What does the number below a marker on western rivers indicate?

The number located below a marker on western rivers refers to the distance from the river's mouth. This practice is commonly used in navigational aids to provide boaters with a reference point for how far upstream they are from where the river meets a larger body of water, such as an ocean or lake. This information is crucial for navigation since it helps boaters understand their position on the river and can assist in planning their travels, especially regarding fuel consumption, timing, and identifying nearby landmarks. It also aids in recognizing changes in river conditions as they move farther from the mouth.

In this context, other information such as harbor distance, water depth, or current speed would be represented using different markers or system notifications entirely. Each of these aspects has specific markers or signs that serve to inform boaters about different navigational details, but the distance from the river's mouth has its distinct marker representation.