Watershed management is the key to reducing hypoxic zones.

In 2008, the newly formed Gulf of Mexico Watershed Nutrient Task Force set a goal: to reduce the hypoxic zone down to 5,000 km2 (1,900 square miles). That same year, Rabalais and Turner concluded that the Gulf ecosystem was becoming more sensitive to nutrient loads. “It’s not the same system as the 1960s,” Rabalais says. “It’s taking less nutrients now to fuel the hypoxia.”

Scientists are still assessing the impact of nutrient runoff on the Mississippi River watershed’s various ecosystems. One way to do this is a process known as biological assessment, the simple act of looking at what lives in a given ecosystem. In some cases this means simply netting, identifying, and counting benthic macroinvertebrates, such as insects and crayfish that inhabit the bottoms of the smaller streams that feed into the Mississippi River. If a stream is unhealthy, there won’t be many organisms present that are sensitive to pollutants. The abundance and diversity of pollution-tolerant and pollution-sensitive species in the sample can be used to “rate” the stream quality. Poor stream quality can sometimes indicate that nutrient runoff or other toxins are polluting the water or that sediments are smothering needed stream-bottom habitat.

biological assessment

The process of sampling an area to see what lives there as a tool to determine how healthy the area is.

benthic macroinvertebrates

Easy-to-see (not microscopic) arthropods such as insects that live on the stream bottom.

According to a 2008 report from the Gulf Task Force, hypoxia is causing “long term ecological changes in species diversity and a large scale, often rapid change in the ecosystem’s food web that will be difficult to impossible to reverse.” This is not surprising, given the condition of other hypoxic zones around the world. For example, after centuries of nutrient runoff from the Danube River, rich mussel beds that had populated the Black Sea for centuries disappeared. Food chains broke, big fish died off, and a seafood economy that had thrived since the Byzantine era evaporated. The sea recovered a bit when the Iron Curtain countries collapsed, fertilizer subsidies fell, and the steady flow of nutrients from the Danube ceased, like a faucet being turned off. Today, the sea is home to a thriving anchovy industry. But the big fish and rich oyster beds have never recovered. In the United States, Chesapeake Bay, home to another hypoxic zone, is struggling mightily against the same fate.

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Still, Strock and others point out that the term dead zone is a misnomer. “It’s a low-oxygen zone,” Strock says. “There are still things living there. And we still have time to save that ecosystem.”

Water quality has always been a concern but perhaps never more so than in 1969. At the time, there were no restrictions on the release of industrial chemical pollutants into bodies of water. That year, the Cuyahoga River in Cleveland, Ohio, made headlines when it caught fire (and not for the first time) because so much oil and other flammable industrial pollutants floated on the surface of the water. This dramatic event helped spur the passage of the 1972 Clean Water Act (CWA), which regulates industrial and municipal (such as sewage treatment plants) point source pollution, with the goal of making all environmental waters “fishable and swimmable.” It does this by setting pollution standards—allowable levels of a pollutant that can be present in environmental waters or released over a certain time period.

Clean Water Act (CWA)

U.S. federal legislation that regulates the release of point source pollution into surface waters and sets water quality standards for those waters. It also supports best management practices to reduce nonpoint source pollution.

pollution standards

Allowable levels of a pollutant that can be present in environmental waters or released over a certain time period.

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KEY CONCEPT 15.6

Good watershed management can reduce nonpoint source pollution. For example, well vegetated riparian areas reduce runoff and act as nutrient sinks.

For example, the U.S. Environmental Protection Agency (EPA), which administers the CWA, protects the public against pathogens in recreational waters (rivers, lakes, coastal areas)—the leading cause of impaired waters in the United States and a major problem worldwide. Globally, exposure to pathogen-polluted water is one of the leading causes of infection; 2 million people die each year of diarrheal diseases linked to unsafe water. The United Nations cites the provision of clean water and sanitation as one of its major development goals (see Chapter 5). In the United States, the EPA allows only very small amounts of fecal bacteria such as E. coli in recreational waters; the presence of fecal bacteria indicates sewage or animal waste contamination. Violations are investigated and addressed at either the federal or state level. (The Safe Drinking Water Act mandates that absolutely no pathogens are allowed in drinking water.) Today, about 65% of U.S. waters meet the fishable/swimmable goal, more than double the number that met that goal prior to the passage of the CWA. (However, we are still far from the goal of 100% compliance with CWA guidelines.)

“We did a good job on point source [pollution],” Echols says. “Back in the late 1960s, we said ‘thou shall not pollute,’ and we made rules and we made people follow them.”

Nonpoint source pollution is a bit trickier. The CWA does not specify, for example, how much nitrogen fertilizer a farmer can apply. And this is not feasible because recommended amounts vary from farm to farm, and runoff potential varies according to rainfall, terrain, and even the crop that is planted. But Echols, Strock, Hicks, and others are working to fix it, just the same. Although they differ in their preferred approaches, most scientists agree that watershed management—management of what goes on in an area around streams and rivers—will be the key to saving the Gulf. They’ve begun to create best management practices (agreed-upon actions that minimize pollution problems caused by human actions) to reduce the amount of pollution being delivered to the Mississippi River. In agriculture, many of these practices focus on ways to decrease the amount of chemicals applied to land areas in the first place and to reduce the potential for soil erosion and runoff.

watershed management

Management of what goes on in an area around streams and rivers.

Recent CWA amendments advocate the use of best management practices and provide funding for their implementation. However, watershed management is not easy to do; after all, many individuals and groups are engaged in many different land uses within any watershed. Identifying how each should address its contribution to nonpoint source water pollution—much less enforcing compliance—is no easy task.

One of the key steps is to restore the watershed’s riparian areas, the land areas close to the water, by maintaining or planting vegetated buffer zones that slow runoff and give the rainwater time to soak into the ground. “Most of our riparian areas—in the Mississippi River watershed, anyway—are not functioning as riparian areas anymore,” Echols says. “We can’t really fix hypoxia until we fix that.” Healthy riparian areas are widely recognized as critical to maintaining good water quality, and projects are under way across the United States to restore and revegetate the riparian areas and watersheds of rivers and streams. In the late 1990s, New York City invested billions of dollars to restore and protect areas in the Catskills and the Delaware watershed supplying its water; thanks to this investment, the city avoided the need to construct high-tech and costly filtration systems. INFOGRAPHIC 15.5

HEALTHY RIPARIAN AREAS PROVIDE MANY BENEFITS

In a managed riparian area, why not allow zone 1 to have managed forest like zone 2?

The thick tangle of undergrowth is important in obstructing the flow of runoff and is most important right next to the stream. Further from the stream's edge, the managed forest is a better choice since the more rapid plant growth rates will help take up any residual fertilizer that ends up in the area as well as enhancing subsurface water flow, increasing the amount of water that soaks into the ground.

riparian areas

The land areas close enough to a body of water to be affected by the water’s presence (for example, areas where water-tolerant plants grow) and that affect the water itself (for example, provide shade).

Another agricultural best management practice is frequently testing the soil to ensure that only the correct type and amount of fertilizer is added as needed; tilling fertilizer directly into the soil (rather than spreading it on the surface) also reduces the potential for loss due to runoff or wind. Farmers can also use a variety of erosion prevention methods, such as planting winter crops in the off season to hold soil in place or planting trees as windbreaks to reduce soil erosion from wind. (For more on sustainable farming techniques, see Chapter 17.) Farmers are also going high-tech, pursuing precision agriculture. They are using GPS technology to guide farm equipment and reduce overlap when working a field, thus reducing disturbance of soil that might lead to erosion. Farmers are also using precision agriculture to guide site-specific applications of chemicals within a single field to minimize the amount used.

Of course, not all of hypoxia’s solutions will come from the farm belt. In suburban areas, lawns can be major nonpoint sources of nitrogen pollution if homeowners apply too much fertilizer. However, the grass also sequesters nitrogen because of its long growing season, preventing it from flowing to the nearest stream. Echols encourages homeowners to limit fertilizer use on lawns and to plant native plants and grasses that do not need fertilizer. Planting a rain garden of water-tolerant plants in low-lying areas that tend to flood in rain events can also help capture water and reduce runoff.

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KEY CONCEPT 15.7

Urban and suburban areas are significant contributors of stormwater runoff, but many steps can be taken to reduce runoff and increase infiltration.

In urban areas, replacing some hard surfaces with porous surfaces such as green space or permeable pavers reduces runoff by allowing water to seep through. For this reason, Chicago has changed a large part of its alley pavement to porous concrete. Green roofs can also help capture rainwater and slow or prevent its release to the environment. Installing curb cutouts in roadways can direct stormwater flow onto natural areas where the water has a chance to soak into the ground rather than flowing directly into a storm drain, which often takes it to a nearby water body. INFOGRAPHIC 15.6

INCREASING INFILTRATION OF STORMWATER

Stormwater that doesn’t soak into the ground can enter storm drains that flow directly to rivers and streams, or cause floods, especially in heavily built-up urban settings. Anything that increases infiltration can help avoid these stormwater problems.

What are some other building or infrastructure methods that could reduce the flow of stormwater? (Consider things like roof size, road width, other pavement options, etc.)

Smaller surfaces such as smaller roofs and roads will decrease the potential for runoff. Two story homes have a smaller roof size than one story homes of the same size. In subdivisions, developers could consider putting in slightly more narrow roads (still allowing for safety concerns) as well as putting sidewalks, on one side only. Vegetated channels next to roads, rather than concrete drainage ditches also provide opportunities for rainwater infiltration. For more specific ideas and short video clips, see Weather and the Built Environment, found at http://www.meted.ucar.edu/broadcastmet/wxbuiltenv/index.htm. (This free website requires that you register and log in - it contains educational information about the geosciences and is supported by the University Corporation for Atmospheric Research.)

Water pollution is a wicked problem with many causes and consequences, as well as multiple stakeholders who often have different opinions about what actions to take. But the success of the CWA in controlling point source pollution in the United States shows that progress can be made. Likewise, steps to address watershed health and reduce the potential for runoff are reducing nonpoint source pollution.

KEY CONCEPT 15.8

Addressing water pollution includes identifying where problems exist, reducing pollution at the source, watershed management to reduce runoff potential, and restoring wetlands.

To address hypoxia in the Gulf of Mexico, the Gulf Task Force has identified a multipronged approach that considers all the causes and consequences of the problem as a triple-bottom line: the environmental needs of the coastal and offshore ecosystems, the social impacts on human communities affected throughout the watershed, and the economic realities that require us to prioritize our actions. INFOGRAPHIC 15.7

GULF OF MEXICO REGIONAL ECOSYSTEM RESTORATION

How is the task force considering the triple-bottom line with their recommendations to reduce the size of the gulf hypoxic zone?

Environmental: Many of these goals address the environmental source of the pollution or its movement through the environment (i.e. reducing fertilizer application and runoff from animal operations, restoring riparian areas and natural wetland and river flow patterns).

Social: The strategies that improve community resilience to storms are the ones most directly considering societal needs; some environmental choices, such as restoration of oyster beds, specifically focuses on local jobs (also an economic issue).

Economic: Reducing fertilizer use can save farmer’s money; restoring riparian areas can be an inexpensive and cost-effective way to reduce runoff potential; acting proactively to identify sentinel species to track may catch problems when they are small, making it easier (and cheaper) to address them; the fact that many strategies are suggested allows flexibility to address the problem in a way that is most affordable or pressing for a given locale.

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Cities (shown in red) and farmland (shown in green) within the watershed of the Mississippi River fuel the Gulf of Mexico’s hypoxic zone in late summer.
NOAA’s Environmental Visualization Lab.

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Firefighters stand on a bridge over the Cuyahoga River in Cleveland, Ohio, to spray water on a tugboat as a fire—started in an oil slick on the river—moves toward the docks at the Great Lakes Towing Company site. This 1952 blaze, one of 13 fires on the river since the late 1800s, was the most costly, destroying three tugboats, three buildings, and the ship-repair yards.
© Bettmann/CORBIS
“Green alleys” like this one in Chicago are those that have been resurfaced with permeable pavement to allow rainwater or snowmelt to pass through the pavement and soak into the ground rather than run off into storm drains which would eventually empty into nearby Lake Michigan.
Peter Wynn Thompson/The New York Times/Redux

A 2013 report from the Gulf of Mexico Nutrient Task Force suggested that while it is unlikely that the goal of reducing the hypoxic zone to 5,000 km2 will be met by 2015 (the hypoxic zone averaged about 14,000 km2 in recent years), it remains a reasonable target for the near future if there is an acceleration in programs that address the problem.

These types of control efforts are gaining increasing significance in a world where human population is still growing and the need for higher agricultural productivity grows with it. Meeting these needs and protecting our water at the same time may get even more difficult due to climate change that is reducing agricultural productivity in many areas worldwide, a trend that is expected to get worse in the future.

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Select References:

Diaz, R. J., & R. Rosenberg. (2008). Spreading dead zones and consequences for marine ecosystems. Science, 321(5891): 926–929.

Environmental Protection Agency. (2011). “Gulf of Mexico Regional Ecosystem Restoration Strategy,” archive.epa.gov/gulfcoasttaskforce/web/pdf/gulfcoastreport_full_12-04_508-1.pdf.

Oquist, K. A., et al. (2007). Influence of alternative and conventional farming practices on subsurface drainage and water quality. Journal of Environmental Quality, 36(4): 1194–1204.

Rabalais, N., et al. (2002). Beyond science into policy: Gulf of Mexico hypoxia and the Mississippi River. BioScience, 52(2): 129–142.

PERSONAL CHOICES THAT HELP

We are facing not only shrinking supplies of easily accessible water but also the potential degradation of this resource due to pollution. By changing products and modifying common practices, we can improve our water quality for years to come.

Individual Steps

Read your city’s water quality report to see which pollutants are prevalent in your area.

Decrease your use of chemicals (fertilizers, pesticides, harsh cleaners, etc.) that will end up in the water supply. For alternatives to traditional yard chemicals, see www.safelawns.org.

Always dispose of pet waste properly. In high quantities, it acts as an oxygen-demanding waste and can also spread disease.

Group Action

Marking storm drains with “Don’t Dump” symbols can remind people not to dump waste liquids down sewer drains. If the drains in your area are not marked, talk to city officials to see if you and other volunteers can mark them.

Policy Change

August is National Water Quality Month. Take steps every day to reduce your water pollution and help raise awareness in August by writing a letter to your local newspaper outlining simple steps people can take to improve water quality.

Robert Brook/Science Source

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