Miami Conservancy District reduces nutrient pollution through credit trading

The Great Miami River (Credit: Austen Verrilli)

Ten years ago, representatives from Dayton, Ohio’s Miami Conservancy District met with citizens from the Great Miami River Watershed to discuss water quality issues they were facing.

“Community members asked us to help them address water quality issues in our rivers and streams,” said Sarah Hippensteel Hall, Miami Conservancy District manager of watershed partnerships. “A major part of the pollution problem is nutrients.”

Agricultural land makes up more than 70 percent of the 5,371 square miles of the Great Miami Watershed. Runoff from farming operations causes nutrient pollution and sediment loading in the river basin.

Hippensteel Hall said watershed groups lacked funds to remediate nitrogen and lacked data on the nutrient pollution trends of the watershed.

Miami Conservancy District staff launched a long-term water quality study while building a credit trading program that would incentivize farmers to reduce their pollution by working with soil and water conservation districts in the area.

So far, the trading program has funded 397 agricultural runoff mitigation projects with about $1.6 million slated to be paid to farmers and agriculture producers for their participation. If all goes to plan, the projects will keep 572 tons of nutrients from entering the watershed.

New regulations will require wastewater treatment plants to reduce nutrients in their outflows, said Mike Ekberg, Miami Conservancy manager of water resources monitoring and analysis. Plant officials can reduce nutrients to their required level by upgrading their facilities, but that is expensive.

“In lieu of costly engineering upgrades, they are going to take some of that money and invest it in projects upstream to keep nutrients out of waterways,” Ekberg said.

Hippensteel Hall said the cost savings to wastewater treatment plants are substantial. She estimates that it would cost plants in the Great Miami Watershed $500 million to upgrade their facilities. “That cost of course is borne by ratepayers who pay the bills to the plant and they just wouldn’t be able to afford it,” she said.

The cost to comply through nutrient runoff reduction at the source will be one tenth of facility upgrades at $50 million for the watershed.

Benefits of reducing nutrients at the source are also much greater to the watershed.  “When you upgrade the plant, all you’re getting is a reduction of that particular chemical coming out of the pipe,” Hippensteel Hall said. “When you install conservation practices you’re also getting increased shade or reduced velocities or reduced sediment loads.”

The typical remediation project relies on cover crops or planting grass in drainage ditches to absorb nutrients and maintain soil.

Miami Conservancy District’s MIke Ekberg demonstrates their flow-through monitoring system (Credit: Austen Verrilli)

As part of the credit trading program’s initiation the Miami Conservancy District set up monitoring stations along the Great Miami and its tributaries. Two stations are on the Great Miami River. One monitoring station is on the Stillwater River and one is on the Mad River.

Gauge houses at each site keep monitoring instruments safe. A pump draws water from the river up to gauge houses where it passes through a flow through tank before returning to the river. YSI EXO Sondes measure parameters such as water temperature, turbidity, specific conductance and oxygen content. Data is streamed to the Miami Conservancy District’s website where the public can view the latest river conditions.

ISCO refrigerated samplers continuously collect samples. Ekberg said samples are analyzed through spectrophotometry by an independent lab for nutrients and other pollutants.

Each monitoring station is situated near a U.S. Geological Survey stream gauge so that water quality data can be coupled with water flow data.

During their six year water quality study from 2005 to 2011, Miami Conservancy District staff found that nitrate and dissolved orthophosphate were the dominant forms of nutrients. The highest annual amount of nitrogen recorded during the study was in 2011, when a total of nearly 29,000 metric tons of nitrogen passed through water by the southernmost monitoring station on the Great Miami near Hamilton, Ohio. That section of river also had the highest corresponding flow.

Study data show typical nutrient concentrations in the river and tributaries for nitrogen ranged from 3.75 milligrams per liter of 4.79 milligrams per liter. Phosphorus concentrations ranged from 0.20 milligrams per liter to 0.31 milligrams per liter.

Looking back at the process, Hippensteel Hall said a large part of the effort required to build the program was developing a trusting relationship with the agricultural community. “We involved them in every single conversation and we used their advice and their expertise to design the program,” she said. “So, the program is based on what they wanted and they thought would work and be acceptable.”

Top image: The Great Miami River (Credit: Austen Verrilli)