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Articles

1971: Vol. XLVIII, No. 2

The Mean Water Level at Pointe-au-Pere As used for the International Great Lakes Datum (1955)

Submitted
August 11, 2015
Published
2015-07-02

Abstract

The use of a number of different vertical control datums in carrying out hydraulic studies, crustal movement investigations and hydrography, in establishing water rights and negotiating water treaties is not only confusing but leads to complications. Because Canada and the United States of America share most of the Great Lakes — St. Lawrence River System, a solution to the problem of an acceptable international vertical control network had to be found. The datum chosen for the system is the mean water level determined at the gauging station at Pointe-au-Pere at the mouth of the St. Lawrence River. This datum is not the same as those used by the U.S. Coast and Geodetic Survey or the Canadian Geodetic Survey. The datum is also quite distinct from both national levelling networks since dynamic elevations or heights are employed rather than the usual orthometric elevations. Furthermore, it takes into account any crustal movement which had taken place prior to the year of levelling and computation. As a co-operative venture shared by Canada and the United States, levelling was carried out from Pointe-au-Pere to the lakehead to establish elevations relative to the new datum at each gauging site and at all bench marks along the route.