Topographical Subsidence Due To

Groundwater and Oil/Gas Extraction

in the Greater Houston Area

.

Aaron Munsart

GEOS 410-900

May 4, 2015

Introduction

Access to clean drinking water has grown to be one of the world’s most important

problems. As the world begins to slowly run out of water, new unsustainable resources will be

tapped to ensure the longevity of humans on this planet. Groundwater, currently, is an important

supply of water worldwide mainly because it is easily distribution. The pumping of groundwater

in the Houston area began in the 1890’s and has rapidly increased in quantity since. Houston has

two main aquifers that supply groundwater to the region: the Chicot Aquifer and the Evangeline

Aquifer.

Although groundwater has characteristics that make it attractive, it also has those that

cause fairly devastating impacts in some places within Houston. Groundwater has many micro

and macromolecules in it that make it very beneficial for people. The pumping and use of

groundwater does not require any expensive purification or treatment processes and the majority

of the resources are well protected from contamination.

Subsidence is not just an anthropogenic process. It also occurs naturally at a speed of

roughly 0.05mm per year. Humans have participated in processes that have enabled that rate to

climb to heights as much as 440 times the natural background rate (Paine 1991). Since 1943,

244,900 hectares of land has subsided on average 30cm, mostly occurring near Galveston Bay.

This increased level of subsidence has resulted in both urban and environmental pressures such

as flooding, expansion of clay sediments, wetland loss, and damage to infrastructure. The

Houston area is an excellent location for a case study in land subsidence because it is a semi-arid

region with high variability in precipitation levels, rapid population growth and thus high

demand for drinking water, diverse and vulnerable ecosystems highly depending on aquifer

functionality, and finally the monitoring/reporting of groundwater extraction by government as

well as private organizations is arguably the most accurate in the United States. In 1975,

estimated costs of land subsidence due to groundwater extraction had reached an astounding $32

million annually. Since 1975, Houston has implemented many different policies and districts to

ensure the protection of groundwater resources and to limit the rapid expansion of land

subsidence. The Fort Bend and Harris-Galveston Subsidence Districts currently monitor and

implement solutions to mitigate this problem.

Case 1 Case 2

Case 3 Case 4

Water is used in virtually every aspect of human life on a daily basis. It is used

commercially, residentially, industrially, and by municipalities. This paper will focus primarily

on the industrial and commercial use of groundwater in the Houston area. I will assess the each

of the four regions in the Houston area by illustrating the impacts of groundwater removal and

the parties participating in it. I will discuss the current social and political policies in place to

ensure the protection of this resource in each region as well as give a recommendation toward a

policy if none exists.

Figure 1. Divisions of the Houston area into its respective

cases/regionsCase 5

Case 1 Case 2

Case 3 Case 4

Case 5Figure 2. Subsidence mapped in

the Houston area; 1906-1987 (Harris-Galveston Subsidence

District)

Process

The city of Houston, TX has experienced high levels of subsidence due to oil/gas and

water extraction for the last 100 years. Seasonal precipitation variability, specifically drought, is

a very important factor that exacerbates the growing problem of land subsidence. Houston

contains all the necessary factors to ensure a high rate of subsidence through agriculture,

industry, and an every growing population as well as a highly complex relationship between

groundwater and the environment. Houston has both wet and dry regions and the regions’

variability with precipitation further ensures this variability and thus the complexity of their

relationships. This method of analyzing case studies is typically used on sparsely vegetated urban

areas; however, Houston is a highly vegetated in comparison to other density populated cities in

the United States. Subsidence is a regional problem; therefore, each region must be looked at

separately to analyze key differences and determine what causes that regions subsidence. The list

of reasons subsidence can occur is short but the variability between regions is high which is why

a case study dividing Houston into 5 different regions is used.

Case 1: North-West Harris County

The north-west region of Houston is characterized by mostly residential and commercial

areas with a distinct lack of heavy industry in comparison to east and south-east parts of

Houston. These residential and commercial areas do not require nearly the amount of water that

other regions of Houston require to operate. This region of Houston also lacks the presence of an

oil production field. Oil production fields in Houston have been linked to several cases of

subsidence and the activation of faults. The region has remained highly vegetated with little to no

effect on karst processes and little to no decrease in river runoff. Land subsidence in this region

is estimated to be only 1.5 feet from1906-1987, according to Figure 2. Subsidence bowls in

north-west and west Houston are known to cause [2 - 4+] cm/year of topographical dip.

Subsidence also occurs along the North Point fault, but due to a different process. Subsidence is

a relatively widespread problem; a term typically used to describe a general broad expanse of an

area. Subsidence along a fault is generally very high over a small spatial distance and is known

as differential subsidence. There are reduced levels of subsidence directly on the fault plane

because the fault itself acts as a hydrologic boundary. Differential subsidence levels of 1cm per

0.1km were measured at the North Point fault (Buckley et al. 2003). The most likely cause of

land subduction in this region is due to aquifer compaction driven by dominant regional forces

such as a decreases level of groundwater extraction in comparison to other regions within

Houston.

Figure 3. Map of Oil/Gas Fields throughout the Houston area (Holtzer & Bluntzer 1984)

Case 1Case 2

Case 3

Case 4

Case 5

Case 2: North-East Harris County

North-east Harris County is characterized by an abundance of oil fields and industrial

complexes that contribute to make up the 2nd highest subsidence rates within the city of Houston.

Nine oil and gas fields are present within this region. Of these nine oil fields, four of them are

present within a relatively high density rate of subsidence centered around the Cedar Bayou oil

field estimated at 5.5ft as of 1987. Although the subsidence rates here are high, differential

subsidence remains low. This means that the rate of subsidence at cedar bayou and barbers hill

were lower in comparison to the surrounding areas. These oil fields are located within close

Table 1. Subsidence associated with oil/gas fields throughout the Houston area corresponding with

Figure 3 (Holtzer & Bluntzer 1984)

proximity to the largest subsidence bowl in Houston at the Goose Creek oil field in Baytown, Tx

and therefore explained by this and a history of faulting in the area. The abundance of oil and gas

fields in this region illustrate the paramount theme of Harris County as hydrocarbon production.

Here, groundwater and oil extraction results in sediment compaction and topographic subsidence

as a result but these adverse effects may not negatively affect the aquifer as a whole. The Chicot

and Evangeline Aquifers within Houston act as a confined aquifer cut off from most recharge.

The vast majority of recharge for these aquifers comes as a result of precipitation north of

Houston nearby Austin County. Since the aquifer cannot recharge itself and it is confined, it may

not subside in some places like Anahuac for instance. Today, this high rate of subsidence has

been severely decreased due to the utilization of surface water since the 1970’s. The majority of

oil field locations in this region exhibit faulting as a result of the high volume and practices used

in oil/gas extraction.

Case 3: Fort Bend County

This region has not exhibited subsidence rates as high as Harris County. Fort Bend

County has more agricultural influence on Houston in comparison to Harris County and less

industrial complexes. Fort Bend County has experienced subsidence rates as high as 4 feet, less

than half that of Harris County. The few (3) amount of oil and gas fields located in this region

can account for the moderate subsidence rates. The Fort Bend Subsidence District manages and

implements various policies to ensure the protection of groundwater within their district. They

place paramount importance on “alternative water supplies”. “It is a requirement that any

alternative water supply not cause groundwater level decline or subsidence in Fort Bend

County.”(Fort Bend Subsidence District’s Regulatory Plan) Although subsidence is not a

relatively large problem in in this region, the county and its subsidence district maintain

groundwater at appropriate levels to not cause harm to the surrounding environment because

they recognize that it could be a problem going into the future if left unnoticed.

Case 4: South-East Harris County and Galveston County

By far, this region represents the bulk of high density subsidence within the Houston

area. Focusing on the Goose Creek Oil Field in Baytown, TX: This oil field exhibits a regional

subsidence rate of two feet in 1978 and nine feet by 1987 according to Figure 2 and 3. Land

subsidence and the activation of faults has occurred here since 1918. There are 240 km of active

faults in Harris and Galveston Counties caused primarily by oil and gas extraction. These faults

coincide with hydrocarbon production fields (Kreitler 1976). In 2003, this area continued to

experience subsidence of 3cm/year (Buckley et al. 2003). In the mid 1920’s, subsidence in this

area at about 3 feet was enough to convert part of the land regime to an open water regime.

Dickinson-Gillock Oil Field in Texas City, TX: Second in intensity of subsidence rate to

Goose Creek, this oil field represents an almost identical situation. The Dickinson-Gillock field

has a subsidence rate estimated at 5 feet. This field and Goose Creek both focus primarily on the

oil refining industry, oil/gas extraction, and water extraction needed in other industrial processes

in the surrounding areas. “According to the Galveston Bay National Estuary Program, there has

been a net loss of 9,960 hectares of estuarine bay marshes due to subsidence followed by a

regional landward advance of the ocean (Zektser et al. 2004).” This high density loss of wetlands

further exacerbates the problem of land subsidence by causing more social/environmental issues.

Since the ocean has advanced onto the shore, a number of new negative impacts can now occur

such as seawater intrusion into the aquifer causing contamination, more damage to infrastructure,

loss of environment for animals within that niche, and loss of property for residential and

commercial areas situated close to the shoreline. Also, the advance of the ocean results in

increased beach erosion. This is a very big problem in Galveston where hurricanes resulting in

tides of 5-6 meters above sea level hit the Texas coast once every ten years (Gabrysch; USGS

1976) Wetland loss due to oil, natural gas, and water extraction has also occurred at the Goose

Creek oil field but not in as high an intensity as many areas in Galveston County.

Other oil fields exist in this region such as the Webster, Franks, and Clear Lake oil fields.

Although these do not result in as high of subsidence rates, they do cause the similar problems

such as increased flooding primarily at Clear Lake and Webster. Both of these areas in the region

are only 16 feet above sea level. According to Figure 2, the region has experienced an average

subsidence rate of 5 feet from 1906-1987. If that rate were to continue, the Clear Lake and

Webster areas could have potentially been under water by the year 2166, only 150 from now.

Thankfully, the subsidence levels here have decreased substantially due to the increased use of

surface waters.

Case 5: Central Houston/Harris County

Although this region has one of the lowest number of oil/gas extraction fields, it has the highest

overall average subsidence rate of about 5.5 feet. Although numerous studies have been made on

the surrounding areas of Houston were oil/gas extraction is at its highest, little scientific insight

exists as to why subsidence in this region is so high. From a social standpoint however, the

answer is fairly simple. Population density is highest in this region; therefore, the necessity for

potable water in this region is the highest. Groundwater extraction would have happened here

first as close to this region as possible until the providers had to move outwards from the city

center to find more water and thus the city began to expand. It is one explanation for urban

sprawl. There is little vegetation here, so there is relatively no harm to the environment being

done at this location, but that doesn’t mean that it is not responsible for environmental

harm/change elsewhere.

Policy Issues Arising

As previously stated in the introduction, the Chicot and Evangeline Aquifers supply

much of the groundwater to the city of Houston and surrounding areas. Groundwater withdrawal

in the Chicot estimates at 103 cubic feet per second and in the Evangeline, it is 529 cubic feet per

second. Five times more groundwater is being pumped out of the Evangeline than the Chicot

Aquifer while the net flow into the Evangeline is only 14.8 cubic feet per second. It is a miracle

that this aquifer doesn’t completely run dry or maybe it is just policy. Today, many policies

established by the Harris-Galveston and Fort Bend Subsidence Districts exist to ensure these

aquifers don’t run dry, the protection of water infrastructure, the protection of the environment,

and urban setting. In 1975, subsidence reached a 13 foot maximum and caused the intrusion of

sea water onto coastal lands and various flooding problems throughout the Houston area. Since

1976, the implementation of policies to limit groundwater extraction have been very successful

using a practice known as “artificial recharge” (Zektser et al. 2004). This ideology was kicked

off through the use of extensometer measurements to correlate a direct relationship between

groundwater extraction and subsidence.

Throughout the mid and late 20th century, the state utilized monitoring and reporting

practices to inform the public of the every growing subsidence problems occurring in Houston.

Over the last 25 years, the state has established subsidence districts and policies to ensure those

problems do not continue. One could almost say that we as Houstonians have successfully

mitigated our losses to a point.

One point that the policies haven’t really covered, is the use of groundwater by the

industrial sector. Although a lot of policies exist to encourage the use of surface water instead of

groundwater, they are not mandatory in some areas. In 2014, Houston established its new Water

Conservation Plan that called on its people to use 1 less gallon of water per day within 5 years. In

2013, the State Water Implementation Fund (SWIFT) lowered the cost of financing water

infrastructure projects. Every year, commercial and residential homes are being matched with

more efficient bathroom and kitchen fixtures that use less water. Numerous conservation

districts, subsidence districts and organizations exist to inform the public about problems of

subsidence and groundwater extraction such as the Texas Water Conservation Society, the Texas

Living Waters Project, the Texas Water Foundation, the Texas Alliance for Water Conservation,

and the list goes on.

The resources to protect groundwater are there and the city of Houston has successfully

used them and implemented them to better protect all water resources in Houston and in the

greater state of Texas. When it comes down to it though, groundwater in Texas is based on

Riparian Doctrine. Groundwater belongs to the owners of the land above it and may use/sold as

private property (Texas Water Law). It is the responsibility of the individual to ensure that

subsidence doesn’t continue to be a growing problem.

Case 1 Regulatory Policies (Harris-Galveston Subsidence District):

1. Groundwater extraction must not exceed 10% of individual’s total water demand.

2. A fee will be applied if condition one is not met.

Case 2 and 5 Regulatory Policies (Harris-Galveston Subsidence District):

1. Groundwater extraction must not exceed 20% of individual’s total water demand.

2. A fee will be applied if condition one is not met.

Case 4 Regulatory Policies (Harris-Galveston Subsidence District):

1. Groundwater extraction must not exceed 20% of individual’s total water demand

unless the individual has a specific certification.

Figure 4. Regulatory areas defined by Harris-Galveston County Subsidence District

Case 1

Case 2

Case 3

Case 4

Case 5

2. An individual may submit a Groundwater Reduction Plan if they wish to receive

said certification.

3. Groundwater extraction must not exceed 70% of certified individuals total water

demand.

4. Beginning with certifications in 2025, the certified individual will be required to

reduce groundwater extraction to comprise no more than 40% of total water

demand.

5. Beginning with certifications in 2035, the certified individual will be required to

reduce groundwater extraction to comprise no more than 20% of total water

demand.

Site 3 Regulatory Policies (Fort Bend Subsidence District):

1. Public supply systems are required must account for 85% of groundwater

pumped.

Goals: Efficiently use groundwater, prevent waste of groundwater, prevent

subsidence, manage surface water resources, and address groundwater resource

problems.

Conclusion

Throughout the 20th century, land subsidence due to water and oil/gas extraction was a rapidly

increasing problem. In 1975, the state along with the support of many public organizations took a

stand against subsidence to establish subsidence districts in Houston to mitigate the problem.

Today, those subsidence districts and organizations operate toward the benefit of the

environment to protect groundwater as a resource and halt the rapid expansion of subsidence

throughout the Houston area. They have been extremely successful through their endeavor as

subsidence rates have decreased to only 2 feet and by 2030 that will have decreased to as much

as 1 foot (Neighbors; Harris County Subsidence District).

References

Buckley, Sean M. "Land Subsidence in Houston, Texas, Measured by Radar Interferometry and

Constrained by Extensometers." Journal of Geophysical Research 108.B11 (2003): n. pag.

Google Scholar. Web. 4 May 2015.

Chrismer, William M., David B. Zilkoski, Lucy W. Hall, Gilbert J. Mitchell, Vasanthi Kammula,

Ajit Singh, and Ronald J. Neighbors. "Fourth International Symposium on Land Subsidence

Houston, Texas, USA 12-15 May 1991." GeoJournal 20.4 (1990): 429-30. Harris County

Subsidence District. Web. 4 May 2015.

<http://hgsubsidence.org/wp-content/uploads/2014/07/GPS-Project.pdf>.

"Contents." International Journal of Feminist Approaches to Bioethics 4.1, Special Issue:

Feminist Perspectives on Ethics in Psychiatry (2011): n. pag. Fort Bend County Subsidence

District. 6 Aug. 1998. Web. 4 May 2015.

<http://www.fbsubsidence.org/assets/pdf/FBGWPlan.pdf>.

Gabrysch, R. K. "Land Surface Subsidence in the Houston-Galveston Region, Texas." US

Geological Survey (1976): n. pag. Google Scholar. Web. 4 May 2015.

Holzer, Thomas L., and Robert L. Bluntzer. "Land Subsidence Near Oil and Gas Fields,

Houston, Texasa." Ground Water 22.4 (1984): 450-59. Google Scholar. Web. 4 May 2015.

Kasmarek, Mark C., and Eric W. Strom. "Hydrogeology and Simulation of Ground-Water Flow

and Land-Surface Subsidence in the Chicot and Evangeline Aquifers, Houston Area, Texas."

Gulf Coast Association of Geological Societies Transactions 52 (2002): n. pag. Google Scholar.

Web. 4 May 2015.

Kreitler, Charles W. "Faulting and Land Subsidence from Groundwater and Hydrocarbon

Production, Houston-Galveston, TX." International Association of Hydrological Sciences

(1976): n. pag. Google Scholar. Web. 4 May 2015.

Morton, Robert A., Julie C. Bernier, and John A. Barras. "Evidence of Regional Subsidence and

Associated Interior Wetland Loss Induced by Hydrocarbon Production, Gulf Coast Region,

USA." Environmental Geology 50.2 (2006): 261-74. Google Scholar. Web. 4 May 2015.

Neighbors, Ronald J., GM. "CIGMAT - 2003 Conference & Exhibition." Subsidence in the

Greater Houston Area – Past, Present and Future (n.d.): n. pag. Harris - Galveston Coastal

Subsidence District. Web. <http://www2.egr.uh.edu/~civeb1/CIGMAT/03_present/5.pdf>.

Paine, Jeffrey G. "Subsidence of the Texas Coast: Inferences from Historical and Late

Pleistocene Sea Levels." Tectonophysics 222.3-4 (1993): 445-58. Google Scholar. Web. 4 May

2015.

Regulatory Plan 2013 (2013): n. pag. Harris-Galveston County Subsidence District. 8 May

2013. Web. 4 May 2015. <http://hgsubsidence.org/wp-content/uploads/2013/07/HGSD-2013-

Regulatory-Plan-with-Amendment.pdf>.

"Rules." Harris-Galveston Subsidence District Rules (2013): n. pag. 11 Sept. 2013. Web. 4 May

2015. <http://hgsubsidence.org/wp-content/uploads/2014/11/RULES2013-09-11.pdf>.

Zektser, S., H. A. LoaIciga, and J. T. Wolf. "Environmental Impacts of Groundwater Overdraft:

Selected Case Studies in the Southwestern United States." Environmental Geology 47.3 (2005):

396-404. Google Scholar. Web. 4 May 2015.