USING WATER-BALANCE AND GROUNDWATER FLOW MODELS TO SUPPORT DECISION MAKING FOR AGRICULTURE AND THE ENVIRONMENT IN CENTRAL WISCONSIN

Balancing the water needs of the environment with those of an important agricultural industry is critical for the environmental and economic sustainability of central Wisconsin. Concerns about increasing use of groundwater for irrigation and declines in streamflows and lake levels in Wisconsin’s central sand plain have motivated the development of modeling tools to help inform local water-management decisions. The Little Plover River is surrounded by irrigated fields and has a long history of groundwater/surface water interaction studies, making it ideal for an updated study using modern techniques. Declines in the river flow and subsequent establishment of public rights flows motivated the Wisconsin Department of Natural Resources to commission a modeling project using state-of-the-practice groundwater science to explore water management and sustainability options for the Little Plover River watershed. The resulting models and analyses might serve as a prototype for addressing similar issues in wider areas of the state.

A soil-water balance (SWB) model and transient groundwater flow model (MODFLOW) simulate pumping, groundwater levels, and streamflows in the region. These models incorporate current hydrogeologic observations, monthly water-use records, and temporally and spatially variable estimates of evapotranspiration and recharge based on cropping and irrigation practices. We are using these models to investigate alternative management scenarios and as educational tools for stakeholders. It is critical that stakeholders gain trust that the science is unbiased and that the modeling tools used provide a means for fairly evaluating the various viewpoints and opinions of how groundwater and surface water (and, thus, water use and environmental stream flow conditions) are connected. Accordingly, our team has participated in numerous public meetings and outreach events with local stakeholders and regulatory officials. The overall project goal represents not only the interface between groundwater and surface water, but also the interface between society, science, and policy.