Water Facts - Worldwide Water Supply
- Water covers about 71% of the earth's surface.
- 326 million cubic miles of water on the planet
- 97% of the earth's water is found in the oceans (too salty for drinking, growing crops, and most industrial uses except cooling).
- 320 million cubic miles of water in the oceans
- 3% of the earth's water is fresh.
- 2.5% of the earth's fresh water is unavailable: locked up in glaciers, polar ice caps, atmosphere, and soil; highly polluted; or lies too far under the earth's surface to be extracted at an affordable cost.
- 0.5% of the earth's water is available fresh water.
- If the world's water supply were only 100 liters (26 gallons), our usable water supply of fresh water would be only about 0.003 liter (one-half teaspoon).
- In actuality, that amounts to an average of 8.4 million liters (2.2 million gallons) for each person on earth.
- This supply is continually collected, purified, and distributed in the natural hydrologic (water) cycle.
If the Earth Were a Globe 28 Inches in Diameter:
- All of the water on the planet would fill less than one cup.
- Only 0.03% of one cup is in rivers and fresh water lakes.
- Slightly more than one drop of water would fill all the rivers and lakes.
Sources of Fresh Water
- Groundwater - water which infiltrates into the ground through porous materials deeper into the earth. It fills pores and fractures in layers of underground rock called aquifers. Some of this water lies too far under the earth's surface to be extracted at an affordable cost.
- Surface-water runoff - precipitation that does not infiltrate into the ground or return to the atmosphere: streams, rivers, lakes, wetlands, and reservoirs.
- Snow that is 4 inches (10cm) deep contains about the same amount of water as 1/3 inch (1 cm) of rain.
Water Use in the U.S.
- 8% domestic use
- 33% agriculture
- 59% industry
- Over 600 gallons per day per person in the U.S. is being diverted for farm irrigation and livestock use from natural aquatic sources.
- More than half the people in the U.S. get their water from groundwater.
Measures of Water Use
- Water withdrawal - taking water from groundwater or surface-water source and transporting it to a place of use.
- Water consumption - water that has been withdrawn and is not available for reuse in the area from which it is withdrawn.
- In the U.S. about three-fourths of the fresh water withdrawn each year comes from rivers, lakes and reservoirs; one-fourth comes from groundwater aquifers.
- 80% of water withdrawn in the U.S. is used for cooling electric power plants and for irrigation.
Home Water Use (Approximate)
|Shaving and allowing the water faucet to run|
|Flushing a toilet|
|Brushing your teeth and allowing the water faucet to run|
|Cooking 3 meals|
|Washing dishes for 3 meals|
|Washing dishes and allowing the water faucet to run|
|Washing a car|
|Taking a bath|
|8 minute shower (5 gallons/minute)|
- A leak that fills up a coffee cup in 10 minutes will waste over 3,000 gallons of water in a year. That's 65 glasses of water every day for a year.
- A leaky toilet can waste over 22,000 gallons of water in one year; enough to take three baths every day.
Garden Water Use
- Americans use about 1/3 more water in the summer than they do the rest of the year because they're watering their lawns.
- There are about 10 million acres of lawn in the U.S., which requires 270 billion gallons of water every week. That's enough to give every person in the world a shower for four days in a row.
- Most lawns only need an inch of water each week.
Water in the Body
- Eye - 95% water
- Total body weight - 75% water
- A gallon of paint or a quart of motor oil can seep into the earth and pollute 250,000 gallons of drinking water.
- A spilled gallon of gasoline can pollute 750,000 gallons of water.
- Aquatic Project WILD; Western Regional Environmental Education Council
- Flying Start Science-Water; Kim Taylor
- Folsom Dam Fact Sheets; Bureau of Reclamation
- Layperson's Guide to The American River; Water Education Foundation
- Living in the Environment, An Introduction to Environmental Science; G. Tyler Miller Jr.
- Water Facts; Water Education Foundation
- 50 Simple Things Kids Can Do To Save The Earth; The EarthWorks Group
This page is produced by Public Affairs, Mid-Pacific Region. Please contact us for additional information or assistance
For assistance or additional information about this website, please contact Public Affairs
Bureau of Reclamation, Mid-Pacific Region
2800 Cottage Way, Sacramento CA 95825-1898
Main 916-978-5100 | FAX 916-978-5114 | TTY 916-978-5608
Reclamation Officials' Telephone Numbers
Last update: September 26, 2012