Dane County Geography

"Driftless" Area or Valley and Ridge

• In the western third of Dane County, this area is the only part of the county that was not affected by the Wisconsin Glaciation. The hills are covered by an irregular layer of soil (quite thin in many places) overlying fractured dolomite or sandstone bedrock.
• This area is characterized by steep ridges and valleys drained by fast-flowing streams, generally without natural lakes or impoundments. Most of the streams are fed by springs and seeps flowing from water-bearing layers of bedrock exposed on hillsides.
• Because of the steep gradients, cool water temperatures, and high dissolved oxygen levels, most of the county's trout streams are located in this portion. These streams generally have fair to good water quality, but are commonly affected by nonpoint source pollution as well as streambank erosion problems.
• The Wisconsin River Valley, located in the northern portion of the valley and ridge region, is a large valley on the northwestern edge of the county and consists of deep, alluvial sand and gravel deposits and extensive marshes in the river's floodplain.

Moraine

• To the east of the Driftless Area, this area has glacial end moraines that create a major drainage divide. Headwaters of many streams of the Wisconsin, Sugar, and Yahara River basins originate here. The moraines include the Johnstown terminal moraine at the western edge of the glaciated area, and the Milton recessional moraine farther east. The moraines include hills and mixed deposits of glacial till (including clay, silt and boulders with sand and gravel layers) which were deposited and left behind as the glaciers retreated. The moraines also included large blocks of remnant ice which formed potholes or kettles, some of which remain as small ponds, marshes, and bogs.

Yahara River Valley

• East of the moraines and in the center of the county, deep glacial deposits dammed up large valleys, forming a chain of large lakes and wetlands. The four largest and most heavily used lakes in the county - Lakes Mendota, Monona, Waubesa and Kegonsa - are found here connected by the Yahara River. These are fertile lakes that support abundant algae and rooted aquatic plant growth, as well as a diverse warmwater fishery including northern pike, bass, and panfish.
• Streams in the Yahara River valley are generally flatter and more sluggish than those in the Driftless Area and fewer are spring-fed. Extensive ditching and wetland drainage has occurred near some water bodies in this area, resulting in water quality impacts and aquatic habitat loss.

Drumlin and Marsh

• The eastern part of the county consists primarily of general glacial deposits with extensive areas of marsh deposits. This area includes many small drumlin hills interspersed with shallow glacial deposits, which created an extensive system of interconnected wetlands with poorly defined drainage.
• Small streams wind slowly through the lowlands, and there are few springs supplying streamflow. The only lakes in this area are small stream impoundments or shallow, marshy lakes. No trout streams are present. A warmwater fishery predominates in the two major streams in the area - Koshkonong Creek and the Maunesha River. Extensive ditching and wetland drainage in this area have also affected water quality and habitat conditions.

Precipitation

Average annual precipitation is about 35 inches, with 68 percent falling from April through September. June is the wettest month, with average precipitation of 4.8 inches, and January is the driest, with about 1.2 inches. Snowfall averages 51 inches per year. Severe storms often occur from late fall through mid-spring. The potential for runoff and severe erosion is often highest in March and early April when heavy rainstorms and snowmelt occur on bare or sparsely covered ground.

Temperature

The temperature ranges from an average of 18.5° F in January to 71.6° F in July. The ground usually begins to freeze at the end of November and thaws in mid-April, reaching an average maximum frost depth of more than 18 inches.

Climate Change

Since 1950, warmer, wetter weather and more frequent extreme storm events have been observed in Dane County. These trends are expected to continue and potentially become more severe, impacting flood risk, water quality, and aquatic ecosystems.
By mid-century, Dane County’s climate may feel more like the historic climate of south-central Illinois, with all seasons warming by at least 5° F. Winter is expected to show the most warming (7°F), resulting in fewer days with frozen conditions. More rapid, intense rain events may generate increased surface runoff and cause localized and flash flooding.

Economy

Dane County's largest employment sectors are government (22%), trade (15%), and business (14%). Total employment in 2020 is projected to be about 376,000. From 2005 to 2025, the most growth is expected in business (about 24,100 jobs), health care (about 12,500), and hospitality (about 9,700). Natural resources, manufacturing, and finance are expected to lose jobs over this time period.

Population

Dane County is the second-largest metropolitan area in Wisconsin and the seat of state government. It is one of the fastest growing counties in the state and is expected to reach a total population of over 600,000 people by the year 2040 – an increase of about 24% over the 2010 population.