Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Effectiveness of agricultural practices on water quality and hydrology: Long-term assessment at multiple scales (118616)

Maria Lemke 1 , David A Kovacic 2 , Mike P Wallace 2 , William Perry 3 , Jackie R Kraft 4 , Terry S Noto 5 , Krista G Kirkham 1
  1. The Nature Conservancy, Lewistown, IL, United States
  2. University of Illinois, Champaign, Illinois, USA
  3. Illinois State University, Normal, Illinois, USA
  4. McLean County Soil and Water Conservation District, Normal, Illinois, USA
  5. Conservation Strategies Consultants, LLC, Rochester, New York, USA

For 20+ years The Nature Conservancy (TNC) in Illinois has worked with agricultural landowners and partners to implement and monitor effectiveness of agricultural conservation practices on water quality and hydrology in the Mackinaw River watershed, located in the Midwestern U.S. state of Illinois. This river is a major tributary to the Illinois River that drains to the Mississippi River and ultimately the Gulf of Mexico. Like much of central Illinois, this 3,000 km2 watershed contains some of the most productive agricultural land in the nation and plays a key role in the state’s economy. Urban development and high nutrient runoff from tile-drained row crop agriculture have stressed freshwater resources, leading to habitat loss and reduced water quality, such that Illinois is one of the highest contributors of nitrogen and phosphorus to Gulf of Mexico hypoxia.  Nutrient exports from Mississippi River Basin states led to mandated nutrient loss reduction plans – Illinois has interim goals of 15% and 25% reduction in nitrate-nitrogen and phosphorus by 2025, with long-term reductions of 45%.  A recent 12-year study conducted by TNC and partners showed small wetlands constructed to intercept and treat agricultural tile runoff that represented 3% of tile-drained farmland area reduced nitrate losses by 15-38% and captured 53-81% of dissolved phosphorus. However, increased intensity of spring precipitation events and nutrient losses associated with climate change require additional assessments of single and multi-practice capacity to meet nutrient loss reduction goals. We increased field-scale wetland analyses to provide more robust assessments of phosphorus removal and cost efficiencies and analyzed watershed-scale effectiveness of constructed wetlands. We will also present research on stacked practices at field and watershed scales. Integrating science into collaborative outreach and implementation is necessary to develop and apply sustainable conservation-based solutions at scale to address water quality goals and sustain diversity in agricultural watersheds.