From space Earth is simply a pale blue dot. It's blue because of all the water on its surface. In fact, a little more than 70 percent of the Earth's surface is covered by water, most of it ocean. But how much water is there, really?
This image (above), produced by the U.S. Geological Survey (USGS), shows all of Earth's water in three small orbs. The big one, over the western United States, is all the water in the world—everything from the salty oceans to the water found deep underground. It looks small compared with the size of Earth, but that sphere's volume is 1.38 billion cubic kilometers and it is about 1,385 kilometers in diameter. The smaller floating sphere in the middle at 272.8 kilometers in diameter represents a subset of that bigger sphere, showing freshwater in the ground, lakes, swamps and rivers. It doesn't include permanent ice—and snowpacks locked in the polar ice caps—which is where much of the world's freshwater is held; humans, unfortunately, do not have access to this supply. The tiny speck next to it represents and even smaller subset of all the water—just the freshwater in lakes and rivers. It, too, seems tiny by comparison with the big orb, but it is 56.2 kilometers in diameter.
To figure out how big these bubbles would be, the USGS looked at estimates for how much water was in everything from the oceans to swamps. It is impossible to measure exactly how much water fills the oceans, let alone how much is trapped deep underground. But taking the best estimates available, the USGS artists computed the size of each sphere and placed them on top of the planet.
So where is all that water? Perhaps surprisingly, although oceans, seas and bays cover 70 percent of the world, they contain about 96 percent of its water—all of it salty. The next biggest category is ice caps, glaciers and permanent snow at the poles and peaks, but that only makes up about 1.74 percent of the world's water. Groundwater, both fresh and salty, is the next highest contributor to the blue orbs, making up an estimated 1.69 percent of the world's water. In fact, there is much more freshwater in the ground than there is on the surface in lakes and rivers (groundwater graphic above).
Humans consume vast quantities of both surface and groundwater every day. In 2005 we used 1.24 trillion liters of surface water and 312.7 billion liters of groundwater daily. So while those orbs might seem surprisingly small, they're sustaining the entire population of Earth both human and all other species.
Read more about what we can expect in the future as climate changes and population continues to grow at the United States Geological Survey What Water Worries Will Climate Change Bring?
Read more about what we can expect in the future as climate changes and population continues to grow at the United States Geological Survey What Water Worries Will Climate Change Bring?
What Happened to Florida's Water?
Two things, recently. Drought and population explosion.
Drought Continues
While much of north-central Florida and South Florida benefited from tropical weather systems in the past week, extreme drought conditions continue for nearly 30% of Florida (see graphic above). Put another way severe to extreme drought conditions cover over 65% of the State of Florida. So if you're wondering where that lakefront property went. . . you can start by blaming climate change and La Niña conditions that have been occurring off-and-on for the past 3 years.
Weather forecasters predict a return to more normal weather conditions as La Niña has ended, but in many parts of Florida it would take 6-8 feet of rain (that's 72-96 inches, or 1,800 to 2,400 mm) of rain to bring lake levels back up to historically normal levels. The graphic above indicates only the amount of precipitation that would be needed to end the current dry land conditions. It does not factor in years of drought that has led to extremely low water levels in lakes, rivers, streams and swamps.
Population Explosion
The other cause of the dwindling water supplies in Florida is over-development, lack of conservation, and a population that is growing exponentially. The U.S. Census for Florida counted almost 7,000,000 residents in 1970. By 2010 that number had nearly tripled to 19,000,000. And that's not counting millions of visitors who are in Florida on any given day or who went uncounted by the Census. According to the Florida Legislature Office of Economic and Demographic Research, by 2030 Florida's population is forecast to grow to 25 million people.