Upper Thames River in Level 1 Low Water Condition (low water update, July 18, 2022)
30 Day Precipitation
The Upper Thames River watershed received an average of 17 mm of precipitation between June 15 and July 15 (about 22% of normal). The long term average for this period is 79 mm, measured at the London Airport and reported by Environment and Climate Change Canada (ECCC).
90 Day Precipitation
The watershed received an average of 137 mm of precipitation between April 15 and July 15 (about 58% of normal). The long term average total for this period is 238 mm, measured at the London Airport and reported by ECCC.
A Level 2 Low Water Condition is triggered if the three month total precipitation falls below 60% of the long term average value.
18 Month Precipitation
The 18 month (January 15, 2021 – July 15, 2022) precipitation measured by ECCC at the London Airport totaled 1340 mm, or about 94% of normal. The 18 month long term average precipitation total for July 15 is 1429 mm.
Monthly Streamflow
The July 15th 30 day average stream flows were generally above the 25th percentile flow rates. However, with little precipitation received over the past two weeks, flows are expected to drop quickly by the end of the month.
Reservoir Status
The UTRCA maintains three large reservoirs and several smaller ones across the watershed. Two of the large reservoirs provide flow augmentation in the summer, meaning they store spring runoff and then slowly release this water back into the river system in the dry summer months. Both Pittock and Wildwood Reservoirs (South Thames River in Woodstock and Trout Creek above St. Marys, respectively) reached target summer elevations this spring and are currently augmenting downstream flow, with their levels slowly decreasing. The water levels at both reservoirs are slightly below the operating guideline elevation (0.15 m below at Pittock, 0.3 m below at Wildwood).
Recommendation
Based on the 90 day precipitation totals across the watershed being below 60% of the long term average (Level 2 trigger), but with still relatively normal 30 day stream flow, it is recommended that the watershed move to a Level 1 Low Water Condition.