Mississippi flooding creating massive 'dead zone' in the Gulf
This article first appeared in the St. Louis Beacon, June 14, 2011 - WASHINGTON - This year's record flood on the lower Mississippi River is likely to cause an unusually large "dead zone" -- about the size of New Hampshire -- in the Gulf of Mexico resulting from deposits of agricultural chemicals and organic matter.The forecast, based on estimates of nutrient inputs compiled annually by the U.S. Geological Survey, was issued Tuesday by a team of scientists from three universities supported by the National Oceanic and Atmospheric Administration.
The forecast of an hypoxic zone between 8,500 and 9,421 square miles may well break the previous known record of about 8,400 square miles, as measured in 2002. But river experts and environmentalists told the Beacon that the early-spring timing of the flood, before many farmers had fertilized fields, may have prevented a far more extensive dead zone, given the volume of floodwaters that are now moving into the Gulf.
"Most farmers in the Midwest didn't have the chance to put down nitrogen fertilizer this year, so the hypoxia [dead zone] may be less" than it could have been, said ecologist William J. Mitsch, who worked on an advisory group a decade ago that examined possible solutions to Gulf dead zones.
Hypoxia is a condition, characterized by too little oxygen, in which most marine life cannot live in bottom and near-bottom water. It is caused by excessive nutrient pollution, mostly from agricultural chemicals, which are carried by the river into the Gulf. Hypoxic zones form off the coasts of Louisiana and Texas every summer.
Many environmentalists contend that lowering levees and increasing the amount of wetlands that absorb floodwaters would filter out much of the organic matter, keeping it from pouring into the Gulf.
"Ten years ago, I was asked by the federal government to help solve the hypoxia problem in the Gulf," said Mitsch, distinguished professor of environment and natural resources at Ohio State University. "We said that there are some things you can do agriculturally, but if you are really serious about solving the problem, you're going to have to have buffers of wetlands and bottomland forests and all that to allow this pollution to run through them first before it gets to river or streams."
Mitsch said his panel suggested that it might take about 5 million acres of created or restored wetlands in the Mississippi River valley to help filter out the farm chemicals and other organic matter that flow into rivers during major floods. This spring's flooding is estimated to have inundated about 6.8 million acres -- much of it farmland -- between Cape Girardeau and southern Louisiana. Millions of other farm acres were also flooded in the Ohio River valley in the same flood.
In the wake of the record-setting flood of 2011, the president of the Mississippi River Commission, Maj. Gen. Michael J. Walsh, has ordered the formation of an Interagency Recovery Task Force to look at lessons that should be learned from this deluge, which set historic flood-gauge levels at many points along the lower Mississippi river.
The Army Corps of Engineers biologist and management official who is leading that group, Scott D. Whitney, told the Beacon that the extent of Gulf hypoxia is one of many issues that federal agencies in the task force might examine. Those agencies include the USGS and the Environmental Protection Agency.
"It's safe to say that a lot of the agricultural chemicals had not yet been put in" at the time the flooding hit the Ohio and lower Mississippi river valleys, said Whitney. "For example, the Birds Point-New Madrid floodway was just getting geared up for planting season" when its levee was intentionally breached, sending flood water pouring into its 130,000 acres of farmland.But Whitney told the Beacon that "the release of large volumes of organic materials and inorganic [chemicals into the Gulf] is obviously reason for concern and the health of the ecosystem as a whole and to the Gulf."
Over the past five years, the average size of the Gulf dead zone has been about 6,000 square miles. This is far larger than the 1,900-square mile target goal set a few years ago by the Gulf of Mexico/Mississippi River Watershed Nutrient Task Force.
That collaboration between NOAA, USGS and university scientists has been trying to expand cooperation among environmentalists, scientists and river experts in the Mississippi River watershed with those who focus on the northern Gulf of Mexico. Scientists said that long-term data sets on nutrient loads and the extent of the hypoxic zone have improved forecast models used by management agencies to understand the reductions in farm chemicals that would be needed to reduce the size of the dead zone.
This May, the stream-flow rates in the Mississippi and Atchafalaya rivers were nearly twice that of normal conditions, according to the USGS, increasing the amount of nitrogen carried by the rivers into the Gulf to about 164,000 metric tons of nitrogen. That is about 35 percent higher than average May nitrogen loads over the last three decades.
"The USGS monitoring network and modeling activities for water quantity and quality helps us 'connect the dots' to see how increased nutrient run-off in the Mississippi watershed during a historic spring flood event impacts the health of the ocean many hundreds of miles away," said USGS Director Marcia McNutt in a statement Tuesday.
She added that "this work on Gulf hypoxia is a great example of interagency teamwork between NOAA and USGS to work across the land-sea boundary."
NOAA. the USGS and the Corps are among the federal agencies that have agreed to form a partnership to try to address better the dead zone issue and other water resources issues.
The actual size of this spring's hypoxic zone will be released following a monitoring survey led by the Louisiana Universities Marine Consortium between in late July and early August.
Jane Lubchenco, the administrator of NOAA, said the forecasts are a valuable tool in assessing the problem. "While there is some uncertainty regarding the size, position and timing of this year's hypoxic zone in the Gulf, the forecast models are in overall agreement that hypoxia will be larger than we have typically seen in recent years."