Significant decline in depth to the water table in the Wisconsin Central Sand Plain (WCSP), especially Portage and Waushara counties, has caused concern over the increase in land area devoted to irrigated agricultural crop production. The decrease in groundwater elevation, lake levels, and stream flows, has significant impacts on aquatic ecosystems, recreational uses of streams and lakes, and property values of riparian lands (Fig. 1). Since 2002, water table levels in parts of the WCSP have dropped over 30 cm per year. Thus, we conducted a study to investigate the interactions between vegetation (irrigated agricultural crops, prairie, and forest) and depth to groundwater in the WCSP. The purpose of this study is to understand the degree to which these groundwater fluctuations are driven by climate changes or increasing irrigated agriculture. After collecting over 18 months of continuous water table elevation data under several vegetation types, we can see effects of vegetation cover and irrigation practices on fluctuation patterns in the water table. The data show clear differences in recharge and discharge behavior of the water table under irrigated crops and natural vegetations. The groundwater monitoring site location within the groundwatershed also influenced recharge characteristics. The impact of seasonal changes on the water table is also apparent. We will continue to expand our current database of groundwater elevations to further understand vegetation and irrigation impacts on groundwater levels.
Soil Science Extension
University of Wisconsin Madison