Lake Levels and Runoff May 9, 2019
It is that time of year when waterfront property owners may begin to wonder what may be coming as lake levels rise through the rest of May and June.
Lake water levels through the winter decreased steadily until the last week of March to a near record low elevation for that time of year. At that time seasonally warm weather started the melt of the low-level snowpack and lake levels rose steadily through April as the melt continued. As reported in the Province’s May 1, 2019 Snow Survey and Water Supply bulletin (https://www2.gov.bc.ca/assets/gov/environment/air-land-water/water/river-forecast/2019_may1.pdf ), the low and mid-level snow packs have now melted . Over the past week or so we have seen a slowing of the rise in the lake level as the higher level snow pack (>1600 m) have not yet ripened and started to melt.
As in past years, we are monitoring the Province’s projections for increases in the rate of runoff in the South Thompson River near Chase (which is directly related to the level of Shuswap Lake. With the forecast of warm weather this week lake levels are expected to rise quickly over the next ten days, increasing as much as 0.7 m (2.3 feet) from current levels.
What does this mean in the context of the expected peak of the lake over the next month or more? Based on the Provincial Snow Bulletin, the snow-pack for the South Thompson River basin was 82% of normal as of May 1. Further, they indicate that there is a low likelihood of flooding occurring in the southern interior (and in particular the South Thompson) this spring from snowmelt. However, they do indicate that May and June are typically wet months and therefore there could be flooding in local areas from rainfall events. Never-the-less we are cautiously optimistic that we will not see flooding around the lakes this year.
We will continue to monitor the runoff forecasts and keep our members informed throughout the remainder of May and June.