This document summarizes a paper analyzing land subsidence due to groundwater and oil/gas extraction in the greater Houston area. It divides the area into 5 cases and discusses the key factors contributing to subsidence in each region, such as the presence of oil/gas fields, population density, and regulatory policies. Subsidence rates vary significantly between regions, from only 1.5 feet in Case 1 to over 5 feet in Case 5. Many policies have been implemented since the 1970s to limit groundwater use and mitigate subsidence, including the establishment of subsidence districts and requirements for groundwater extraction to not exceed a percentage of total water demand.

1. Topographical Subsidence Due To
Groundwater and Oil/Gas Extraction
in the Greater Houston Area
.
Aaron Munsart
GEOS 410-900
May 4, 2015

2. 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.

3. 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/regions
Case 5
Case 1 Case 2
Case 3
Case 4
Case 5
Figure 2. Subsidence mapped in
the Houston area; 1906-1987
(Harris-Galveston Subsidence
District)

4. 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

5. 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 1
Case 2
Case 3
Case 4
Case 5

6. 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)

7. 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

8. 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

9. 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

10. 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.

11. 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.

12. 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

13. 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

14. 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.

15. 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.

16. 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.