This data release is a compilation of water chemistry data used to create water chemistry maps for the Calgary-Lethbridge Corridor (CLC) project. The source dataset is from Alberta Environment and Parks' Alberta Water Well Information Database (AWWID). Data have been processed for relevancy and outliers were removed but values are as received from Alberta Environment and Parks database. The dataset contains 564 records. All records were used for interpolation.
This dataset supplements Alberta Geological Survey Report 91, which includes details on the data processing and TDS concentration mapping in the CLC project area.
Any errors in the original data were carried into this dataset and no systematic checking of attributes from original data source was undertaken. Some obvious errors in the AWWID were corrected. For example, we fixed the records that had the top and bottom of the screened/perforated interval reversed in the original database.
Water well locations from the AWWID may be up to 800 m from their correct locations where the well is located to the centre of the section. The elevation of the well was calculated from a 400 m digital elevation model (DEM) which was resampled from the Shuttle Radar Topography Mission fifty metre resolution digital elevation model with bathymetry (SRTM 50 m DEM). Because the well elevation is derived from the 400 m DEM based on surface location, elevation accuracy is affected by the variability of the local topography and the potential locational inaccuracy. Any error in elevation may influence the allocation of the well data into the modelled hydrostratigraphic unit (HSU) as the land surface elevation was used to calculate the top and bottom screen elevation. This is especially true where there are large changes in elevation within a quarter section, such as along the banks of rivers or in the Porcupine Hills and Okotoks Uplands. These sources of error are not unique to the CLC and are encountered in any hydrogeological study that uses the AWWID, unless further refinement of well locations is undertaken.
The allocation of wells into HSUs is based on the modelled 3D gridded surfaces and the elevation of the middle of the screen, rather than the lithology at the screen interval in a particular well. The elevation of the middle of the screen was not retained in this dataset. While there is generally good agreement between the lithology of the borehole at the mid-screen depth, elevation in the well, and the HSU allocation, there are cases where the allocated HSU does not match the lithology of the associated borehole for the well. In spot checks, this appeared to be more common in areas where there was sparse data control for modelling the hydrostratigraphic surfaces, and in areas of variable elevation in the modelled surfaces (e.g., slope breaks in the bedrock topography). Errors in allocation will also be greater where the HSUs are thin (e.g., Battle HSU, HSU S1, at subcrop edges), or where the middle of the screen is located close to the boundary between two HSUs, where the well screen may straddle multiple HSUs.
Data are compiled from the AWWID and have been collected over decades, by different parties, and using different methods.
There is only one record for each "AWWID_ID", although geographic coordinates (latitude/longigtude) may be the same for different wells, often because the AWWID wells have been located as being in the middle of a quarter section or section.
Null values were assigned where attributes were not present.
AWWID data, current up to March, 2013 (records ranging in time from 1972-2001), provided water chemistry information in the upper approximately 200 m of the subsurface. Data in feet were converted to metres.
Selection criteria for AWWID wells were as follows:
Chemical analyses that included major-ion chemistry were exported from the AWWID;
Chemical analyses from wells with no screen interval information, with multiple screen intervals, with screen intervals longer than 15 m, and with erroneous or incomplete chemical analyses were excluded;
TDS was determined for each analysis by summing the concentration of major constituents;
Acceptable charge balance error was constrained to ±10%;
Analyses which reported CO3 and pH < 8.3 were excluded;
Outliers were manually removed during the mapping of each HSU based on substantial differences in screen depth, and unexplained anomalous values.
This dataset includes only those wells that were used in the production of final TDS concentration maps.
It contains wells which are located inside the study area boundary but also those wells outside the boundary that fall within a 10 km buffer of the boundary. There are 564 records in total.