Groundwater Response to Drought and Seasonal Precipitation Changes

The Wisconsin central sands is a loosely-defined region characterized by a thick (often >30 m) mantle of sandy materials overlying rocks of low permeability. Due to the sandy soils, irrigated agriculture has been growing steadily in the region since the 1950’s, when irrigation systems and high capacity wells became inexpensive and easy to install. This has resulted in Central Wisconsin having the greatest density of high capacity wells in the state. Recent low lake and river levels have increased concerns that unfettered groundwater pumping for irrigation will undermine the availability of groundwater to support surface waters and domestic uses. In this study, the response of three groundwater monitoring wells and precipitation from five climate stations were examined. Through statistical analysis, significant precipitation increases were identified during the summer (2-3 mm/year) and winter (0.5 mm/year) in the southern part of the study area, but no significant change during any season was determined in the northern portion. Additionally, monitoring well response to drought has increase through time as irrigated agriculture has grown. This research may be useful in the prediction of lake and river response to changes in seasonal precipitation and extended periods of drought.