Boating here mostly means big water held at a level. Franklin D Roosevelt Lake covers 286.3 square kilometers, 70,746 acres, and Lake Umatilla is close behind it at 201.1 square kilometers. Water that size makes its own afternoon chop, and the part that decides your day is never the middle of it. It is the shoulder where a submerged creek channel drops away, or the flat that runs out from a point that used to be dry ground. Lake Chelan at 131.2 square kilometers and Lake Washington at 88.3 are busy in a different way, with the ramp queue and the traffic rather than the distance. The question at the trailer is the same on all of them. How much water is under the boat once you leave the part everybody runs.
The Washington pack carries 3,105 charted water bodies. 2,054 of them are named, which ranks the pack twelfth of the 48 state packs for named water, and 168 of those named lakes are bigger than a square kilometer, thirteenth of 48. The outlines come from the National Hydrography Dataset. The depth on them is built from state elevation surveys, because a reservoir does not get a nautical chart, and that pairing is what makes a lake here something you can plan a route across against your draft instead of a blue shape with a label on it.
3,105 charted water bodies puts this pack in the middle of the 48 by raw count, at twenty-eighth. The number worth looking at is the named one. 2,054 of those water bodies carry a name, twelfth of 48, so two out of every three pieces of water you can tap give a name back. Of the named water, 168 lakes are larger than a square kilometer, which ranks thirteenth.
A name is a practical thing at six in the morning. You search the water you are towing to rather than scrolling around the map trying to recognize a shape. When two arms of the same system lie next to each other and look alike from the boat, the labels settle which one you are in.
The 168 figure is the one that describes a day out. A square kilometer is roughly 247 acres, so those are lakes with enough room that the run to the far end is worth planning before you make it.
| Lake | Charted surface area |
|---|---|
| Franklin D Roosevelt Lake | 286 km² (70,746 acres) |
| Lake Umatilla | 201 km² (49,693 acres) |
| Lake Chelan | 131 km² (32,420 acres) |
| Lake Wallula | 114 km² (28,096 acres) |
| Coeur d'Alene Lake | 108 km² (26,687 acres) |
| Banks Lake | 108 km² (26,663 acres) |
| Priest Lake | 94 km² (23,253 acres) |
| Lake Washington | 88 km² (21,819 acres) |
| Lake Bonneville | 78 km² (19,324 acres) |
| Wanapum Lake | 58 km² (14,233 acres) |
| Potholes Reservoir | 57 km² (14,184 acres) |
| Ross Lake | 46 km² (11,490 acres) |
The twelve largest named lakes the Washington pack carries, by charted surface area, measured from the chart polygon itself. The pack carries 3,105 charted water bodies in all, 2,054 of them named, and 168 named lakes larger than one square kilometer.
Inland depth in Helm is built from state elevation surveys rather than from nautical charts, and the water bodies themselves come from the National Hydrography Dataset. Nobody makes an ENC for an irrigation pool. That is the whole reason a reservoir in this pack is charted water with contours and a depth reading on it. Every reading carries the date of the survey behind it, so you can see how old the measurement under you is.
A reservoir also sits at whatever level it is being held at, and that changes how you read a contour on one. The basin does not move. The shape a contour describes, the drop off the end of a point or the old creek bed running down the middle of an arm, is the same in October as it was in May. What moves is the surface above it. So read the contours as the shape of the bottom first, then account for where the pool is being held on the day you launch, and the line you actually care about is the one that has come up or down to meet you.
Potholes Reservoir, Banks Lake and Franklin D Roosevelt Lake all work that way. The cove that had eight feet of water over its mouth on one trip is the same cove on the next one, with the same bottom in it, sitting under a different amount of water. How your draft shades that water and how the router treats it is the same on every pack and is covered elsewhere on this site.
Franklin D Roosevelt Lake is the largest named water in the pack at 286.3 square kilometers, 70,746 acres. Lake Umatilla comes second at 201.1 square kilometers, 49,693 acres. Set those against Lake Washington, 88.3 square kilometers and 21,819 acres, and the top of this pack is more than three times the surface of the lake most people picture when somebody says lake.
Some of the middle of the list is closer than it looks. Coeur d'Alene Lake and Banks Lake come out a tenth of a square kilometer apart on the chart polygons, 108.0 against 107.9, which works out to 26,687 acres and 26,663 acres. Twenty four acres between them. Lake Chelan sits above both at 131.2 square kilometers, 32,420 acres, with Lake Wallula between at 113.7. Ross Lake at 46.5 square kilometers and Riffe Lake at 45.1 are near enough the same that either one is a full day if you run it end to end. Potholes Reservoir, 57.4 square kilometers and 14,184 acres, has more than twice the surface of Moses Lake at 27.0 square kilometers and 6,672 acres, which surprises people who have only launched on one of them.
The packs are cut to a rectangle rather than to a state line, so water along an edge belongs to more than one of them. Coeur d'Alene Lake and Priest Lake, 94.1 square kilometers, come up in the Idaho pack as well. Water along the southern edge does the same thing with the Oregon pack. If your season runs across a border, the pack you download is the one that covers the drive, not the one named after where you live.
Download the pack at home on wifi and the chart stops depending on a signal, which matters on a reservoir where the service drops out as soon as you get down between the walls of a canyon arm.
Once it is on the phone, the working parts of a day on the lake do not need the network:
Fishing a lake in this pack, a saved spot with contours around it is worth more than a waypoint on its own, because next season you can see whether the water came back up over it. Spots, routes and the logbook sync across devices. On the tow up to something you have never launched on, Helm puts the chart on the vehicle screen through CarPlay, so the arm of the lake you are aiming for is in front of you before you back down the ramp.
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.
Depth. Both carry contours and a depth reading built from state elevation surveys, with the outline itself from the National Hydrography Dataset. On the pack's own polygons Lake Chelan measures 131.2 square kilometers, 32,420 acres, and Banks Lake 107.9 square kilometers, 26,663 acres. Each reading shows the date of the survey it came from.
Read the contours as the shape of the basin, which does not change, and then account for how the pool is being held the day you go. The old channel, the drop off a point and the flat at the back of a cove are in the same places. The surface over them is what moves, so a contour tells you the shape you are running across and the current pool level tells you how much water is sitting on top of it.
The packs are cut to a box rather than to the state line, so water near the eastern edge lands in this pack and in the Idaho pack. Coeur d'Alene Lake, 108.0 square kilometers, and Priest Lake, 94.1 square kilometers, are both in that overlap. You get the same chart either way, so download whichever pack covers the rest of the water you run.
Helm Boating