Two lakes sit at the top of this pack and there is barely a square kilometer between them. Lewis and Clark Lake measures 101.1 square kilometers off the chart polygon, or 24,982 acres. Lake McConaughy measures 100.1, or 24,735 acres. That is 247 acres of difference across water where the far shore is a committed run. Eight of the twenty largest waters in the pack are named Reservoir outright, which is the first thing worth knowing before you plan a day on any of them, because a reservoir sits at whatever level somebody is holding it at.
The pack carries 4,342 charted water bodies. Of those, 1,324 carry a name, and 95 of the named lakes are larger than a square kilometer. The outlines come from the National Hydrography Dataset, and the depth inside them is built from state elevation surveys rather than from a nautical chart. That is what turns a reservoir from a blue shape into water you can draw a route across and check against the draft of your own boat.
With 4,342 charted water bodies this pack stands eighteenth of the forty-eight state lake packs, ahead of thirty of them. By named water it stands twenty-fourth with 1,324, and by named lakes over a square kilometer it stands twenty-fifth with 95.
Those three ranks together describe the shape of the water better than any one of them does on its own. Subtract the 95 from the 1,324 and 1,229 named waters in this pack are under a square kilometer. Small water carrying a name is most of what is here, and it is charted the same way the big lakes are. The pond twenty minutes from the house has an outline and depth under it, so a morning on it can be planned rather than guessed at.
| Lake | Charted surface area |
|---|---|
| Lewis and Clark Lake | 101 km² (24,982 acres) |
| Lake McConaughy | 100 km² (24,735 acres) |
| Harlan County Lake | 52 km² (12,751 acres) |
| Calamus Reservoir | 20 km² (4,992 acres) |
| Lake Andes | 19 km² (4,720 acres) |
| Swanson Lake | 19 km² (4,646 acres) |
| Sutherland Reservoir | 12 km² (2,941 acres) |
| Lovewell Reservoir | 12 km² (2,842 acres) |
| North Sterling Reservoir | 11 km² (2,644 acres) |
| Merritt Reservoir | 10 km² (2,520 acres) |
| Sherman Reservoir | 10 km² (2,422 acres) |
| Johnson Lake | 9 km² (2,199 acres) |
The twelve largest named lakes the Nebraska pack carries, by charted surface area, measured from the chart polygon itself. The pack carries 4,342 charted water bodies in all, 1,324 of them named, and 95 named lakes larger than one square kilometer.
Nobody draws a NOAA chart for Merritt Reservoir. The coast gets surveyed by a federal hydrographic program and an inland lake does not, so inland depth in Helm is built from state elevation surveys instead, with the water bodies themselves coming from the National Hydrography Dataset. That pairing is the reason a reservoir appears here as charted water with contours on it.
The second thing about a contour on a reservoir is that the pool it was measured against moves. The dam holds the lake wherever it is being held that month, so a line that means one thing in June means something else after a summer of drawdown. The old creek channel stays where it always was. What changes is how much water is standing over the shoulders on either side of it, and the shoulder is what a boat finds in October on a cove it ran easily in May. Enter your draft once and Helm shades the water you cannot cross, which puts that shoulder on the screen while you still have room to turn.
Third place is a long way down from the top two. Harlan County Lake covers 51.6 square kilometers, 12,751 acres, roughly half of either lake above it and more than twice the size of anything below it. Calamus Reservoir is fourth at 20.2 square kilometers, 4,992 acres, a fifth the size of Lewis and Clark. Lake Andes at 4,720 acres and Swanson Lake at 4,646 acres sit close enough behind Calamus that the three of them read as one size class.
Below Merritt the pack settles into a run of lakes within a few hundred acres of one another. Sherman Reservoir at 2,422 acres, Johnson Lake at 2,199, Lake Minatare at 1,952, Prewitt Reservoir at 1,878, Branched Oak Lake at 1,754, Harry Strunk Lake at 1,705, Lake Maloney at 1,581, Hugh Butler Lake at 1,483, Julesburg Reservoir at 1,408 and Twin Lakes at 1,310. Ten lakes inside 1,112 acres of range, which means a trailer boat can treat most of them as the same kind of day.
The packs are cut to a rectangle rather than to a state line, so water near the edge sits in two packs at once. A lake up against the South Dakota, Iowa, Missouri or Kansas boundary is carried here and in the neighboring pack, and either one puts the same water on your screen.
A ramp out here is often past the last bar of service, so the pack goes onto the phone at home on wifi. After that the chart, the depth shading, routing, the measure tool and the anchor alarm all keep working with nothing on the signal bar.
Before you leave, draw a line with the measure tool from the ramp to wherever you mean to end up. You get distance, bearing and a depth profile along that line, with the shallowest point on it marked rather than averaged into the rest. Across 24,735 acres it is worth knowing in advance which way you can cut and which way you cannot.
In July the real question on open water that size is what the wind does at four in the afternoon, and that is a column you read before you hitch up. If the day turns into a night on the hook in a cove, set an anchor radius and Helm wakes you if the boat drags. It runs on GPS, so no service is needed for it. On the tow out, CarPlay puts the chart on the vehicle screen, and the ramp you are hunting for is in front of you before you get there.
Inland lake depth comes from state elevation surveys rather than from nautical charts, and a reservoir sits at whatever level it is being held at that week. Treat the shape and the depth as a guide, keep a lookout, and verify locally.
Lewis and Clark Lake, at 101.1 square kilometers, or 24,982 acres, measured from the chart polygon itself. Lake McConaughy is within a square kilometer of it at 100.1, or 24,735 acres, which puts 247 acres between them. Harlan County Lake is third at 51.6 square kilometers, or 12,751 acres. Packs are cut to a rectangle rather than to the state line, so a lake near a border is carried in more than one pack.
From state elevation surveys, not from a NOAA nautical chart, since no nautical chart is drawn for an inland reservoir. The water body outline comes from the National Hydrography Dataset. Together that gives you contours and a depth number on the water itself, shaded against the draft you enter once. Read it knowing the pool level moves with how the dam is being operated that season.
It carries 4,342 charted water bodies, which is eighteenth among the forty-eight state lake packs. Of those, 1,324 are named and 95 of the named lakes are larger than a square kilometer, so 1,229 named waters in the pack are smaller than that. All of it works offline once the pack is downloaded to the device.
Helm Boating