The Land & Water Resources Department is responsible for maintaining lake levels for the four major lakes in Dane County: Lake Mendota, Lake Monona, Lake Waubesa and Lake Kegonsa. Minimum and maximum lake levels were set by the Wisconsin Department of Natural Resources in 1979 and are listed below in the information tabs for each lake. For information on the 2018 flooding, please visit our Flood Facts & Initiatives webpage.
October 18, 2024 – All lakes (Mendota, Monona, Waubesa, and Kegonsa) are within the summer water level orders. The future weather forecast is predicting dry weather. The goal is to manage water levels to the midrange of the summer water level orders. We will continue to monitor weather forecasts and provide updates on the current status of lake levels.
Navigational buoys in the Yahara River and Lakes are currently being removed. Please use caution on the water due to removal of buoys that would normally mark hazards and navigation. In November, water levels will transition to winter lake levels by opening all the dams for the Yahara Lakes. This change in November is expected to drop lake levels below summer minimum.
Babcock lock is closed for navigation.
LaFollette lock is closed for navigation.
| Lake | Date | Lake Level | Min | Summer Max | 1% Flood |
|---|---|---|---|---|---|
| Mendota | N/A | N/A | N/A | N/A | 852.8 |
| Monona | N/A | N/A | N/A | N/A | 847.7 |
| Waubesa | N/A | N/A | N/A | N/A | 847.0 |
| Kegonsa | N/A | N/A | N/A | N/A | 845.8 |
*Current lake levels are updated daily from the United States Geological Survey (USGS) and are expressed in feet above sea level. These values are provisional data from USGS which are subject to revision based on a thorough review to ensure accuracy. Final data are usually published within 6 months of the end of the water year (Sept 30). For additional information, see the USGS website Real-Time Data for Wisconsin: Yahara River and Lakes or the booklet Understanding Lake Data (PDF) from University of Wisconsin Extension. The 1% Flood column in the table above is the 1% annual chance flood, also known as the 100-year flood.
Elevations are reported in feet above the National Geodetic Vertical Datum of 1929 (NGVD29). Prior to 1973, the datum was the Sea Level Datum of 1929, commonly referred to as mean sea level (MSL). See Vertical Datum and Floodplain Information below for additional details.
Minimum/maximum target lake levels are provided through orders from the Wisconsin Department of Natural Resources, see lake tabs below for links to orders. Lake levels are managed in accordance with the Dane County Lake Level Management Guide for the Yahara Chain of Lakes, which was approved by the Lakes & Watershed Commission on 10/13/2010 and underwent a peer review by a group of experts convened by the Dane County Board of Supervisors in 2012. Dane County’s goal is to maintain the following target ranges:
Note: Pursuant to Res-419 2020, adopted by the Dane County Board of Supervisors on April 8, 2021, "the Land & Water Resources Department has the flexibility to manage lake levels within the prescribed ranges proactively guided by weather forecasts."
Lake Mendota General Statistics:
Lake Surface Area: 9,842 ac
Max. Depth: 82'
Historic High: 852.74' (on June 6, 2000)
Lake Level Orders - Findings of Fact, Conclusions of Law and Order
The document contains information on water levels and flow that will be established and adhered to as closely as possible by reasonable and proper operation of the Tenney Park Dam. Summer is defined as the period between the first spring runoff occurring after March 1 and October 30. Water levels are given as feet above mean sea level datum.
Wisconsin Department of Natural Resources Document 3-SD-77-808, 1979 (PDF)
Lake Monona General Statistics:
Lake Surface Area: 3,274 ac
Max. Depth: 64'
Historic High: 848.52' (on September 6, 2018)
Previous High: 847.86' (on June 16, 2008)
Previous High: 847.48' (on June 15, 2000)
Lake Level Orders - Findings of Fact, Conclusions of Law and Order
The document contains information on water levels and flow that will be established and adhered to as closely as possible by reasonable and proper operation of the Babcock Park Lock and Dam. Summer is defined as the period between the first spring runoff occurring after March 1 and October 30. Water levels are given as feet above mean sea level datum.
Wisconsin Department of Natural Resources Document 3-SD-77-819, 1979 (PDF)
Lake Waubesa General Statistics:
Lake Surface Area: 2,080 ac
Max. Depth: 34'
Historic High: 847.86' (on September 6, 2018)
Previous High: 847.22' (on June 17, 2008)
Previous High: 847.05' (on June 17, 2000)
Lake Level Orders - Findings of Fact, Conclusions of Law and Order
The document contains information on water levels and flow that will be established and adhered to as closely as possible by reasonable and proper operation of the Babcock Park Lock and Dam. Summer is defined as the period between the first spring runoff occurring after March 1 and October 30. Water levels are given as feet above mean sea level datum.
Wisconsin Department of Natural Resources Document 3-SD-77-819, 1979 (PDF)
Lake Kegonsa General Statistics:
Lake Surface Area: 3,209 ac
Max. Depth: 31'
Historic High: 845.74' (on June 21, 2018)
Previous High: 845.72' (on June 16, 2008)
Previous High: 845.04' (on June 6, 2000)
Lake Level Orders - Findings of Fact, Conclusions of Law and Order
The document contains information on water levels and flow that will be established and adhered to as closely as possible by reasonable and proper operation of the LaFollette County Park Lock & Dam. Summer is defined as the period between the first spring runoff occurring after March 1 and October 30. Water levels are given as feet above mean sea level datum.
Wisconsin Department of Natural Resources Document 3-WR-1116, 1979 (PDF)
Temporary Kegonsa Dam Water Levels Order Amendment effective April 2, 2009 (PDF)
All elevation data is reported in relation to a vertical datum and it is critical to know the vertical datum when evaluating elevation information, such as lake levels and topography. Failure to take vertical datum into account can result in erroneous conclusions about water level impacts on shorelines and shoreland structures.
As of June 2013, there are effectively 4 vertical datums established by the National Geodetic Survey (NGS) in use in the Madison area: the National Geodetic Vertical Datum of 1929 (NGVD 29); and the 1991, 2007 and 2012 adjustments of the North American Vertical Datum of 1988 - NAVD 88(1991), NAVD 88(2007) and NAVD 88(2012). Old references to a U. S. Geological Survey (USGS) datum in the Madison area are generally assumed to mean NGVD 29. According to high-accuracy NGS bench marks in the Madison area, these datums are essentially parallel in the Madison area to within a few hundredths of a foot, with their average separations expressed below as equivalent elevations for a theoretical bench mark at NGVD 29 elevation = 845.60 ft. Note that these equivalencies are averages, only appropriate for a particular point if its elevation has been correctly measured relative to a bench mark with a correct elevation, and if no movement has occurred since measurement.
NGVD 29 = 845.60 ft
NAVD 88(1991) = 845.40 ft = NGVD 29 - 0.2 ft (as predicted by NGS VERTCON 2.0 software)
NAVD 88(2007) = 845.51 ft = NAVD 88(1991) + 0.11 ft
NAVD 88(2012) = 845.57 ft = NAVD 88(2007) + 0.06 ft
The Federal Emergency Management Agency's Flood Insurance Rate Maps use the NAVD88(1991) datum, based on the 0.2 ft shift between NGVD29 and "NAVD88" assumed for Dane County in Flood Insurance Study Number 55025CV001B revised January 2, 2009. The lake level orders for the Yahara Lakes and the USGS gauging station water elevations are reported in NGVD29. Using the conversions above, subtract 0.2 ft from the county/USGS NGVD29 lake levels to compare them to the NAVD88(1991) elevations in the 2009 FEMA flood maps.
Information provided by D. Rodman, Professional Land Surveyor. For more information on Madison-area vertical datums please see here: http://danrodman.tripod.com/
1% Probability of Flooding Every Year (also known as the 100-year floodplain**)
| Lake | NGVD29 | NAVD88(1991) | NAVD88(2012) |
| Mendota | 852.8' | 852.6' | 852.77' |
| Monona | 847.7' | 847.5' | 847.67' |
| Waubesa | 847.0' | 846.8' | 846.97' |
| Kegonsa | 845.8' | 845.6' | 845.77' |
**100-Year Flood Elevation: the 100-year flood elevation establishes the extent of the 100-year floodplain. The 100-year floodplain is the area that has a 1% probability of flooding every year, and where predicted flood water elevations above mean sea level have been established. Properties in the floodplain are considered to be at high risk of flooding under the National Flood Insurance Program (NFIP). Construction in these areas must meet local floodplain zoning ordinance requirements, including evidence that principle structures are above the 100-year flood elevation as shown on the adopted floodplain maps. For more information on floodplains, please visit the Dane County Planning & Development website.
