What you need to know before you start:
NOTE: More than one abstraction well can be handled with WQN10. You therefore have the option to divide the proposed volume of water between the proposed wells. However separate assessments might have to be run to investigate if taking the full proposed volume from one well (if possible) could affect neighbouring wells beyond the permitted levels.
The WQN10 application will:
The CalcMin is the groundwater level that is exceeded 80% of the time in the month May. A water level data series of 10 years is needed before the 80% level can be estimated. For wells without sufficient groundwater level observations the CalcMins are spatially interpolated from wells that do have CalcMins based on long term water level data. Another assumption is that the ground level between wells is relatively straight which only applies to some extent within the Canterbury Plains area. Therefor interpolated CalcMins are only provided for this area. Some newer wells might not have a CalcMin assigned yet. The program will interpolate when possible and mark that with a comment.
Using the Web WQN10 Application has 8 steps:
There are three ways to enter one or more new abstractions into the web form:
This web application links directly to Environment Canterbury's databases so can only accept valid consent numbers and well numbers. Please contact Customer Services if you suspect errors.
If a mistake is made or the user wants to perform a new assessment, pressing the “Reset Form” button will remove the wells from the list and reset to the default parameter values.
Figure 1 Step 1 - Add Wells for proposed abstraction location(s)
Step 1 b editing well details in the selected abstraction locations:
When assessing a “virtual well” or proposed well, it is possible to edit the details of the well before generating the PRN file by clicking on “edit” next to the well to be altered (this will not change the data in Environment Canterbury's databases). This is the place to input the Q7 and Q150 values to the virtual well. Press UPDATE when you have entered the depth and Q7/Q150. If you are entering a “Virtual Well” or assessing a well with missing data, it is possible to edit all other information before you run the actual assessment in Step 5. See step 4 for how to edit/add these values.
Figure 2 Edit details of selected locations
The search radius, minimum drawdown and nominal flow rate should be left as specified by the WQN10 schedule. You can change them if you (for example) want to run the model for a larger area, or if you want to include every individual drawdown in the total cumulative drawdown of all abstractions (rather than to ignore drawdowns less than 0.1m). A flow rate of 0.12 L/s is the permitted 10 m³/day for domestic and stock water (this might vary per location and size of property). Increasing the maximum search radius will exponentially increase the number of wells in the assessment. You cannot increase the area of interest with the existing PRN file as the set of wells is limited to the search radius initially set there when you created the PRN file. You will have to create a different (larger) PRN file.
Figure 3 Default Parameters for extracting surrounding well locations and default flow
In this step you create an input file with all information of surrounding wells that will be used by the model. Press the “Generate PRN File” button to start the process which may take up to a couple of minutes.
A pop-up screen will appear asking where the file should be saved on the user's computer. The file can be relocated and renamed as desired but do not change the extension of the file (“.prn”).
Figure 4 “Step 3” form before generating the PRN data
Figure 5 After the PRN data has been generated red circle for the PRN filename appears
At this stage you can download the PRN file (press Download PRN file) to your computer but you don’t have to. The browser will show when the download is completed. You can then inspect the CSV file in Notepad or MSexcel or any other ‘plain’ editor program. You can also make changes to the data with these programs where necessary, e.g. complete some of the additional information for virtual wells, change the number of wells in your selection, add more virtual wells, or update locations/screens /CalcMins of wells in the file.
It is critical that you do not alter the layout of file, only change the data in the ‘columns’. If you use MSexcel make sure that you save the PRN back as a CSV file (Commas Separated Values) and that you haven’t inadvertently changed the date formats. You won’t have these problems with Notepad or Notepad++ but reading the file ‘manually’ is a bit harder. The first line in the PRN files contains the columns headers (see appendix 2 (pdf 950 kB)).
If you want to use this edited data in the WQN10 application then re‑upload the modified PRN file. Press the “Choose file” button and browse to the location on your computer of the altered PRN file.
For the user convenience two graphs are displayed. The first one is a simple count of how many wells have a certain depth (well depth) grouped in classes of a meter around the proposed well. The second graph, screen distribution, is how many screens are recorded for all the wells in the PRN file at a 1 m interval classes. For example, if a well has a screen between 10 and 20 m this screen is counted at each 1 m class between 10-11 m and so on till 19-20 m class. This can help visualise where the aquifers might be.
Figure 6 Step 4 after pressing the ‘Run Data Check’
The WQN10 application uses a few default parameters, mostly based on assumptions, to make up for a lack of detailed actual information for wells like screen lengths and pump length. If you have more detailed information you can add/edit that in your PRN file and include a comment in the final assessment. As in Step 2, it is best to run with the default settings specified in the WQN10 Schedule in the NRRP. The difference with step 2 parameters is that the settings there are used to create a PRN file and that the settings in step 5 are used in the well interference assessment model ‘run’.
Figure 7 Model run parameters
If the ‘Lodgement Date’ checkbox at the top is selected then all wells will have their notification date or lodgement date taken into account. All wells with a later notifiable date in their application than the target well will not be ‘pumping’ in the model run as the RMA uses a first-in-first-served principle. This option is handy for example when you run several assessments for several applications in the same area that could be based on the same PRN file with different centre wells selected each time. The Notified dates are editable in the PRN file e.g. for virtual points. Please look at the WQN10 figure in the appendix 1 (pdf 950 kB) to better understand the parameters used.
Selection of the model type and parameters is probably the most difficult part of the WQN10 process as you will have to justify the choices and understand the differences is the model options. Again, we assume that you are familiar with the models and limitations of models.
Figure 8 Model and aquifer parameter selections
The simplest model is the Theis model, requiring only a Transmissivity and a storativity value. The Hantush-Jacob requires an additional parameter of the Leakage Factor or K’/B’. This parameter field only appears in the form after you have selected this model. The Hunt-Scott and Hunt-Scott + Shallow each require an extra parameter of Specific Yield of the overlying layer and the Transmissivity of the overlying layer. For the last two models it is important that you specify a depth in the Well Depth Range box. This value will be used to split up the wells in two layers; above the top of the pumped aquifer for shallow, and the rest between the top and the bottom (default 999m). Any wells with their top of screens below this last level will be ignored.
The file will download to your PC, store it and open it with MSexcel for easy sorting. We recommend sorting the file in MSexcel on Column N in descending order below the last centre well so the wells are in order of drawdown experienced by the new proposed abstraction.
The column descriptions are shown in appendix 3. Column “<well> DD_OK” shows the outcome of the test. Some comments to indicate special cases are noted by the program in the PRN file (Appendix 3 (pdf 950 kB)) or while running the model in two ‘comments’ columns in the output file. They can be helpful for the interpretation of the results.
You probably want to examine the ‘problem’ cases and whether they can be eliminated, for example:
If none of the affected wells can be excluded for the above reasons, well interference effects might have to be considered as a possibility. If the aquifer parameters cannot be derived from any of the involved wells, we recommend that an aquifer test is conducted to better determine the aquifer parameters and possibly measure the interference effects directly. In cases where the proposed wells aren’t drilled yet, potential interference problems can be avoided by shifting the proposed location to where the interference is below the set limits. Other mitigation options can include changing screen depth, e.g. when shallow wells would be affected the proposed take can be shifted to a deeper aquifer to avoid affecting the shallow wells.
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