Freshwater on the land surface is a vital part of the water cycle for everyday human life. On the landscape, freshwater is stored in rivers, lakes, reservoirs, creeks, and streams. Most of the water people use everyday comes from these sources of water on the land surface.
• Water Science School HOME • Surface Water topics • The Water Cycle •
Water cycle components » Atmosphere · Condensation · Evaporation · Evapotranspiration · Groundwater flow · Groundwater storage · Ice and snow · Infiltration · Freshwater lakes and rivers · Oceans · Precipitation · Snowmelt · Springs · Streamflow · Sublimation · Surface runoff
One part of the water cycle that is obviously essential to all life on Earth is the freshwater existing on the land surface. Just ask your neighbor, a tomato plant, a trout, or mosquito. Surface water includes the lakes, reservoirs (human-made lakes), ponds, streams (of all sizes, from large rivers to small creeks), canals (human-made lakes and streams), and freshwater wetlands. The definition of freshwater is water containing less than 1,000 milligrams per liter of dissolved solids, most often salt.
As a part of the water cycle, Earth's surface-water bodies are generally thought of as renewable resources, although they are very dependent on other parts of the water cycle. The amount of water in rivers and lakes is always changing due to inflows and outflows. Inflows to these water bodies will be from precipitation, overland runoff, groundwater seepage, and tributary inflows. Outflows from lakes and rivers include evaporation, movement of water into groundwater, and withdrawals by people.
So, the amount and location of surface water changes over time and space, whether naturally or with human help. During the last ice age when glaciers and snowpacks covered much more land surface than today, life on Earth had to adapt to different hydrologic conditions than those which took place both before and after. And the layout of the landscape was different before and after the last ice age, which influenced the topographical layout of many surface-water bodies today. Glaciers are what made the Great Lakes not only "great," but also such a huge storehouse of freshwater.
Surface water keeps life going

Credit: NASA
Water on the land surface really does sustain life, and this is as true today as it was millions of years ago. Dinosaurs likely gathered at the local watering hole 100 million years ago, just as antelopes in Africa do today. And, since groundwater is supplied by the downward percolation of surface water, even aquifers are happy for water on the Earth's surface. You might think that fish living in the saline oceans aren't affected by freshwater, but, without freshwater to replenish the oceans they would eventually evaporate and become too saline for even the fish to survive.
As we said, everybody and every living thing congregates and lives where they can gain access to water, especially freshwater. Just ask the billions of people living on Earth! Here's a satellite picture of the world at night. The most obvious thing you can see is that people live near the coasts, which, of course, is where water, albeit saline, is located. But the interesting thing in this picture are the lights following the Nile River and Nile Delta in Egypt (the area within the purple-outlined box). In this dry part of the world, surface-water supplies are essential for human communities. And if you check the price of lakefront property in your part of the world, it probably sells for much more than other land.

Usable fresh surface water is relatively scarce
To many people, streams and lakes are the most visible part of the water cycle. Not only do they supply the human population, animals, and plants with the freshwater they need to survive, but they are great places for people to have fun. You might be surprised at how little of Earth's water supply is stored as freshwater on the land surface, as shown in the diagram and table below. Freshwater represents only about three percent of all water on Earth and freshwater lakes and swamps account for a mere 0.29 percent of the Earth's freshwater. Twenty percent of all fresh surface water is in one lake, Lake Baikal in Asia. Another twenty percent (about 5,500 cubic miles (about 23,000 cubic kilometers)) is stored in the Great Lakes. Rivers hold only about 0.006 percent of total freshwater reserves. You can see that life on Earth survives on what is essentially only a "drop in the bucket" of Earth's total water supply! People have built systems, such as large reservoirs and small water towers to store water for when they need it. These systems allow people to live in places where nature doesn't always supply enough water or where water is not available at the time of year it is needed.

The World's Water - Distribution of Earth's Water
The Earth is a watery place. But just how much water exists on, in, and above our planet? About 71 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you.
This bar chart shows how almost all of Earth's water is saline and is found in the oceans. Of the small amount that is freshwater, only a relatively small portion is available to sustain human, plant, and animal life.
-
In the first bar, notice how only 2.5 percent of Earth's water is freshwater.
-
The middle bar shows the breakdown of freshwater. Almost all of it is locked up in ice and in the ground. Only a little more than 1.2 percent of all freshwater is surface water.
-
The right bar shows the breakdown of surface freshwater. Most of this water is locked up in ice, and another 20.9 percent is found in lakes. Rivers make up 0.49 percent of surface freshwater. Although rivers account for only a small amount of freshwater, this is where humans get a large portion of their water from.
Water source | Water volume, in cubic miles |
Water volume, in cubic kilometers |
Percent of total water | Percent of total freshwater |
---|---|---|---|---|
Fresh groundwater | 2,526,000 | 10,530,000 | 0.8% | 30.1% |
Groundwater | 5,614,000 | 23,400,000 | 1.7% | -- |
Total global water | 332,500,000 | 1,386,000,000 | -- | -- |
Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp. 817-823.
Do you really like lakes? Or maybe you'd rather sit by the ocean, or maybe a waterfall is your favorite?
Cast your vote for your favorite water body and see how thousands of others all over the world voted.
Sources and more information:
More topics and other components of the water cycle:
Precipitation and the Water Cycle
Streamflow and the Water Cycle
Snowmelt Runoff and the Water Cycle
Evaporation and the Water Cycle
The Atmosphere and the Water Cycle
Condensation and the Water Cycle
Infiltration and the Water Cycle
Sublimation and the Water Cycle
Surface Runoff and the Water Cycle
Ice, Snow, and Glaciers and the Water Cycle
Groundwater Flow and the Water Cycle
Groundwater Storage and the Water Cycle
- Overview
Freshwater on the land surface is a vital part of the water cycle for everyday human life. On the landscape, freshwater is stored in rivers, lakes, reservoirs, creeks, and streams. Most of the water people use everyday comes from these sources of water on the land surface.
• Water Science School HOME • Surface Water topics • The Water Cycle •
Water cycle components » Atmosphere · Condensation · Evaporation · Evapotranspiration · Groundwater flow · Groundwater storage · Ice and snow · Infiltration · Freshwater lakes and rivers · Oceans · Precipitation · Snowmelt · Springs · Streamflow · Sublimation · Surface runoff
Lakes are valuable natural resources, both for human and non-human life. One part of the water cycle that is obviously essential to all life on Earth is the freshwater existing on the land surface. Just ask your neighbor, a tomato plant, a trout, or mosquito. Surface water includes the lakes, reservoirs (human-made lakes), ponds, streams (of all sizes, from large rivers to small creeks), canals (human-made lakes and streams), and freshwater wetlands. The definition of freshwater is water containing less than 1,000 milligrams per liter of dissolved solids, most often salt.
As a part of the water cycle, Earth's surface-water bodies are generally thought of as renewable resources, although they are very dependent on other parts of the water cycle. The amount of water in rivers and lakes is always changing due to inflows and outflows. Inflows to these water bodies will be from precipitation, overland runoff, groundwater seepage, and tributary inflows. Outflows from lakes and rivers include evaporation, movement of water into groundwater, and withdrawals by people.
So, the amount and location of surface water changes over time and space, whether naturally or with human help. During the last ice age when glaciers and snowpacks covered much more land surface than today, life on Earth had to adapt to different hydrologic conditions than those which took place both before and after. And the layout of the landscape was different before and after the last ice age, which influenced the topographical layout of many surface-water bodies today. Glaciers are what made the Great Lakes not only "great," but also such a huge storehouse of freshwater.
Surface water keeps life going
Sources/Usage: Some content may have restrictions. Visit Media to see details.Nile Valley in Egypt—Water makes the desert bloom as seen in this satellite picture of the Nile Valley in Egypt.
Credit: NASAWater on the land surface really does sustain life, and this is as true today as it was millions of years ago. Dinosaurs likely gathered at the local watering hole 100 million years ago, just as antelopes in Africa do today. And, since groundwater is supplied by the downward percolation of surface water, even aquifers are happy for water on the Earth's surface. You might think that fish living in the saline oceans aren't affected by freshwater, but, without freshwater to replenish the oceans they would eventually evaporate and become too saline for even the fish to survive.
As we said, everybody and every living thing congregates and lives where they can gain access to water, especially freshwater. Just ask the billions of people living on Earth! Here's a satellite picture of the world at night. The most obvious thing you can see is that people live near the coasts, which, of course, is where water, albeit saline, is located. But the interesting thing in this picture are the lights following the Nile River and Nile Delta in Egypt (the area within the purple-outlined box). In this dry part of the world, surface-water supplies are essential for human communities. And if you check the price of lakefront property in your part of the world, it probably sells for much more than other land.
Sources/Usage: Some content may have restrictions. Visit Media to see details.View the full image from NASA. Usable fresh surface water is relatively scarce
To many people, streams and lakes are the most visible part of the water cycle. Not only do they supply the human population, animals, and plants with the freshwater they need to survive, but they are great places for people to have fun. You might be surprised at how little of Earth's water supply is stored as freshwater on the land surface, as shown in the diagram and table below. Freshwater represents only about three percent of all water on Earth and freshwater lakes and swamps account for a mere 0.29 percent of the Earth's freshwater. Twenty percent of all fresh surface water is in one lake, Lake Baikal in Asia. Another twenty percent (about 5,500 cubic miles (about 23,000 cubic kilometers)) is stored in the Great Lakes. Rivers hold only about 0.006 percent of total freshwater reserves. You can see that life on Earth survives on what is essentially only a "drop in the bucket" of Earth's total water supply! People have built systems, such as large reservoirs and small water towers to store water for when they need it. These systems allow people to live in places where nature doesn't always supply enough water or where water is not available at the time of year it is needed.
Sources/Usage: Public Domain. Visit Media to see details.The World's Water - Distribution of Earth's Water
The Earth is a watery place. But just how much water exists on, in, and above our planet? About 71 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you.
This bar chart shows how almost all of Earth's water is saline and is found in the oceans. Of the small amount that is freshwater, only a relatively small portion is available to sustain human, plant, and animal life.
-
In the first bar, notice how only 2.5 percent of Earth's water is freshwater.
-
The middle bar shows the breakdown of freshwater. Almost all of it is locked up in ice and in the ground. Only a little more than 1.2 percent of all freshwater is surface water.
-
The right bar shows the breakdown of surface freshwater. Most of this water is locked up in ice, and another 20.9 percent is found in lakes. Rivers make up 0.49 percent of surface freshwater. Although rivers account for only a small amount of freshwater, this is where humans get a large portion of their water from.
One estimate of global water distribution Water source Water volume,
in cubic milesWater volume,
in cubic kilometersPercent of total water Percent of total freshwater Fresh groundwater 2,526,000 10,530,000 0.8% 30.1% Groundwater 5,614,000 23,400,000 1.7% -- Total global water 332,500,000 1,386,000,000 -- -- Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp. 817-823.
Do you really like lakes? Or maybe you'd rather sit by the ocean, or maybe a waterfall is your favorite?
Cast your vote for your favorite water body and see how thousands of others all over the world voted.Sources and more information:
-
- Science
More topics and other components of the water cycle:
Filter Total Items: 15Precipitation and the Water Cycle
The air is full of water, even if you can't see it. Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water droplets—clouds. When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail... all forms of precipitation, the superhighway moving water...Streamflow and the Water Cycle
What is streamflow? How do streams get their water? To learn about streamflow and its role in the water cycle, continue reading.Snowmelt Runoff and the Water Cycle
Perhaps you've never seen snow. Or, perhaps you built a snowman this very afternoon and perhaps you saw your snowman begin to melt. Regardless of your experience with snow and associated snowmelt, runoff from snowmelt is a major component of the global movement of water, possibly even if you live where it never snows. Note: This section of the Water Science School discusses the Earth's "natural"...Evaporation and the Water Cycle
Evaporation is the process that changes liquid water to gaseous water (water vapor). Water moves from the Earth’s surface to the atmosphere via evaporation.The Atmosphere and the Water Cycle
The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Water at the Earth's surface evaporates into water vapor, then rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation.Condensation and the Water Cycle
Condensation is the process of gaseous water (water vapor) turning into liquid water. Have you ever seen water on the outside of a cold glass on a humid day? That’s condensation.Infiltration and the Water Cycle
You can't see it, but a large portion of the world's freshwater lies underground. It may all start as precipitation, but through infiltration and seepage, water soaks into the ground in vast amounts. Water in the ground keeps all plant life alive and serves peoples' needs, too.Sublimation and the Water Cycle
Solid, liquid, and gas - the three states of water. We see water freeze, transforming into a solid form such as ice, and we see water evaporate, turning into gas, but... have you ever seen ice transform directly to gas? This process is called sublimation and you can read all about it below.Surface Runoff and the Water Cycle
Runoff is nothing more than water "running off" the land surface. Just as the water you wash your car with runs off down the driveway as you work, the rain that Mother Nature covers the landscape with runs off downhill, too (due to gravity). Runoff is an important component of the natural water cycle. Note: This section of the Water Science School discusses the Earth's "natural" water cycle...Ice, Snow, and Glaciers and the Water Cycle
The water stored in ice and glaciers moves slowly through are part of the water cycle, even though the water in them moves very slowly. Did you know? Ice caps influence the weather, too. The color white reflects sunlight (heat) more than darker colors, and as ice is so white, sunlight is reflected back out to the sky, which helps to create weather patterns.Groundwater Flow and the Water Cycle
Yes, water below your feet is moving all the time, but not like rivers flowing below ground. It's more like water in a sponge. Gravity and pressure move water downward and sideways underground through spaces between rocks. Eventually it emerges back to the land surface, into rivers, and into the oceans to keep the water cycle going.Groundwater Storage and the Water Cycle
The ground stores huge amounts of water and it exists to some degree no matter where on Earth you are. Lucky for people, in many places the water exists in quantities and at depths that wells can be drilled into the water-bearing aquifers and withdrawn to server the many needs people have.