Lake Levels & Information

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. 

Notices

Updated:  December 1, 2017 
Lake water levels are being lowered towards winter operating levels.  The locks at Babcock County Park and LaFollette County Park are open to navigation and those dams are completely open in full flow condition.  Navigational buoys in the Yahara River and Lakes have been removed.
Slow-no-wake rules currently apply to Crystal Lake. 

Lake Levels*

Lake Date Lake Level Winter Min Target Max 100-year
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 845.2
 Chart Lake Levels
Map of Lake Mendota, Lake Monona, Lake Waubesa, Lake Kegonsa


*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. 

Minimum/maximum target lake levels are provided through orders from the Wisconsin Department of Natural Resources, see lake tabs below for links to orders.  Dane County uses these target levels to manage lake levels:

  • Summer goals (first runoff event after March 1st) - maintain water levels at the mid-range of summer minimum/maximum target levels
  • Winter goals (starting November 1st) - maintain water levels between winter minimum and summer minimum target levels

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 the Vertical Datums & Floodplain tab below for more information.

 

Information

Lake Monona General Statistics:
Lake Surface Area: 3,274 ac
Max. Depth: 64'
Historic High: 847.86' (on June 16, 2008)
Previous High: 847.48' (on June 15, 2000)
More Information (UW Center for Limnology)
 

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)

  • Summer Minimum Water Level: 844.7'
  • Summer Maximum Water Level: 845.2'
  • Winter Minimum Water Level: 842.2'
  • Additional requirement: maintain a 4.9' difference with Lake Mendota.

Lake Mendota General Statistics:
Lake Surface Area: 9,842 ac
Max. Depth: 82'
Historic High: 852.74' (on June 6, 2000)
More Information (UW Center for Limnology)

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)

  • Summer Minimum Water Level: 849.6'
  • Summer Maximum Water Level: 850.1'
  • Winter Minimum Water Level: 848.2'
  • Additional requirement: maintain a 4.9' difference with Lake Monona.

Lake Waubesa General Statistics:
Lake Surface Area: 2,080 ac
Max. Depth: 34'
Historic High: 847.22' (on June 17, 2008)
Previous High: 847.05' (on June 17, 2000)
More Information (UW Center for Limnology)

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)

  • Summer Minimum Water Level: 844.5'
  • Summer Maximum Water Level: 845.0'
  • Winter Minimum Water Level: 842.0'
  • Additional requirements: a minimum discharge of 50 cfs must be maintained at the Babcock Park Lock and Dam between April 1 and May 15. At all other times, a minimum discharge of at least 10 cfs shall be maintained.
Lake Kegonsa General Statistics:
Lake Surface Area: 3,209 ac
Max. Depth: 31'
Historic High: 845.72' (on June 16, 2008)
Previous High: 845.04' (on June 6, 2000)
More Information (UW Center for Limnology)
 

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)

  • Summer Minimum Water Level: 843.0'
  • Summer Maximum Water Level: 843.5'
  • Winter Minimum Water Level: 841.85'

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 845.2' 845.0' 845.17'
 

**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 Dane County Planning & Development's website.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/

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