McMillan and partners at Purdue take a holistic approach to conducting and communicating water quality outcomes in the St. Mary’s Watershed

When it comes to determining the impact of agricultural best management practices on water quality on the watershed scale – the science can be noisy. No one knows that more than Sara McMillan. McMillan, who is an Associate Professor in the Department of Agricultural and Biological Engineering at Purdue University, studies how humans impact nutrient cycling in aquatic and wetland ecosystems.

“It can be hard to untangle which practice or which action leads to a certain outcome. There is an inherent amount of uncertainty when you look at the watershed scale due to the variability in such things as storms, season, soil type, and land practices. That uncertainty is really hard to communicate to landowners and producers who want to know whether they are making a difference,” notes McMillan.

To combat this issue, McMillan and partners are taking a holistic approach through the St. Mary’s Watershed Initiative.

Sara and her team manage the water quality sampling and analysis for the project and have been monitoring water quality in the watershed for three years now – at the watershed and local stream level. The team partnered with the U.S. Geological Survey to install stream flow gauges at the outlets of two small watersheds which provide real time flow monitoring. Her team couples this with daily and event-based sampling using auto-samplers and a unique partnership with a local farmer to capture pulses of sediment, nutrients, and other pollutants. The team also samples stream water and tile inputs at multiple points throughout these two watersheds monthly and conducts twice annual biological assessments of fish and macroinvertebrates communities and instream habitat. They also monitor soils in the watershed to help identify the link between field and soil processes and stream water quality. Collectively, these efforts help give the team a map of local water quality conditions, how the watersheds could impact downstream water quality in Lake Erie, and how both relate to on-the-ground conservation efforts.

In addition, to creating a holistic picture of water, stream and soil conditions in the watershed, the team is also working to understand existing conservation education and outreach efforts and identify opportunities for future outreach and engagement. The Natural Resources Social Science Lab at Purdue is a part of the project team and is conducting interviews and surveys in the watershed to better understand the drivers of landowner decisions and where producers are getting conservation and water quality information.

The team is highly collaborative with over 10 community, county and state partners which participate in a project advisory group and provide feedback on the team’s work and their methods going forward.

“We have been very intentional in working to take in the feedback from the advisory team and making changes accordingly. For example, we had originally planned to only do water quality monitoring on a monthly-basis because many of the sites were close to two hours away, but we heard from our advisory team that we needed to do a better job understanding flow-driven nutrient export. So, we worked with our partners at USGS and installed stream flow gauges and even worked with one of the producers to install as ISCO automated water samplers at the watershed outlets, one of which is close to his farm,” notes McMillan.

McMillan and her team also got feedback that the community and landowners who are participating really wanted to know what they were finding in their fields, so their team has been working to share additional updates on their findings and virtual field trips of sampling trips and short clips of findings to replace the field days we would normally host to increase transparency and encourage engagement.

The team also recently started hosting a webinar series with the community where they feature the project team along with local extension and state agency experts discussing soil organic matter, cover crops, phosphorus holding capacity, and more. In addition to presentations from experts, the webinars also allow the team to discuss how the talks relate to what they are seeing in the water quality outcomes they are collecting in the watershed.

“We started hosting the webinars in the morning and then repeated them in the evenings and we have really seen a lot of engagement and we get to be a little creative with how we share our information. It’s as fun as a Zoom Meeting can be!  We get a different crowd for each session – in the morning we tend to see more agency staff and retired producers whereas in the evening we are having a lot of producers join,” notes McMillan. “Hosting the webinar at two different times has really been a great way to engage.”

The teams monitoring efforts have already shown interesting findings. For example, soil monitoring in the watershed has shown that cover crops and conversation tillage has not only decreased soil loss and increased soil organic matter, but it has also been correlated with an increase phosphors adsorption capacity.

“These conservation practices are allowing the soil to act more like a sponge for phosphorus, which in turn should lead to additional water quality benefits downstream,” notes McMillan. “It always great when you have interesting findings from your data, but its even better when you are able to effectively engage with the community to communicate those findings. That is when you know you are making a difference.”

Sara McMillan, Purdue University

Sara McMillan is an Associate Professor in Agricultural and Biological Engineering at Purdue University where she and her students focus on water quality impacts in agricultural and urban settings. She has over 15 years of experience in research, design, and assessment of restoration and conservation projects. She combines field based monitoring with modeling tools to understand and mitigate the impacts of changing land use and climate on water quality.