Water Use in the U. More than half the people in the U. 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 Water consumption - water that has been withdrawn and is not available for reuse in the area from which it is withdrawn.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. Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.
Of that, only about 1. Most of our drinking water comes from rivers and streams. This water is the lifeline of ecosystems around the world. Clean fresh water is a limited and valuable resource. In this module, students consider the question: will there be enough fresh water? Students explore the distribution and uses of fresh water on Earth.
They explore models of porosity and permeability, run experiments with computational models, and hear from a hydrologist working on the same question. Students explore maps to discover the distribution of fresh water resources on Earth, and they examine graphs to discover how fresh water supplies are used by humans.
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Background Info. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Writers Ari J. About 70 percent of the planet is covered in ocean, and the average depth of the ocean is about 12, feet 3, meters.
Ninety-eight percent of the water on the planet is in the oceans, and therefore is unusable for drinking because of the salt. Less than 3 percent of the planet's water is fresh, but about 1. Another 0. Only about 0. That's still thousands of trillions of gallons, but it's a very small amount compared to all the water available. One problem facing the cycle of water on Earth is water contamination. Chemicals that go into the water often are very difficult, if not impossible, to remove.
One potential source of contamination of water is runoff, the overland flow of water. While precipitation causes the runoff to occur, stripping vegetation from land can add to the runoff in a particular area.
The sediment and soil from these areas, not to mention any pesticides or fertilizers that are present, are washed into the streams, oceans, and lakes.
What happens to the rain after it falls depends on many factors, such as the intensity and duration of rainfall, the topography of the land, soil conditions, amount of urbanization, and density of vegetation. A common misconception about rain that it is tear-shaped, when in actuality it is shaped more like a hamburger bun. Rain drops also are different sizes, due to the initial difference in particle size and the different rate of coalescence.
Glaciers and icecaps are referred to as storehouses for fresh water. They cover 10 percent of the world's land mass. These glaciers are primarily located in Greenland and Antarctica. The glaciers in Greenland almost cover the entire land mass. Glaciers begin forming because of snowfall accumulation. When snowfall exceeds the rate of melting in a certain area, glaciers begin to form. This melting occurs in the summer. The weight of snow accumulating compresses the snow to form ice.
Because these glaciers are so heavy, they can slowly move their way down hills. Glaciers affect the topography of the land in some areas. Ancient glaciers formed lakes and valleys. The Great Lakes are an example of this. Glaciers range in length from less than the size of a football field to hundreds of miles long. They also can reach up to 2 miles thick.
Glaciers melting can have a tremendous effect on the sea level. If all of the glaciers were to melt today, the sea would rise an estimated feet, according to the USGS. Glaciers have had a tremendous effect on the formation of the Earth's surface and are still influencing the topography everyday. Groundwater is defined as water that is found beneath the surface of the Earth in conditions of percent saturation if it is less than percent saturation, then the water is considered soil moisture.
Ninety-eight percent of Earth's available fresh water is groundwater. It is about 60 times as plentiful as the fresh water found in lakes and streams. Water in the ground travels through pores in soil and rock, and in fractures and weathered areas of bedrock.
The amount of pore space present in rock and soil is known as porosity. The ability to travel through the rock or soil is known as permeability. A "high" permeability and porosity value means that the water can travel quickly. Groundwater can be found in aquifers. An aquifer is a body of water-saturated sediment or rock in which water can move readily. There are two main types of aquifers: unconfined and confined.
An unconfined aquifer is a partially or fully filled aquifer that is exposed to the surface of the land. Because this aquifer is in contact with the atmosphere, it is impacted by meteoric water and any kind of surface contamination.
There is not an impermeable layer to protect this aquifer. In contrast, a confined aquifer is an aquifer that has a confining layer that separates it from the land surface. This aquifer is filled with pressurized water due to the confining layer. If the water is pressurized at a high enough value, when a well is drilled into the confining aquifer, water rises above the surface of the ground.
This is known as a flowing water well. The pressure of the water is called the hydraulic head. Groundwater movement, or velocity, is measured in feet or meters per second.. In some areas, the bedrock has low permeability and porosity levels, yet groundwater can still travel in the aquifers. Groundwater can travel through fractures in the rock or through areas that are weathered. Limestone, for example, weathers in solution, creating underground cavities and cavern systems.
At the land surface, these areas are known as "karst".
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