The vertical allowances provided on CAN-EWLAT are with respect to Mean Water Level (MWL) epoch 2010 (Robin et al., 2016). In addition to the MWL epoch 2010, CAN-EWLAT also provides the following water level target heights:

• Lower Low Water Large Tide (LLWLT) epoch 2010,
• Higher High Water Large Tide (HHWLT) epoch 2010 and

All are provided for each TG and SCH site relative to the known datum/reference levels:

• North American Datum of 1983(Canadian Spatial Referencing System) {NAD83(CSRS)epoch 2010},
• Canadian Geodetic Vertical Datum of 1928 (CGVD28),
• Canadian gravimetric geoid model of 2013 (CGG2013).

Values relative to these references are provided using the following terminology, for example MWL_CGVD28, defining the height of MWL with respect to CGVD28. Positive values indicate that MWL is above CGVD28.

In the absence of additional tidal effects it may be assumed that all water level targets evolve vertically with relative sea level rise. Water level targets on the CAN-EWLAT site at TG stations are derived from observations. Targets at SCH sites are determined using a combination of both water level observations and modeled tides between observation sites. Potential average inaccuracies for both TG and SCH site water level target estimates can be approximately +/- 10 to 20 cm. However, inaccuracies may be larger for areas with limited observations, or where tidal behavior is either changing over time or has not been appropriately approximated by the modeling methods employed.