Upper Thames River Watershed moves to Level 1 Low Water Conditions (low water update, July 14, 2020)
One Month Precipitation
The Upper Thames River watershed received an average of 53 mm of precipitation in June (about 67% of normal), ranging from 40 mm in Stratford, to 80 mm in London. The long term average for June is 80 mm, measured at the London Airport and reported by ECCC.
Three Month Precipitation
The watershed received an average of 160 mm of precipitation from April to June (about 68% of normal), ranging from 130 mm in Stratford, to 223 mm in London. The long term three month average total for April to June is 237 mm, measured at the London Airport and reported by ECCC. If the three month total precipitation falls below 80% of the long term average value, a Level I Low Water Condition is triggered.
18 Month Precipitation
The 18 month (January 2019 – June 2020) precipitation measured by Environment Canada at the London Airport totaled 1505 mm, or about 106% of normal. The 18 month long term average precipitation total for the end of May is 1422 mm.
Monthly Streamflow
June stream flows were generally above 50th percentile flow rates, which indicate normal conditions for this time of year. Looking at seven day average flows, however, they are dropping and any rain received over the remainder of the summer is unlikely to boost flows for any extend period.
Recommendation
Based on the three month precipitation being below the level I threshold in most of the watershed, and on stream flows dropping, it is recommended that the watershed move to a Level I Low Water Condition.