Geology Research Paper on Edwards Aquifer System

Geology Research Paper on Edwards Aquifer System


The study looks at Edwards aquifer system. It discusses the history and all major features of the system. The benefits of the system to the community are outlined and the possible issue that could affect the system also identified. The article concludes that the system is very important and should be preserved by all means necessary.


Aquifer refers to a body of permeable water-bearing rock. It could also be used to refer to the unconsolidated rock materials that allow water to be extracted from water well. In this study, the writer looks at Edwards Aquifer system. Aquifers could store and transmit the stored water to streams, springs, and wells (Maclay and Ted 535). This water could then be used for various purposes such as domestic, industrial and agricultural use. It is important to study Aquifers to understand how to protect and preserve them. The system is important because it provides a means by which human beings could use the underground water for their own use. Some aspects of Edwards aquifer system are worth studying and the study would look at them in details.

Edward Aquifer System

This system is regarded as one of the most prolific and unique ground water systems among the world’s artesian aquifers. It was first used by the Spanish missionaries in the early 1700s as their source of water. The water from this source played a huge role in the decisions to have settlements in the area as well as the establishment of the Alamo mission (Maclay 4135). The scope served by the system makes it one of the biggest naturally occurring resources in the world. The system serves a number of industrial, domestic, recreational and agricultural entities. It serves approximately 2 million citizens and covers an area of about 8,800 square miles. The system also covers thirteen counties in the southern region of central Texas.

The system is managed by an authority created by an Act of Texas state legislature. The Edward aquifer authority act was enacted in 1993.The role of the authority was to ensure that the permitting system is in the right condition. The aquifer is not far from San Antonio city; the seventh largest city in America.


The system lies within the fault zone of Balcones. The aquifer’s uniqueness lies within its big size and the geologic anomaly of the area. Millions of years ago (approximately 65 million), the occurrence of the tectonic processes had resulted in the depositing of sediments (Maclay 4136). It is believed that the fault between the Edward plateau and the gulf resulted from the heavy weight of the deposited sediments. The water storage capacity of the system, the characteristics of its flow, its capability in water production and the efficiency of its ability to recharge makes it a one of a kind aquifer system.

To the north of the system, there is the Edward plateau (Scanlon 136). This forms the highest level of the area covered by the aquifer. The floor of the plateau is made of strategically occurring rocks and limestone materials. The flow of water at this point heads towards the lower grounds. Below the rocks lies then Balcones fault zone. Edwards aquifer beings after the Glen Rose formation though in some areas it is covered by the bad-water lines.

The aquifer covers up to six counties. Most of the water in the aquifer comes from the Edward plateau on the higher grounds. The water catchment area for the water found in the aquifer lies about 4450 square miles. The water is then directed to the plateau finally being discharged into the aquifer.


The water in the aquifer moves from the higher ground towards the lower regions (Barker and Ann n.p). In hydrogeology, the water flow is divided into three main regions; artesian, recharge and contributing zones. Edwards aquifer is a karst aquifer, which means that it can store and carry more water than the gravel and sand aquifers (Maclay and Ted 537).

The Contributing Zone

This zone is located in the upper area (Edwards plateau). The area is also known as the Texas Hill country. The primary vegetation of the area is made of cedar and oak which form a thick and rugged cover. The thick vegetation is the catchment area for the aquifer. The water from the rain forest infiltrates the ground. This water could enter streams or run underground on the water table aquifer. The water on the water table and on the run-off passes through impermeable limestone before reaching the recharge zone. The runoff and water table aquifer in this region include the Helotes creek and Cibolo creek.

Recharge Zone

This area covers approximately1250 square miles. This zone is where the fractured and faulted limestone emerges at the ground surface. The Edward limestone allows a large amount of water to flow into the underground aquifer (Scanlon 137). This is the reason why the Edward limestone is called the fault zone. A higher percentage of recharge occurs at this point as water the limestone formation and enters underground. When a big percentage enters underground, the recharge is referred to as the allogeneic discharge.

The man-made lake called Medina Lake which was built in this region forms the largest contributor of water to the aquifer. It should be noted that at the discharge zone, there are no overlying rocks on top of Edwards as it is fully exposed to the surface. The unconfined aquifer has a water table whose water level depends on the amount of precipitation.

The confinement of a large proportion of Edwards plateau within a rose limestone and clay geologic features means that the area has no water table. Some of the physical features in this zone include Seco Creek project, Hills and Dales pit cave (Scanlon 156). The project channeled large volume of water into the Aquifer.

Artesian Zone

The artesian zone lies between two impermeable formations; Del Rio on top and Glen rose below. The entrance of new water in the aquifer creates pressure on the existing water. Significantly high pressure pushes water onto the ground surface. This creates springs and artesian wells. Examples of such discharges are the Cormal springs and San Marcos Springs. The water users in Bexar County are the reasons why the San Pedro and San Antonio springs are dry most of the time. When the water levels in the aquifer rises, it ignites spring water flow.

How It Works

The system maintains its water balance through the input (recharge) and output (Discharge). The contributing zones collect water then directs it into the recharge zone. The water would then leave the aquifer system in two ways; either as spring discharges or as wells discharge. The Edwards aquifer authority is responsible for ensuring that the recharge and discharge creates a healthy water balance in the aquifer system.

Water Quality

The water from Edward aquifer system is certified as a source of safe drinking water for the over 1 million people. The water has not recorded any incidence of pollution and therefore the quality is rated as high (Todd and Larry n.p). The authority carries out regular testing on water from the aquifer to determine its suitability for use as drinking water. Substances such as the bacteria, pesticides, ions among other potentially harmful materials have always remained below the maximum contaminant level. The presence of dissolved nitrates would not cause scare as they are well below the MCL. The recharge zones of the Aquifer are protected by various organizations because contaminations from these regions could find their way to the lower regions.

Advantages of the System

Over 1.7 million people rely on the aquifer for their livelihood. San Antonio and Austin cities rely on their system for their industrial, domestic and municipal use. The system is used hugely by farmers for irrigation purposes and other industries (McCarl 1257). The economic practices in the area put pressure on the water level in the aquifer leading to salinity. The deposits of natural salts in the area affect the quality of water in the system.


As a natural resource, the system needs preservation to ensure it serves the future generations. This study shows that the system has influenced many lives and has benefitted millions of people. The government through the authority should ensure that it is well taken care of and protected.




Works Cited

Barker, René A., and Ann F. Ardis. The hydrogeological framework of the Edwards-Trinity aquifer system, west-central Texas. No. 1421-B. USGPO, 1996.

Maclay, Robert W. Geology, and hydrology of the Edwards Aquifer in the San Antonio area, Texas. No. 95-4186. US Geological Survey, 1995.

Maclay, Robert W., and Ted A. Small. Carbonate geology and hydrology of the Edwards aquifer in the San Antonio area, Texas. No. 83-537. US Geological Survey, 1984.

McCarl, Bruce A., et al. “Limiting pumping from the Edwards Aquifer: an economic investigation of proposals, water markets, and spring flow guarantees.” Water Resources Research 35.4 (1999): 1257-1268.

Scanlon, Bridget R., et al. “Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Case study, Barton Springs Edwards aquifer, USA.” Journal of Hydrology 276.1 (2003): 137-158.

Todd, David K., and Larry W. Mays. Groundwater hydrology edition. Vol. 1625. Hoboken, NJ: Wiley, 2005.