Well Datevarient TOC

If the TOC (top of casing) varies with time, such as may be encountered with subsidence or excavation of the ground surface ESdat is able to track this and apply these variations to the water level depth/elevation conversions.

The timevariant TOC is entered into the "Wells_Datevariant_TOC" table.  If data is entered here the TOC value for that well in the Wells table is ignored in standard ESdat outputs.

This table allows the following interpolation methods in standard ESdat outputs:

Linear Interpolation, which is used in subsidence situations, where the TOC values used for water level conversions are interpolated between the TOC values recorded before and after that water level was recorded.  The image below shows the TOC values used in ESdat outputs before, between, and after two TOC survey events that have been entered.

No Interpolation, which is used where benching, excavation, or sudden changes in elevation have occurred.  Users can enter both a survey date, and an effective date, and the effective date if entered is the date at which the change is applied.  The image below shows the TOC values used before, between, and after two TOC data points.

Timevariant TOC corrected groundwater levels are only output in data grids / graphs / tables using the "Water Levels AHD Using Timevarient TOC" view in Data Explorer.  Other groundwater views don't use Timevarient TOC in outputs.