Managing Runoff to Reduce the Dead Zone
Managing Runoff to Reduce the Dead ZoneWhat can be done to reduce the size of the dead zone?
The dead zone in the Gulf of Mexico is primarily a result of runoff of nutrients from fertilizers and manure applied to agricultural land in the Mississippi River basin. Runoff from farms carries nutrients with the water as it drains to the Mississippi River, which ultimately flows to the Gulf of Mexico. If a number of nutrients reaching the Gulf of Mexico can be reduced, then the dead zone will begin the shrink.
Since 2008, the Hypoxia Task Force, led by the U.S. Environmental Protection Agency and consisting of five federal agencies and 12 states, has been working to implement policies and regulations with the aim of reducing the size of the dead zone in the Gulf of Mexico. Many of the strategies for reducing nutrient loading target agricultural practices including (USEPA, The Sources and Solutions: Agriculture).
- Nutrient management: The application of fertilizers can vary in amount, timing, and method with varying impacts on water quality. Better management of nutrient application can reduce nutrient runoff to streams.
- Cover Crops: Planting of certain grasses, grains, or clovers, called cover crops can recycle excess nutrients and reduce soil erosion, keeping nutrients out of surface waterways.
- Buffers: Planting trees, shrubs, and grass around fields, especially those that border water bodies, can help by absorbing or filtering out nutrients before they reach a water body.
- Conservation tillage: Reducing how often fields are tilled reduces erosion and soil compaction, builds soil organic matter, and reduces runoff.
- Managing livestock waste: Keeping animals and their waste out of streams, rivers, and lakes keep nitrogen and phosphorus out of the water and restores stream banks.
- Drainage water management: Reducing nutrient loadings that drain from agricultural fields helps prevent degradation of the water in local streams and lakes.
Watch the following video from the US Department of Agriculture about strategies to reduce nutrient loading into the Mississippi River:
Video: Preventing Runoff Into The Mississippi River (1:44)
Transcript: Preventing Runoff Into The Mississippi River
Introduction
Bob Ellison, USDA: A US Department of Agriculture initiative is helping Missouri farmers keep farm field runoff from reaching the Mississippi River. USDA's Natural Resources Conservation Service is working with producers through the Mississippi River Basin healthy watersheds initiative, or MRBI.
The MRBI Project
Andy Hodge, USDA NRCS: The focus of the MRBI project is to hopefully cut down on sediment, nutrients, and pesticides that are moving down the Mississippi River to the Gulf of Mexico. USDA NRCS and initiative partners are working with farmers to determine which conservation practices and which conservation systems work best on their farms to keep runoff from reaching the Mississippi.
Conservation Practices
Troy Chockley, USDA NRCS: What we're trying to do is identify what conservation practices will have the biggest impact in the reduction of nutrient transport to the Mississippi River, which eventually makes it to the Gulf of Mexico. One such conservation practice is terracing.
Tarracing
Mitch Krueger, USDA NRCS: By building the terraces it controls erosion, which then reduce the sediment. By reducing sediment we're also going to be reducing the hypoxia issue in the Gulf.
Outro
Karen Brinkman, USDA NRCS: We wanted to then monitor what effects we could have on reductions by putting out monitoring stations, such as this one so we could be able to determine that what benefits we were having with the cost share dollars we were putting on the land. Landowners interested in learning more about how to protect their soil and reduce runoff should contact their local NRCS office. I'm Bob Ellison for the US Department of Agriculture.
Activate Your Learning
Review the graphs below and answer the questions that follow. Figure 4.2.11 presents the size of the hypoxic zone in the Gulf of Mexico from 1985 to 2014. The U.S. Environmental Production Agency led a task force in 2008 that identified a goal to reduce the five-year average of the size of the dead zone to less than 2,000 square miles by 2015.
Text description of the Dead Zone Size graph.
Bar graph showing annual dead zone size from 1985 through 2014. The horizontal axis shows years, and the vertical axis shows size in square miles, ranging from 0 to 9,000 in increments of 1,000. Teal bars represent the size measured each year. The year 1989 is marked “n.d.,” indicating no data.
Dead zone size varies considerably between years. The smallest measured area is approximately 1,700 square miles in 2000. The largest is approximately 8,500 square miles in 2002, with another peak of about 8,400 square miles in 2008. The final bar, for 2014, shows approximately 5,000 square miles.
A red dashed horizontal line labeled “Action Plan Goal” marks approximately 1,900 square miles. Nearly every annual measurement exceeds this goal. A second red dashed line, spanning the final five years and labeled “5-yr Average,” marks approximately 5,800 square miles—about three times the goal.
Text description of the Annual Nitrogen Load graph.
Bar graph showing annual values from 1980 through 2011. The horizontal axis shows years. The vertical axis shows nitrogen load in millions of metric tons, ranging from 0 to 2.5 in increments of 0.5.
Blue bars show substantial year-to-year variation. The highest loads occur in 1983 and 1993, at approximately 2.2 million metric tons. The lowest occur in 2000 and 2006, at approximately 0.8–0.9 million metric tons. Most annual values fall between 1.1 and 1.9 million metric tons.
A red line labeled “5-year average” runs from approximately 1997 to 2011. It declines from about 1.5 million metric tons to approximately 1.2 million in the mid-2000s, then rises to about 1.5 million by 2011. The average highlights a decline followed by a rebound, while the bars show the larger fluctuations between individual years.
Text description of the Annual Phosphorus Load graph.
Graph titled “Annual Total Phosphorus Load” showing annual values from 1980 through 2011. The horizontal axis shows years. The vertical axis shows phosphorus load in thousands of metric tons, ranging from 0 to 250 in increments of 50.
Green bars show substantial year-to-year variation. The highest load occurs in 2008, at approximately 210,000 metric tons, followed by 2010 at approximately 195,000 metric tons. The lowest loads occur in 2006, at approximately 75,000 metric tons, and 1985, at approximately 80,000 metric tons. Most annual values fall between 110,000 and 175,000 metric tons.
A red line labeled “5-year average” extends from approximately 1997 through 2011. It fluctuates around 130,000–150,000 metric tons through much of the period, then rises to approximately 180,000 metric tons by 2011. The average shows an overall increase toward the end of the record despite large annual fluctuations.