Late summer brings water quality concerns to Wellington
WELLINGTON COUNTY – Late summer and early fall can bring a combination of conditions that can lead to water quality issues, especially in the small, shallow lakes that populate Wellington County.
Warm water, lower water levels, congregations of waterfowl along shorelines and thunderstorms create a perfect storm of conditions for poor water.
And the effects can occur on two very different timelines.
Heavy rainfall rapidly washes fecal material from animals, as well as other sources of contamination, from shorelines and surrounding landscapes into lakes and rivers.
“Heavy rainfall can increase E. coli and other bacteria in lakes and rivers by washing contaminants from shorelines, fields, streets and other surrounding land into the water,” said Tyler Black, an environmental health specialist with Wellington-Dufferin-Guelph Public Health.
“Wind and waves can also stir up sand and sediment, which can impact bacterial levels in the water.”
The result is water with potentially hazardous levels of E. coli bacteria.
The period immediately following a major rainfall is particularly important, with E. coli levels rising within 24 to 48 hours.
Water quality can change quickly after rainfall, Black said, and swimmers should be especially cautious and consider avoiding swimming for at least 48 hours after heavy rainfall, particularly if the water is cloudy or there is visible debris or runoff.
Swimming in contaminated water can increase the risk of gastrointestinal illness as well as skin, ear, eye and respiratory infections.
There is also a second, slower process that can follow summer storms.
The same runoff that carries fecal material also delivers nutrients such as phosphorus and nitrogen into lakes and rivers. Under the right conditions, those nutrients fuel the growth of cyanobacteria, photosynthetic bacteria commonly referred to as blue-green algae.
Cyanobacterial blooms are particularly a concern beginning in late summer or early fall, Black said, once the water has had time to warm up enough to support the bacteria.
Unlike the relatively rapid E. coli response, cyanobacterial blooms may develop over days or weeks as nutrients interact with warm summer water, sunlight and relatively calm conditions. When blooms are significant enough, they can produce toxins.
Cyanobacteria occurs naturally in freshwater, Black said, but some blooms can produce toxins that are harmful to people and animals. It is not possible to tell by looking at a bloom whether toxins are present, so any suspected bloom should be treated as potentially harmful.
People using local waterways, and particularly those bringing dogs with them, should be aware of both the short- and long-term impacts of storms in late summer and early fall.
Dogs may drink directly from lakes and rivers or enter shallow shoreline areas where bacteria can accumulate, potentially increasing their exposure.
Residents can reduce their risk by:
- checking local public health and conservation authority information before swimming;
- being cautious about entering water shortly after heavy rainfall;
- avoiding water that appears discoloured or has visible surface scum and
- preventing pets from drinking untreated surface water.
Suspected blue-green algae blooms should be avoided, Black said, with children and pets kept away from affected water.
