---

Lake Mendota (15.4 sq. mi., max. depth 85 ft., volume 133 billion gals., discharge 21 billion gals./yr.) is a glacial lake that formed 15,000 years ago. Although much larger during the last glacial period, the lake shrank as ice reformed its basin. The ancient lake bed is evident in sediments bordering the present day lakeshore, and covers many areas including University Bay, most of the isthmus, Tenney Park, Warner Park, Truax Field, Cherokee Marsh and much of Middleton. Lake Mendota was originally mesotrophic (moderately fertile). Nutrients and sediments washed into the lake from various human activities have since made the lake eutrophic (overly nutrient-rich), so that weeds are abundant and periodic algae blooms occur. At times the water resembles pea soup and has a bad odor from decaying algae. Wetlands that once covered extensive areas around the lake have been filled in, drained, or were flooded when the lake level was raised with the 1849 construction of a dam at present-day Tenney Park. This loss of wetlands contributed to further water quality degradation. Wetlands act as detention ponds, storing polluted runoff and filtering our nutrients before releasing the water back into lakes and streams. The largest and first of the four Madison lakes, Mendota strongly influences water quality in lakes Monona, Waubesa and Kegonsa.

---

Distance: 25 Miles. Difficulty: moderate, few hills.

1. Picnic Point, Class of 1918 Marsh, University Bay Marsh and University Athletic Fields. (University Bay Dr., W end of UW campus) These wetlands are remnants of a larger wetland area that was filled in for the UW athletic fields or became submerged when the lake level was raised. This low, flat area is lacustrine plain, the ancient lake bed of glacial Lake Yahara, which formed when glacial debris and ice blocked the Yahara River, raising water levels and flooding an area much larger than that covered by Lake Mendota today. Fine, clay-rich sediments deposited in the lake environment drain poorly, lead to wet soil conditions favorable to wetland plants and the formation of peat. The ridge bearing the UW and VA hospitals is an isolated bit of end moraine, piled rock and debris that formed at the edge of the receding glacial ice sheet.

Picnic Point, accessible by a bike trail, is an excellent place to see migrating birds, especially warblers. Offering protection and shallow water, University Bay attracts all kinds of waterfowl grebes, common loons, mergansers and scoters have been observed here. South of the road, the Class of 1918 Marsh provides a superior spot to get a close look at puddle ducks, Sora Rails, common yellowthroats and many others that are difficult to see. It is important wildlife habitat and a popular stopover for migrating waterfowl.

2. Except for this quarter-mile stretch, Willow Creek is completely enclosed in culvert and is fed mostly by storm sewers that drain Madison's near west side, including Hilldale Mall. Sediment carried into the lake has formed "Gull Island" and rendered the near-shore lake significantly shallower. Water quality in the creek is generally poor. University Bay and Lake Mendota drives were originally designed as part of a park-and-pleasure-drive system, established in 1892, that extended west from here to Merrill Springs (see marker at bridge), looping back through University Heights. Just past Willow Creek, a Native American bird effigy mound can be seen on the right, behind the UW Natatorium. Although many have been destroyed, hundreds of these 500-to-1500 years-old mounds, are clustered around Madison. Whether mound-building was done as a monument to the dead who were sometimes buried in them, for religious purposes, simply as art, as a seasonal clan ritual, or for some other reason is not known, but it clearly played an important role in Native American culture.

3. UW Center for Limnology and Water Science and Engineering program (N. Park St. and Lake Mendota). UW-Madison has made contributions to the science of limnology (the study of lakes). Research on Lake Mendota (often called "the most studied lake in the world") has been conducted here for over a century. The UW research vessel Limnos can be seen from here, anchored off Picnic Point.

4. "Mansion Hill" is an area with many buildings of historical importance, including a former Governor's mansion (130 E. Gilman). The hill is one of a series of glacial drumlins, cigar-shaped hills formed under moving glacial ice, located along the south shore of Lake Mendota. Other drumlins include those bearing UW's Washburn Observatory, Bascom Hall, and the State Capitol.

5. Tenney Park, Tenney Locks, Lake Mendota outlet (the Yahara River). The Tenney Locks artificially raise the level of Lake Mendota by approximately 3 feet. A dam constructed here in 1849 flooded many wetlands bordering the lake. Coupled with a lowering of water levels in Lake Monona, this yielded sufficient "hydraulic head" to power a sawmill. Tenney Park sits atop an old landfill, closed before WW II. Many closed landfills in Dane County require ongoing monitoring and, at times, remedial action. Across much of the isthmus, the watershed boundary follows the area immediately along the shoreline, so most of the surface runoff here goes to Lake Monona. Much of this part of the isthmus was originally wetland (like University Bay, a part of the old lacustrine plain), that was filled in, lot-by-lot with sand, and then covered with a thin layer of topsoil.

6. The Lake Mendota Yacht Club has launched scow-class racing sailboats from the piers and dolly-and-rail system here since 1903.

7. Warner Park beach and the small creek that drains the Warner Park lagoons. The flat stretch along here marks another piece of lacustrine plain. Lake Mendota still has 34 common fish species such as large and small mouth bass, walleyes, northern pike, white bass, perch and bluegills. Developing wetlands and raising the water level destroyed many existing spawning areas.

8. Westport Meadows Park is also situated on lacustrine plain, which is now a shoreland wetland. Surface water passing through these wetlands on its way to the lake is cleansed of sediments and excess nutrients, protecting water quality in the lake. In 1993, high lake levels lifted about 12 acres of wetland vegetation so it floated like a mat. Winds blew the mat to the south shore of the lake.

9. The Yahara River is Lake Mendota's largest tributary. The upper Yahara River watershed extends into southern Columbia County, draining 32% of the watershed and contributing 22% of the lake's surface water input. Token Creek (11% of the area, but yielding 27% of the surface water), another major tributary, flows into the Yahara about five miles upstream from here. Soil eroded from farms, construction sites, etc., and washed into the river settled here in such quantities that a million-dollar dredging project was needed in 1994 to keep the river's outlet into Lake Mendota navigable.

10. Another major tributary is Sixmile Creek which drains 16% of the watershed area, and delivers about 15% of the lake's surface water input. It is joined 1/2 mi. S of here by Dorn Creek before entering Lake Mendota. A conservation area featuring a fish nursery, creek access, woods and wetlands is situated just upstream and is reached by a foot trail from Woodland Dr. just 1/2 mi. N of CTH M.

11. Dorn Marsh public hunting area (wetlands border Dorn Creek from W of CTH Q to CTH M, S of CTH K and N of Oncken Rd.). These wetlands cleanse farmland runoff of nutrients and contaminants before it enters Dorn Creek on its way to Sixmile Creek and Lake Mendota. Dorn Creek drains about 6% of the Lake Mendota watershed while contributing about 7% of the surface water input.

12. Providing shoreline access to Lake Mendota, Governor State Nelson Park encompasses wooded drumlins, wetlands, Native American effigy mounds and restored prairie. Prairie-oak savannah was the predominant landscape in Dane County at the time of settlement. Fires maintained the open prairies but fire-resistant bur oaks were able to survive in the otherwise open grasslands.

13. Pheasant Branch Creek Nature Preserve (Pheasant Branch Rd. between Balzer Rd. & CTH M). Observers have seen more than 175 species of birds at this large conservation park, which features lowland forest, a meandering stream, a sedge meadow, a pond, and shrub and wetland habitats. A nature trail accessed from a parking lot on east side of the road leads through Middleton to USH 12. The prominent hill on the east side of the road is part of Dane County's newest park. The new park's entrance is 0.7 miles south of the corner at Balzer and Pheasant Branch Road.

14. On the right side of the road is the site of the Middleton Hills development, designed to be pedestrian-friendly by mixing commercial and residential uses at a medium density. This development is an alternative to low-density suburban developments designed around automobile use.

15. Pheasant Branch Creek drains about 8% of the Lake Mendota watershed, delivering about 5% of Mendota's surface water input.

16. Spring Harbor and Merrill Springs Park. A network of storm sewers and drainageways leading all the way to West Towne Mall empties here. Spring Harbor was originally more than 20 feet deep. However, urbanization increased stormwater runoff which scoured waterways and eroded soil from construction sites, and deposited it here. The harbor was dredged in 1996. Efforts to stabilize drainageways and installation of stormwater detention basins such as those on Mineral Point Rd. at Gammon Rd. have helped slow siltation in the lake. Less construction as the area has matured has also helped. Springs can be seen in Merrill Springs Park by following the waterway upstream for 100 yards or so.

17. Madison water utility municipal well. Virtually all domestic water in the watershed comes from groundwater. Municipal wells such as this one tap a deep (500-1000 feet) sandstone aquifer. Increasing use has led to a regional drawdown of the water table, centered around Madison. This has altered the movement of the groundwater and affected springs and seeps, so that in some cases, areas where groundwater once discharged have become areas of recharge.

webmaster