This grid represents the distribution of hydraulic head in the Paskapoo hydrostratigraphic unit (HSU). It is a result of a geostatistical model which was constructed using publicly available data from the Alberta Government's Alberta Water Well Information Database (AWWID).
The hydraulic head surface was mapped at a regional scale using many years of data, thus providing a good indication of regional groundwater flow within the unit rather than site-specific values.
The following statistics describe the accuracy of the geostatistical layer used to create the final grid.
Mean error: -0.029 m
Root mean square error: 12.84 m
Mean Standardized Error: -0.0002
Root mean square standardized: 0.986
Average Standard Error: 12.48 m
The potential for up to approximately 566 m (sometimes approximately 1131 m) of horizontal accuracy error may also introduce errors in the surface elevation, which is derived from the provincial 25 m DEM, based on the location of the well. This error is likely on the order of plus/minus 5 m but may be 10s of metres in areas where there are large changes in elevation. Additionally, most wells have a casing which sticks up above the land surface from which measurements of water level are usually recorded. The calculation of hydraulic head does not take into account the elevation difference between the top of the casing and the land surface because this number is not always recorded in the AWWID. These sources of error are not unique to this study and are encountered in any hydrogeological study that uses the AWWID, unless further refinement of well locations is undertaken.
The mid-point of the sampled interval is also a calculated value and its accuracy is dependent on the accuracy of the measured depths and elevations provided in the well header. These values are somewhat inconsistent for the water wells because many of them are not surveyed.
Step 1 (Modelling the surface): An empirical Bayesian kriging algorithm was used in the ArcMap 10.8.1 Geostatistical Analyst extension to interpolate the hydraulic head values and create a grid of the head surface of the Paskapoo HSU.
Method Report:
Output surface type: Prediction
Power: 1
Neighbourhood type: Standard
Maximum neighbours: 15
Minimum neighbours: 10
Sector type: 1 sector
Samples: 35 268
Cell size: 500 m
Step 2 (Grid Alterations): The final grid was clipped based on the extent of the Paskapoo HSU, and spatial distribution of data.