Nelson Issue Brief: Nitrate contamination in drinking water and groundwater

What Affects a Rural Town's Well Water?

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Michael Cardiff, Department of Geology, UW-Madison, cardiff@wisc.edu

Like many smaller municipalities in Wisconsin, Spring Green, in Sauk County, is experiencing increasing nitrate concentrations in the wells supplying its drinking water. Through DNR-funded research, we measure nitrate entering the groundwater under different management conditions and crop types. We are also working with farmers near Spring Green to assess how climate and agricultural practices contribute to the nitrate leaching to groundwater beneath agricultural fields.

Farmer participation is crucial to the success of this project. We have found that consistent communication with farmers about our goals, experimental plans, and preliminary findings has helped to build trust in this relationship and avoid interference with farm operations. Farmers can supply vital specialized information, including records of irrigation, nutrient applications, and planting plans.

We use edge-of-field wells and an inert tracer in order to calculate net nitrate leaching from fields. In Spring Green we have quantified the contribution of a portion of a field to nitrate in groundwater as climatic conditions, crop plantings, and fertilizer applications have all varied. We will ultimately develop a dataset capable of relating nitrate mass loss from fields to climate, crop, and fertilizer management conditions. We will thus produce a real-world database as a basis for recommending agricultural best practices for nitrate management.

This data will also help municipalities determine economical methods for reducing nitrate concentrations at municipal wells, which may include incentivizing change in crop types, revised fertilization rates, land purchases or deepening of water supply wells.

Learn more about nitrate contamination