The Canadian tide and water level data archive presently holds water level observations reported from over a thousand stations, with the earliest dating back to 1848. The number of observations spans on average 6 years per station, with 60 stations measuring water levels for over 50 years. Over 800 stations are subjected to appreciable effect of tides, and for most of these stations, the Canadian Hydrographic Service (CHS) calculates and publishes predictions of the water levels associated with the vertical movement of the tide. Observations from the CHS Permanent Water Level Network are added on a daily to monthly basis. Data are also exchanged annually with the Water Survey of Canada.