This dataset is part of the regional hydrogeological mapping of the Calgary-Lethbridge Corridor (CLC) in southern Alberta. It represents the concentration of total dissolved solids (TDS) (in mg/L) of the Horseshoe Canyon / St. Mary River hydrostratigraphic unit (HSU) interpolated from wells in Alberta Envrionment and Parks' (AEP) Alberta Water Well Information Database (AWWID). The TDS concentration was mapped at a regional scale using many years of data, thus providing a good indication of regional water chemistry within the unit rather than site specific values.
This dataset supplements Alberta Geological Survey Report 91, which includes details on the data processing and interpolation in the CLC.
The following statistics describe the accuracy of the interpolated final clipped grid in relation to the input TDS point data:
Root mean square error = 644 mg/L
Mean error = -102 mg/L
Standard deviation = 648
Maximum error = + 901 mg/L / -1745 mg/L
The methodology used to create this grid dataset is documented in AGS Report 91. The AWWID dataset (from which TDS values were sourced) was current up to April 2013.
Step 1 (Modelling the data): Simple Kriging algorithm was used in the ArcMap Geostatistical Analyst extension to interpolate the TDS values and create a grid of the TDS concentration in the Horseshoe Canyon / St. Mary River HSU. Wells in the AWWID are often only located to the middle of the quarter section (or sometimes section) and thus co-located data points exist. In these cases a mean of the TDS was used for the interpolation.
The selection criteria for AWWID chemical analyses used to create this grid are documented in AGS Report 91, and the final selection of wells in DIG 2016-7273.
Method Report:
Method: Kriging
Type: Simple
Output type: Prediction
Trend type: None
Variogram: Semivariogram
Number of lags: 12
Lag size: 8992
Nugget: 0.41
Measurement error percentage: 100
Model type: Gaussian
Range: 48064
Anisotropy: No
Partial sill: 0.866
Total points: 100
Cell Size: 400 m
Root mean square error (considering only final clipped grid): 644 mg/L
Step 2 (Grid Alterations): Areas of the original extent of the grid results were clipped based on 1) the absence of the St. Mary River/Horseshoe Canyon Formation; and 2) the area being outside a buffer area, which consists of areas of contiguous 5000 m buffers around wells.