Potential Discharge Areas - June 2021

Description

The Potential Discharge Areas provide an indication of those regions where a groundwater-surfacewater interface may be possible. This is broadly defined as those areas where an uncorrected Water Table gridded surface (i.e. the Data Driven Water Table, WT0) intersects a Vertical Reference (i.e. a DEM).

• Type
  • Raster - Gridded on 100m cells. A 50m cell working resolution was chosen with the final result resampled to a 100m cell final grid.
• Geographic Extent
  • Entire ORMGP Study Area (with a 25km buffer).
• Maintenance Standard
  • Periodically updated as new wells are added into the ORMGP database.

Georeferencing and Accuracy

• Horizontal Datum
  • North American Datum 1983
• Vertical Reference
  • Well elevations set to MNR DEM (2006 Version 2, 10m cell resolution) based on Accuracy, below
• Horizontal Accuracy
  • Based on accuracy of well locations - refer to ORMGP Database Manual

Data Sources and Restrictions

• Use Constraint
  • None - in accordance with ORMGP disclaimer
• Citation
  • Oak Ridges Moraine Ground Water Program (2021) Potential Discharge Areas
• Agency Originator
  • Oak Ridges Moraine Groundwater Program (ORMGP)
• Agency Distributor
  • Oak Ridges Moraine Groundwater Program (ORMGP)

Methodology

• Data Source - Wells
  • The Water Table (the Data Driven Water Table, WT0) was created by interpoating the static water levels from all wells (ORMGP database, as of 20210615) where the bottom of the screen is less-than (or equal-to) 20 m deep. Wells up to 50 m deep were incorporated within the Oak Ridges Moraine boundary. It should be noted that the measured static water levels reflect measurements from wells that were drilled in all seasons as well as in wetter and dryer years. So the water table presented here is the average water table. For wells with more than one measurement all water levels are averaged. Given the dynamic nature of the groundwater system, it should be noted that the actual water table at any given time of year may be on the order of up to 2 or 3 metres higher or lower than reflected in the map.
• Rasterization
  • The input dataset (i.e. shallow groundwater levels) were rasterized at a 50m resolution and averaged.
• Interpolation - Water Table
  • Interpolated in Surfer using Kriging (with the ‘auto’ model setting, i.e. 64 point search).
• Potential Discharge Areas
  • Potential groundwater discharge areas are mapped in areas where this water table surface exceeds surface elevation. That is, subtracting the interpolated Water Table from the Vertical Reference surface, all negative values are indicative of this condition. These negative values are set to a value of ‘1’ (indicating presence) while all other values are removed.
• Source/Citations
  • The database of wells in the ORMGP includes all of the MOECC water well records as well as additional geotechnical/hydrogeological wells that have been entered into the database from other sources (consultant reports, Ontario Geological Survey, consultant databases, partner agency staff, etc.). Water levels are measured at nearly all wells at the time of drilling. The recorded static water level may or may not effectively reflect the water table position, depending upon when it was measured. Usually upon completion of drilling the well is pumped to estimate well capacity - sometimes insufficient time has passed to record a ‘true’ static water level (i.e. the well has fully recovered after pumping).
  • Refer also to ‘Oak Ridges Moraine Groundwater Program (2021) Water Table’ for additional details.
• Replaces or Updates
  • Oak Ridges Moraine Groundwater Program (2019) Potential Discharge Areas.
• Significant Changes
  • Wells incorporated in the ORMGP database since the previous version of this dataset have been included within the interpolation process.
• Contact
  • Mike Doughty (mdoughty@owrc.ca)

Last Modified: 2022-03-31