Sediment and nutrient loading progress being made in Grand Lake St. Marys

By Matt Reese

After ongoing concerns about water quality, Grand Lake St. Marys was declared a distressed watershed in 2011. The lake’s notorious water quality issues generated a mountain of bad press and much of the blame was being placed on agriculture in one of the most highly concentrated livestock watersheds in the country.

The “distressed” designation led to a ban on winter manure application and placed strong emphasis on other nutrient management practices for farms in the watershed. The changes were challenging, costly to implement in some cases and required significantly higher management. But so far, it seems, they are working.

“We’ve seen some real changes in the watershed and the agricultural practices,” said Bill Knapke with Cooper Farms, who farms in the watershed. “Fertilizer sales have really changed dramatically since all of the livestock producers have developed nutrient management plans and are doing all of their soil testing and testing their manure. They are probably doing a better job of managing the nutrients they produce on their farms and have come to the conclusion that they didn’t need to be buying as much commercial fertilizer. We have seen a reduction in the amount of nutrients being applied in the watershed in both commercial fertilizer and manure, but we haven’t seen a decline in yields. Farmers are still producing excellent yields year in and year out and it has probably improved their bottom line.”

Knapke said the nutrient management plans being implemented on farms in the watershed are both helping reduce nutrient loss and improving overall efficiency.

“Nutrient management plans look at storing nutrients on the farm and when you apply them. Part of the rules was to not have manure application between Dec. 15 and the spring. Guys are doing a better job of land applying the nutrients and the are also using cover crops that can take up those nutrients and store them for next year’s crop,” he said. “When we look at sustainability in grain production and our overall carbon footprint, the better we can produce grain, the better we are at producing protein through the poultry and pork. We are looking at a lot of different things that help farmers better use nutrients.”

The on-farm efforts — in addition to various measures taken by the non-ag sector in the watershed — are showing up as significantly reduced nutrient levels entering the lake, according new research from Stephen Jacquemin at Wright State University’s Lake Campus.

“Grand Lake St. Marys watershed has drawn attention over the past decade as water quality issues resulting from nutrient loading have come to the forefront of public opinion, political concern, and scientific study. Grand Lake St. Marys is 250 square kilometers which makes it a smaller watershed,” Jacquemin said. “When you are trying to affect positive change and bring down nutrient loads to improve water quality, it certainly becomes more manageable when you can see the entire problem at once.”

The research analyzes water quality before and after the 2011 “distressed” designation. The objective of Jacquemin’s study was to assess long-term changes in nutrient and sediment concentrations before and after the winter manure ban and other rules and best management practices including cover crops, manure storage or transfers, and buffers were implemented.

The research looked at variation in total suspended solids, particulate phosphorus, soluble reactive phosphorus, nitrate, and total nitrogen concentrations from daily Chickasaw Creek water samples spanning 2008 to 2016. Chickasaw Creek drains around 25% of the watershed area. The research results are very encouraging.

“We saw reductions in sediment and nutrient loading. These changes varied based on the time of year and the water flow but we saw reductions from 20% to 50% and sometimes even 60% in sediment and nutrient loading. These are extremely substantial nutrient decreases,” Jacquemin said. “It is difficult in this case to attribute this to any one practice because there were a number of good practices implemented at that same time. But we can say that since that time we have seen great reductions. The runoff is coming from fields and it was good to see everyone tackle that. The ag producers did a number of outstanding things. We certainly have a ways to go but we are heading in the right direction.”

In addition, Jacquemin is looking at additional benefits from the installation of wetlands in the watershed to capture nutrients from the water.

“We have been monitoring the wetlands for a year or so now. The preliminary results show extremely promising data. We are seeing 50% reductions in nitrates during summer loading periods and close to 80% reductions in phosphorus during loading periods. Most importantly we are seeing that these wetlands are able to process around 20% to 30% of the actual stream that they are filtering,” he said. “These wetlands are located on Prairie Creek and Coldwater Creek. There are still a number of tributaries that could benefit from wetlands. The two wetlands we have are doing outstanding.”

Wetland installation is costly, but effective.

“The cost to put in a wetland depends on the design. There is no recipe. There are no set guidelines, but any good wetland will be a series of increasingly shallow ponds that are occupied by vegetation that can filter out the nutrients as they go through,” Jacquemin said. “From a cost perspective, the wetlands of Grand Lake have cost millions of dollars, but they are effective. They work. The watershed has ultimately benefitted from their inclusion.”

There is additional work being done to create wetlands out into the lake to filter more nutrients and a larger percentage of the water entering the lake.

“There is a way in a large shallow lake that you can expand wetlands out into the lake. We call these our littoral wetlands. The idea is to build vegetation embankments right around the mouths of the tributaries which slow down the water and filter water so it drops out sediment before it has the chance to get out into the rest of the lake,” he said. “Retaining walls are being created in the lake to build new wetlands. We are looking at that more this summer. We have made incredible progress and we are on the right path, but it is not done. There is always something more that can be done. This is not a situation that happened overnight and we are not going to get out of it overnight.”

Jacquemin’s research on water quality monitoring was published in the Jan-Feb 2018 issue of the Journal of Environmental Quality.