Takeaway: HydroForecast accurately predicted unprecedented high flows with very high accuracy (0.95 KGE three days ahead). Despite the model having never seen this level of flows in the basin, it correctly forecasted the timing, magnitude, and limb of a nearly 10x increase in flow.
Event description: In late April 2019, the Rouge River at Bell Falls reached dangerous water levels never before seen due to heavy spring rains mixed with melting of an elevated snowpack. Hydro-Québec reported that by April 1 soil moisture levels from snowpack were 177 percent of normal and rainfall was 210 percent of normal. This extreme weather caused unprecedented high flows, swelling the river to a one thousand year event. A state of emergency was declared. Residents below the dam were evacuated out of an abundance of caution and, though the dam did not fail, insured flood damages downstream on the nearby Ottawa River were widespread and estimated upwards of $200 million. Following the event, Hydro-Québec announced plans to increase flow volume capacity through modification of turbines to help prevent future risk from similar events.
Coincidentally, the April 2019 event fell during the validation period for HydroForecast’s Rodeo setup period, which is the time that Upstream Tech tested the model as if it were running in real-time using data it has never seen before. HydroForecast captured the timing of the rising limb and recession of this significant event quite well, and also forecasted the magnitude for the duration of the event and the entire freshet period within the 50% confidence intervals.