Earth's Water Supply 

We often hear about the importance of not wasting water, water shortages due to droughts, and even that some people in the world don’t have access to the water they need. But that’s hard for many of us to relate to when it’s just so easy for many of us to turn on a faucet whenever we want and get pretty decent fresh water without much effort or concern. Plus it’s hard to comprehend water shortages when it seems like there is water all over the planet. It’s time to get a fresh perspective on fresh water.

Although water covers nearly ¾ of the Earth, or about 75% of the Earth, the amount that humans can actually drink is quite small. Of all the water on Earth, only about 1% is usable fresh water available to humans and animals right now. Every person and animal on Earth must have clean drinking water in order to survive. Beyond survival, people need fresh water for other purposes too, such as sanitation (keeping everything clean!).

Imagine 100 glasses of water in front of you. Imagine that one of those glasses of water (only one!) has usable fresh water in it. The other 99 glasses are off limits because the water they contain is in the form of ice, vapor, or salt water; or, it is otherwise unfit due to being overtaken by chemicals and organisms. Some of the glasses are trapped beneath large piles of dirt. Only one of the 100 imaginary glasses in front of you contains usable fresh water you can use right now. The rest are off limits. That’s how it is on Earth – only 1% of all the water on Earth is ready, available, useful water. Why does it seem like there is so much more water than that?

*That’s probably because we don’t realize that 97% of all the water on Earth is salt water – neither ready, available, nor useful the way fresh water is. The remaining 3% what we call fresh water. Fresh water is naturally occurring water on Earth's surface in ice sheets, ice caps, glaciers, icebergs, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. But think about these places, can you drink the water that is in ice caps, glaciers, or underground? That’s where things become tricky.

**Most of that small 3% sliver of freshwater, is trapped in places not easily accessible to the organisms that need it. Sixty nine percent is trapped as ice and snow in ice caps and glaciers, and 30% is hidden underground, as groundwater. This leaves only one percent of all the freshwater available on the surface of the planet!

***Of that tiny one percent of available freshwater, most of it is again hidden or not readily available. About 8 percent is found in the atmosphere as clouds and water vapor, 39 percent is hidden as soil moisture and 1 percent is in you and all other living organisms. This leaves 52% of this water in rivers and streams. 

As you know, water is the only substance on Earth that exists naturally as a solid, liquid, and a gas. Rain, hail, sleet, snow, mist, fog, clouds, and all those breaths of every living thing – those are all either solids, liquids, or gases. And water never sits still. It is constantly moving from one place to another and is frequently changing from one form to another. During the natural water cycle, water is constantly changing states between liquid, vapor, and ice. It falls to the earth from the sky as a liquid or solid. It evaporates into the atmosphere as a gas. It flows underground and in the ocean. It freezes in mountains then melts to the rivers below. Rivers flow to oceans and so on.

Water in all of its forms is vital to Earth’s many creatures and ecosystems. That must be why the average person is composed of approximately 50 – 60 % water. Not to mention that about 70% of your brain is water, 80% of your blood is water, and 90% of your lungs is water! Your average chicken, tree, and pineapple are all about ¾, or 75% water! And we all need a steady supply of water to survive. But we’re all sharing about the same amount of water that we had billions of years ago – even though there are more of us today than ever before.

Although we have about the same amount of water today that we had billions of years ago, the demand for it is much greater today than it ever was. So it’s not that our supply is shrinking. The problem is that the demand is steadily increasing while the supply stays about the same. (Actually, some of the supply is getting polluted). Not only is the population increasing, but humans overall consume much more water than they actually need. When the demand becomes greater than the supply, there will not be enough water to satisfy every human’s need for water. Experts warn that we are approaching the limit of physical, economic, and environmental demands on the renewable freshwater supply.

So, as you continue to hear about the importance of not wasting water, water shortages due to droughts, and even that some people in the world don’t have access to the water they need, you now hopefully have a better understanding of why that is. It’s easy for most of us to turn on a faucet whenever we want and get pretty decent fresh water without much effort or concern, and it’s hard to comprehend water shortages when it seems like there is water all over the planet, but knowing that only about 1% of all the water on Earth is usable fresh water available to humans and animals gives a fresh perspective on fresh water. Think about the graphs you created the next time you open the faucet and let the water run.