exponents
of m. To decrease the maximum 1/m by several log cycles, enter "-1"
in the first box (means 1/10-1 as the minimum) and enter"-3" in
the second box.
6. To fit the curve to the data, depress the mouse button and move the mouse
pointer. The type curve will follow the mouse's movements which the button
is down, centering itself around the pointer. The procedure is easiest if
the button is pressed continuously until the best fit is obtained.
7. After getting the best fit to the data, choose the Select Matchpoint
menu item. Select an arbitrary match point (You don't have to select W(m)
= 1 and 1/m = 1 as the match point, since the program will do all the calculation)
by moving the mouse pointer to the desired location and pressing the mouse
button. The program will computer the matchpoint coordinates and display
them on the screen. The match point may be changed by choosing Select Matchpoint
again and repeating the procedure.
8. Pull down the Calculations menu and select Output units; choose feet
and days. To calculate T and S, choose Compute T/S/K. The program will display
the values at the top of the window.
9. To make a printout, press "Command-Shift-3" keys all at once.
This will make a snap-shot image of the screen. The output file will appear
as "Picture 1", "Picture 2" on the Hard disk. Double
click on the Picture icon and it will be opened in TeachText, you then can
print the plot from TeachText. You can also import the images into your
favorite drawing program (such as Canvas) as a PICT file.
Tutorial 2 - Cooper and Jacob method
We will perform a straight-line (Cooper and Jacob method) on the same data
set "Lohman_p19.pump".
1. Choose the Cooper and Jacob t-s, 1946 menu item under Solutions. The
program will produce a semi-log plot of drawdown as a function of time and
a straight line that can be moved to fit the data. Drag the endpoints of
the line by locating the pointer below the x-axis (by clicking any space
below the x-axis) or to the right of the graph box and holding down the
mouse button. You need adjust the line from both both sides (below x-axis
and right of box) to get the best fit (need practice!).
2. After achieving the best fit, pull down the Calculations menu and select
Output units; choose feet and days. Now you can select Computer T/S/K. The
program will find t0 and calculate T, S, and tcritical for u<0.05. Data
before tcritical should not have been considered in fitting the line.
Exercise 1
A well has been drilled in order to test the hydrologic properties of an
aquifer. It was pumped at a rate of 220 gal per minute (1 gal = 0.134 ft3),
while an observation well 824 feet away was used to observe drawdown. The
drawdown and time data are shown on page 66 of Lee and Fetter.
Now open file 'Lee_p66.pump' (or as a practice, you can create your own
file,which can be assembled using any wordprocessing program, spreadsheet,
or text editor that can created ASCII formatted files. When using a word
processing program, be sure to save as "ASCII" or "text only").
The file looks like the following:
'PUMP'
'Data from p 66 of Lee and Fetter (1994)'
C -- Units:
'days' 'feets'
C -- Q r
42451 824
C -- Time s
0.00239 0.4
0.00347 0.74
0.0043 1.00
0.00555 1.35
0.0064 1.55
0.0086 2.08
0.0115 2.70
0.0139 3.02
0.0209 3.95
0.0417 5.71
0.0694 7.03
0.139 8.45
0.223 9.87
0.264 10.20
0.347 10.98
In this input file, the first variable string 'PUMP' indicates the test
method offered by time-drawdown aquifer-test data. Next the title is read.
Next line is a comment line, indicated by a 'C' in the first column. Comment
line are ignored in executing the program. Input units are also specified
by character strings. Units for times can be 'seconds', 'minute', or 'days'.
'days' is specified in this input file; length specifier include 'inches',
'feets', and 'meters'. Q is the pumping rate (has been converted to ft3/day)
and r is the distance (in ft) between pumping well and observation well.
Data in two columns are time and drawdown.
Use Macpump and perform the following modeling:
1. Compute the T and S of aquifer using the Theis method employed in Macpump.
2. Compute the T and S of aquifer using the Cooper and Jacob method employed
in Macpump.
3. Do your results agree with those calculated by hand in the previous lab?
Exercise 2
In the final exercise, we will calculate the T and S of fractured Opelika
metamorphis schist underneath the Auburn Fisheris Field Station. Now open
file 'fish.slug' (or as a practice, you can create your own file,which can
be assembled using any wordprocessing program, spreadsheet, or text editor
that can created ASCII formatted files). The file contains the H/H0 as a
function of time based on our field slug test. Now open the input file I
have prepared for you
'Slug test'
C -- time length
'seconds' 'feets'
C -- H H0 LWell rWell rgrvpck
3.1 0.9 300. 0.33 0.076
C -- Time head
0. 0.9
5 1.85
10 2.08
15 2.22
20 2.35
25 2.45
30 2.51
40 2.61
50 2.68
60 2.73
70 2.77
80 2.79
90 2.82
100 2.84
.. ..
.. ..
In the input file:
H: depth of initial water surface (from landsurface) = 3.1 feet
H0: depth of water surface immediately after adding water = 0.9 feet
h: depth of water (from the surface) at time t
rwell: raduis of well casing = 0.33 feet
Note1: Data collected by pressure tranducer are heights of water column
above the initial water level (=H-h). In the input file, you need to enter
your data as h (depth of water), rather than height of water column collected
by transducer. Calculate h using 'h = H - water height' (I have done this
for you). The program calculates 'H/H0' as _F(H-h,H-H0)
Note 2: The parameters "Lwell" (Length of the well screen) and
rgvpack (radius of gravel pack, see Fig 7.21 of Fetter) are not required
in the slug test designed by Cooper et al. (1967), but they are required
for the Hvorslev test (p. 247, Feeter), a special slug test for piezometers
that do not fully penetrate an aquifer.
Use Macpump and perform the following modeling:
1. Compute the T and S of aquifer using the Cooper et al. (1967) method
employed in Macpump.
2. Do your results agree with those calculated by hand in the previous lab?