SNOW PACK/LAKE LEVELS May 8, 2018
May has arrived and the level of Shuswap Lake is increasing rapidly in response to the warmer weather and melt of the low and mid-level snow pack. Things have changed since our last posting on this subject. Recent articles in the press and on television have documented the flooding in some watersheds and the continuing risk of floods elsewhere in BC. The May 1, 2018 Snow Survey and Water Supply Bulletin prepared by the BC. Provincial River Forecast Centre has been posted (https://www2.gov.bc.ca/assets/gov/environment/air-land-water/water/river-forecast/2018_may1.pdf) and provides the most current information. Snowpack indices in the South Thompson watershed have increased in the past month from 109% to 126% of normal in response to the cool wet weather experienced during the first three weeks of April. This compares with an index of 104% in 2012, 99% in 2016 and 109% in 2017 all recent years when there were high water levels on the lake.
To put this all in context, typically 100% of the annual snow pack will have accumulated by May1. Low and mid-level snowmelt would normally be well advanced and the high level snow-melt would have started. Examination of data for the high elevation snow courses show that melt at these elevations was just starting on May 1.
The volume runoff forecast for May to July, which includes runoff from snow melt and rain has increased to 108% of normal, up from 103% at the beginning of April. This measurement is for the South Thompson River at Chase (at the outlet of Little Shuswap Lake). As noted previously, the lake level is rising rapidly (~10 cm/day) and is tracking the 2012 and 2017 increases in water level quite closely. With melt of the high level snow pack just starting the risk of higher than normal water levels this spring is a real possibility.
In the May 8 edition of the Vancouver Sun there was a report, attributed to the Provincial River Forecast Centre, that modelled water levels in the Thompson River at Spences Bridge, downstream of Kamloops Lake and the Nicola River, could reach 1 in 100 year levels this spring. While not directly applicable to Shuswap Lake, it is a further indicator that we could expect water levels approaching those seen in 2012 and 2017. The forecasted weather conditions for the next couple of weeks are for some precipitation then a return to warm weather and if correct would continue the trend in increasing water levels observed over the past two weeks.
Click on the date to view the current Snow Survey and Water Supply Bulletin for May 1, 2018
If you needed to sandbag to protect your property in 2012 you could need to do it this year as well - the sooner the better and our Regional District is helping by providing bags and sand. Click for sand bag and sand locations.