Low Water Conditions in the Upper Thames Watershed听
The summer's hot, dry weather has led the Low Water Response Team for the Upper Thames River watershed to declare a Level 1 Low Water advisory. The advisory is part of a to inform the public of local low water conditions.听
The key indicators used to evaluate low water conditions are precipitation over the past one month and three months, and stream flows over the past month. The 糖心直播 (UTRCA) measures flows at more than 30 stations across the Thames River and many of its tributaries. Some stations date back as far as 1915, and many others were installed in the 1950s. This gives Mark Helsten, UTRCA Senior Water Resources Engineer, a long-term comparison with current flows and an understanding of how the current data compares with long-term statistics.鈥疨recipitation is measured at more than 20 locations across the watershed.听
The watershed received an average of 46 mm of rain between August 1 and August 31, which is about 58% of the long-term average for that period. Rainfall over the past three months (June 1 鈥� August 31) was approximately 73% of normal. A Level 1 Low Water Condition is triggered if the three-month total precipitation falls below 80% of the long-term average.听
Flows in some streams across the watershed are at the low end of normal, with others experiencing lower than normal flows. The main North and South Thames Rivers are not affected as much as they are supported by water released from the UTRCA's reservoirs at Wildwood (St. Marys) and Pittock (Woodstock) Conservation Areas, respectively. Water is stored in these two reservoirs during the spring runoff, and then slowly released in the dry summer months to increase downstream flows in the main rivers.听
Low water conditions can have an impact on the amount of water available both for human use and for aquatic life.听听
In drier years, streams shrink back to isolated pools, or in some reaches dry up entirely. This disrupts natural connectivity, preventing fish and other aquatic organisms from moving between habitats to feed or escape stressors.鈥疐ish must cluster in shrinking pools. While this can temporarily sustain them, crowding increases predation pressure 鈥� you might see greater numbers of herons feeding in areas with isolated pools.鈥�听
UTRCA Aquatic Biologist, Erin Carroll, shared dramatic photos of a drain south of St. Marys. Erin and her crew found seven fish species (Creek Chub, Western Blacknose Dace, White Sucker, Brook Stickleback, Central Stoneroller, Bluntnose Minnow, Northern Redbelly Dace) at the site on June 20. On July 24, the same streambed was cracked earth.鈥疪ecent site visits across the watershed found other small streams that are much lower than normal.听听
Roulston Drain on June 20, 2025
White Sucker
Roulston Drain on July 24, 2025
Extended periods of below normal precipitation can also affect groundwater,听 which is an essential source of drinking water for many municipalities and residents. Groundwater plays a vital role in sustaining the baseflow of rivers and streams, too. Declining groundwater levels can reduce the natural discharge of groundwater to surface water, placing added stress on both human needs and aquatic life.听
Long-term monitoring by the UTRCA since 2001 has shown a decreasing trend in groundwater levels at many Provincial Groundwater Monitoring Network wells. These findings highlight the importance of proactive groundwater conservation to protect both groundwater and surface water resources for future use.听
The Low Water Response Team encourages people, businesses, and industries that rely on local surface water or groundwater to conserve water.听 Many watershed municipalities have water conservation programs in place. 听
The City of London and some other communities take water from Lake Huron and Lake Erie. While they may also have water conservation programs, these initiatives will not improve flows in the Thames River or its tributaries.听
The UTRCA watershed is not the only area experiencing dry conditions. The shows dry conditions in many regions, including Level 3 conditions in eastern Ontario.听