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Exercise 5: Adding Data Trend Correction

NOTE: Data Trend Correction Tools are only available in the AquiferTest Pro edition.

This exercise demonstrates the Data Trend Correction feature in AquiferTest. The AquiferTest project for this exercise is already created; the exercise deals specifically with the aspect of adding a data trend correction to the drawdown values. For more information on the trend correction, please see Data Pre-Processing.

[1] Start AquiferTest and click on the (Open other project...) button, or if AquiferTest was already, started then select File/Open from the main menu.

[2] Browse to the folder "C:\Users\Public\Documents\AquiferTest Pro\Exercises\", and select the project: TrendEffects.hyt

[3] Click [Open].

The pumping test consists of one fully penetrating pumping well, pumping at 0.001 m3/s for 30,000 s. Drawdown is observed at an observation well located 10 meters away.

[4] Select the Water Levels tab. Take a moment to review the time - drawdown data for Well 2 that was observed for this pumping test.

[5] Select the Analysis tab and the Analysis Graph. Make note of the results obtained for Transmissivity and Storativity, using Theis analysis.

You will now add the trend correction to the observed drawdown measurements.

[6] Return to the Water Levels tab. Add a Data correction, by clicking on the “down” arrow beside the Add Data Correction button, and selecting Trend Correction.

The Calculate Trend dialog will appear, as shown in the image below:

 

[7] In the Observation well drop-down menu, select Well 2 (your observation well)

[8] Click the "Click here to import the data from a file." link above the data table.

[9] Browse to the folder: "C:\Users\Public\Documents\AquiferTest Pro\Exercises\Supporting Files" and locate the file Trenddata.xls. This file contains daily measurements of time (s) vs. water level (m) data, recorded by a logger, for 42 days.

[10] Click [Open]. You will see the data points displayed in the table and the calculated trend line appear on a graph to the right of the table.

Below the graph you will see the calculated Trend coefficient displayed. (If this is not visible, click on the Click here to refresh the graph and update the results link below the graph).

At the bottom of the dialog, there will be a label indicating if the trend is significant, which is determined by t-test. In this example, the calculated trend coefficient is -2.58 E-7 m/s (or -2.22 cm/day). The negative sign indicates that the water levels tend to RISE by 2.22 cm/day. The trend is significant; as such, the drawdown values should be corrected with the trend coefficient.

 

[11] Click [OK] to close the dialog.

 

[12] The correction data has been imported and the Time/Water Level table now has two new columns - Trend correction, and Corrected drawdown used in analysis.

Corrected drawdown is calculated using the trend coefficient. To obtain the corrected drawdown, the Trend Correction value is added to the observed drawdown. In this example, the Corrected Drawdown is slightly greater than the observed drawdown.

[13] Switch to the Analysis tab.

[14] Click on the (Automatic Fit) icon, to fit the data to the type curve. Take note of the new aquifer parameter values. In this example, the values only changed marginally, since the change in drawdown due to the trend is very slight.

 

[15] Click the Reports tab. A Trend report may be printed from the water level branch of the navigator tree in the Reports tab. This report will display the trend data with corresponding graph, and the t-test statistics. An example is shown below.

 

This completes the exercise. You may now exit AquiferTest or proceed to the barometric correction exercise.

 

 

 


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