Historic flooding along the Arkansas River will cause environmental issues far away from the Natural State, a federal agency said.
The National Oceanic and Atmospheric Administration is forecasting a Gulf of Mexico hypoxic zone of proportions far larger than normal this summer.
Also known as a dead zone, the hypoxic zone is mainly caused by human activity, such as farming or sewage discharge, that produces excess amounts of the nutrients phosphorus and nitrogren. Those nutrients "stimulate an overgrowth of algae, which eventually die, then sink and decompose in the water," according to the NOAA forecast announcement this month. That deprives the area of oxygen, killing or keeping away aquatic life.
The flooding becomes a factor in rivers' and lakes' nutrient concentrations when floodwaters rise onto land and collect whatever is in the soil. Near a farm, those nutrients could be existing or residual animal waste applied to the ground as fertilizer. Near a sewage or industrial facility, they could be existing or residual biosolids or food processing wastewater.
Floodwaters flowed down the Arkansas River this spring and into the Mississippi River, which also flooded and will ultimately release its water into the Gulf of Mexico.
"Generally when we have higher flow, you do see a higher load going to the Gulf," said Ryan Benefield, deputy director of the Arkansas Natural Resources Commission and an Arkansas representative on the U.S. Environmental Protection Agency's Mississippi River/Gulf of Mexico Hypoxia Task Force.
In Arkansas, a high amount of nutrients in the water can build up into longer-term water quality issues, too, Benefield said.
But with the flooding this year, Benefield said the water's higher nutrient levels likely went down when the water receded. Areas like the Gulf would see higher levels because of the lack of river flow through them.
The nutrients that end up in the Gulf of Mexico hypoxic zone come from the Mississippi and Atchafalaya rivers. The Atchafalaya is an offshoot of the Mississippi that stretches from about Fort Adams, Miss., to the Atchafalaya Bay, more than 100 miles southwest of New Orleans. The Mississippi runs through New Orleans and stretches about 100 more miles southeast before ending in the Gulf of Mexico.
Despite the distance between the rivers' deltas, NOAA expects nutrients from both of them to together form a 7,829-square-mile dead zone, roughly the size of Massachusetts.
It's less than 2017's hypoxic zone, which was 8,776 square miles, but it's more than the five-year average, which is 5,770 square miles. NOAA will measure the hypoxic zone in early August.
The task force's goal is reducing the hypoxic zone to 1,900 square miles.
Record-high water levels have carried substantial nutrient runoff from the land.
Nitrate loads in May, before much of the flooding had subsided in Arkansas, were 18% above the long-term average in the Gulf of Mexico. Phosphorus loads were 49% above the long-term average.
Those averages are what's important, Benefield said.
If a person looked at this year's nutrient loading, he'd think Arkansas wasn't making much progress, he said. If the person looked at a dry year, he'd think Arkansas was making more progress than it was.
Last year's hypoxic zone was much smaller, he said, but factors such as westerly winds and Gulf waves may have affected the measurement just before government officials took it.
"That's why you really have to look at it as long-term averages," he said.
Officials at the Arkansas Natural Resources Commission work with farmers to reduce nutrient levels and administer a federal grant program that is designed to protect priority watersheds.
A sampling of nine programs in Arkansas reduced tens of thousands of pounds of phosphorus, nitrogen and sediment during fiscal 2017, according to the 2018 Progress Report on Coordination for Nonpoint Source Measures in Hypoxia Task Force States.
Many of the state's programs are voluntary, and critics have argued that the EPA and states are relying too much on voluntary measures to reduce nutrients.
The Mississippi River Collaborative, an organization of conservation groups in the 10 states that abut the Mississippi River, has advocated for clearer water quality standards, better oversight of what is being discharged into or running off into water bodies, and implementation plans for reducing nutrients that detail what should be reduced where and by whom.
Conservationists in Arkansas have argued for numeric nutrient standards in Arkansas' waters, but the Arkansas Department of Environmental Quality has contended that setting those standards is difficult.
Instead of numeric thresholds, the department has narrative descriptions explaining what is acceptable in state waters. Not every state has numeric nutrients standards, but some do.
The department has set numeric nutrients standards for the Beaver Lake watershed in Northwest Arkansas and has looked at setting them elsewhere.
The department sets nutrient limits in wastewater discharge permits.
The department plans to implement numeric nutrient standards for the Gulf Coastal Plan, department spokesman Donnally Davis said in an email, and is currently collecting water samples.
The Office of Water Quality permitting staff has been implementing a strategy for the inclusion of requirements for nutrient monitoring. All major municipal dischargers are currently monitored on a quarterly basis to assess levels of total phosphorus, nitrates and nitrites. Davis said the monitoring schedule will be adjusted to annual assessments if, after five years, the given discharger's nutrient levels are consistent, there have been no changes made to the plant and there are no other industrial contributions.
State Desk on 06/30/2019
Print Headline: State's water adding to dead zone as nitrogen, other nutrients flow into Gulf, NOAA says