Due to a history of flooding along Lake Champlain, and in response to long-standing international agreements, the National Weather Service (NWS) Northeast River Forecast Center (NERFC) has developed a forecast model for the Lake Champlain watershed. This 21,328 km² basin, includes contributing area in Vermont, New York and Quebec. Daily river stage forecasts are produced on several tributaries to Lake Champlain as well as lake level forecasts at the lake outlet. Weekly ensemble stream flow predictions providing forecasts for 45 days into the future are also provided for each forecast point including the Lake Champlain level at Rouses Point. All products are graphically displayed on the NERFC website. These longer range forecasts are serving as a demonstration of the NWS Advanced Hydrologic Prediction Services which is designed to expand the information content of hydrologic outlooks through improved graphical presentations and probabilistic outlooks.

Nineteen sub-watersheds were calibrated using the NWS River Forecast System (NWSRFS). The NWSRFS includes the Sacramento Soil Moisture Accounting model, unit hydrograph analyses, a snow accumulation and depletion model, reservoir operations and routing schemes, and channel routing. The channel and reservoir/lake routing routines use both hydrologic and dynamic routing methods.

Dynamic routing of each sub-watershed hydrograph into Lake Champlain was completed using the NWS FLDWAV model. Sub-watershed lateral inflow is routed through Lake Champlain to the Richelieu River. The use of the dynamic routing technique allows for a forecast water level at other points of interest in the lake, including Burlington. Hydrologic Engineering Center’s River Analysis System (HEC-RAS) was used to develop the backwater profile along and through the controlling sections at Saint Jean’s Shoal.

Wind effects can have a significant impact on lake levels. An inland version of the Sea, Lake, and Overland Surge from Hurricanes (NWS-SLOSH) is in the development stage and is being coupled with the National Center for Environment Prediction (NCEP) Aviation (AVN) model for its forecast wind data. This model output will be used to refine the hydrologic/hydraulic model output for Lake Champlain levels in the short-term.

Forecasts were available throughout Spring 2001 when a significantly above average snowpack occurred in the basin. Available products allowed emergency managers in both the United States and Canada to monitor the potential for serious flooding in the basin.