Nutrient Runoff

Charlie Poukish from the Maryland Department of the Environment explains what fuels algae blooms and how they can spell trouble for underwater life. (Steve Droter)

A line graph of nitrogen loads over time, with peaks in 2004, 2011 and 2019. The graph is on an image of a body of water with a pipe channeling the flow of water into it. — The amount of nitrogen that enters the Bay fluctuates from year to year and is strongly correlated with rainfall. Spikes in nutrient runoff in 2011 and 2019, for example, were mostly due to above average rainfall during those years. (Data provided by the U.S. Geological Survey.)

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The line graph shows the span of time from 2000 to 2021 and nitrogen loads from 0 to 600 million pounds. It begins between 200 million and 300 million pounds in 2000, drops to its lowest below 200 million in 2002, then quickly rises to a peak well above 500 million in 2004. From there, it decreases to a low point in 2009, just above 200 million, before increasing to just above 500 million in 2011. In the next year it drops to just below 300 million and stays between 200 and 300 million until 2018, when it rises to above 400 million and then nearly 500 million in 2019. In 2020 it drops back to between 200 and 300 million, with an increase closer to 300 million at the end of the chart in 2021.

A line graph of phosphorus loads over time, with the highest peak in 2011 and smaller peaks in 2004 and 2018. The graph is on an image of a body of water with a pipe channeling the flow of water into it. — The amount of phosphorus that enters the Bay fluctuates from year to year and is strongly correlated with rainfall. Spikes in phosphorus runoff in 2011 and 2019, for example, were mostly due to above average rainfall during those years. (Data provided by the U.S. Geological Survey.)

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The line graph shows the span of time from 2000 to 2021 and phosphorus loads from 0 to 60 million pounds. It begins in 2000 just above 10 million pounds and drops slightly in 2001 and 2002 before surging up to over 35 million in 2003 and almost 40 million in 2004. It then drops to just over 20 million and continues dropping to 10 million in 2009 before increasing again, to a huge peak of over 60 million in 2011. It then drops to around 15 million in 2012 and stays relatively stable until dipping 10 million in 2015, then returning to around 15 million. It jumps again in 2018 to over 40 million, then drops steadily to return to around 15 million in 2020. In 2021, the last year shown, there is an increase to 20 million.

FAQ

Where do nutrients come from?

In general, nutrients like nitrogen and phosphorous reach the Chesapeake Bay from three sources: wastewater treatment plants; urban, suburban and agricultural runoff; and air pollution. Nutrients can also come from natural sources, like soil, plant material and wild animal waste.

What affects the amount of dissolved oxygen in the water?

Temperature, nutrient pollution, the way water flows in the Bay, and the shape of the Bay’s bottom all interact with each other to affect the amount of oxygen in the water.

What pollutants are found in wastewater?

Depending on the source, some wastewater can contain nutrient or sediment pollution, or dissolved chemical contaminants.

What are best management practices?

Best management practices, or BMPs, are conservation practices that can reduce a farm’s nutrient and sediment pollution while maintaining a productive farming operation. Some common agricultural BMPs include conservation tillage, cover crops, forest buffers, streamside fencing and manure storage areas.

How does farming affect the Chesapeake Bay?

Agriculture is the single largest source of nutrient and sediment pollution entering the Chesapeake Bay. But well-managed agricultural lands can offer the Bay watershed a number of benefits and services, including restored rivers and streams and valuable insect, bird and animal habitat.

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Terms

Nutrients

Chemicals that plants and animals need to grow and survive but, in excess amounts, can harm aquatic environments. Elevated levels of the nutrients nitrogen and phosphorous are the main cause of poor water quality in the Chesapeake Bay.

Eutrophication

The process of excess nutrients accelerating the growth of algae, ultimately depleting the water of dissolved oxygen.

Algae bloom

A dense population of algae whose growth is fueled by excess nutrients. Algae blooms can block sunlight from reaching underwater grasses, and their decomposition can rob the water of dissolved oxygen and suffocate marine life.

Point source

A source of pollution that can be attributed to a specific physical location - an identifiable, end-of-pipe "point." The vast majority of point source discharges of nutrients are from wastewater treatment plants, although some come from industries.

Phosphorus

A type of nutrient contributing to the Bay's poor water quality. While phosphorus is vital to plant life, human activities--like applying fertilizers or using household cleaners--contribute more phosphorus than the Bay's waters can handle. Elevated phosphorus levels cause more algae to grow, blocking out sunlight and reducing oxygen for fish, crabs and other Bay life.

Nitrogen

A type of nutrient that contributes to the Bay's poor water quality. While nitrogen is needed for plant growth, human activities--like driving cars or applying fertilizers--contribute more nitrogen than the Bay's waters can handle. Elevated nitrogen levels cause more algae to grow, blocking out sunlight and reducing oxygen for fish, crabs and other Bay life.

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