Review of 2019 Summer Weather and Water Management Across the TSW Reservoirs with Focus on Mississagua Chain of Lakes CCRAI Meeting – August 17, 2019 Ted Spence CCRAI Board member; Chair CEWF and Professor Emeritus in Environmental Studies York U. 1
The Trent-Severn Watershed(Source: Parks Canada Water Levels Website)
Reservoir & Flow-Through (RAFT) Lakes • In the “Haliburton Sector” (Haliburton County and northern Peterborough County) there are 35 reservoirs – • 17 in the Gull River system (23,669 ha-m storage), • 13 in the Burnt River System (7,609 ha-m storage), and • 5 in the Central Lakes area (12,388 ha-m storage) including the Mississagua chain of lakes, Anstruther , Eels, Jacks and Crystal lakes. • The reservoir seasonal water level changes of up to 10 feet (3.4 m) combined with severe flow constraints at some points downstream (e.g. Minden, Peterborough) • There are also challenges to maintaining navigable water levels on connecting rivers and flow-through lakes and minimum flows and levels for fisheries management.
Key Water-Flow & -Level Constraints • TSW priorities public safety (flood management and water supply) and canal navigation; • Minimum flow at Peterborough for water supply and sewage treatment; • Maintaining the Canal Regulations draught limits is understood to govern the drawdown from the reservoirs; • While aiming to maintain reservoir levels within historic norms
Recent Experience • In last three summers reservoir levels have been good for us but TSW has had to continuously adjust to extreme weather conditions. • 2016 extreme rain and flooding in March, record setting drought May to August. • 2017 early snowmelt, extreme rain early May, flooding and continuing excess rainfall. Higher than normal levels all summer and into fall. • 2018 extreme rain/snow/ice in April followed by drought conditions and spotty rainfall through to end of July and a Very wet August. • Now in 2019 extreme snowpack and very wet spring then more than 6 weeks of drought with only local rainfall events.
2019 Mississagua Lakes Water Management Experience • Dam remained at winter setting throughout March and April. • Higher than normal snowpack combined with April rainfall resulted in exceptional reservoir filling to above full with logs still out. • Same conditions applied throughout Trent Basin - too much water and storage full. Canal opening delayed because of high water and flows. • Strategy at Mississagua through May and into June was to pass as much water as possible while reacting to rainfall to avoid flooding. High river flows and active log operations. • In mid June some logs still out as they worked to manage level back down to normal range. • From early July - Drought conditions and minimum flows on Canal with draw from reservoirs.
2019 View at Mid-August • With climate change the year to year variability is increasing and we are seeing more extreme events including drought periods in 2016, 2018 and 2019. • In 2019, even with 3.5 times the normal snowpack at end of March and 180% of normal rain in April the flood levels were less than in 2017. • Strategy at Mississagua through May and into June was to pass as much water as possible while reacting to rainfall to avoid flooding. Then hold above normal level. • From early July - Drought conditions and minimum flows on Canal with draw from reservoirs. • We need significant rainfall basin wide NOW to avoid the risk of extreme drawdown.