Illinois researchers searching for the best ways to reduce nitrates in drinking water are looking to an unlikely tool: a remote-controlled airplane.
In the Mackinaw River watershed in Central Illinois, The Nature Conservancy and partners are working to reduce high nitrate levels in water by filtering agricultural run-off through wetlands, a tactic that research shows can reduce nitrates by 50%.
These particular types of wetlands are specifically constructed to collect and retain water from tile drainage. Tiling is an underground system of tubing that drains wet fields. These tiles then drain water—and untreated nitrates and phosphates from the field—directly into the river.
The challenge: Tiling is underground. You can’t detect it with your eyes. Literally millions of miles of tile run under Illinois farm fields, so locating tile patterns in farm fields is imprecise at best.
Enter the remote-controlled airplane.
The plane may look like a larger-version of your typical hobby aircraft (it has a nine-foot wingspan). But it operates on technology similar to that which powers military drones. The model being used in Illinois is called the Pteryx, built by a Polish company that specializes in drone technology. The first-ever Pteryx operated in North America is run by Illinois State University professor of geography Jonathan Thayn.
Here’s how it works: The plane is equipped to detect near-infrared wavelengths, wavelengths on the light spectrum that people are unable to detect. Water absorbs near-infrared wavelengths. A lake (or wet field) will show up as black when photographed with a near-infrared camera.
The plane is thus flown over a field after rainfall, photographing it every few seconds. It will be flown periodically in subsequent days. The near-infrared camera will be able to detect what parts of the field are drying out fastest, indicating the presence of tiles.
“Near-infrared is an awesome wavelength,” says Thayn. “It can even detect what trees are suffering from drought, so it can easily show us when ground is wet and when it is drying out.”
Of course, flying a remote-controlled airplane over farm fields presents challenges. First, an airplane can only be flown over fields where landowners have given permission.
The plane is programmed to fly a set grid, so its exact flight path is predetermined. (Thayn has a remote-control device that can bring the plane down in the event of another aircraft in the area).
“The plane has to be within your vision so you can steer it to safety if necessary,” says Thayn. “If the battery is low, the plane turns around and glides back towards you on its own.”
Piloting the aircraft has been a learning process for Thayn; he has turned to the help of a friend who flew military drones for the Navy for assistance.
Despite a nine-foot wingspan, the plane only weighs about fifteen pounds. Thayn takes it to the field and gives it a heave into the air. Batteries run the engine to give it lift. Once it is in the air, it glides on currents, while following its programmed grid.
When it has run its grid, Thayn uses the remote control to land it. But it’s not easy: On his first flight, it crashed into a power line. At the time of my visit, it was being repaired due to crashing on take-off.
It still offers great hope for wetland restoration.
“When you see the images, it is pretty clear where the tile lines are located,” says Thayn. “The plane gives you phenomenally detailed data. It will have the Conservancy put wetlands in the right spot, so that they can really make a difference in reducing nitrates entering streams.”