What is Going On With Wehr’s Lake?

First, thank you for noticing and being concerned. We are concerned as well and are working towards finding possible solutions. 

It is helpful to know some background information about the lake to understand its challenges. 

  • Mallard Lake (also called Whitnall Park Pond) is a shallow, 16-acre lake that collects runoff from a 10.3 square mile area. Water flows into the lake from drainage ways and two spring fed creeks, Tess Corners Creek and Pheasant Creek.
  • Our lake is manmade. Workers from the Civilian Conservation Corps built it in the 1930s to provide a recreational lake in the developing Whitnall Park. They dug out a basin and built a dam to hold back the water flowing in from Tess Corners and Pheasant creeks. Water flows over the dam/waterfall and continues to join the Root River. To learn more about the history of the lake visit: https://youtu.be/hLOvm-CAMe4

What is Causing the Lake to Decline?

Like many things in nature, the answer is not one simple explanation. There are many factors impacting the health and appearance of Mallard Lake. The major ones are: 

More water and pollutants are flowing into it.

  • Why more water? Land use within our watershed has gone from open/agricultural to suburban development in the last 40 years. More roofs, parking lots, and roads mean more water is running into creeks and drainage ways rather than soaking into the ground. The water carries soil, fertilizer, and other pollutants into the lake.
  • The streams and drainage ways that direct water into our lake have become highly degraded, allowing more soil and other debris to get into the lake.
  • Climate change is making intense rain events more common. Heavy rain creates more erosion. The soil moved by the water is deposited in the lake, making it shallow. Watch the impact of an extreme rain event in this video from 2020: https://youtu.be/46L_GCDMJFg

Pondweeds spread as the lake becomes shallower.

  • Deposition of soil from runoff and decomposition of pond plants is filling in the basin, making the lake very shallow. 
  • The majority of the pond is now under 3 feet in depth and is estimated to be only 10 feet at its deepest point. Its original depth was over 15 deep. 
  • Pond plants thrive in shallow water where they can root and get  light. Water lilies and other emergent plants have spread outward as the lake has filled with sediment. 

Excess nutrients cause an overgrowth of pond plants. 

  • Plants require naturally occurring nitrogen and phosphorus to grow. Water running off land in the watershed brings in high levels of these nutrients from fertilizer . Eroding soil also contributes to the lake’s nutrient load. This extra “fertilizer” creates an overgrowth of plants.

What is Wehr doing to fix these problems?

We are working to understand the causes.

  • An engineer from Milwaukee County Parks Planning, staff, and interns at Wehr are actively working with partners to best understand these issues. Our partners include:
    • Southeastern Wisconsin Regional Planning Commission: watershed management and planning resources
    • Citizen Monitoring Program: water quality data
    • City of Franklin : storm water management from adjacent properties

We are designing solutions to improve water quality

In 2022, the Friends of Wehr Nature Center hired Stormwater Solutions Engineering LLC to design a green infrastructure solution to Wehr’s south drainage way. Conversations are continuing with Parks Planning and City of Franklin involving working together toward a solution to the problem.

What can you do to help?

  • Provide your support for improving the water quality of Mallard Lake at Wehr Nature Center by attending a Franklin Environmental Committee meeting. 
  • Share your stories of how you have enjoyed Mallard Lake or witnessed changes  to its health over the years. Contact the Milwaukee County Parks at https://county.milwaukee.gov/EN/Parks/Contact
  • For all other questions or comments, contact Carly Hintz, Director of Wehr Nature Center at Carly.Hintz@milwaukeecountywi.gov or 414-425-8550.