Volume 195: The Coordinating Committee 

on Great Lakes Basic Hydraulic and Hydrology 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 the 

St. Lawrence in the Atlantic Ocean. The drainage 

basin, (figure 1) which includes the surrounding 

land and water surface, covers more than 400,000 

square miles from Duluth, Minnesota in the west 

to Trois Riviéres, Quebec on the St. Lawrence 

River. Eight U.S. states and two Canadian 

provinces 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 and are the largest 

fresh water system in the world. Joint use of these 

waters requires internationally coordinated basic 

hydraulic and hydrology data.

Figure 1: The Great Lakes Basin

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, a concerted effort to study and evaluate 

the data used by both countries was required.

With the arrival 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 the 7th of 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 

Great Lakes

Update
Vol. 195 Great Lakes Update July 2016

Page 2

States and Canada, charged with the responsibility 

for collecting and compiling the Great Lakes 

hydraulic and hydrologic data.

Recently, the 100th meeting of the Coordinating 

Committee was held on the 3rd and 4th of May 

2016, once again in Ottawa. This meeting 

celebrated the seven plus decades of international 

collaboration between the United States and 

Canada, and while methods, data sources and data 

requirements have changed, the need for 

consistency across the international border 

remains a paramount goal of the Committee.

Committee Highlights

The Committee is ad hoc in nature, meaning its 

success requires leveraged resources from the 

federal governments. Experts from federal 

agencies in both the United States and Canada 

meet and discuss Great Lakes issues regularly. 

U.S. participating agencies include:

• U.S. Army Corps of Engineers (USACE)

• National Oceanic and Atmospheric 

Administration (NOAA)

• U.S. Geologic Survey (USGS). 

Canadian federal agencies include:

• Environment and Climate Change Canada 

(ECCC)

• Natural Resources Canada (NRCan) 

• Fisheries and Oceans Canada (FOC).

All of the participating agencies have water 

management roles or related oversight in the Great 

Lakes region. The roles and responsibilities of the 

Committee are wide ranging and include:

• collecting, compiling, using, or 

disseminating data related to hydraulics, 

hydrology, vertical control and water 

levels for the Great Lakes – St. Lawrence 

River System

• serving in an advisory capacity to provide 

international standardization of hydrologic 

& hydraulic data for the federal agencies 

involved in monitoring and managing 

water quantity 

• supporting and facilitating agreement on 

the methods/procedures used in 

collecting/computing related data as well 

as the publication and distribution of 

coordinated data and results

• determining and reporting the uncertainty 

in the basic data to the extent practicable

Six members make up the current Committee, with 

each country having a chairperson, a general 

member and a secretary. The chairpersons serve 

in a general manager role and are well versed in 

Great Lakes water management issues. The 

members serve as management aides, while the 

secretaries lead the preparation of minutes, 

meeting venue selection and handle all 

correspondence of the Committee. The 

Committee generally meets twice each year, with 

the spring meeting led by the Canadian contingent 

and the fall meeting led by the U.S.

Committee Work

Currently, four Subcommittees perform the 

technical work undertaken by the Committee. 

These subcommittees conduct required technical 

studies through collaboration with the appropriate 

agencies. Current Subcommittees are:

• Vertical Control/Water levels

• Hydraulics

• Hydrology

• Coordinated Routing Model Update
Vol. 195 Great Lakes Update July 2016

Page 3

Vertical Control/Water Levels

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.

A planned datum update will occur over next 

several years with a planned implementation in 

2025 and the Vertical Control – Water Levels 

Subcommittee will again have an active role in its 

development and implementation.

Figure 2: NOAA water level station at Mackinaw 

City, MI (courtesy of NOAA)

The Vertical Control/Water Levels Subcommittee 

also works on water level gauging activities. 

NOAA operates and maintains fifty-three gauges

(Figure 2) in the Great Lakes - St. Lawrence River 

basin; FOC operates and maintains thirty-three 

gauges; and USACE operates and maintains eight. 

Coordination on all elements is required for a 

quality gauging station.

Hydraulics

The Hydraulics Subcommittee documents

methods for conducting hydraulic field 

measurements (Figure 3). 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.

Figure 3: Measurements in the Niagara River

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, such as the International 

Upper Great Lakes Study. Ice and weed 

retardation values are generally agreed upon at the 

same time. 
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Page 4

Hydraulic modeling methods are currently being 

evaluated and coordinated by the Subcommittee. 

Methodologies and standards for modeling are 

being agreed upon and modeling efforts are under

way for all connecting channels and the St. 

Lawrence River.

Hydrology

The Hydrology Subcommittee spends a great deal 

of effort in coordinating forecasted water levels for 

the Great Lakes and official water level statistics. 

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.

A prime example of a coordinated Great Lakes 

product is The Monthly Bulletin of Water Levels 

for the Great Lakes, which accompanies this 

article. Each month staff from the USACE in 

Detroit, MI and staff from the ECCC office in 

Cornwall, Ontario produce forecasts, using a 

variety of scientific methods. Prior to release, the 

results from each office are meshed into the final 

product, which is then distributed to customers on 

both sides of the international border. 

Recent focus of the Hydrology Subcommittee has 

been on identifying and documenting the evolving 

methods in use to collect and estimate 

precipitation, runoff and evaporation. These 

components together make up the net basin supply 

to the Great Lakes and are the primary influences 

on water level fluctuations.

Coordinated Routing Model Update

This new Subcommittee is focusing on the 

coordination, review and development of an 

improved hydrologic routing/regulation model 

that will efficiently and accurately simulate water 

levels and flows in the Great Lakes and the 

connecting channels.

A routing model takes estimates of the components 

of the water supply to the lakes and converts them 

to lake levels and channel flows using coordinated 

equations and coefficients. The new model will 

employ modern computer programming and 

incorporate the most up to date Great Lakes 

regulation strategies. All other sub-committees 

will have input to the development of the new 

routing model. Engagement with current and 

potential users will ensure that the new model is 

adaptable to changing needs. 

More Information

Like this article, future Great Lakes Updates will 

be included in various editions of the Monthly 

Bulletin. Topics will rotate between Great Lakes

hydrology and lake levels and other less technical 

pieces relevant to the Great Lakes as a whole. 

February’s Monthly Bulletin will typically include 

an annual summary from the prior year. All of our 

past Update Articles can be read online here:

http://www.lre.usace.army.mil/Missions/GreatLakesInform

ation/NewsandInformation/GreatLakesUpdateArticles.aspx

If you have an idea for an Update Article topic, we 

would love to hear it. Please send your ideas via 

email to hhpm@usace.army.mil.

The Detroit District also has a Facebook page 

which can be found here:

https://www.facebook.com/pages/Detroit-District-USArmy-Corps-of-Engineers/144354390916