Great Lakes Seasonal Hydrological Forecasting Products (Experimental)

The Great Lakes Advanced Hydrologic Prediction System (AHPS) was developed in the mid-1990s as a framework for simulating and predicting the large-scale hydrology of the Laurentian Great Lakes. It includes software for processing historical and near real-time meteorology and propagating that meteorology through GLERL's Large Basin Runoff Model (LBRM) and Large Lake Thermodynamics Model (LLTM). The AHPS consisted of underlying model and data processing code written primarily in Fortran, along with a MS-Windows GUI that was coded in Pascal using the Delphi RAD tool. Please note that the Great Lakes experimental AHPS project is separate from the similarly-named National Weather Service Advanced Hydrologic Prediction Services.

GLERL's AHPS was run experimentally in a semi-operational mode, by GLERL, until 2016. In 2017, AHPS was superseded by the development of the Great Lakes Seasonal Hydrological Forecasting System (GLSHFS). GLSHFS uses the same underlying model components as AHPS (LBRM and LLTM), but the data processing code was significantly modified to standardize file formats and improve modularity. The Windows-centric GUI was eliminated in favor of a portable command line interface that allows for use of GLSHFS on multiple platforms. During this period, additional modifications were made to LLTM and LBRM, including changes to the native evapotranspiration algoirthm, and modifications to accommodate alternative solar radiative forcing variables.

With the development of GLSHFS, operational product dissemination was fully transferred to the United States Army Corps of Engineers - Detroit District, and GLERL discontinued semi-operational runs of the legacy AHPS system. As of November 2018, USACE-Detroit publishes water level forecasts derived from their operational implementation of GLSHFS. These forecasts are available directly from USACE at:

For access to any of the other AHPS/GLSHFS variables (e.g. net basin supply) that were formerly available from GLERL, please contact the USACE office at .

Please note that official lake level forecasts are published routinely in the USACE Detroit District Monthly Bulletin of Great Lakes Water Levels.


Data Questions

General Information & Media Inquires


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