How much of the earth is sea water

They are only small in relation to the size of the Earth. This image attempts to show three dimensions, so each sphere represents "volume. The smaller sphere over Kentucky represents Earth's liquid fresh water in groundwater, swamp water, rivers, and lakes.

The volume of this sphere would be about 2,, mi 3 10,, km 3 and form a sphere about Yes, all of this water is fresh water, which we all need every day, but much of it is deep in the ground, unavailable to humans.

Do you notice the "tiny" bubble over Atlanta, Georgia? That one represents fresh water in all the lakes and rivers on the planet. Most of the water people and life on earth need every day comes from these surface-water sources. The volume of this sphere is about 22, mi 3 93, km 3. The diameter of this sphere is about Yes, Lake Michigan looks way bigger than this sphere, but you have to try to imagine a bubble almost 35 miles high—whereas the average depth of Lake Michigan is less than feet 91 meters.

The vast majority of water on the Earth's surface, over 96 percent, is saline water in the oceans. The freshwater resources, such as water falling from the skies and moving into streams, rivers, lakes, and groundwater, provide people with the water they need every day to live.

Water sitting on the surface of the Earth is easy to visualize, and your view of the water cycle might be that rainfall fills up the rivers and lakes.

But, the unseen water below our feet is critically important to life, also. How do you account for the flow in rivers after weeks without rain? In fact, how do you account for the water flowing down a driveway on a day when it didn't rain?

The answer is that there is more to our water supply than just surface water, there is also plenty of water beneath our feet. Even though you may only notice water on the Earth's surface, there is much more freshwater stored in the ground than there is in liquid form on the surface. In fact, some of the water you see flowing in rivers comes from seepage of groundwater into river beds. Water from precipitation continually seeps into the ground to recharge aquifers , while at the same time water in the ground continually recharges rivers through seepage.

Humans are happy this happens because we make use of both kinds of water. In the United States in , we used about billion gallons 1, billion liters of surface water per day,and about Although surface water is used more to supply drinking water and to irrigate crops, groundwater is vital in that it not only helps to keep rivers and lakes full, it also provides water for people in places where visible water is scarce, such as in desert towns of the western United States.

Without groundwater, people would be sand-surfing in Palm Springs, California instead of playing golf. For a detailed explanation of where Earth's water is, look at the data table below.

Notice how of the world's total water supply of about Of total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Note: Percentages may not sum to percent due to rounding. One estimate of global water distribution Percents are rounded, so will not add to Earth's water is almost everywhere: above the Earth in the air and clouds and on the surface of the Earth in rivers, oceans, ice, plants, and in living organisms.

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Your message to the editors. Your email only if you want to be contacted back. Send Feedback. Thank you for taking time to provide your feedback to the editors. About billion gallons per day of surface water is used by humans. About 77 billion gallons of groundwater are used each day. Problems also exist in contamination of the water supplies. This further limits the amount of water available for human consumption. Water is found in many different forms and in many different places.

While the amounts of water that exist seem to be plentiful, the availability of the water for human consumption is limited. Surface waters can be simply described as the water that is on the surface of the Earth. This includes the oceans, rivers and streams, lakes, and reservoirs.

Surface waters are very important. They constitute approximately 80 percent of the water used on a daily basis. In , the United States alone used approximately , billion gallons of surface water a day. Surface waters make up the majority of the water used for public supply and irrigation.

It plays less of a role in mining and livestock industries. Oceans, which are the largest source of surface water, comprise approximately 97 percent of the Earth's surface water. However, since the oceans have high salinity, the water is not useful as drinking water. Efforts have been made to remove the salt from the water desalination , but this is a very costly endeavor.

Salt water is used in the mining process, in industry, and in power generation. The oceans also play a vital role in the hydrologic cycle, in regulating the global climate, and in providing habitats for thousands of marine species. Rivers and streams constitute the flowing surface waters. The force of gravity naturally draws water from a higher altitude to a lower altitude.

Rivers obtain their water from two sources: groundwater, and runoff. Rivers can obtain their water from the ground if they cut into the water table, the area in which the ground is saturated with water. This is known as base flow to the stream. Runoff flows downhill, first as small creeks, then gradually merging with other creeks and streams, increasing in size until a river has formed.

These small creeks, or tributaries, where the river begins are known as the headwaters. Springs from confined aquifers also can contribute to rivers. A river will eventually flow into an ocean. A river's length can be difficult to determine, especially if it has numerous tributaries.

The USGS Web site defines a river's length as "the distance to the outflow point from the original headwaters where the name defines the complete length. The land that is upgradient of any point on the river is known as the drainage basin or watershed. Ridges of higher land, such as the Continental Divide, separate two drainage basins.

Flowing water is extremely powerful and plays an important role in creating the landscape and in humans' lives. Flowing water is used for numerous reasons including irrigation and hydroelectric power production. Rivers erode the landscape and change the topography of the Earth by carving canyons and transporting soil and sediment to create fertile plains.

Rivers carry soil and sediment that have been washed into the river when it rains or snow melts. The faster the water moves, the larger the particle size the river is capable of carrying. The USGS measures how much sediment a river carries by measuring the streamflow, or the amount of water flowing past a given site; and the sediment concentration.

Sediment in the river can be helpful and harmful. Sediment, when deposited on the banks and in the flood plain, makes excellent farmlands. However, sediment can harm and even destroy dams, reservoirs and the life in the stream.

Also, during floods, these sediments can be left behind as sticky, smelly mud in unwanted places. Measuring the streamflow is accomplished by determining the stream stage and the stream discharge. The stream stage, or datum, is the height of the water surface, in feet, above an arbitrary reference point.

The stream discharge is a measurement of the amount of water that is flowing at a particular point in time. It is measured in cubic feet per second. A discharge measurement determines the amount of water that is flowing in the river at any given stream stage.

In order to make this measurement, the width of the river, and the water's depth and velocity at various points must be measured at several different stream stages. A cross-section of the river is divided into intervals and the area of each interval is calculated. If the velocity was measured at different depths on the same vertical interval, then the velocity is averaged. To determine the discharge for the interval, the area is multiplied by the velocity.

To find the entire stream's discharge, an average of all the intervals' discharges is calculated. It is important to take discharge measurements of the stream at various stream stages, even flood stage.

A river reaches flood stage when the river overflows its banks. The flood stage can be determined by measuring the gage height, or simply the height of the water in the stream measured from the river's bottom. The streamflow can increase exponentially as the gage height increases. Thus, a small increase in gage height may indicate that a river has reached its flood stage. Floods are a fairly common, yet dangerous, natural disaster. They normally occur because a storm or rapid snow melt has produced more runoff than a stream can carry.

Dams failing, landslides blocking stream channels, and high tides are some other causes of flooding. Weather patterns can greatly influence when and where flooding will occur. By studying these patterns, geologists can determine the susceptibility of a region to having a flood at certain times of the year. The recurrence interval, measured in years, describes the magnitude of a flood.

Changes in the drainage basin, such as harvesting timber or housing developments, can change the magnitude of a flood. The normally dry land that becomes covered with water during a flood is known as the flood plain.