Historical Lake Levels REVISED

July 4 addition:

Lake Monona fell 0.10' yesterday to 847.17, a significant increase in the pace.

Contrary to my original post, Lake Monona first exceeded 847 (adjusted for datum change) in 1928, not 1993. The maximum reading on Lake Monona exceeded 847 (adjusted) again in March 1937 and yet again in July 1950, July 1993, June 1996, June and July 2000, August 2007, and June and July 2008.

In the past, Lake Monona stayed at 847 or higher for a day or a few days (five consecutive days max). That changed in 2000, 2007 and 2008.

In 2000, however, Lake Monona stayed above 847 from for 38 days from June 5 through July 12. In August and September 2007, Lake Monona stayed above 847 for 18 days from August 24 to September 10.

In 2008, Lake Monona has been above 847 since June 10 (twenty-five days and counting).

July 3, 2008 Revision:

I spoke with Kevin Connors Director of Dane County Land & Water Resources Department last evening. He said there was an adjustment of some 2.5' to the lake datum points about 20 years ago. That would account for the jump in maximum lake levels in 1979.

It appears that this change occurred on October 1, 1979. The lake level went from 841.14 on September 30 to 844.85 on October 1, a change of about 3.71'.

I have completed the adjustments.



Will complete further revisions later.
Original Post with Adjusted Elevations (and necessary edits):
My son and I took a drive over to the Tenney Park last evening to look at the roaring whitewater pouring through the locks. While there we chatted with the friendly lockmaster, Greg Anderson of Monona. It's quite a sight (the water, not Greg). Tenney Park Locks - Dane County Parks It gives you some ideaq of the forces at work in our lakes right now. Awesome and potentially terrible.


Lake level data from Dane County. There is a wealth of lake information on the County's web site. You can also retrieve historical data back to 1915 and put it into charts and graphs.

Current Lake Monona level as of 06-20-08 is 847.77

The all-time high is 847.86 on June 16, 2008.

Summer Target min 844.70
Summer Target max 845.20
100-Year Flood Elevation* 848

* 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.

Historical Levels for Lake Monona

1915-1930
Summary of readings
Minimum reading 840.5 (adjusted 844.21)
Maximum reading 843.66 (adjusted 847.37)
Average reading 841.65 (adjusted 845.36)

1931-1945
Summary of readings
Minimum reading 839.97 (adjusted 843.68)
Maximum reading 843.59 (adjusted 847.30)
Average reading 841.06 (adjusted 844.77)

1946-1960
Summary of readings
Minimum reading 839.98 (adjusted 843.69)
Maximum reading 843.48 (adjusted 847.19)
Average reading 841.25 (adjusted 844.96)

1961-1975
Summary of readings
Minimum reading 839.61 (adjusted 843.32)
Maximum reading 842.97 (adjusted 846.68)
Average reading 841.34 (adjusted 845.05)


1976 to September 30, 1979
Summary of readings
Minimum reading 839.93 (adjusted 843.64)
Maximum reading 842.95 (adjusted 846.66)
Average reading 841.13 (adjusted 844.84)

No adjustment required after October 1, 1979

October 1, 1979 through 1990
Summary of readings
Minimum reading 843.87
Maximum reading 846.29 (October 10, 1986)
Average reading 845.01

1991 to 2000
Summary of readings
Minimum reading 843.61
Maximum reading 847.47 (June 15, 2000)
Average reading 844.96

2001 to June 20, 2008
Summary of readings
Minimum reading 843.44
Maximum reading 847.86
Average reading 844.97


From the Belle Isle Neighborhood Website:

High Water Levels 2007(847.46') Month Closeup
High Water Levels 2004(846.85')
High Water Levels 2000(Record 847.48')
High Water Levels 1993(847.12')