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".
The voids in the rock, created as limestone goes into solution, can cause collapses at the land surface. These collapses are known as sinkholes. Sinkholes are often a direct conduit to the groundwater and areas where contamination can easily infiltrate the aquifers.
Sinkhole areas also can have land subsidence as mass wasting occurs in areas with a sudden change in slope and contact with water. Land subsidence may or may not be noticeable in some areas because it appears as hills and valleys due to the very large size. As groundwater becomes more of a source for drinking water, the problem of sinkholes and land subsidence could increase.
Porosity and permeability of the sediment, soil, and bedrock in the area also affects the recharge rate of the groundwater. This means that in some areas, the groundwater can be pumped out faster than it can replenish itself.
This creates a number of problems. One of these problems is called "drawdown," a lowering of the aquifer near a pumping well. This can occur in areas where the well is pumping faster than the groundwater aquifer is recharged. Drawdown creates voids in the bedrock and can lead to additional land subsidence or sinkholes as there is no longer water present and the void cannot hold the weight of the material above and collapses.
Because groundwater is a very plentiful source of fresh water, it must be a protected resource. In many areas, however, groundwater is not protected. Once an aquifer is contaminated with chemicals or petroleum, it is difficult, if not impossible, to clean up. Therefore, prevention of contamination is paramount. Karst areas pose a difficult problem because anything spilled on the surface travels quickly and easily into the aquifer.
Many times, surface water also is in direct contact with undergroundwater, and depending on if the stream is feeding the groundwater a losing stream or if the groundwater is feeding the stream a gaining stream this can create a problem with contamination of the groundwater.
There is also the problem of saltwater intrusion present in coastal regions, such as Florida where over-pumping of the groundwater draws the denser saltwater up into the aquifer. It is the source of life on Earth and quite possibly beyond — the discovery of traces of water on Mars aroused excitement because it was the first indication that life may have existed there. Water is hard to transport over long distances, and our needs are growing, both for food and industry.
Everything we do requires water, for drinking, washing, growing food, and for industry, construction and manufacturing. With more than 7. Providing water to those who need it is not only vital to human safety and security, but has huge social and economic benefits too. Children lose out on education and adults on work when they are sick from easily preventable diseases.
Girls in developing countries are worst off, as they frequently stop going to school at puberty because of a lack of sanitation, and girls and women travelling miles to fetch water or forced to defecate in the open are vulnerable to violence.
Providing affordable water saves lives and reduces the burden on healthcare, as well as freeing up economic resources. Climate change is bringing droughts and heatwaves across the globe, as well as floods and sea level rises. Pollution is growing , both of freshwater supplies and underground aquifers. The depletion of those aquifers can also make the remaining water more saline.
Fertilisers leaching nitrates into the supplies can also make water unsuitable for drinking or irrigation. Cape Town in South Africa provided a stark example of what can happen when water supplies come under threat.
For years the city was using more water than it could sustainably supply, and attempts to curb wastage and distribute water supplies more equitably to rich and poor had fallen short of what was needed. By late last year, a crisis point had been reached. Taps would run dry. There would be no more water. The poor are worst hit.
The number of water-scarce areas is increasing: Cape Town is just the beginning. Water is, after all, a renewable resource; sustaining its uses should be relatively easy. But in reality, we can have too much water or too little water at different times, and the water available may be of too poor quality.
Water availability is often constrained by natural processes associated with the hydrologic cycle and geologic setting, or by jurisdictional boundaries of governmental authorities and water law.
Water supply is also constrained by existing infrastructure to deliver available water. Our ability to ensure enough clean water for human uses is strongly influenced by the cost of water delivery and the price of and demand for water. Thus, many factors and trends affect the availability of water in space and time. Because H 2 O does not cross the boundaries of our atmosphere, either to or from outer space, Earth has held the same quantity of water for eons.
Thus, water is in a continuous flux from evaporation to precipitation, resulting in the recycling, purification, and redistribution of it. However, the quality of water and the fraction of H 2 O in each water phase gaseous, liquid, solid at a given location are subject to change. Currently, more than 99 percent of all water on Earth is unavailable for human use because it is too saline in the form of seawater or is frozen as glaciers, ice, or snow.
With a stored volume of about two million cubic miles, groundwater remains the largest component of freshwater available for humans.
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