If all the Earth’s water – including its rivers, lakes, groundwater, seawater and glacial icecaps – were contained in a bubble, that bubble would measure 860 miles (1,385km) in diameter. According to the US Geological Survey (USGS), the volume of all this water is about 332.5 million cubic miles (1,386 million km3).
The picture on the preceding page, by Jack Cook of the Woods Hole Oceanographic Institution, illustrates the relative size of that water-filled sphere compared to the size of Earth.
Another way to think of it is that if we represented the size of Earth with a basketball, all the water on the planet would fit into a ping pong ball and the available fresh water would be smaller than a popcorn kernel.
About 3,100 mi3 (12,900 km3) of additional water, mostly in the form of water vapor, is contained in the atmosphere at any given time. If it were distributed evenly and all fell as precipitation at once, the Earth would be covered with one inch (25mm) of water.