How deep is Portage Lake?

Portage Lake is at least 40 feet deep. That figure is the deepest surveyed sounding in the Michigan DNR Inland Lake Contours survey, a point measurement rather than a closed contour, so the deepest line you can actually trace on the map is the 35 ft contour, and the water may run deeper still.

Where is the deepest part of Portage Lake?

The deepest charted water on Portage Lake lies inside the 35 ft contour, toward the eastern side of the lake. That contour encloses 6.5 acres, 2.5% of the mapped water, so it is a small target on a small water, the depth chart above gives the contour to line up on.

How much of Portage Lake is shallower than 15 feet?

About half. The 15 ft contour encloses 121 acres of the roughly 257 acres inside the outer 1 ft line, so the other half of the water is shallower than 15 feet. The sharpest drop is between 1 and 5 feet, where the mapped water sheds 55 acres.

How accurate is this Portage Lake 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.

Michigan lake depth maps

Portage Lake depth map

Portage Lake in Jackson County, Michigan reaches a depth of more than 40 feet at its deepest surveyed sounding. Portage Lake is charted here across 8 closed depth contours, from the 1 ft line down to 35 ft, enclosing about 257 acres of water. Half of that water lies inside the 15 ft line, and only 6.5 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 August 19, 2026

Portage Lake depth chart: 8 depth contours from 1 to 35 ft

Data: Michigan DNR Inland Lake Contours (public record), retrieved August 2026 · depths change over time · not for navigation

Portage Lake depth chart data: water enclosed by each contour
Depth contour	Water inside it	Share of mapped water
1 ft	257 acres	100%
5 ft	202 acres	79%
10 ft	153 acres	60%
15 ft	121 acres	47%
20 ft	71 acres	28%
25 ft	34 acres	13%
30 ft	20 acres	7.6%
35 ft	6.5 acres	2.5%

Acreages are computed from the closed Michigan DNR Inland Lake Contours contour rings, with islands subtracted. Shares are of the 257 acres inside the outermost charted contour (the 1 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 40 ft sounding, marked as a point rather than a closed contour, so it is not charted as a band.

Fishing Portage Lake: an evenly graded bottom

The survey encloses about 257 acres of Portage Lake inside its 1 ft contour, and half of that water lies inside the 15 ft line, so the bottom falls away at a steady rate rather than shelving off or dropping in one step. Between 1 and 5 ft the mapped water sheds 55 acres in 4 ft of depth, the sharpest change on the chart, start on that band, because it is where the bottom stops being flat. 6.5 acres, 2.5% of the mapped water, lie inside the deepest 35 ft contour, toward the eastern side of the lake. With 40 ft at its deepest there is no true cold-water layer here, so structure does the work the thermocline does elsewhere: fish the points and inside turns where the 1 and 5 ft lines pinch together, hardest in early season and again as fish follow bait back down in autumn.

Ice fishing on Portage Lake

Portage Lake's 40 ft is a workable ice depth, enough water to hold fish all winter, without the slow freeze-up of a big basin. First light belongs on the 35 ft hole, all 6.5 acres of it; as the sun gets up, move onto the 1–5 ft break, and spend the middle of the day on the flats inside the 15 ft line. Check ice thickness locally before you walk out.

Portage Lake depth map FAQs

How deep is Portage Lake?: Portage Lake is at least 40 feet deep. That figure is the deepest surveyed sounding in the Michigan DNR Inland Lake Contours survey, a point measurement rather than a closed contour, so the deepest line you can actually trace on the map is the 35 ft contour, and the water may run deeper still.
Where is the deepest part of Portage Lake?: The deepest charted water on Portage Lake lies inside the 35 ft contour, toward the eastern side of the lake. That contour encloses 6.5 acres, 2.5% of the mapped water, so it is a small target on a small water, the depth chart above gives the contour to line up on.
How much of Portage Lake is shallower than 15 feet?: About half. The 15 ft contour encloses 121 acres of the roughly 257 acres inside the outer 1 ft line, so the other half of the water is shallower than 15 feet. The sharpest drop is between 1 and 5 feet, where the mapped water sheds 55 acres.
How accurate is this Portage Lake 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 Portage Lake

South Lake depth map · 88 ft max · 10 mi away
Bruin Lake depth map · 48 ft max · 12 mi away
Halfmoon Lake depth map · 87 ft max · 13 mi away
Pickerel Lake depth map · 56 ft max · 14 mi away
Silver Lake depth map · 47+ ft max · 15 mi away

Mapped fishing venues near Portage Lake

Portage Lake in the venue directory covers access and fishing details for this water.

South Lake · 10 mi away
Bruin Lake · 12 mi away
Halfmoon Lake · 13 mi away

Fishing in Michigan needs a state license: Michigan fishing license guide · all Michigan venues