The Explainer

Can Nature Take the Nasty Out of Your Drinking Water?

Sibley grove at Franklin demonstration farm in the Mackinaw River watershed. Photo © The Nature Conservancy (Timothy T. Lindenbaum)
Sibley grove at Franklin demonstration farm in the Mackinaw River watershed. Photo © The Nature Conservancy (Timothy T. Lindenbaum)

August 23, 2016

Follow Matt

Turn on the tap, and out comes your drinking water. But what if you’re pouring a big old glass of nasty nitrates? 

What’s Going on?

Nitrates pose health risks to pregnant women and babies. It’s been implicated in blue baby syndrome, starving infants’ brains of oxygen.

But even if you’re a healthy adult, do you really want to be gulping down nitrates? No, of course not.

Where are the nitrates coming from? In the Midwest, it’s often from farming practices. Farmers use fertilizers. When it rains, the excess fertilizers run into the river – and your drinking supply. This is exacerbated by the practice of tiling – running plastic tubes under the field to drain it quicker. It’s like a firehose of nitrates.

Engineered fixes are expensive. The city of Des Moines spends $5800 a day to reduce nitrates in the water supply.

But nature provides its own filter.

What the Science Says

Wetlands are nature’s filters; they sift out many of the nutrients and sediment from water. Could wetlands also filter nitrates?

Yes, if they are designed correctly.

In Illinois, the Conservancy is experimenting with wetland design to maximize nitrate removal.

TNC staff Aquatic Ecologist, A. Maria Lemke with TNC conservationist and farmer, Tim Lindenbaum and TNC partner, farm owner John Franklin (left to right) discuss wetland pond water monitoring devices. The farm is used as both a test facility for conservation oriented agricultural practices and as a demonstration-farm of those practices. Photo © The Nature Conservancy (Mark Godfrey)
TNC staff Aquatic Ecologist, A. Maria Lemke with TNC conservationist and farmer, Tim Lindenbaum and TNC partner, farm owner John Franklin (left to right) discuss wetland pond water monitoring devices. The farm is used as both a test facility for conservation oriented agricultural practices and as a demonstration-farm of those practices. Photo © The Nature Conservancy (Mark Godfrey)

To be effective, the wetlands must be located so the tiles flow into the wetland. Size is key: farmers want to maximize land in crop production, so the smaller the better.

Researchers found that wetland that is 5 percent the size of the drainage area was effective in removing 50 percent of the nitrates flowing through. Larger wetlands had diminishing returns.

Why It’s Important

Wetlands can be a cost-effective way to reduce nitrates. Ion-treatment, an intensive chemical-based plan, requires extensive staffing and produces its own waste materials.

Wetlands not only reduce nitrates, but also phosphates and other pollutants.

Wetlands of course provide other benefits, including wildlife habitat and recreational areas.

The Bottom Line

Wetlands alone won’t solve the nitrates issue. The state of Illinois alone has 12 million tiled acres – far more than wetlands can address. And agricultural policies favor plowing every available acre, reducing the incentive for farmers to include wetlands as part of their operations.

But wetlands can be an important tool in many watersheds, providing a cost-effective method to reduce nitrates while providing many other benefits. It’s feasible that many cities could be raising a glass – of clean, unpolluted water – to nature’s filter, the wetland.

Matt Miller

Matt Miller is director of science communications for The Nature Conservancy and editor of the Cool Green Science blog. A lifelong naturalist and outdoor enthusiast, he has covered stories on science and nature around the globe. Matt has worked for the Conservancy for the past 14 years, previously serving as director of communications for the Idaho program. More from Matt

Follow Matt

Join the Discussion

Please note that all comments are moderated and may take some time to appear.

2 comments

  1. So what happens when the soils and ground water under the wetland become saturated with nitrates over the term of the project? Wetland proposals for Imperial Valley in California note that there is a lifespan limit to wetland efficacy, likely resulting in a need to remediate the nitrates that were put in the soil due to the remediation effort.