Using Climate Predictions in Great Lakes Hydrologic Forecasts

The Great Lakes Environmental Research Laboratory’s (GLERL’s) Advanced Hydrologic Prediction System (AHPS) illustrates the technology for those interested in using climate predictions in water resources decisions. It provides 1—6-month probability outlooks for 25 hydrology variables over the 121 watersheds and 7 lake surfaces of the Great Lakes basin, including simultaneous water levels on all lakes. The system incorporates both current conditions, antecedent to a forecast, and multiagency, multi-area, multi-period climate outlooks of meteorology probabilities. Extended water level forecasts are evaluated over three periods to determine the value of antecedent conditions and meteorological outlooks in making them. The suitability of GLERL’s AHPS forecasts is also considered relative to existing US and Canadian forecasts. While the use of antecedent conditions adds considerably to Great Lakes forecasting ability, the use of existing meteorological outlooks adds little. GLERL’s AHPS appears better than, or as good as, other Great Lakes forecasts and offers the advantage of improvement as better near real time data streams and improved process models become available. Forecasts that utilize climate predictions are used in several water resource decision settings, as illustrated here.