USGS water quality technician Kelly Brady is a foot soldier in the war against hypoxia. He takes water samples once a month that end up being used in the recent USGS study.
On a recent trip, the Missouri River looked deceptively smooth, but Brady knew it could quickly turn deadly. On average, 88,500 cubic feet of water – enough to fill an Olympic-size swimming pool – slip past here every single second. If water were oil, the volume of the entire BP oil spill could pass by in five minutes.
Brady launched the work boat, a 26-foot sealed-hull aluminum skiff that he jokes looks like a gunboat out of “Apocalypse Now.” “It’s supposed to be unsinkable and self-righting, but I don’t want to try that out,” he said. “I like swimming, but I don’t want to do it on the job.”
The crew used a laptop, radar and high-precision GPS to find sampling locations. A crane hanging over the front of the boat dipped a Teflon-lined sampler into the water and hauled up several liters of water. Brady and his team processed the samples in mobile labs in the back of their trucks. These were put on ice and shipped to Denver for analysis.
Brady’s data are essential for keeping tabs on water quality. Dale Blevins, a USGS scientist emeritus who is an expert on the Missouri River, has studied historical nitrogen concentrations in the river in the past century. "It’s a cycle; it goes up and down," he said. "We’re in upward trend in one of those cycles and we’re about to bust out the top of where we’ve ever been before." Why? He’s not sure.
The total nitrogen concentration in the Missouri is not much different now than in the early 1900s, Blevins said. But most of that used to be organic nitrogen, whereas now, it's mostly nitrate, a form that many algae and other organisms can take in directly.
"It has reached almost its maximum concentration by time it reaches St. Joe," Mo., he said. "If you look at the location where the nitrate’s coming from, those are pretty much agricultural areas."
There is another possible explanation for the increasing nitrate numbers, a third view that blames neither today’s farms nor urban areas. The pollution could come from historic nitrogen deposits – the legacy of years of earlier excess that is just now showing up.
The USGS study found that a lot of nitrate poured into the river even when the water flow was low. One might expect heavy rain to wash nutrients off the land, but where did nitrate come from under dry conditions?
Sprague concluded groundwater was the source. Rain falls on the surface, percolates through the soil and drains out from days to decades later.
Norfleet, the USDA soil scientist, said nitrogen could stay in an aquifer for years before finally spilling into streams. “It’s kind of like having clogged arteries,” he said. “It’s going to take a while to clean those out.”
If groundwater really is responsible, it could take years for conservation measures to make a significant difference in the Gulf.
“Even if we stopped applying nitrogen now, the groundwater’s going to have a lot of nitrogen in it for 5 to10 years, or in some places, 20 to 30 years,” said Andrew Hug, an analyst with the Environmental Working Group who focuses on agriculture’s environmental impact. “It’s going to take a long time to fix this problem.”
Iowa farmers and Louisiana fishers
Up at the top of the watershed, Bill Northey spends a lot of time thinking about the Gulf’s dead zone. As secretary of the Iowa Department of Agriculture and Land Stewardship, he looks for science-based ways to maintain farm productivity while also reducing runoff to the waters below.