Barron County Nitrate Study

Introduction: Barron County is located in NW Wisconsin. The county’s twenty-five townships cover a total area of 864 square miles. The topography is gently rolling hills which taper to outwash plains along the Yellow and Red Cedar Rivers.

Agriculture is the principal industry in Barron County and the population is mostly rural. Dairy farming, turkey raising, and vegetable farming are the most important agricultural activities. Recreation is also an important industry. In many parts of the county agricultural activities are intensely practiced in close proximity to both heavily used recreational areas and concentrations of permanent rural residences.

Approximately 55% of the county’s population is rural and is served by private wells. Two major aquifers (water producing geological formations) provide the county’s well water. The shallower sand and gravel aquifer overlies the sandstone aquifer throughout the county. While they are separate geological units, the groundwater between them is hydraulically interconnected.

In recent years, the public has become increasingly concerned over the potential impact of agricultural activities on well water quality. In response, Barron County, Wisconsin Geological and Natural History Survey, and Department of Natural Resources have collected numerous samples from county wells. These have been analyzed for nitrate which when found in elevated concentrations may indicate contamination of groundwater by agricultural practices.

Nearly 800 wells were sampled between 1980 and 1986. Approximately 202 of the wells sampled in the intensely farmed and irrigated outwash plains of Prairie Lake and Barron Townships, were found to exceed the safe drinking water standard of 10 milligrams per liter nitrate. Also, many wells in Dallas Township, an important agricultural area, were found to exceed the nitrate standard.

Due to the need for additional information to accurately assess the problem in the three townships, the Department of Natural Resources conducted a follow-up study in 1986. The objective of the study was to evaluate the relationship of nitrate concentrations to well construction and location. Items evaluated were well depth, casing depth, casing penetration into the groundwater, water table depth, soil type, land use, drainage, water bearing formation, and overall well construction. The following report discusses and summarizes the study findings.