Navigation:  Demonstration Exercises and Benchmark Tests >

Exercise 4: Confined Aquifer, Multiple Pumping Wells

 

In this exercise you will learn how to use AquiferTest to not only determine aquifer properties using discharge and drawdown data, but also how to use these values to predict the effect that an additional pumping well will have on drawdown at the observation well. You will also learn how to predict the drawdown in a well at any point in the effective area of the pumping well(s).

This exercise is divided into 3 sections: To begin, you will create a Theis analysis to determine the aquifer parameters. Then, you will examine the effect a second pumping well will have on the drawdown at the observation well used in the first section. Finally, you will predict the drawdown at a well at any point in the effective radius of the pumping wells.

Determining Aquifer Parameters

 

[1] Launch AquiferTest and from the landing page ensure that the "Create Pumping Test" box is checked and choose the "Create a new project" button. If you already have AquiferTest open, create a new project by clicking the (New) button from the toolbar, or select File/New from the main menu.

[2] Complete the fields in the pumping test tab, as follows:

In the Project Information frame:

Project Name: Exercise 4

Project No.: 4

Client: ABC

Location: Your Town

In the Pumping Test frame:

Pumping Test: Theis - Multiple Pumping Wells

Performed by: Your Name

Date: filled in automatically

In the Units frame

Site Plan: ft

Dimensions: ft

Time: min

Discharge: US gal/min

Transmissivity: ft2/d

Pressure: mbar

In the Aquifer Properties frame

Thickness: 40

Aquifer Type: Unknown
 

[3] In the Wells table, complete the following information for the first (pumping) well:

Well 1

Name: Water Supply 1

Type: Pumping Well

X: 350

Y: 450

R: 0.3

L: 50

r: 0.25

Next, create two additional wells.

Click Click here to create a new well, to add a new pumping well

Well 2

Name: Water Supply 2

Type: Not Used (this pumping well will be activated later in the exercise)

X: 350

Y: 100

R: 0.3

L: 50

r: 0.25

 

Click Click here to create a new well, to add a new observation well

Well 3

Name: OW-1

Type: Observation Well

X: 350

Y: 250

R: 0.06

L: 50

r: 0.05

 
 

[4] Click on the Discharge tab

[5] Select Water Supply 1 from the well list

[6] Select Variable in the Discharge frame

[7] Enter following values in the Discharge Table, and the discharge tab should look like the image below:

Time

Discharge

1440

150

[8] Click on the Water Levels tab.

[9] Select OW-1 from the well list. For this exercise, the data set will be imported from an excel file.

[10] From the main menu, select File/Import/Import Data...

[11] Browse to the folder:
C:\Users\Public\Documents\AquiferTest Pro\Exercises\Supporting Files\" and select the file Exercise4.xls.

[12] Click [Open]

[13] Enter Static Water Level of 4.0

[14] Click on the (Refresh) button in the toolbar, to refresh the graph. The calculated drawdown appears in the Drawdown column and a graph of the drawdown appears to the right of the data.

[15] Select the Analysis tab

[16] Select “OW-1” in the Data from window

[17] Click on the (Automatic Fit) icon, to fit the data to the type curve. The analysis graph should look like the image below, and the calculated parameter values should be:

Transmissivity = 3.02 E3 ft2/d

Storativity = 7.06E-4

[18] Since the automatic fit uses all data points, often it does not provide the most accurate results. For example you may wish to place more emphasis on the early time data if you suspect the aquifer is leaky or some other boundary condition is affecting the results.

In this case, there is a boundary condition affecting the water levels / drawdown between 700 - 1000 feet south of Water Supply 1. You need to remove the data points after time = 100 minutes.

There are several ways to do this, either by de-activating data points in the analysis (they will remain visible but will not be considered in analysis) or by applying a time limit to the data (data outside the time limit is removed from the display). You will examine both options.

[19] From the Main menu bar, select Analysis/Define analysis time range, or select this option from the Analysis frame of the Project Navigator panel. This function allows you to remove the data points from your automatic data fit, and also removes them from your analysis graph.

The following window will open:

[20] Select “Before” and type in 101. This will include all the data-points before 101 minutes and will remove all the data-points after that period.

[21] Click [OK].

[22] Click on the (Automatic Fit) icon and see how the graph has changed. The points after 100 minutes are no longer visible (change the axes’ Min and Max values if necessary to see the effect).

[23] The parameters in the Results frame have changed to

Transmissivity = 4.48E3 ft2/d

Storativity = 4.27E-4
 

[24] Now restore the graph to normal: select Define analysis time range again and selecting All.

[25] Click [OK].

[26] Click on the (Automatic Fit) icon, to fit the data to the type curve.

[27] You will now exclude the points by another method. Click (Exclude) icon above the graph. This exclude function allows you to remove data points from your automatic data fit, but retains the data points on your analysis graph. The following dialog will appear:

[27] Type in 101 in the “Start” field and 1440 in the “End” field.

[28] Click [Add].

[29] Highlight the added time range.

[30] Click [OK].

[31] Click on the (Fit) icon, to fit the data to the type curve.Your analysis graph should look like the image below (notice that the defined time range has been highlighted, indicating that these values are not included in the current analysis):

[32] The curve change is identical to the “Define analysis time range” option (as evident from the calculated parameters in Results frame), however the points are still visible on the analysis graph.

[33] The parameters in the Results frame should now be similar to the following:

Transmissivity = 4.48E3

Storativity = 4.27E-4

Determining the Effect of a Second Pumping Well

In this section, the second pumping well will be activated, and AquiferTest will predict the drawdown that would occur as a result of two pumping wells running simultaneously.

In the previous section, the aquifer parameters (Transmissivity and Storativity) were calculated with the Theis method. In order to maintain these values, you need to “lock” the parameters.

[34] Click on the Analysis Parameters button , or select View / Analysis Parameters from the main menu.

[35] Click on the both “padlock” icons beside the parameters.

[36] Click on the [X] button to close the Parameters dialog

[37] Click on the Pumping Test tab

[38] In the Wells table, select WaterSupply2 from the well list

[39] To “turn on” the second pumping well, change the type from Not Used to Pumping Well

[40] Click on the Discharge tab

[41] Select WaterSupply2 from the well list

[42] Select the Variable discharge option

[43] Enter the following values in the table, and the discharge tab should look like the image below::

Time

Discharge

720

150

1440

0

These values indicate that the Water Supply 2 well was turned on at the same time as the Water Supply 1, however, whereas Water Supply 1 pumped for 1440 minutes (24 hours) at a constant discharge of 150 US gal/min, Water Supply 2 only ran at that rate for 720 minutes (12 hours) and was then shut off.

[44] Select the Analysis tab

[45] You will see that the theoretical drawdown curve no longer goes through the observed points; instead the curve is below the data, indicating that the predicted drawdown at OW-1 has increased as a result of activating the second pumping well. You will also notice a rebound after 720 minutes, corresponding to the shut-off of Water Supply 2. As a result, the total discharge from the two wells decreases to 150 gpm (from 300 gpm) and the resulting drawdown is less.

NOTE: You may need to modify the max value for the drawdown axis to see the entire curve.

AquiferTest calculates the theoretical drawdown curve, using the Transmissivity (T) and Storativity (S) values calculated earlier in this exercise.

NOTE: The Theis analysis assumes a Constant discharge, however, when the 2nd pumping well with a variable discharge rate was added, the model assumptions were automatically updates to reflect this change.

[46] Expand the Model Assumptions frame of the Analysis Navigator. Notice that the assumption for discharge has been updated to Variable.

Using this procedure, AquiferTest allows you to predict the effect of any number of pumping wells on the drawdown at a well.

Predicting Drawdown at Any Distance from the Pumping well

In this section, an imaginary observation well will be added at the property border, close to the pumping test site. The following procedure will allow you to predict the drawdown at that well (or any well at a given set of coordinates).

 

[47] Return to the Pumping Test tab, and locate the Wells table.

Create a well with the following parameters:
 

Name: OW-2

Type: Observation Well

X: 700

Y: 850

R: 0.30

L: 50

r: 0.25

 
 

[48] Select the Water Levels tab

[49] Select OW-2 from the list of wells.

Enter the following “dummy” data points for this well.

Time

Water Level

1

1

200

1

400

1

600

1

800

1

1000

1

1200

1

1440

1

[50] Enter the Depth to static water level of 0. The Water Levels tab should look like the image below:

NOTE: These values are dummy points. They are used to establish the time period in which you are interested - the water level values are irrelevant since you are going to PREDICT them. AquiferTest simply requires water level data to accompany the time intervals.

[51] Click on the (Refresh) button in the toolbar, to refresh the graph.

[52] Return to the Analysis tab

[53] Check the box beside “OW-2

[54] Click on the (Automatic Fit) icon, to fit the data to the type curve. The analysis graph should look like the image below:

The calculated values for the Transmissivity and Storativity for OW-2 are different from those for OW-1, since the automatic fit attempted to fit the curve to the dummy values you entered for the drawdown. To calculate the predictive drawdown curve, you must change the Transmissivity and Storativity values for OW-2 to match those of OW-1. You will assume that the aquifer parameters at OW1 are the same as those at OW2.

[55] Match your Results panel as shown below by typing directly into the results panel.

 

 

[56] Click anywhere on the Results navigation panel to apply the changes. The following graph is produced:

The upper curve is the predicted drawdown in the well at the new coordinates.

The actual data points for OW-2 have no bearing on the new drawdown curve. The curve is the predicted drawdown that would occur, if there were two pumping wells, one running at 150 US gal/min for 24 hours, and another with the same pumping rate, but for only 12 hours. You can see that the drawdown at OW-2 is less than that observed at OW-1. This occurs because OW-2 is located further away from the pumping wells, so the effect is not as pronounced.

[57] Print the desired reports by selecting the Reports tab and checking the boxes beside the reports you wish to print.

[58] Click on the (Print) button in the tool bar, or select File/Print from the main menu.

[59] Save your project by clicking on the (Save) icon or selecting File/Save as from the main menu.

This concludes the exercise. The next exercise deals with applying data trend corrections. You have a choice of exiting the program, or to proceed to the next exercise.

 

 

 


Page url:https://www.waterloohydrogeologic.com/help/aquifertest/index.html?at_chapter75.htm