A Groundwater Model for the Central Sands of Wisconsin: Assessing the Environmental and Economic Impacts of Irrigated Agriculture

Problem Overview: The central sand plain of Wisconsin (Hole and Germain, 1994) is 6,400 km² of predominantly sandy outwash soils, formed as the last glaciers retreated 10,000 years ago. The soils of this region have little inherent productivity, and early in the century barely supported agriculture. Research conducted in the 1940’s by the (then) College of Agriculture of the (then) University of Wisconsin, however, demonstrated that these plains could in fact be very productive if the low water carrying capacity and fertility of the sandy soil was compensated for by irrigation and additional nitrogen inputs. A widespread irrigated vegetable industry soon grew in central Wisconsin, drawing several major vegetable processing plants to the region and enhancing the economy by providing jobs and demanding local goods and services. Today, the total economic impact of potato production alone in the Central Sands is on the order of $280 million annually.

The economic success in the Central Sands, however, has come at a cost to the environment. State and federal standards for drinking water are currently exceeded in more than 20% of wells in Portage County, and exceedence rates are as high as 70% in some regions where irrigation activities are particularly concentrated. Groundwater nitrate in excess of the drinking water standard forced closure of the Whiting municipal well from 1978 to 1991, until a $670,000 nitrate removal facility became operational. Wells in the city of Plover began exceeding the nitrate standard in 1993, forcing installation of a nitrate removal facility costing over $2 million. Plover now spends $6/lb to remove nitrate from its drinking water that was introduced at a cost of only 22 cents/lb as fertilizer.

So there are apparently conflicting interests in the Central Sands. Rising groundwater nitrate concentrations due to increased agricultural activity conflict with state and federal water quality standards. Compliance with these standards taxes municipal funds both through the costs of remediation efforts and through the erosion of farm and corporate incomes and associated revenues should agricultural regulation be required. Portage County is currently engaged in a groundwater management planning exercise to deal with the effects of agricultural pollution, but finds its efforts stymied by information gaps on the causes, effects, and economics of agriculture and groundwater pollution. This process is further complicated in that it requires building consensus between contentious groups of stakeholders; past attempts to bring these groups together have proven ineffectual, decaying into dispute and finger pointing.