Water Security in Armenia, WI: Modeling for Informed Decision Making in a Nitrate Impacted Watershed

Many rural communities are dependent on groundwater for both their economic productivity (i.e., agricultural uses) and for drinking water. When these combined uses present conflict, the ability of hydrogeologists and regulators to provide guidance to rural stakeholders is often hindered by sparse groundwater quantity and quality data. Nitrogen leached to groundwater, via the ionic form of nitrate, represents a diffuse groundwater quality concern that impacts many communities in Wisconsin, and there is increasing need for guidance to aid communities; for example, a homeowner may ask “how deep should my drinking water well be, and where should it be screened to limit the likelihood of nitrate contamination?”. We present a simplified approach for providing guidance on such questions. Data needs for this approach include remotely-sensed landcover and climate data, boundary conditions for the modeled region, depth to bedrock, and data on locations and pumping rates of existing high-capacity wells. Via processing of MODFLOW and MODPATH model results, we estimate land covers contributing to source waters for any hypothetical drinking water well in the region. We demonstrate this approach in a region spanning Juneau and Wood counties, WI. The results of our risk assessment tool – when compared with sampling results – indicate that wells where high nitrate concentrations have been observed have a high percentage of water originating from cropland.