Tutorial 2: Predictive Analysis

Sometimes it is necessary to determine how the pumping well(s) will affect other wells in the area (e.g. if there are private water wells nearby); however, it is often the case that you do not have access to one or more of the wells or the wells might not yet be installed. In such cases, it is useful to evaluate and estimate the effect of pumping wells on other locations wells before drilling, installing, or accessing an observation well at this new location. In this exercise you will simulate a well at a specific location and estimate how pumping wells affect drawdown at the location of the simulated well.

Estimating Water Levels at a New Location

In this section we will estimate the drawdown at a new location based on the pumping analysis and scenario from Tutorial 1.

[1] If you are continuing on from Tutorial 1, Return to the Pumping Test tab. Otherwise, open the file:
 
 C:\Users\Public\Documents\AquiferTest Pro\Tutorials\Tutorial 2.HYT

[2] Create a new well by clicking "Click here to create a new well" link under the wells grid.

For the new well set the information as follows:

•Name: OW-2

•Type: Observation Well

•X: 700

•Y: 850

•Elevation: 0

•Benchmark: 0

•Penetration: Fully

•R: 0.30

•L: 50

•r: 0.25

The well is created as "Observation" by default, however, you can change the type of any well by clicking in the Type field once to activate it and then again to produce the drop-down menu.

[3] Click on the Water Levels tab.

[4] Select OW-2 from the frame in the upper left corner.

[5] Enter 0 as the Static Water Level.

Now you need to enter water level data for the new well. You will enter a few "dummy" points which will be used to set the timeline for the curve. The water level measurements can be any values, but for simplicity, a value of 1 will be used.

Enter the following values in the Water Level table:

[6] Click Theis from the Analyses frame of the Project Navigator to move to your Theis analysis. Note that the second observation well, OW-2, now shows up in the Data from list.

[7] Check the box next to OW-2 to display this data set.

For this dummy well, you will not apply the automatic fit, since there are no observed water levels, and the automatic fit would be meaningless. Instead, you will use the Transmissivity (T) and Storativity (S) values that were calculated for OW-1 (in the first part of this exercise). Then, assuming that the aquifer parameters are identical at OW-2, you will manually assign these identical values, and observe the theoretical drawdown curve.

Under the Results frame, set the parameters for OW-2 to those values that were calculated for OW-1:

•Results - OW-2, T, type: 4.48E3

•Results - OW-2, S, type: 4.27E-4

Your graph should now look similar to the one shown below:

The upper curve represents the "predicted" drawdown in well OW-2, that is the estimated drawdown estimated to occur at the location of OW-2 if there were two active pumping wells an infinite, homogenous isotropic aquifer (T = 4,480 ft2/d, S = 4.27x10-4], one running at 150 gal/min for 24 hours and another with the same pumping rate, but only for the first 12 hours. The simulated drawdown at OW-2 is less than the simulated drawdown at OW-1 because the OW-2 is farther away from the pumping wells, so the effect is not as pronounced.

Using this procedure, you can derive estimates for the drawdown in a well at any distance based on the forward usage of a supported analytical solutions with a set of parameters and underlying assumptions.

Returning to static level conditions

AquiferTest can also be used to estimate how long it will take for water levels to return to static conditions once the pumping test has concluded.

[8] Return to the Discharge tab

[9] Select Water Supply 1.

The test lasted 1440 minutes and it ran at a constant discharge of 150 US gal/min. Now that you are considering the time after the pump was shut off, it is necessary to define a stop time, and as such, you must use the Variable discharge type.

[10] Select Variable in the Discharge frame

[11] In the Discharge table enter the following values:

You also need to turn off Water Supply 2.

[12] Select Water Supply 2.

[13] Set the discharge type to Constant

[14] Enter 0 for the Discharge rate.

Next, you need to establish the timeline for OW-2.

[15] Click on the Water Levels tab

[16] Select OW-2 from the wells list. In addition to the data you already have there, enter the following values:

[17] Click on Theis under the Analyses frame of the Project Navigator to return to your Theis analysis.

[18] Expand the Time axis by clicking the Reset button on the analysis toolbar or by and setting the Maximum to 10,000

You can see that the theoretical drawdown curve for OW-2 rises sharply when the pumping well is shut off (at 1440 min) and recovers asymptotically to initial conditions at later times.

You can get a more precise estimate of the recovery time by transforming the Drawdown axis to a log-scale, increasing the number of Major units on the Time axis to 10 and adding grid lines as shown below:

Based on this analysis, we can estimate that it would take approximately 5,000 to 9,000 minutes (~3.5 to 6 days) for the water to return to near static conditions (i.e. within 1-2 inches of antecedent water level).

Creating a Report

Now that you have entered your test data and conducted the appropriate analyses, you may want to print out a report. Using AquiferTest you can print out the information from any part of the AquiferTest that is currently active, or you can choose which reports to print at the same time using the Reports tab.

[19] Click on the Reports tab.

To the left of the print preview is the Report navigator tree. This tree contains all the data that has been entered and/or calculated in AquiferTest. From this tree you can choose which sections to include in your report and which to leave out.

[20] Check the box beside Site Plan, Wells, and Confined Aquifer Analysis. Note that checking the box beside Confined Aquifer Analysis automatically checks all options available - which can be seen by opening all the branches of this part of the tree.

Note that you can define your company information and logo in the Report section of the Options window, which is accessed by clicking Tools > Options from the main menu.

[21] To print the selected reports select File/Print or simply click the Print button in the toolbar.

In the next tutorial, you will analyze well-bore storage effects using diagnostic plots.

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