EPA Research Partner Support Story: Water nitrate contamination
Partners: Oregon Department of Environmental Quality (DEQ); Oregon Department of Agriculture
Challenge: Improve surface and groundwater nitrate contamination from agriculture
Resource: Collaborating with farmers to assess the effectiveness of fertilizer best management practices
Project Period: 2017 – 2022
Groundwater nitrate contamination affects thousands of households in the Southern Willamette Valley Groundwater Management Area (GWMA) in Oregon. To reduce non-point source loading of nitrogen to groundwater and surface water, successful approaches are needed within affected communities to integrate science, outreach and management efforts. A partnership was formed that brings together commercial farmers, Oregon Department of Agriculture, soil and water conservation districts and EPA to assess the current state of groundwater in the Valley, and to evaluate best practices in fertilizer management.
“EPA ORD scientists have made significant contributions to the monitoring program in the southern Willamette Valley Groundwater Management Area. Their technical expertise has enhanced analyses of complex hydrological systems, as well as informed Oregon DEQ synthesis of multi-scale factors impacting nitrate concentrations in the southern Willamette Valley.” – Oregon DEQ Joni Hammond (former Acting Director)
In this collaborative project, scientists measured nitrate leaching from 14 fields in the Valley. They shared the data with farmers and discussed best practices for fertilizer application that would reduce the leaching. Scientists documented the effectiveness of these practices on their fields and now are seeing positive results for less nitrate leaching in some fields. This work was published in Nutrient Cycling in Agroecosystems.
EPA ORD scientists also recently published a study of deep soil leaching and storage within a corn crop in the Valley. ORD scientists learned that approximately 29% of nitrogen inputs leached below 3 m in the soil, while 27% was stored within the soil. Deeper soil storage is less accessible to future crops and leaves a legacy that allows groundwater nitrate contamination to persist. Understanding the long-term role of this soil storage is key for both agricultural sustainability and water quality.
In addition, EPA ORD scientists have provided stable isotopic analyses to identify the causes of high temporal nutrient variability within local wells. These efforts have helped illuminate complex groundwater-surface water interactions and greatly improved Oregon DEQ’s monitoring program for the groundwater management area. This works has been published and ORD efforts helped to reduce potential new inputs of nitrate into the groundwater system and understand the complex dynamics of groundwater in general.
EPA ORD scientists also worked with Oregon Department of Environmental Quality and Oregon State University Extension to produce a story map and a data dashboard about the GWMA that allows the community to learn about well water nitrate sources, issues and progress in the GWMA.