How a new mini-wetland creates a natural filter for a PEI farm field

A watershed group in eastern PEI is experimenting with a new mini-wetland that will filter pollutants, fertilizers and pesticides from water trickling from the neighboring agricultural field.

The new vegetated ditch will also absorb carbon and create wildlife habitat.

The Souris and Area Branch of the PEI Wildlife Federation is one of the partners in the project.

“It will be an elongated ditch, wider than a normal drainage ditch would be,” says project manager Jake MacKinnon.

“The idea is that it holds water and encourages it to stagnate, and all the nutrients in the water will help feed what should hopefully turn into a thriving wetland site.

“It should help filter any runoff coming from the nearby agricultural field, as well as provide lots of habitat for birds, vertebrates and amphibians.”

Easier to build

The Souris River Basin Group has been working with local farmers to add other wetlands as part of the Living Labs project.

But MacKinnon says the mini-wetland is a new concept.

“These sites were designed as a more low-impact version of a fully constructed wetland,” MacKinnon said.

“The idea is that it takes up a lot less footprint in the field, so it’s much easier to implement. You could have a bunch of smaller sites that are widespread compared to one or two bigger ones.

It took the watershed group several days to build the new mini-wetland.

“The biggest factors for us on this site were a low grade, which meant we weren’t going to catch too much runoff. Because this is an experimental site, we want to have a fairly controlled input,” MacKinnon said.

“We also wanted to have it near a watercourse to make sure that — assuming it works — it will also have a beneficial impact on the local ecosystem.”

MacKinnon said the researchers will take samples every two weeks along the new mini-wetland and test them for nitrogen levels.

He said the field next to the mini-wetland will have potatoes next season, “where we tend to see the greatest amount of nitrates. That should give us a pretty good sample year to see very quickly what kind of an impact this ditch going to make.”

Wetlands are one of the strongest carbon sinks we have at our disposal.—Jake MacKinnon, Souris and Area Branch of the PEI Wildlife Federation

MacKinnon said reducing greenhouse gas emissions by storing carbon in the mini-wetland is another goal of the pilot.

“Actually, sequestering carbon is one of the main goals of this project,” he said. “Wetlands are one of the strongest carbon sinks we have at our disposal.”

Climate change

A research scientist at Agriculture and Agri-Food Canada said the idea for the project comes from the United States, where they are widening existing ditches and planting vegetation to slow the flow of water and reduce pollutants.

Audrey Murray said PEI doesn’t have the same types of ditches, so they build wetlands on the side of farms instead.

“Wetlands are almost the perfect device for natural water treatment,” said Murray.

“Our hope is that we will be able to essentially increase the percentage of wetland in agricultural ecosystems[and[takesomeoftheagriculturallandbackforwetland”[en[eendeelvandelandbouwgrondterugtenemenvoorwetland”[and[takesomeoftheagriculturallandbackforwetland”

Murray said the new mini-wetlands also provide protection against potential threats from changing weather patterns.

“One of the biggest challenges, especially for PEI, that we face with climate change is extreme rainfall,” she said.

“So at that extreme rainfall, instead of all the water reaching the waterway, the river, the water held in the wetland will later reach the river. So the big storm surge in the river will be flattened and prevent flooding of that river.”