Hydrology and hydrologic process within and around the Preserve greatly influence the quality and health of its diverse biotic communities. A significant ridgeline runs east-west through the northern portion of the Preserve, bisecting Eagle Heights Woods, Bills Woods, and the base of Picnic Point. Areas north of the ridgeline drain north, while areas south drain toward University Bay Drive, where grassy swales infiltrate and conduct water to the lake near University Bay Marsh.
Gullies, rivulets, and outwash flows, with their attendant erosion, are the result of changes in the vegetation and built environment of the Preserve. Large areas under roof and asphalt in the surrounding area convey excessive storm water downhill rather than infiltrating it at the source. A lack of ground layer vegetation in many of the wooded areas throughout the Preserve allows surface water to erode organic material in the soil. Concentrated areas of storm water runoff from culverts and pipes create point-source erosion problems. The physical impacts of these several processes can be seen throughout the Preserve.
Additionally, the Willow Creek Watershed—which is much larger than most people realize—has a substantial impact on the quality of water in Willow Creek and University Bay.
The physical boundaries of this watershed extend well beyond the UW-Madison campus and include much of west central Madison as shown in the map. Storm water from this large urban area conveys with it pollutants from city streets, waste from yards and parking lots, and sediment. The greatest of these impacts occurs at Willow Creek. Willow Creek exhibits extreme peaks in flow from storm events and spring floods during which millions of gallons of storm water enter the Willow Creek system and ultimately end up in University Bay.
Other areas also suffer from storm water runoff that is concentrated and conveyed from beyond the edges of the Preserve, including Raymer’s Cove and Tent Colony Woods where gullies convey water from Lake Mendota Drive and along the Howard Temin Lakeshore Path where storm sewers empty to Lake Mendota.
Learn More!
Watch the Water Walk video series: A virtual tour of Wisconsin’s Yahara Watershed