States develop plans to address gulf hypoxia
By Janet Kubat Willette
Date Modified: 02/05/2013 4:18 PM
WASECA, Minn. – The dozen states that contribute the most nutrients to the Mississippi River are finalizing plans on how to stem the loss of nutrients to the river.
The plans are required as a result of the 2008 Gulf Hypoxia Action Plan, which challenges states in the world's fourth-largest watershed to find ways to achieve a 45 percent reduction in nutrients flowing into the Gulf of Mexico. Plans need to be submitted by the end of 2013.
In Iowa, draft plans have been released and comments are accepted through Jan. 4. Minnesota's plan is in the beginning stages, but set to be completed by the end of 2013, said Dave Wall, speaking at the Iowa-Minnesota-South Dakota Drainage Research Forum held Nov. 20 in Waseca. Wall is senior hydrologist at the Minnesota Pollution Control Agency.
In Minnesota, researchers are attempting to identify a baseline to base guidelines on. The baseline will take into account progress made since the early 2000s, Wall said.
Metropolitan point source pollution has dropped significantly over the last five years and changes in livestock rations have reduced phosphorus in manure. There have also been reductions in the amount of manure running off feedlots.
Improvements are also being made in nitrogen use, he said, but at the same time land use changes are occurring that lead to more nitrogen use.
Nitrogen trends depend on the time period being evaluated, the location being evaluated, the influence of groundwater and statistical methods used. It also depends on if load or concentration is being measured. Concentration is simply how many milligrams are detected in a sample. Load is concentration multiplied by flow. There has to be flow to have a load, Wall said.
Why does Minnesota need to reduce nitrates and phosphorus leaving the state? Not only are there concerns about downstream loads, but also about Lake Pepin and Lake Superior.
Recent data suggests that Minnesota is the sixth largest contributor of nitrogen to the Gulf of Mexico, Wall said.
Minnesota's reduction strategy will look at both point and non-point sources of pollution, Wall said.
One idea is to concentrate on the watersheds with the greatest nitrate loads to make the greatest impact. They have a pretty good idea where those watersheds are, Wall said.
It's estimated that widespread adoption of multiple best management practices in field will reduce nitrate loss by 10 percent to 30 percent. Costs associated with implementation of these practices nor the likelihood of adoption hasn't yet been determined.
Whatever goal that is set must be meaningful and achievable, Wall said.