2021 Runoff Report - May Edition
Runoff Review and Forecast Estimate
The mountain snowpack as well as current lake levels are very similar to the runoff of 2019. The 2019 snow melt started slowly and about 3 weeks earlier than this year, providing the lake with lots of opportunities to drain out some snow water before reaching its peak on the 6th of June. With a total lake level rise of 2.736m and a subsequent peak level of just 347.591m, 2019 has set the lowest recorded lake peak in 25 years.
Starting at a lake level of 245.077m and just 222 cm (8.7 in) higher than 2019, Shuswap Lake levels have now risen by 1.98m (78 in) as of today. Based on the slightly lower snow pack of 2019, first estimates suggest that Shuswap Lake will have to rise another 3 ft before reaching its final peak slightly below 348.000m this year before the mountains running out of sufficient snow water to further affect the lake levels. Therefore, no significant flooding is being expected this year; perhaps except minor spill-overs in some lower floodplains as well as into some farmland along the lower Shuswap River.
However and like every year, extreme weather patterns can always become a game changer. So far, this spring season has been notably cooler than usual and with barely any rain. This has caused a slow snow melt, resulting in less water reaching the Shuswap Lake. The few occasional rain showers have also been mostly mild, thus barely affecting lake levels in the short term. That is going to change as the weather will be warming up considerably next week to 30°C (86F) and potentially higher. Such hot air can hold much more moisture which, a some point, can lead to substantial downpours in the mountains and further contribute to a faster rise of lake levels; especially near the lake peak period. However, as lake levels might just be marginally affected, the highest risk might be for temporarily over-loaded mountain creeks and rivers.
Given the approaching heat wave, the Shuswap Lake level rise is certain to speed up by mid next week. Beyond that, we just have to wait and see how the weather develops during the week thereafter.