Distribution of Total Dissolved Solids in the Milk River Hydrostratigraphic Unit

This map depicts the distribution of total dissolved solids (TDS) in groundwater in the Milk River hydrostratigraphic unit (HSU). The map is a result of a simple kriging technique using publicly available water chemistry data from Alberta Environment and Parks' (AEP) Alberta Water Well Information Database (AWWID) and formation water chemistry data from oil and gas well drillstem tests and production fluids, as well as compiled information from the scientific literature. The distribution of TDS 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. The uncertainty of prediction is depicted on an inset map, which shows the residual values (predicted values minus measured values) plotted at each location to indicate where underprediction and overprediction occurs. One additional inset map shows the distribution of hydraulic head. The geometry and variable thickness of the Milk River HSU are illustrated on schematic cross-sections. The regional lithostratigraphy and hydrostratigraphy of the Milk River HSU and overlying and underlying units are highlighted in a table.