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Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data

    The Great Lakes - St. Lawrence River system extends southerly and easterly from the headwaters of tributary streams in northern Minnesota and western Ontario, to the Gulf of St. Lawrence in the Atlantic Ocean. The drainage basin (which includes the surrounding land and water surface) covers more than 400,000 square miles (1,000,000 square kilometers) from Duluth, Minnesota in the west to Trois Rivières, Québec on the St. Lawrence River. Eight states of the United States and two provinces of Canada border on the Great Lakes - St. Lawrence River system. The waters of this vast system of lakes and their outlet channels are shared by the United States and Canada. Joint use of these waters requires internationally coordinated basic hydraulic and hydrologic data.

    Prior to 1953, responsible Federal agencies in Canada and the United States independently collected and compiled data pertaining to the hydraulic and hydrologic characteristics of the Great Lakes and St. Lawrence River, with only superficial and informal coordination of some of the data. As a consequence, the same basic data developed on different bases and datum planes, were often not compatible. To remedy this situation required a concerted effort to study and evaluate the data used by both countries.

    With the advent of extremely high lake levels in 1952 and the impending hydroelectric power and navigation developments in the St. Lawrence River system, Canadian and U.S. agencies recognized that continued independent development of basic data would be illogical. They realized that early agreement on the hydraulic and hydrologic characteristics of the system was of paramount importance. Therefore, the U.S. Army Corps of Engineers and the Canadian Departments of Transport, Mines and Technical Surveys and Resources and Development, opened negotiations early in 1953 for the purposes of establishing a basis for development and acceptance of identical data by both countries. The negotiations culminated in a meeting of representatives of the interested agencies in Ottawa on 7 May 1953.

    At that meeting, the Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data was established. This committee serves in an advisory capacity to the agencies of the United States and Canada who are charged with the responsibility for collecting and compiling the Great Lakes hydraulic and hydrologic data.

    Currently the Committee consists of six members; a chairperson, member and secretary for each of the two countries. The Committee generally meets twice annually, alternating locations between the United States and Canada. The Committee has three subcommittees, as follows: Vertical Control - Water Levels, Hydraulics, and Hydrology. These subcommittees are directed to conduct the required technical studies through collaboration with the appropriate agencies of Canada and the United States. Occasionally, ad-hoc subcommittees are formed in order to accomplish certain tasks.

    Major accomplishments of the Vertical Control - Water Levels Subcommittee include the establishment of the International Great Lakes Datum (IGLD) 1955 and the revised IGLD 1985. The revision to the datum was required due to the continued effects of crustal movement, new surveying methods, and the deterioration of the zero reference point gauge location. Additionally, vertical movement is studied to provide an estimate of the change expected between the published dynamic heights related to the IGLD 1985 and true dynamic heights continuously changing with time. This helps planning for future upgrades of the datum.

    The Vertical Control - Water Levels Subcommittee also works extensively on water level gauging activities. The National Oceanic and Atmospheric Administration (NOAA) operates 53 gauges in the Great Lakes - St. Lawrence River basin; the Canadian Hydrographic Service (CHS) operates 34 gauges; and the Corps of Engineers operates 18. Coordination on all elements required for a quality gauging station is continuous. The subcommittee has also published the "History of Water Level Gauges" for the basin. These reports document the history of the operation of water level gauges on the Great Lakes and their outflow rivers including locations, bench marks, relocations and maps.

    The Hydraulics Subcommittee has documented methods for conducting hydraulic field measurements Discharge data in the connecting channels of the Great Lakes are important data elements in all studies of levels and flows. As such, consistency in the collection of these data sets is important. Additionally, a report documenting all sites at which discharge measurements had been made in the past was completed. This includes location maps, measurement techniques, computation methods, water level readings and tables of the actual discharges.

    The Hydraulics Subcommittee also coordinates actual monthly flow values for the St. Clair, Detroit and Niagara Rivers. These are done periodically and are reported for use in further Great Lakes studies. Ice and weed retardation values are generally agreed upon at the same time. Hydraulic modeling is currently being coordinated by the subcommittee. Methodologies and standards for modeling are being agreed upon and modeling efforts are underway for all connecting channels and the St. Lawrence River.

    The Hydrology Subcommittee spends a great deal of effort in coordinating forecasted water levels for the Great Lakes. It is important that there is one coordinated information base issued to the public so there is not confusion about which set of numbers an individual should use. The actual data values that make up the forecast bulletins are coordinated as well as the graphics and text on the document itself.

    Many individual pieces of hydrometeorologic data that go into the forecasting process are also coordinated to ensure the same base of information is being used for all work. Monthly mean water levels, outflows, precipitation and net basin supplies are all discussed. These data are also used in many Great Lakes studies.

    Occasionally, ad-hoc subcommittees are formed in order to accomplish certain tasks. An ad-hoc group has been created to oversee the development of a consistent model to simulate the regulation and routing of outflows and levels in the Great Lakes to be used by all agencies. Another ad-hoc group has recently been created to assist in the updating of coordinated physical data for the Great Lakes basin. The group will be looking at drainage areas, shoreline lengths, lake volume and depths and general dimensions, storage capacities and basin delineations. Many of these data themes have been analyzed in the past, but due to many new technologies, the resultant physical data from these analyses will be more accurate. Having the data available for use in a geographic information system base will also be an excellent improvement.

    The Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data was created to ensure the agencies of the United States and Canada, charged with the responsibility for collecting and compiling relevant data, had a mechanism for agreeing on past and present data concerns. This has led to an excellent working arrangement between agencies in the two countries and an overall best management of the key resources of the Great Lakes basin. While the objectives of the committee and each subcommittee have experience small changes over the years, the Committee's existence for over 50 years is a testament to necessity, acceptance and cooperation.