Yahara Portal

Explore the legacy and future of the Yahara Lakes and Watershed

Lakes and Streams

The Yahara Watershed (click image on right for map), or land area that drains into the Yahara River and lakes, covers 359 square miles, more than a quarter of Dane County. Much of the watershed is farmed; however, the watershed also contains most of the urban land of the Madison metropolitan area. In addition, the Yahara Watershed includes some of the largest wetlands that are left in Dane County. The lakes’ watershed includes all or parts of five cities, seven villages and sixteen towns, and is home to about 350,000 people.

Glaciers primarily shaped this area. About 15,000 years ago the glacier ice reached its maximum with the Madison area covered by about 1,000 feet of ice. About 12,000 years ago Glacial Lake Yahara connected all the present lakes, stood about 12 feet higher than present Lake Mendota, and encompassed about twice the current water area. Moving glacial ice also widened the valleys, created hills in the shape of elongated teardrops (called drumlins) and created poorly drained areas where wetlands formed. Sometimes called “the Yahara River Valley,” the area represents the far western edge of the last glacier advancement.

The ice also left glacial deposits of silt, sand, gravel and rock up to 350 feet deep. These deposits dammed up the existing, larger pre-glacial valleys, and formed the Yahara chain of lakes. The region is typically flat with gently undulating hills, a result of the glaciers flattening hills and filling former valleys. The gentle relief resulted in slower-moving streams and rivers than those found in the southwestern Driftless Area of Southwest Wisconsin that was not covered by glacial ice. The watershed area has rich, young (less than 15,000 year old) soils.

The First Humans

Humans first inhabited this area about 11,500 years ago, living first by hunting and gathering and more recently by agriculture. The Native Americans left behind many artifacts, including hundreds of earthen mounds, many shaped like animals (Effigy Mounds). By periodically setting fire to the land, they shaped the prairie-oak savanna landscape that greeted the European settlers. When European-style farming began in the 1830s, dramatic transformations to the land and water began. Soil eroded from the new farms and washed into the lakes. People began to notice nuisance algae blooms as early as the 1880s. Draining and filling the surrounding wetlands exacerbated the problem, because wetlands had kept the sediment and nutrients from entering the lakes. Since pre-European settlement we have lost about 50 percent of the wetlands around the Yahara Lakes.

Problems and Promise – The Lakes in Modern Times

Local water quality is a direct reflection of land use. As the 20th century progressed, water quality in this area declined in direct proportion to the population growth. Sewage from growing villages and cities, along with manure and fertilizers running off from farms, added bacteria and more nutrients. As the urban and suburban areas grew, so did the area covered by streets, parking lots, roofs and sidewalks. This has increased the amount of runoff, which erodes waterways, increases flooding frequency and intensity, and carries contaminants directly into the lakes.

Recent years have brought progress as well as challenges. Municipal sewerage is treated and the effluent diverted away from the lakes. Wetlands are better protected; however, population is increasing rapidly, generating much new construction while farms support ever-greater numbers of livestock. Recognizing these trends, county and state officials have been partnering with other local units of government, farmers, developers, and citizens to reduce non-point or runoff pollution. This kind of pollution includes excess nutrients, sediment, pesticides and toxic chemicals that are washed into the water from farms, fields, developing land, and streets. It is the greatest threat to the Yahara River and its lakes.

Adoption of conservation farming practices such as grass waterways, contour farming, safe manure storage and handling, minimal tillage, crop rotations, and buffer strips greatly help pollution reduction in rural areas. In developing and suburban/urban areas, reducing erosion from construction sites and reducing runoff are essential to water quality improvement. The use of proper seeding and mulching, rain gardens, bio-infiltration, filter fabric fencing, storm water detention ponds, and other conservation practices all assist in the effort.

Source: Yahara Waterways Trail Guide – 2007 – Dane County 

Facts About the Yahara Lakes and Watershed

In the upper reaches of the Mississippi River Basin, the Yahara Lakes are a string of freshwater pearls along the Yahara River watershed. The river flows 45 miles south from headwaters just north of the Dane and Columbia county line through lakes Mendota, Monona, Waubesa and Kegonsa until its confluence with the Rock River below Indianford in Rock County. The Rock eventually joins the Mississippi at Rock Island.

With the University of Wisconsin perched on the shore of Lake Mendota, and Edgewood College along Lake Wingra, the Yahara lakes have been the focus of extensive research for more than 100 years. Lake Mendota has earned the title “the most studied lake in the world,” and the other lakes in the system aren’t far behind. But all that research hasn’t spared the lakes in the Capitol region the fate of being laden with nutrient pollution that spurs the vast algae blooms that choke the lakes each summer, or other problems that take away from their beauty and value for recreation and wildlife.

 Source of table below:  UW Center for Limnology


Surface area (ha)

Volume (million m3)

Max depth (m)

Mean Depth (m)

Shoreline length (km)

Direct Drainage Area (km2)

Total Drainage Area (km2)

Shoreline development factor

Flushing rate

Lake Mendota










Lake Monona










Lake Wingra










Lake Waubesa










Lake Kegonsa