An Inch of Water. What's it Worth?

An extra inch of water depth in a port = larger ships, millions of dollars worth of additional cargo.

The arrival of the COSCO Development, the largest ship to ever call on Savannah, Georgia. Credit: Billy Birdwell, U.S. Army Corps of Engineers

Supersized Ship in Savannah

Hundreds of workers, tourists, and other well-wishers gathered along the Savannah riverfront to observe the arrival of the COSCO Development, the largest ship ever to call on Savannah, Georgia. The ship, capable of carrying up to 13,092 twenty-foot-equivalent units (TEUs) passed by Savannah City Hall on May 11, 2017, on its way to berth at the Georgia Ports Authority Garden City Port just upstream of the Talmadge Memorial Bridge. The Savannah District of the U.S. Army Corps of Engineers is deepening the harbor and shipping channel to accommodate more of these massive vessels. The Savannah Harbor Expansion Project (SHEP) will deepen the harbor from its current 42-foot depth to 47 feet over the next few years. Credit: Billy Birdwell, U.S. Army Corps of Engineers

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.

NOS is 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 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:

  • 36 John Deere tractors, worth more than $2.4 million

  • 9,600 laptop computers, valued at $8.5 million

  • 358,000 pounds of wheat, worth more than $30,000

  • 1,540 55-inch televisions, worth approximately $3 million

Consider that carrying more cargo on a single trip means fewer trips overall 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.

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In 2017, the Port of Los Angeles/Long Beach increased the draft for incoming ships from 65 feet to 66 feet as a direct result of NOAA's Precision Navigation Project, with a future goal of a 69-foot draft. Each additional foot of draft allows carriage of 40,000 additional barrels of crude oil, and 69 feet would eliminate the need for lightering. The increase was made possible, in part, by the expansion of the physical observing infrastructure at the port, including forecasts for wave and swell conditions from the National Weather Service, water level data from the Center for Operational Oceanographic Products and Services, wave buoy data from the U.S. Integrated Ocean Observing System, shoreline data from the National Geodetic Survey, and high resolution bathymetry from the Office of Coast Survey. The project showcases how NOAA supports the increasingly complex decisions mariners make as they navigate ever-larger ships through U.S. ports, especially decisions related to underkeel clearance. This flagship project integrates private-sector innovation and NOAA data streams for safe navigation of deep-draft ships.

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