3. Data Management in GWHAT

3.1. Importing Data

Time series of water level and weather data must first be imported in GWHAT before groundwater hydrographs can be plotted or analyzed. The format in which the data must be saved, so that they can be imported successfully, is described in Section 3.2.

Importing water level and weather datasets in GWHAT is done by clicking on one of the icons that are located in the Water Level Dataset or in the Weather Dataset section of the tabs Plot Hydrograph or Analyze Hydrograph (see Fig. 3.1). This opens a window named Import Dataset (shown in Fig. 3.2), where a valid water level or weather data file can be imported.

Fig. 3.1 Presentation of the panel to manage water levels and weather datasets.

Selecting a water levels or weather data file from the Import Dataset window (shown in Fig. 3.2) is done by clicking on the icon. After a valid data file has been selected, the information relative to the climate or piezometric station is displayed in the section Dataset info of the Import Dataset window. This information is read from the header of the selected data file. Missing or wrong info can be entered or corrected from Import Dataset window before importing the dataset by clicking on the button Import. The dataset is then added to the project file and is referenced in the list of imported water level or weather datasets (see Fig. 3.1) by the name that was entered in the field Dataset name.

Fig. 3.2 Presentation of the Import Dataset windows to import water levels (to the left) and weather (to the right) data files.

Important

A valid dataset name is at least one charater long and can’t contain any of the following special characters:   \  /  :  *  ?  ”  <  >  |

3.2. Input data files format

This section describes the format in which daily weather and water level datasets must be saved so that they can be imported in GWHAT as described in Section 3.1. GWHAT includes a tool to download and automatically save daily weather data from the Canadian Daily Climate Database [1] in the appropriate format (see Section 4). Moreover, GWHAT provides an automated, robust, and efficient tool to fill the gaps in daily weather data records that is presented in Section 5. There is currently no tool in GWHAT to automatically download and format groundwater levels time series. However, these data can be downloaded free of charge for the province of Quebec from the Groundwater Monitoring Network of Quebec [2] and for several Canadian provinces from the Groundwater Information Network (GIN) [3].

3.2.1. Weather data files

GWHAT can read weather data saved in comma-separated values (csv) or tab-separated values (tsv) text files with UTF-8 encoding. An example of correctly formatted data file is presented in Fig. 3.3.

The file header contains information about the station name, province, latitude, longitude, elevation and climate identifier. The dataset is composed of daily maximum, minimum, and mean air temperature in °C and total precipitation in mm. nan values must be entered where data are missing. Data must also be in chronological order, but do not need to be continuous over time. That is, missing blocks of data (e.g., several days, months or years) can be completely omitted in the time series.

Fig. 3.3 Example of a correctly formatted weather data file.

Note

Preferably, the gaps in the daily weather records must have been filled before importing them. Otherwise, a value of 0 is assumed for days where precipitation is missing and the missing values for air temperature are evaluated by linear interpolation. GWHAT provides an automated, robust, and efficient tool to fill the gaps in daily weather data records that is presented in Section 5.

3.2.2. Water level data files

GWHAT can read water level data from either coma-separated text files (csv) encoded in UTF-8 or from an Excel spreadsheet (xls or xlsx). An example of correctly formatted water level data file is presented in Fig. 3.4. This file is also available in the folder of the project example that is distributed with GWHAT (see Section 1.1).

The file header contains information about the well name, identifier, province, latitude, longitude, and elevation. The data must be saved in chronological order. The first column of the data must contain the time in excel numeric format. The second column must contain the water level, given in metres below the ground surface. The third and fourth columns correspond, respectively, to the barometric pressure and the Earth tides. The use of barometric pressure and the Earth tides data will be discussed in more details in Section 9.

Fig. 3.4 Example of a correctly formatted water level data file. This file is available in the folder of the project example that is distributed with GWHAT.

Important

Water levels must be in metres below the ground surface. The name of the labels of the header and of the data columns (e.g., Well Name, Well ID, Date) must be respected for the program to read the content of the file correctly.

3.3. Exporting Data

It is possible to export the currently selected weather dataset to a coma-separated text file (with UTF-8 encoding) or an Excel spreadsheet (xls or xlsx) by clicking on the icon as shown in Fig. 3.5. The dataset can be exported in a daily, monthly or yearly format. Note that the export of water level datasets is currently not available in GWHAT.

Fig. 3.5 Tool to export weather datasets in a daily, monthly, or yearly format to a csv, xls, or xlsx file.

Footnotes

[1]	http://climate.weather.gc.ca/

[2]	http://www.mddelcc.gouv.qc.ca/eau/piezo/

[3]	http://gin.gw-info.net/service/api_ngwds:gin2/en/gin.html