Limited aquifer vs. unlimited aquifers
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Groundwater
Groundwater is the water present beneath Earth’s surface in rock and soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table.
Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.
Frozen soil
Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earth’s subsurface contains some water, which may be mixed with other fluids in some instances.
Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water. Therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of usable water storage in the United States, and California annually withdraws the largest amount of groundwater of all the states.[1] Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, including the Great Lakes. Many municipal water supplies are derived solely from groundwater.[2] Over 2 billion people rely on it as their primary water source worldwide.[3]
United States groundwater law
Groundwater can either be privately owned or publicly owned. Groundwater owned by the State is usually distributed through an appropriation system. Privately owned groundwater may allow unlimited production or limited production rights based on land ownership or liability rules. It is possible to regulate the spacing of wells and groundwater production under any of these systems, but the methods, effectiveness and results of that regulation varies greatly from one system to the next depending on the type of aquifer to be regulated.
Effective regulation is tailored to both the hydrology and economics of the region to be regulated. Below is a short discussion of each system and the advantages and disadvantages of each.
Distribution of the Earth’s water
Earth is known as the “Blue Planet” because 71 percent of the Earth’s surface is covered with water. Water also exists below land surface and as water vapor in the air. Water is a finite source. The bottled water that is consumed today might possibly be the same water that once trickled down the back of a wooly mammoth. The Earth is a closed system, meaning that very little matter, including water, ever leaves or enters the atmosphere; the water that was here billions of years ago is still here now. But, the Earth cleans and replenishes the water supply through the hydrologic cycle.
The earth has an abundance of water, but unfortunately, only a small percentage (about 0.3 percent), is even usable by humans. The other 99.7 percent is in the oceans, soils, icecaps, and floating in the atmosphere. Still, much of the 0.3 percent that is useable is unattainable. Most of the water used by humans comes from rivers. The visible bodies of water are referred to as surface water. The majority of fresh water is actually found underground as soil moisture and in aquifers. Groundwater can feed the streams, which is why a river can keep flowing even when there has been no precipitation. Humans can use both ground and surface water.
Distribution of the water on Earth
- Ocean water: 97.2 percent
- Glaciers and other ice: 2.15 percent
- Groundwater,: 0.61 percent
- Fresh water lakes: 0.009 percent
- Inland seas: 0.008 percent
- Soil Moisture: 0.005 percent
- Atmosphere: 0.001 percent
- Rivers: 0.0001 percent.
Surface water is far easier to reach, so this becomes the most common source of potable water. About 321 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
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 1990, the United States alone used approximately 327,000 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.
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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.
Classification of aquifers
Confined aquifers
They are those bodies of water found accumulating in a permeable rock and are been enclosed by two impermeable rock layers or rock bodies. Confined Aquifers are aquifers that are found to be overlain by a confining rock layer or rock bodies, often made up of clay which might offer some form of protection from surface contamination.
The geological barriers which are non-permeable and found exist between the aquifer causes the water within it to be under pressure which is comparatively more than the atmospheric pressure. The presence of fractures, or cracks in bedrocks is also capable of bearing water in large openings within bedrocks dissolving some of the rock and accounts for high yields of well in karst terrain counties like Augusta, Bath within Virginia. Groundwater flow through aquifers is either vertically or horizontally at rates often influenced by gravity and geological formations in these areas.
Unconfined aquifer
Unconfined Aquifer unlike confined aquifers are generally found located near the land surface and have no layers of clay (or other impermeable geologic material) above the water table although they are found lying relatively above impermeable clay rock layers. The uppermost boundary of groundwater within the unconfined aquifer is the water table, the groundwater in an unconfined aquifer is more vulnerable to contamination from surface pollution as compared to that in confined aquifers this been so due to easy groundwater infiltration by land pollutants.
Fluctuation in the level of groundwater varies and depends on the stored up groundwater in the space of the aquifer which in turn affects the rise or fall of water levels in wells that derive their source from aquifers. Unconfined aquifers have a storative value greater than 0.01. “Perched aquifers” (Figure 3) are special cases of unconfined aquifers occurring in situation where groundwater bodies are separated from their main groundwater source by relatively impermeable rock layers of small areal extents and zones of aeration above the main body of groundwater The quantity of water found available in this type of aquifer is usually minute and available for short periods of time.
Threats to aquifers
By 2010, about 30 percent of the Ogallala Aquifer’s groundwater had been tapped, according to a 2013 study from Kansas State University. Some parts of the Ogallala Aquifer are now dry, and the water table has declined more than 300 feet in other areas. More than two-thirds of this Ogalalla aquifer groundwater could be drained in the next several decades, the study found.
“The water levels have just been going down, down, down,” Phillip said. “A lot of that system was recharged 10,000 years ago during the most recent glacial period, and what we’re doing now is mining the water. We’re taking out old water that isn’t being replenished.”
The same problem is increasingly found throughout the world, especially in areas where a rapidly growing population is placing greater demand on limited aquifer resources — pumping can, in these places, exceed the aquifer’s ability to recharge its groundwater supplies.
How old is water in the Aquifer?
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