There’s a spot in Harper Park, the 150-acre wooded greenspace in Peterborough’s south end, where you can occasionally sit and watch as coldwater springs from an aquifer below bubble up around you.
“You can see water coming up like you’ve turned on a drinking fountain,” says Kim Zippel, Otonabee Ward councillor and one of the park’s strongest champions over the years. “And then it goes back down, and then it comes up again, two feet away.”
“It’s just the coolest thing,” says Zippel, whose efforts led to the Harper Park wetland being designated as provincially significant in 2017.
The aquifers in Harper Park are an ancient source of groundwater, a remnant of a glacial lake that mostly dried up thousands of years ago. They are replenished by precipitation, which they store and then slowly release back into the watershed. In this way, they serve as the headwaters for one of Peterborough’s most ecologically sensitive watercourses: Harper Creek.
It’s helpful to think of Harper Creek more as a creek system, with a southern branch and a northern one. Both originate in the Harper Park wetland, and both are tributaries of the larger Byersville Creek, which flows out to the Otonabee River after all three converge under the railroad tracks just west of the Kingsway.
From its groundwater source deep in the park, the southern tributary meanders through swamps and woods for about a kilometre. It then exits the park just east of the City’s composting facility and crosses under Harper Road in a culvert. On the other side of the road, South Harper Creek bends toward the northeast, and then runs alongside the Canadian Pacific railway tracks for a few hundred metres before merging with North Harper Creek and Byersville.
The northern branch of the creek doesn’t travel through the park for as long. Its groundwater source is near the northeastern corner of the park, which it exits at the corner of Rye Street and Harper Road. From there, the creek flows in a ditch alongside Rye Street, its path punctuated by no less than ten culverts. At Webber Avenue, the creek veers south toward the railroad tracks and the confluence with Byersville and South Harper creeks.
For most people in Peterborough, this creek system is out of sight. Unless you’ve had reason to visit the business park it flows through or walk along the railway tracks, you may never have seen it.
Harper Park, too, has remained relatively obscure. When she first started exploring it, the park was “a bit impenetrable because it was a wetland,” Zippel remembers. “And there weren’t any trails. There was no signage telling people that [the park] was there.”
For a long time, this obscurity led many to discount and doubt the ecological significance of Harper Park and Harper Creek, Zippel says. But now, after a decade’s worth of studies that were kickstarted by citizen scientists and naturalists, the creek’s profile has been raised, and so too has the profile of its most remarkable inhabitants: a rare population of brook trout.
At home in a ditch
Zippel was first introduced to Harper Creek about a decade ago by Tom Whillans, a professor in the School of the Environment at Trent University. On their way home from a field trip for a course in wetland management planning, Whillans stopped Zippel and her fellow students at the corner of Harper and Rye.
“Guess what, there’s brook trout here,” Zippel remembers Whillans telling the group.
“And all [we saw was] this ditch along Rye Street,” she says. But it was true, the fish were there, swimming in between the culverts.
For Ian Boland, the City of Peterborough’s senior watershed project manager, this 100-metre stretch of creek along Rye Street is the most precious in the city. And like Zippel, Boland still speaks about it with a sense of surprise.
“If you didn’t know what you were looking for, you’d hardly notice it,” he says. “You wouldn’t think there’s great habitat there. There’s hardly any vegetation around it.”
But the brook trout “have just the right amount of groundwater,” Boland says. “There’s the right amount of sediment, the right amount of ripple-pool sequences. They just seem to thrive in that little section.”
The story of these brook trout is incredible. But to understand it, you have to start more than 10,000 years ago, when a glacial lake covered all of Harper Park and much of the southern half of what we now call the City of Peterborough. The lake, along with many other watercourses that have long since disappeared, was formed by meltwater as the last glacier retreated from the region.
Brook trout thrive in the kind of cold water that the glacier left behind as it melted, and it was in this period of glacial retreat and abundant freshwater that brook trout likely found their way to Harper Park, Jacob Bowman says. Bowman is an avid angler and Trent University biology student. He studied the brook trout in Harper Creek for an award-winning high school science fair project.
Gradually, the glacial lake and the streams that used to drain it dried up. But the wetland in Harper Park, with its aquifers that store, purify and release rainwater, have continued to feed Harper Creek and sustain the brook trout population since then.
For some time now, these fish have been confined to the Harper Creek and Byersville Creek subwatersheds. But that doesn’t mean they don’t move around. Researchers recently tracked the fish with radio transmitters, and observed them swimming over two kilometres through the creek in less than a week.
Still, there is no way in or out of this creek system for the brook trout, and that leaves them isolated. To prove the point, studies have shown that they’re genetically distinct from other brook trout in the province of Ontario. “They’re unique,” says Boland. “Those fish have been there for thousands and thousands of years.”
A rarity in Canada
The presence of these fish is made all the more notable by their rarity. “There are very few examples of brook trout living in urban areas in Ontario, [or even] Canada,” Whillans says. “It’s just really uncommon.”
Brook trout “are a very sensitive species to development, and it doesn’t take long for development to eliminate them,” Whillans continues.
Whillans says it’s the consistent supply of cold, clear groundwater coming from Harper Park that allows the brook trout population to survive in this unlikely location.
But while they’ve shown resilience in this business park, the brook trout in Harper Creek do face significant pressures as the watershed urbanizes around them.
For example, those groundwater springs in Harper Park aren’t the only water source of the creek anymore. Stormwater from the neighbourhood west of the park spills into the watershed, which threatens to raise the temperature of the creek to levels beyond what the trout can thrive in. The stormwater also brings silt along with it, clouding the water and hiding the pebble substrate that the trout prefer.
“There are all these little artificial tributaries that are impacting the creek,” Zippel says of the stormwater runoff in the watershed.
To guide future development decisions in the area and to chart a plan for protecting the creek, the City of Peterborough is developing a subwatershed plan for Harper Creek.
But Zippel has already seen damage done to the park in the time since she first fell in love with it.
Now, when she visits, she finds the experience disconcerting. “Sometimes it’s hard for me to go back and walk through, because it is changing, and it’s degrading,” she says. “Going in and walking there now doesn’t relieve stress for me, because I see the changes. I see the increase in invasive [species], the damage the ATVs have done.”
In any case, Zippel doesn’t get as many opportunities to visit the park these days; her duties as a councillor mean she doesn’t have the time to be the champion for it that she used to be. But perhaps sometime soon, Zippel will connect with Harper Creek again. In June, she announced that she would not be running in the 2022 municipal election, writing on her blog that she believes her energy “will be more effective at the grassroots level.”
“I think when I’m done with council, I’ll just be a tour guide of Harper Park,” she said, half-joking but half-serious, when I spoke on the phone with her this summer.