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An Inch of Water: What's It Worth?

cargo ship passing under a bridge


An inch of water. Doesn’t sound like much. But did you know that having an extra inch of water to pass through can allow a ship to load and carry an additional 58,000 pairs of athletic shoes valued at more than $5 million?

Our nation’s ports are the lifelines of our economy. In 2016, foreign trades through U.S. ports were valued at $1.5 trillion—$475 billion exports and $1.0 trillion imports were moved by vessels. When goods travel through ports, it means they are traveling via ship.

At NOS, we are in the business of making sure that mariners—and the goods they are transporting—make it to their destinations safely and quickly. Just as airplane pilots need to know current weather and ground conditions, ship captains need to know exactly what's going on in the water and in the air. NOS monitoring systems supply mariners with the real-time data they need, providing information such as water levels, wind and current speeds and directions, and water temperature. But what does this have to do with that inch of water?

A ship needs a certain amount of water in order to float and not touch bottom. This water depth is called the ship’s “draft.” The more cargo a ship carries, the more the ship will weigh, meaning it will sink more and require more draft. Even a slight decrease in the depth of a waterway will require a ship to reduce the amount of cargo it is carrying. On the flipside, more water means more cargo. This, in turn, translates into fewer trips being needed to transport goods.

Accurate data provided by NOS are crucial to making decisions regarding ship draft and cargo loads. In the absence of this information, mariners would need to be much more conservative in their draft estimates, or risk additional maritime accidents.

Still not convinced about that inch? Let’s look at some more stats.

With one more inch of draft, a ship can transport an additional:


Consider that carrying more cargo on a single trip means fewer trips overall needed to transfer the same amount of materials. That’s good for the safety of our waterways, it’s good for the environment, and because it saves money, it’s good for your wallet.