The direction of groundwater flow normally follows the general topography of the land surface. In Portage County, a groundwater divide is formed by a glacial moraine that runs from north to south through the center of the County.4, 7
As the diagram shows, groundwater flowing west of this divide empties or discharges into the Wisconsin River system or watershed and groundwater flowing east of the divide empties into the Tomorrow River system.7
Groundwater moves extremely slowly---usually inches per day, whereas rivers move more swiftly--feet per second (ft/sec). However, in the sandy soils of Central Wisconsin, groundwater moves more quickly, between 1-5 feet per day.5 Even at this rate, groundwater and substances dissolved in it may take 5 years to travel about 1 mile. In comparison, a small twig moving downstream in a river at about 1-2 ft/sec would only take about 1 hour to travel 1 mile.