Effects of climate change in Wisconsin: Flooding in the south, drought in the north
Recent weather patterns in Wisconsin have radically altered the landscape, although the type of change you see depends on where you are in the state. In northern or central Wisconsin, some lakes are drying up due to an extended drought. By contrast, heavy rains in southern Wisconsin have left people struggling to cope with floods, wet basements, and high lake levels.
Lake extremes are related to levels of both surface water and groundwater. Understanding the connections between weather patterns, hydrologic systems, and climate change is key to helping us anticipate and respond effectively. It’s also important to helping communities make informed decisions about remediation efforts.
Flooding in southern Wisconsin
Following intense rainfall in June 2008, much of southern Wisconsin was under water. In some areas, notably around Spring Green, floodwaters remained for months. Why so long? The water couldn’t drain because the underground water table was already at land surface. Before floodwaters could dissipate, the entire aquifer (the underground layer of rock that holds water) had to lower.
Groundwater flooding lasts much longer than flooding of streams or rivers. The water table may slowly decline as groundwater flows towards and discharges to nearby rivers and streams. Following the summer’s heavy rains, water levels in some wells in southern Wisconsin were nearly 10 feet above their historic highs.
Seepage lakes (lakes that have no streams flowing into or out of them) are also susceptible to groundwater flooding. When water table levels rise, so do lake levels, submerging beaches and flooding shoreline developments.
Read about groundwater flooding in Spring Green, Wisconsin: http://www.uwex.edu/wgnhs/news.htm
Community response to groundwater flooding
As the climate changes, groundwater flooding is likely to become more common than in the past. Builders and developers need to consider how high the water table may get when designing and locating buildings and highways. Subsurface structures (basements, septic systems, etc) need to be sited above the highest expected water table elevation. This might be many feet above the “average” water table. Hydrogeologic and hydrologic data provide information about how high the water table may rise.
Drought in northern Wisconsin
Where southern Wisconsin has been hit by too much rain and snow, northern and central Wisconsin has been suffering from an extended drought. That part of the state has received significantly less precipitation than normal over the last 4 years, resulting in falling water levels. Some lakes are at their lowest level in 70 years.
Prolonged drought hurts boat access and compromises water quality. Lakes may also suffer fish kills.
For more details about the impact of falling water levels on northern lakes, read the Journal Sentinel’s May 23, 2009 article by Lee Bergquist: www.jsonline.com/news/wisconsin/45924602.html
Wisconsin Department of Natural Resources lakes FAQ (dnr.wi.gov/lakes/commonquestions)
University of Wisconsin–Extension Lakes Program (www.uwsp.edu/cnr/uwexlakes/)
Great Lakes Environmental Research Laboratory (www.glerl.noaa.gov/pubs/brochures/lakelevels/lakelevels.pdf)
Sea Grant Institute—Climate change in the Great Lakes region (www.seagrant.wisc.edu/ClimateChange)
U.S. Drought Monitor (http://www.drought.unl.edu/dm/monitor.html)
USGS WaterWatch (waterwatch.usgs.gov/?m=real&w=gmap®ions=wi)
USGS Wisconsin groundwater conditions (wi.water.usgs.gov/data/groundwater.html)
Wisconsin Association of Lakes (wisconsinlakes.org)
Wisconsin Initiative on Climate Change Impact (wicci.wisc.edu/workinggroups/stormwater)
Updated September 22, 2009