Finding Wisconsin lake depth maps
Almost every depth chart you will find for a Wisconsin lake traces back to one place: a survey run by state biologists, drawn by hand, scanned as a PDF, and posted to the DNR document library. Knowing how those sheets were made tells you which parts of them to believe.
Where the charts come from
The Wisconsin DNR maintains a lake page for each surveyed waterbody, keyed by a Waterbody Identification Code (WBIC). Where a depth survey exists, the lake page links a scanned map sheet. Those scans are the original record — everything else, including the contours on this site, is derived from them.
The surveys span roughly seventy years of technique. Sheets from the 1940s through the 1960s were run by the Wisconsin Conservation Department with lead lines and, later, early sonar, with contours inked between sounding runs. Later sheets use denser electronic sounding. Both kinds are still in active circulation, and the DNR page rarely leads with the date — you usually have to open the sheet and read it off the title block.
Dating a sheet before you trust it
- Title block. Survey year, the surveying agency, and often the crew are printed in a corner. “Wisconsin Conservation Department” dates a sheet to 1967 or earlier — that was the agency's name before it became the DNR.
- Contour interval. Older sheets tend to use a coarse 10-foot ladder. Anything shallower than the first contour is undifferentiated on the map, which on a shallow lake can mean most of the basin.
- Shoreline detail. Section lines, named farms, and hand-lettered landmarks indicate an older sheet. Compare its shoreline against the current lake outline: bays that have filled or been dredged show up immediately as mismatches.
- Spot soundings in open water. Dense scattered numbers usually mean a sonar-era survey; sparse ones mean the contours between them are long interpolations.
What LakeList does with them
Scanned sheets are hard to use on the water — you cannot zoom into a JPEG of a 1964 map and get a depth at a point. LakeList digitizes selected surveys into contour data you can pan, zoom, and view in 3D, georeferenced against the DNR's own lake polygon so the contours land in the right place on the map.
That conversion is checked by hand before anything is published: traced depths have to match the depth labels printed on the original sheet, and the fitted shoreline has to hug the drawn one. Surveys that fail that check stay unpublished rather than shipping as plausible guesses. Where a published surface is interpolated between surveyed lines rather than traced directly, the lake page says so and labels it a modeled estimate — not a survey.
Wisconsin lakes with interactive depth contours
These lakes have digitized, QA-checked contours you can inspect directly in the browser:
- Allequash Lake — 5-ft contour interval, to 20 ft
- Big Muskellunge Lake — 5-ft contour interval, to 70 ft
- Crystal Lake — 5-ft contour interval, to 65 ft
- Lake Mendota — 10-ft contour interval, to 80 ft
- Presque Isle Lake — 10-ft contour interval, to 60 ft
- Sparkling Lake — 5-ft contour interval, to 60 ft
- Trout Lake — 10-ft contour interval, to 110 ft
Many more Wisconsin lakes link the official DNR depth-map source directly from their lake page even where contours have not been digitized yet.
Reading the chart once you have it
Contour spacing, closed rings, and the gap between spot soundings all change what a sheet is actually telling you. How to read a lake depth map covers that in detail.
None of these charts are navigation charts. They are historical surveys, they predate most of the hazards you care about, and they are drawn to a water level that no longer necessarily applies.