Michigan lake depth maps
Lake Thumb depth map
Lake Thumb in Charlevoix County, Michigan reaches a depth of 152 feet. Lake Thumb is charted here across 16 closed depth contours, from the 5 ft line down to 150 ft, enclosing about 506 acres of water. Half of that water lies inside the 40 ft line, and only 1.3 acres lie inside the deepest one. Every contour is on the interactive map below, free and without an account.
Data: Michigan DNR Inland Lake Contours (public record). Contours closed, checked and area-computed by Jordan Carter, founder of GilledIt · page updated
Lake Thumb depth chart: 16 depth contours from 5 to 150 ft
Data: Michigan DNR Inland Lake Contours (public record), retrieved August 2026 · depths change over time · not for navigation
| Depth contour | Water inside it | Share of mapped water |
|---|---|---|
| 5 ft | 506 acres | 100% |
| 10 ft | 438 acres | 87% |
| 20 ft | 358 acres | 71% |
| 30 ft | 256 acres | 51% |
| 40 ft | 181 acres | 36% |
| 50 ft | 134 acres | 27% |
| 60 ft | 107 acres | 21% |
| 70 ft | 88 acres | 18% |
| 80 ft | 70 acres | 14% |
| 90 ft | 48 acres | 9.4% |
| 100 ft | 32 acres | 6.4% |
| 110 ft | 19 acres | 3.7% |
| 120 ft | 10 acres | 2.1% |
| 130 ft | 6.3 acres | 1.3% |
| 140 ft | 4.5 acres | under 1% |
| 150 ft | 1.3 acres | under 1% |
Acreages are computed from the closed Michigan DNR Inland Lake Contours contour rings, with islands subtracted. Shares are of the 506 acres inside the outermost charted contour (the 5 ft line), which is the outer edge of the mapped water, several state files carry no 0 ft shoreline line, so this is not the same as a share of the lake's published surface area. The survey also records a 152 ft sounding, marked as a point rather than a closed contour, so it is not charted as a band.
Fishing Lake Thumb: a wide shallow flat over a deep hole
Inside its outermost 5 ft contour the survey charts about 506 acres of Lake Thumb, with the 40 ft line enclosing half of it, so the bulk of this Charlevoix County water sits on a shallow flat, with the real depth packed into one part of the basin. The sharpest change on the chart is between 5 and 10 ft, where the mapped water loses 68 acres in 5 ft of depth, that band is the contour to work first, because it is where the bottom stops being flat. The deepest 150 ft contour holds 1.3 acres, under 1% of the mapped water, toward the northeastern corner of the lake. 152 ft of water makes this a two-story fishery: warm-water fish hold the 5-to-40 ft ground while the basin can stay cold below the summer thermocline, and the traffic between the two runs along the 5–10 ft break at first and last light.
Ice fishing on Lake Thumb
Lake Thumb freezes later and less evenly than the shallow waters around it, and the winter bite sets up on the first real break rather than out over the 150 ft hole. The 5–10 ft band on the chart above is that edge: 68 acres of bottom tilt away there, and panfish and walleye slide up and down it through the day. Late ice pushes fish back onto the 5-to-40 ft flat. Check ice thickness locally before you walk out.
Lake Thumb depth map FAQs
- How deep is Lake Thumb?
- Lake Thumb reaches a maximum depth of 152 feet in the Michigan DNR Inland Lake Contours survey. Most of it is far shallower: the survey charts 16 closed depth contours over about 506 acres, and half of that water sits inside the 40 ft line. The 152 ft figure is a single recorded sounding rather than a closed contour, so the deepest line you can actually trace on the map is 150 ft.
- Where is the deepest part of Lake Thumb?
- The deepest charted water on Lake Thumb lies inside the 150 ft contour, toward the northeastern corner of the lake. That contour encloses 1.3 acres, under 1% of the mapped water, so it is a small target on a big lake, the depth chart above gives the contour to line up on.
- How much of Lake Thumb is shallower than 40 feet?
- About half. The 40 ft contour encloses 181 acres of the roughly 506 acres inside the outer 5 ft line, so the other half of the water is shallower than 40 feet. The sharpest drop is between 5 and 10 feet, where the mapped water sheds 68 acres.
- How accurate is this Lake Thumb depth map?
- The contours come from the Michigan DNR Inland Lake Contours survey, retrieved August 2026 and last rebuilt on August 19, 2026. Depths change over time with water levels and sediment, so treat this map as a planning guide for fishing, and never use it for navigation. Acreages are computed from the published contour geometry, not from a separate area survey, so read them as close approximations.
Depth maps for lakes near Lake Thumb
- Walloon Lake depth map · 100+ ft max · 14 mi away
- Big Lake depth map · 81 ft max · 15 mi away
- Lake Charlevoix depth map · 122 ft max · 18 mi away
- Burt Lake depth map · 73 ft max · 20 mi away
- Big Chub Lake depth map · 74+ ft max · 21 mi away
Mapped fishing venues near Lake Thumb
Lake Thumb in the venue directory covers access and fishing details for this water.
- Walloon Lake · 14 mi away
- Big Lake · 15 mi away
- Gook Creek · 16 mi away
Fishing in Michigan needs a state license: Michigan fishing license guide · all Michigan venues