﻿ Demonstration Exercises and Benchmark Tests > Exercise 4: Confined Aquifer, Multiple Pumping Wells

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# 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 four sections: To begin, you will create Pumping Test and perform a Theis analysis to estimate 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 estimate the predicted drawdown at a well at any point in the effective radius of the pumping wells.

## Create the Pumping Test and Enter the Data

In this section of the Exercise, you will create a new Pumping test project:

[1] Launch AquiferTest and from the Welcome screen, ensuring that the "Create Pumping Test" box is checked, 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: Multiple Wells

Project No.: 4

Client: ABC

In the Pumping Test frame:

Pumping Test: Theis - Multiple Pumping Wells

Date: filled in automatically

In the Units frame:

Site Plan: ft

Time: min

Transmissivity: ft2/d

Dimensions: ft

Discharge: US Gal/min

Pressure: mbar

In the Aquifer Properties frame:

Aquifer Thickness: 40 m

Type: Unknown

Bar. Eff. (BE): Leave blank

Your fields should now look similar to the figure below:

[3] In the Wells table, Click the text "Click here to create new well" to create a total of three well records. Enter the following data into the Wells table:

 Name Type X[ft] Y [ft] R[ft L [ft] r [ft] 1 Water Supply 1 Pumping Well 350 450 0.30 50 0.25 2 Water Supply 2 Not Used* 350 100 0.30 50 0.25 3 OW-1 Observation Well 350 250 0.06 50 0.05

*Note: this pumping well will be activated/used later in the Exercise.

Your Wells grid should now look similar to the following figure:

[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\SupportingFiles\" and select the file Exercise4.xls.

[12] Click [Open]

[13] Enter Static Water Level of 4.0

[14] Click the Refresh button in the main 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.

## Pumping Test Analysis - Estimating Aquifer Parameters

In this section of the Exercise, you will estimate aquifer parameters based on a Theis analysis:

[15] Select the Analysis tab

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

[17] Click the Apply Graph Settings dropdown button in the analysis graph toolbar and select the "linear" option. In the Time axis frame of the Analysis Navigation panel, set the Value format to "0".

[18] Click the Fit button, to auto-fit the data to the type curve.  The analysis graph should look similar to the image below:

The resulting calculated parameter values should be approximately:

Transmissivity (T) = 3.02 E3 ft2/d

Storativity (S) = 7.06E-4

### Excluding Data from the Analysis

By default, the automatic fit uses all data points. In some cases, this may 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. Conversely, you may wish to place more emphasis on late time data if you suspect that well storage effects are affecting the results.

In the case of this Exercise, there is a boundary condition between 700 to 1,000 feet south of Water Supply 1 that affects the measured water levels/drawdown. To account for this, you will 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 in this exercise.

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

[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 the Fit button and observe how the analysis graph changes.

The data points after 100 minutes are no longer included in the graph. The Min and Max values of the Time and Drawdown axes have been updated to reflect the shorter duration of the test.  Note, you can scroll the mouse wheel forwards/backwards to zoom out/in to see the clipped data. You can also adjust the axes using the Axis settings in the Analysis Navigation panel on the right side of the Analysis Graph or reset the axes using the Reset button in the Analysis graph toolbar.

[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 select All.

[25] Click [OK].

[26] Click the Fit button, to fit the data to the type curve.

You will now exclude the points by another method.

[27]  Click Exclude button in the Analysis graph toolbar. 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.

[29] Highlight the added time range.

[30] Click [OK].

[31] Click the Fit button, 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 ft2/d

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 be used to estimate the predicted 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 “padlock” icons beside both of 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 Water Supply 2 well was turned on at the same time as the Water Supply 1; however, whereas Water Supply 1 was 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 and .

[45] In the Drawdown axis frame of the Analysis panel, change the following settings:

Maximum = 8.0 m

Value format = 0

Major Unit = 4

Your Analysis graph should look similar to the following:

AquiferTest has calculated the theoretical drawdown curve for the specified pumping scenario, based on the "locked" Transmissivity (T) and Storativity (S) values that were estimated in the first part of this exercise.

You will see that the theoretical drawdown curve no longer fits 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 in the predicted water levels 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: 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 at any well with 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 and enter the Depth to static water level of 0.

[50] 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

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 the Refresh button in the toolbar, to refresh the graph.

[53] Check the box beside “OW-2

[54] Click the Fit button, to auto-fit the data to the type curve. The analysis graph should look similar to 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. For the purposes of this evaluation, you will assume that the aquifer parameters representative of conditions at OW2 are the same as those at OW1. To calculate the predictive drawdown curve, you must change the Transmissivity and Storativity values for OW-2 to match those of OW-1.

[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 coordinates of the newly specified OW-2. It bears repeating that the "dummy" data points for OW-2 (entered during Step 50 above) have no influence or meaning relative to 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 farther away from the pumping wells, so the effect is not as pronounced.

## Printing the Report

In this section of the Exercise, you will print the report of your analysis:

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

NOTE: You can add your company information and logo to the space in the upper left of the report page(s) by selecting Tools > Options from the main menu and adjusting the settings in the Reports tab.

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

[59] Save your project by selecting File > Save As, and define a project name (e.g. Example 4.HYT).

This concludes the exercise. The next exercise will demonstrate the application of trend corrections to water level data. You have the option to exit the program or to continue on to the next exercise.