By Monica Nkhoma

 

http://www.kgs.ku.edu/Publications/PIC/pic23.html

The picture above illustrates an aquifer and the cycle of how the water gets recharged back into the ground.  Much of the freshwater we use is taken from underground aquifers – natural reservoirs beneath the surface of the earth.

The definition of an aquifer means “water bearer,” however, many people think that aquifers are underground lakes.  Aquifers are underground layers of rock or sand that allows movement of water between layers of porous rock.  When it rains or snows, water will filtrate into the soil through holes or cracks until it reaches the zone of saturation.  When all of the spaces are filled with water instead of air, the zone of saturation occurs.  The water that seeps through the soil reaches the zone of saturation and then will reach an impermeable layer of rocks.  The impermeable layer of rocks will not allow any water to penetrate further into the earth.  The water that sits above the impermeable layer and between rocks or sand is known as the aquifer.  The impermeable layer is known as the aquitard or aquilude.

In order for the water to move throughout the aquifer; there are two main forces that will cause the ground water to mover.  The first force that causes water to move is, caused by gravity.  This causes water to move from higher to lower elevation.  Essentially this is how the water is penetrated through the soil.  The second force that causes water to move is pressure.  Together, these forces make a driving force called the hydraulic head.  Not only does water have to forces that cause it to move, but water is only able to move through certain types of rocks.  There are four different types of rocks that water has the ability to move through and they are porous sedimentary, volcanic, porous and sedimentary rocks[1]

There are three types of aquifers and they are unconfined, confined and perched.

In the unconfined aquifers, the water table is located at the outermost part of the aquifer.  The water in the confined aquifer is usually the water that receives runoff, snowmelt etc.  To keep it simple, unconfined aquifers have no confining layers.

The confined aquifer has confining layers between the water level and the ground level.  The water in this type of aquifer runs between two beds of impermeable layers.

The final type of aquifer is known as the perched aquifer.  Perched aquifers are aquifers that have no confining layer below the ground level and sit above the main water table.[2], [3]

Figure 1  Schematic of confined and unconfined aquifers.  The upper aquifer is the unconfined, while the lower aquifer (below the shale) is the confined aquifer.

 

Source:  USGS  http://pubs.usgs.gov/gip/gw_ruralhomeowner/ 

Figure 2  Schematic of perched aquifer.  Notice that aquifer is located above the water table.  The water table is the top of the water surface in the saturated part of the aquifer.  Source:  USGS

 

Aquifers are recharged (re-filled) by both natural and man-made means.  One type of man-made recharge is by means of injection wells; surface water collected from storm water runoff, for example, is pumped back into the aquifer by means of injection wells. 

Figure 3  Schematic showing various means by which aquifers are recharged.  Injection well recharge is shown at the right of the drawing.  Source:  USGS

 

The Ogallala Aquifer

            The largest aquifer in the world is known as “The Great Ogallala Aquifer” and it is located in the United States.  It is known as a confined aquifer because it confined between two layers of impermeable materials.  The Ogallala is approximately 174,000 miles running through eight states and they are, Nebraska, Wyoming, South Dakota, Kansas, Colorado, Oklahoma, New Mexico and Texas.  The Ogallala also varies in thickness from 1ft. to 400 ft. of water.  The Ogallala is also responsible for feeding the middle third of the United States through industrial, agricultural and drinking usage.

            However, we are experiencing an extreme issue with the massive Ogallala because the water source is running dry.  The Ogallala relies on rain water, and runoff, and snowmelt to recharge but, the water source is being depleted faster than it is being recharged.

            Not only is the great Ogallala being depleted, the aquifer is also becoming contaminated by the ground water.  Ground water is seeping into the aquifer through the wholes that have been drilled into it for all types of purposes such as artificial recharge, recycled water, landfill seepage, and harmful pesticides and chemicals that are being used.

            A lot of the technology used such as artificial recharge sounds like it would be a benefit however, by doing so we are not only disturbing the environment but we are allowing other things to enter as well.

As a result of recycling the water, we are noticing that it is affecting the water quality.  Some of the water that is being recycled and put back into the aquifer isn’t always the best which is compromising people’s health.  If the Ogallala had to be drained and refilled, it would take at least 6000 years to refill this massive water source.  Much of the contamination that has occurred happened by the man made technologies. [4], [5]

 

 

 

 

Environmental

 

Some of the environmental problems that have been occurring associated with drilling are that there are pollutants entering the aquifers.  The pollutants in the aquifers are coming from the surface water from the drilling.  Basically due to the fact that there are some states that are experiencing water shortages, the technology in drilling is helping to replenish the water that is being used by over consumption and rapid withdraw. 

Many states are experiencing water shortages however, but, I would like to focus on the state of Florida.  The government has issued a water fund to the state of Florida to help with the people with the water crisis.  One of the ideas that the government issued was to create a way to help the Florida aquifers recharge.  So they started to drill into the aquifers and create injection wells.  Injection wells are used as an artificial way to recharge the ground water.  The injection wells are sixty feet into the ground and the water that is penetrated through these wells are treated sewage effluent, storm water runoff, and waters from natural streams from different zones. 

This method is known as the ASR (Aquifer Storage Recovery).    Although this sounds like a great idea to recharge the ground water, it is having a very negative impact.  This form of technology is causing the aquifers to be heavily polluted because some of the water sources aren’t filtered all the way.  Not only that, this is having a very negative impact on the wild life in Florida because many of the animals are losing their natural habitats due to our rapid consumption. The adverse effect from this method is that it will eventually increase the loss of wildlife habitat.  Some of the species that will be affected is the Florida Panther, Florida Manatee, and the Wood Stork to name a few[6].

www.connectedwater.gov.au/images/Framework_Wa

The picture above is another example of artificial recharge.  This is the method that was incorporated in Florida called the ASR (Aquifer Storage Recovery).

Technology

In order to get fresh drinking water from these aquifers, the types of technologies that were created give people easy access to water.  Drills and pumps were developed so that more water could be taken from the aquifers at a faster rate.  These water pumps were created for drinking consumption, industrial use and agricultural use.  This helps reduce the amount of time that humans would need to obtain water.  Even though these technologies were created, there have been significant problems associated with them.  There is becoming an over usage of water consumption which is causing a water scarcity problem.  The rain water and snow melt that is suppose to re-charge the aquifers can’t because we are using water more rapidly and more frequently.[7]

Some of the advantages of the artificial recharge of ground water are,

·       very inexpensive and there are no special tools needed to do it

·        improve groundwater if injected with high quality water

·       System is easy to operate

·       Environmentally attractive

Some of the disadvantages of artificial recharge of ground water are,

·        Potential for contamination to occur

·        It can cause disturbances in soil and vegetation

·        Degrade the aquifer

·        Artificial recharge may not be economically feasible

In the United States, we use more water than the rest of the world.  Most of the time, the water that is used isn’t taken into consideration. 

Conclusion

According to “Population” by, William Ryerson, “everyday approximately 156,000 people die but, 381,000 are born.  Essentially, this is a net daily growth of 225,000 human beings.[8]  This tells us that, there are more people than there are resources.  Even though there is always innovation and technology, it doesn’t mean that is can make up for what we have already lost.  In most cases, technology is usually a short term fix to a problem.  I believe that through education and consistency, we can get many people to work together to create a way to solve our crisis issues.  In addition to that, we need to identify some sort of control over these problems and who will be responsible.  This issue cannot be prolonged any further and needs a permanent fix.