Part of the earth's largest surface freshwater system, Lake Erie is a vital source of drinking water for 11 million people. Researchers Anna Michalak, Tom Bridgeman, and Pete Richards are studying how farming practices and severe weather can increase the amount of fertilizer-derived nutrients in the water, which diminishes water quality and threatens the lake's ecosystem and the public's health. "Sustainability: Water" is produced in partnership with the National Science Foundation.
Sustainability - Water - Nutrient Loading in Lake Erie
ANNE THOMPSON, reporting:
Beautiful, powerful, and life-sustaining - North America's Great Lakes make up the largest fresh water system on the surface of the Earth. Of the five Great Lakes, Lake Erie is the shallowest and holds the least amount of water, yet it is vital to the region's industries, economy, and public health.
ANNA MICHALAK (Stanford University): The water itself is used for everything from drinking water to irrigating crops, for boating, for fishing, both commercial fishing and sport fishing. And so really, any activity that you think of that uses lake water is affected by the quality of that water.
THOMPSON: In the 1960s, Lake Erie's water quality was so bad some people called the lake "dead." Then, government policies and industrial clean-up efforts greatly restored its health. But since the 1990s, scientists have, once again, seen a decline in Lake Erie's water quality and a resurging problem with algal blooms. In 2011 toxic blue-green algae covered a sixth of Lake Erie with the largest toxic bloom ever recorded there - a problem visible from space.
THOMAS BRIDGEMAN (University of Toledo): We don’t want the Great Lakes to become a cesspool of green scum. We want water that is healthy, enjoyable, and safe.
THOMPSON: Tom Bridgeman, a freshwater ecologist at the Lake Erie Center in Toledo, Ohio, is participating in a five-year study, funded by the National Science Foundation, to evaluate the impacts of climate change, farming practices, and public policy on water quality. Ecologist Anna Michalak leads the team.
MICHALAK: And it’s only once we understand how that system is working currently that we can really hypothesize about what types of mechanisms, whether it’d be governance mechanisms or scientific solutions, might actually help with the water quality in the Great Lakes.
THOMPSON: Algal blooms are generally caused by an excess amount of nutrients in the water that feed algal growth - what is called eutrophication. The most common of these nutrients is phosphorus, found in fertilizers. And how are these algae-feeding nutrients getting into Lake Erie? Scientists point to the combination of two primary causes: farming practices, such as spraying fertilizers on the surface without mixing it into the soil, and changes in rainfall patterns. With a gentle rainfall on fertilized fields, the nutrients are allowed to seep into the soil as food for crops. However, precipitation patterns have changed recently, with more intense spring rainfall. These heavy rains create more runoff that washes over the soil surface, taking more fertilizer with it into ditches, streams, and rivers that flow into the lake.
BRIDGEMAN: And it’s only a matter of hours between when water enters a ditch to when it enters Lake Eerie. It’s a very quick trip from field to lake.
THOMPSON: As part of the study, Bridgeman and his team are collecting water samples at six different locations where water enters Lake Erie's western basin. They filter the water and measure the types and amounts of algae. The water samples are sent to the National Center for Water Quality Research in Tiffin, Ohio, to be analyzed for phosphorus. Water quality specialist Pete Richards, also part of the NSF study, uses the data to understand the complex relationships among precipitation, land use practices, and nutrient runoff to the lake.
R. PETER RICHARDS (Heidelberg University): To try to deal with only one piece of it can be useful, but it’s never going to capture the whole story. So, it’s something that really has to be done integrating many different disciplines and understandings.
THOMPSON: One solution is something called variable rate technology, which some farmers, like Bret Margraf in McCutchenville, Ohio, use to apply different amounts of fertilizers in different parts of the field. Using GPS, Margraf locates specific points in his field where he takes soil samples. The samples are tested for nutrients, allowing Margraf to map the fertility of his field and apply only what is needed, where it's needed.
RICHARDS: There is a concept called the Four R’s- the right place, the right amount, the right time, and the right method. That sort of encapsulates this idea of trying to be smart about the way we use the nutrients.
THOMPSON: To manage the amount of nutrients coming into Lake Erie, scientists, farmers, communities, and policy makers are working together to find solutions for better farming practices and improved water quality on the lake.
BRIDGEMAN: The minute that we stop putting fertilizers into the water, it will start to clean itself up. And within a couple years, it will be healthy again. So, that’s one of the hopeful things about Lake Eerie is that it rebounds very quickly.
THOMPSON: Beautiful and irreplaceable, Lake Erie and the entire Great Lakes system are an important natural resource unlike anywhere else on earth.
In modern America, we have access to clean, fresh water every day. Each time we turn on the tap, plumbing systems instantly bring this important resource into our homes. Despite its importance for life, though, fresh water is an extremely rare resource on Earth. Less than 3 percent of the water found on Earth is fresh water, and the remaining 97 percent is salt water, such as what is found in the ocean.
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