Boating this water means running a long way from the ramp. Lake Mead and Lake Powell are canyon reservoirs, and the arms reach back far enough that a cove which looks like a short hop on a phone screen turns into a real run with fuel attached to it. Lake Havasu and Lake Mohave are the river held behind a dam, open in places and pinched in others, with the old channel still down there under the boat. Lake Pleasant and Theodore Roosevelt Lake are the water people tow to for a day and come home from the same night. What all of them have in common is that the level is not fixed. The shoreline in April is not the shoreline in September, and what that does to the ground under you is worth understanding before you plan a run.
The Arizona pack charts 1,150 water bodies. Of those, 438 carry a name, and 42 of the named ones measure more than a square kilometer. The largest the pack carries is Lake Mead at 546.1 square kilometers, or 134,944 acres, and behind it Lake Powell at 266.8 square kilometers, 65,928 acres. Each of them arrives with depth on the water itself, contours and a number rather than a blue polygon with a label on it.
The Arizona pack charts 1,150 water bodies. Of those, 438 are named, and 42 of the named ones are over a square kilometer, which is a little under 250 acres. The rest is the small water the National Hydrography Dataset records everywhere, stock tanks and ponds nobody is launching a boat on. It is charted because leaving it out would mean deciding on your behalf which water counts.
The figure worth knowing about this pack is the scale at the top of its list. Lake Mead, the largest lake the pack carries, measures 546.1 square kilometers from the chart polygon itself, or 134,944 acres. Lake Powell is 266.8 square kilometers and 65,928 acres. Lake Mohave and Lake Havasu follow at 27,429 and 18,483 acres. Put the second, third and fourth of those together and they still come to less water than Mead on its own, 111,840 acres against 134,944. Very few of the 48 state packs have a single name at the head of the list that runs that far ahead of the next one.
| Lake | Charted surface area |
|---|---|
| Lake Mead | 546 km² (134,944 acres) |
| Lake Powell | 267 km² (65,928 acres) |
| Lake Mohave | 111 km² (27,429 acres) |
| Lake Havasu | 75 km² (18,483 acres) |
| San Carlos Reservoir | 53 km² (12,998 acres) |
| Lake Pleasant | 37 km² (9,143 acres) |
| Theodore Roosevelt Lake | 37 km² (9,044 acres) |
| Mormon Lake | 20 km² (4,893 acres) |
| Alamo Lake | 12 km² (3,039 acres) |
| Goose Lake | 11 km² (2,718 acres) |
| Bartlett Reservoir | 9 km² (2,199 acres) |
| Apache Lake | 8 km² (2,076 acres) |
The twelve largest named lakes the Arizona pack carries, by charted surface area, measured from the chart polygon itself. The pack carries 1,150 charted water bodies in all, 438 of them named, and 42 named lakes larger than one square kilometer.
There is no NOAA nautical chart for a reservoir. The federal charting effort follows navigable coastal water, and a lake held behind a dam in the desert is not on that list. Inland depth in Helm is built from state elevation surveys instead, and the water bodies themselves come from the National Hydrography Dataset. That pairing is the whole reason San Carlos Reservoir or Lake Pleasant arrives as charted water instead of a shape with a name printed on it.
The elevation survey is a measurement of the lake bed, and it is what puts a contour and a depth number on the water. The hydrography gives the outline and the name. With your own draft entered, what comes out of that on the screen is the flat at the mouth of a cove showing itself while you still have room to turn, and a line you draw across the water reporting its shallowest point rather than an average. How the depth sources merge, and the survey date that sits behind any single reading, is a subject of its own on the depth page.
Surface elevation on these lakes is the result of what came into the system over the winter and what is being released downstream, and it moves through the year. On the Colorado River reservoirs it is a number people follow season to season. This is the part that catches somebody who learned to read charts on salt water, where the datum is a low water mark and the tide is published in advance for the hour you plan to be there.
Here is the honest way to read a contour on one. The contours follow the shape of the bed, and the bed does not move. What moves is the surface over it. A charted depth is the water standing over the bed at the level the survey was referenced to, so when the lake is held lower, every one of those numbers has less water over it by however far the surface has fallen, and the shoreline walks out toward what used to be open water. The shape stays true at any level. The submerged creek channel and the point that comes off the bank are where the survey put them whether the lake is full or down.
So the habit worth having before a tow is to look up the surface elevation the operator posts for the day and carry it in your head as an offset while you read the chart. In a low year, which ramp still reaches water is a question for the marina rather than for anybody's software.
Measured from the chart polygon itself, this is the head of the list.
Lake Pleasant and Theodore Roosevelt Lake are worth putting side by side. They come out within 99 acres of each other, 9,143 against 9,044, which is close enough to treat them as the same amount of water to get across when the wind stands up in the afternoon.
Below those eight the list steps down in a hurry. Alamo Lake is 3,039 acres and Goose Lake is 2,718. Bartlett Reservoir at 2,199 acres and Apache Lake at 2,076 are within a couple of hundred acres of each other, and Apache is better than three times the size of Saguaro Lake, which measures 618 acres. Lake Mead covers more than two hundred times the water Saguaro does. Higher up, Lyman Lake is 1,310 acres, Rogers Lake 1,186 and Upper Lake Mary 815, small enough that the wind for the afternoon is most of what you need to know.
Several of the largest names here sit on or near a state line. The packs are cut to a box rather than to a border, so a lake in that position can arrive inside more than one pack, and the neighboring packs are Nevada, Utah, California and New Mexico. On the water it makes no difference, since the lake is charted from whichever of them is on the phone.
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.
The Arizona pack carries it, at 546.1 square kilometers or 134,944 acres, which makes it the largest lake in the pack by a wide margin. The packs are cut to a box rather than to a state line, so a lake sitting on a border like this one also falls inside the neighboring pack, Nevada in this case. Either way the water comes with depth on it instead of an outline.
Depth. Lake Powell measures 266.8 square kilometers, 65,928 acres, and the depth under it is built from state elevation surveys of the bed, while the water body itself comes from the National Hydrography Dataset. There is no NOAA nautical chart for a reservoir, so that is where an inland contour has to come from. Enter your draft and the water too thin for your boat shades on the chart.
Take the shape from the chart and the level from the operator. The contours follow the bed, so the old creek channel, the humps and the points are where the survey put them at any elevation. What changes when the lake is held lower is that every charted depth has less water standing over it, by however far the surface has fallen. Look up the posted surface elevation for the day you are going and carry that as an offset. The Colorado River reservoirs and the storage lakes like Theodore Roosevelt Lake both move a long way through a year.
Helm Boating