An 85-metre zone of protection around drinking water reservoir lakes and transmission creeks has been recommended by a local aquatic biologist in a presentation to the managers of water utilities in B.C.
Heather Larratt was speaking at a meeting of the Water Supply Association of B.C. in Kelowna Friday on a study she undertook of source water protection zones.
“There’s no substitute for source water protection,” she warned.
Although existing uses would likely have to be grandfathered, such a requirement could be applied to proposals for any new construction or activities, she noted.
In fact, she questioned whether we shouldn’t be purchasing back the lakefront cottages on reservoir lakes.
B.C. is behind the times when it comes to protecting domestic watersheds. In many other parts of the world, including China and Chile, they are purchasing back watershed land in order to protect drinking water quality, she said.
Larratt has 30 years experience as an aquatic biologist, consulting throughout the Okanagan and across the country, working for both government and corporations.
She told the water utility administrators that water is what makes a lake a lake.
“Of the total, 25 per cent is the mud lining the bottom, 25 per cent is the shape of the bowl, and 50 per cent is the incoming water quality,” she said.
The water quality changes during its storage in the lake, as algae increase, sediments and cysts go down and usually nutrients also go down, while pH goes up, she explained. “When you say ‘lakes,’ everyone envisions different things,” she said.
And, many people just don’t recognize that their little activities can make a big difference to the quality of water in the lakes they use for one purpose or another.
Urban areas are under threat, and intake protection zones would help to protect drinking water, she said.
That would be a scientific way to define a small zone that is the most vulnerable, but a manageable area, in size, without having to deal with the entire lake.
She has been conducting experiments to determine exactly what is ‘the’ most critical zone in the area of an intake, considering such variables as water currents, weather, wind patterns and depth.
Keeping within a two-hour travel time for a contaminant, a 300-400 metre zone would help to protect an intake, she determined.
That would be a zone within which no new stormwater outfalls would be permitted, for instance.
However, she says she hasn’t yet been able to find a political vehicle for protecting the water within that protection zone, and is now looking for ways to implement the zoning.
“It’s all about protecting drinking water at its source,” she commented.
Particularly in multi-use watersheds such as in the Okanagan, it’s most critical to protect spots near intakes, as well as in the watersheds, with a protection zone around the margins of reservoir lakes and creeks which carry drinking water from the reservoir to the treatment plant and the users, she explained.
That would be a no build, no disturb, no machine protection zone, which she proposes should be 85 metres from the high water mark.
If the zone is vegetated, that zone could provide protection from 90 per cent of contaminants, she figures.
As well, she believes that new activities wanting to move into a watershed should have to prove they won’t impact water quality, instead of the opposite being proven after the fact.
True cost accounting should be applied before new activities in domestic watersheds are approved, she advised. The alternative of increasing treatment downstream is considerably more expensive than what she’s suggesting, she pointed out.