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Information on Research Based Hydrologic Input/Output Measurements

Accurate hydrologic data (precipitation, runoff, evaporation, net basin supplies, and more) are required for simulation, forecasting, and water resource studies on the Laurentian Great Lakes and their basins. These data are derived from quality controlled meteorological and hydrological input data. The raw data utilized were collected from several sources, so the periods of record for each lake vary. NOAA-GLERL has been compiling this data since the mid 1980s.

CROLEY, T.E., II, and T.S. HUNTER. Great Lakes monthly hydrologic data. NOAA Technical Memorandum ERL GLERL-83, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB95-173076/XAB) 83 pp. (1994).

View data spreadsheets.


Monthly estimates for over-land and over-lake precipitation are compiled for each of the Great Lakes. Data prior to 1930 (1918 for Lake Superior) were computed by the Lake Survey District of the U.S. Army Corps of Engineers and the National Ocean Survey. Data for 1930-1947 (1918-1947 for Lake Superior) were computed at the Great Lakes Environmental Research Laboratory (GLERL) from monthly station values. Data for 1948 to present were computed at GLERL using daily station data.

Relevant articles:

CROLEY, T.E., II, and H.C. HARTMANN. Resolving Thiessen Polygons. Journal of Hydrology, 76:363-379 (1985).

QUINN, F.H. and D.C. NORTON. Great Lakes Precipitation by Months, 1900-80. NOAA Data Report ERL GLERL-20, 29 pp. (1982).

National Climatic Data Center. Surface Land Daily Cooperative Summary of the Day TD-3200. National Climatic Data Center, Asheville, North Carolina (1987).

Atmospheric Environment Service. Climatological Station Data Catalogue, Ontario. Environment Canada, Downsview, Ontario (1981).

Simulated Evaporation

NOAA-GLERL Great Lakes Evaporation Model

Monthly evaporation estimates were derived from daily evaporation estimates generated by the NOAA-GLERL Great Lakes Evaporation Model. This is a lumped-parameter surface flux and heat-storage model. It uses air temperature, wind speed, humidity, precipitation and cloud cover averaged over area. These data are sufficiently available since 1950 (1953 for Georgian Bay). Over-land data are adjusted for over-water or over-ice conditions. Surface flux processes are represented for short-wave radiation and reflection, net long-wave radiation exchange, and advection. Atmospheric stability effects on the bulk transfer coefficients are formulated and used with the aerodynamic equation for sensible and latent heat surface fluxes.

Relevant articles:

CROLEY, T.E.II. Lumped modeling of Laurentian Great Lakes evaporation, heat storage, and energy fluxes for forecasting and simulation. NOAA Technical Memorandum ERL GLERL-70, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB89-185540/XAB) 48 pp. (1989).

CROLEY, T.E.II. Verifiable evaporation modeling on the Laurentian Great Lakes. Water Resources Research25(5):781-792 (1989).

CROLEY, T.E., II, and R.A. ASSEL. A One-Dimensional Ice Thermodynamics Model for the Laurentian Great Lakes. Water Resources Research, 30(3):625-639 (1994).

3D Ice-Hydrodynamic Coupled Model (ICEPOM)

Modeled evaporation from a 3D ice-hydrodynamic coupled model, ICEPOM. The hydrodynamic part is based on the Princeton Ocean Model and the ice part includes 2D dymamic model with the Elastic-Viscous-Plastic rheology and 1D thermodynaimc model. The daily evaporation for 2003-2012 is calculated from the hourly outputs of the evaporation flux [kg/m2/s] at the water surface. When ice cover exists in a computational cell, the evaporation flux is weighted by an open water fraction.

The two sets of data currently available on the dashboard are simulating evaporation at two locations where sensors have been deployed to monitor evaporation as well as other hydro-climatic variables. These locations are PERMS1 at Toledo Light #2 Structure and PERMS2 at the City of Toledo Water Intake crib, both in Western Basin, Lake Erie. More information on those sensors can be found here.


Fujisaki-Manome, A., J. Wang, X. Bai, G. Leshkevich, and B. Lofgren (2013), Model-simulated interannual variability of Lake Erie ice cover, circulation, and thermal structure in response to atmospheric forcing, 2003–2012, J. Geophys. Res. Oceans, 118, doi:10.1002/jgrc.20312.


Runoff data is computed from watershed runoff estimates by using streamflow records from major rivers, available from the U.S. Geological Survey for U.S. streams and the Inland Waters Directorate of Environment Canada for Canadian streams. Daily runoff values provided by these agencies were summed for each watershed within a lake basin. The runoff was extrapolated over ungaged areas; between 22% and 43% of the Great Lakes basin remains ungaged (Lee, 1992) thus the potential for error exists in runoff estimation. Weights were assigned to each non-overlapping streamflow gage by dividing its drainage area by the watershed area. Daily watershed runoff estimates were computed by summing all daily station values in the watershed and then dividing by the sum of their weights, to extrapolate for ungaged areas.

The Ogoki diversion flow is indirectly included in the runoff estimate for Lake Superior. It cannot be separated from measured runoff at Lake Superior since it is added upstream, in Lake Nipigon, and its timing obscured by routing through Nipigon and connecting channels to Lake Superior. The Ogoki diversion is about 0.8% of Lake Superior runoff.

Relevant Articles:

Showen, C.R.. Data formats for U.S. Geological Survey computer files containing daily values for water parameters. U.S. Geological Survey, Reston, Virginia (1980).

Inland Waters Directorate. Supplying Hydrometric and Sediment Data to Users, Second Edition. Water Resources Branch, Environment Canada, Ottawa, Ontario (1980).

LEE, D.H. Computation of net basin supplies: a comparison of two methods. Final Report Subtask 19.1.2a (Scenarios Based Upon 1900-1989 Supplies), Task 19.1.2, Task Group 2, Working Committee 3, Phase II - International Joint Commission Levels Reference Study, Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan (1992).

Net Basin Supplies (NBS)

The water supplies to a lake, referred to as the net basin supplies (NBS), are defined in terms of their components via the following forumula:

NBS = P + R - E

where P is over-lake precipitation, R is basin runoff to the lake, and E is lake evaporation. (Note: since Lake Superior runoff indirectly includes the Ogoki Diversion, NBS values reported here include the Ogoki diversion on Lake Superior.)

Lake evaporation is estimable from 1950 on (1955 on Lake Huron), since wind speed and humidity data exist only since 1948 (1953 on Georgian Bay) and 2 years are used for model initialization. Thus, NBS from the above equation from 1950 (1955 for Lake Huron) are reported here.

L2SWBM - Large Lake Statistical Water Balance Model

Water balance models are often employed to improve understanding of drivers of change in regional hydrologic cycles. Most of these models, however, are physically-based, and few employ state-of-the-art statistical methods to reconcile measurement uncertainty and bias.

Starting in 2015, NOAA-GLERL, along with its partners at CIGLR, began developing a water balance model under a Bayesian Markov chain Monte Carlo framework. Through this model, we generate new estimates of monthly runoff, over-lake evaporation, over-lake precipitation, and connecting channel flows for each of the Great Lakes. The new model reconciles discrepancies between model and measurement-based estimates of each component while closing the Laurentian Great Lakes water balance.

Find out more about the L2SWBM generated estimates of the above variables, along with channel flows, diversions, and changes in storage.