8/20/25 – Everyone understands the need for financial audits; they prevent fraud. But what about performance audits? They can prevent waste. Yet how many government agencies routinely audit the implementation of plans they adopt?
Vermont Failed to Implement Half of Priorities in Emergency Plan
In Vermont last year, the state audited its performance in achieving its five-year hazard-mitigation plan. According to the Associated Press story, the plan is developed by Vermont Emergency Management every five years to identify natural hazards facing the state and take steps to reduce risk, including flooding risk.
But an audit released last year after a major flood found that only a third of the 96 actions, and half of the priority actions in the 2018 plan had been completed. Had flood-mitigation measures been completed in a timely manner, the audit says, communities affected by the floods would have been better able to withstand them.
State lawmakers said they were gravely concerned over the lack of progress. “The findings in this report are shocking and deeply troubling,” one said.
The director of the State’s Emergency Management Department called the plan “aspirational.”
But the audit focused on missed opportunities that could have lessened the severity of the floods, such as improved building codes, that would have helped communities recover faster. That sounds pretty practical to me.
Improved Harris County Building Codes Reduced Flood Damage 20X
A study by a former Harris County Engineer John Blount found subdivisions built to new, higher building codes before Hurricane Harvey experienced 20 times less damage than those that weren’t. Building codes are updated internationally every year, but Texas last updated its building codes in 2021.
New Floodplain Maps Years Past Due
Everyone agrees on the need for updated flood maps based on Atlas 14. But Harris County’s are years behind schedule. And some counties still base their flood maps on data acquired in the 1980s. In the meantime, people keep building and buying in floodplains based on outdated information. And one in every five Texans lives in a floodplain. Are we creating the conditions for future disasters?
Plans Without Financial Pathways
Why do we continually build plans that are not actionable? That are so long, no one can read or remember them?
We spent seven years building a state flood plan. It has a $54.5 billion price tag. But since 2019, the state legislature has allocated only $1.4 billion to the state’s Flood Infrastructure Fund.
Houston’s Resilience Plan? Just five years after its introduction, it’s now a maze of dead links and appears to have virtually disappeared from the web.
Harris County’s Flood Bond? Eight years into a ten year plan that’s 40% complete, HCFCD’s executive director claims they are $1.3 billion short already, but has been trying for months to explain why.
Ike Dike? Hurricane Ike struck Houston in 2008. Congress approved the project in 2022. The Corps estimated the cost at $57 billion in 2023. TWDB is still studying ways to break it down into bite sized chunks.
Flood Tunnels? In 2022, HCFCD produced a 1,860 page study projecting the cost for eight to be $30 billion. We’re still studying pilot projects on that one.
In the summer of 2020, the San Jacinto River Authority, City of Houston, Montgomery County and Harris County Flood Control District released a 3,600 page study about how to reduce flooding in the San Jacinto River Basin. At the time, it had a $3.3 billion price tag. So far, the partners have not constructed one recommendation.
Harvey Flood. Photo by Sally Geis.
We Need More of a Business Mentality in Government
In my opinion, we need less nonsense and more commonsense. Who would accept a position with a job description that’s 3,600 pages long? Or a monumental list of deliverables without any budget?
It’s good to dream. But we need government leaders who know how to produce results on a budget. Just like business leaders do.
I’d rather see one project in construction than a hundred sitting on a credenza.
Bob Rehak
Perhaps performance auditors can help us turn that around.
Posted by Bob Rehak on 8/20/25
2913 Days since Hurricane Harvey and 6183 since Ike
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/09/20170829-IMG_5756.jpg?fit=1200%2C800&ssl=18001200adminadmin2025-08-20 21:43:182025-08-21 08:35:12Need for Performance Audits To Ensure Timely Flood-Plan Implementation
8/18/25 – The Montgomery County (MoCo) water war has produced a number of unintended casualties in the last decade. They include:
Water ratepayers
Flood victims
Conroe’s reputation as the fastest growing large city in America
Developers
Area infrastructure
Homeowners living near fault lines
Neighbors in Harris County
Groundwater storage capacity to help the area bridge droughts
Science
Unfortunately, those who profited from excessive groundwater withdrawals aren’t the ones paying the price.
Subsidence problems in southern Montgomery County – once thought to be solved by the San Jacinto River Authority’s (SJRA) Groundwater Reduction Plan (GRP) – have recurred. And despite settlement of a long running lawsuit on 8/14/25, there’s still plenty of hurt to go around.
How It All Started
To comply with the Lone Star Groundwater Conservation District‘s (LSGCD) rules to reduce groundwater pumping in Montgomery County, the San Jacinto River Authority (SJRA) introduced its Groundwater Reduction Plan (GRP) in 2009. The plan addressed the need to ensure adequate water supply for the county’s rapidly growing population using surface water from Lake Conroe.
The LSGCD’s rules, adopted in 2006, mandated a 30% reduction in overall groundwater pumping. In 2010, LSGCD also capped groundwater use, starting in 2016, at 64,000 acre-feet per year.
That gave the SJRA time to sell bonds, complete a half-billion dollar surface-water-treatment plant at Lake Conroe, and build a 55-mile pipeline-distribution system.
Then, the water war erupted.
Defectors Undermine Success
When water rates went up to pay for surface water, the City of Conroe, City of Magnolia, Quadvest, and Woodlands Oaks sued to get out of their GRP contracts. That, in turn, led to:
Conroe’s nine-year legal battle that made several round trips to the Texas Supreme Court.
Rate increases on participants still in the plan to make up for shortfalls created by those who left it.
Legal and fiscal uncertainty that burdened other GRP participants left covering shortfalls caused by the non-paying entities.
Uncertainty about the ability to service debt on bonds.
Significant legal fees affecting both sides, including water ratepayers.
Subsidence: Briefly Halted
Ironically, all this happened as the groundwater reduction plan started to reduce subsidence. Areas in The Woodlands that had subsided consistently for years saw subsidence virtually level off. But the success was brief.
Subsidence in The Woodlands at the monitoring station with the longest history. When surface water became available, subsidence virtually plateaued…until political changes at the LSGCD.
The leveling off lasted between three and four years. Then subsidence accelerated again. The trigger this time: politics.
The newly elected board was sworn in during November, 2018, shortly before the graph above turned down again.
Groundwater Levels Decline with Changes in Groundwater Regulations
The newly elected LSGCD board removed conservation rules from their regulatory plan, leading to a rejection of the plan by the Texas Water Development Board (TWDB). This introduced uncertainty regarding the regulatory framework for groundwater management and the GRP’s role within it.
Several cities disputed the SJRA’s ability to raise rates for surface water. Conroe initially refused to pay a rate increase implemented in 2016, and Magnolia followed suit. The SJRA responded by suing the cities for breach of contract.
These legal challenges created significant financial strain for the SJRA and its other customers. Unpaid fees caused shortfalls that had to be covered by other GRP plan participants. The recent settlement has resolved the dispute between SJRA and Conroe. But legal battles may still continue with others.
Meanwhile, southern Montgomery County has experienced the steepest well declines in the entire region.
From 1977 to 2025, maximum water level decline in the Chicot-Evangeline (undifferentiated) aquifer occurred in The Woodlands where water levels fell more than 400 feet. Likewise, water levels in the Jasper aquifer declined more than 250 feet near The Woodlands during the same time period.
Every water well drilled into those aquifers that USGS monitors in Montgomery County with the exception of two experienced significant water-level declines since the LSGCD board became elected. See below.
As subsidence worsened, so did flooding in many parts of The Woodlands, especially those near streams whose gradients changed and those who lived near down-thrust faults that created bowls in the landscape.
Water Capacity Crunch Led to Development Moratorium
The U.S. Census Bureau rated Conroe the fastest‑growing large city in America for the period from July 1, 2015, to July 1, 2016. However, within several years, Conroe experienced a water-capacity shortfall and imposed a development moratorium (Aug 29, 2024).
TCEQ later approved a temporary reduction in the required water-supply allocation per connection—from 0.60 to 0.46 gpm—so projects could restart under tighter per-lot assumptions. For a year, that pause reportedly stalled plats, permits, and site work citywide.
It even affected large commercial projects. The Conroe Courier reported that Kelsey-Seybold was considering pulling a $24 million medical facility. Construction could not move forward because of concerns about water infrastructure capability.
With the settlement announced last Friday, Conroe has ended the development moratorium for now, but projects must use the TCEQ-approved 0.46 gpm through Feb. 2029. But the City’s plan reviewers will reportedly press for conservation fixtures/phasing until new supply is online.
The Greater Houston Homebuilders Association said the moratorium had had “detrimental effects on every facet of our industry from concrete to roofers, to pools to developers and builders.”
Under the terms of last week’s settlement, SJRA will provide additional water to Conroe. Heather Ramsey of the SJRA said that, “The additional surface water should keep them from using additional groundwater to accommodate their growth.” But in the meantime…
Homes Near Fault Lines Damaged
Deregulation of aquifer groundwater withdrawal in Montgomery County by the LSGCD led to declines in area water wells.
As Conroe and surrounding areas pumped more and more groundwater, subsidence continued. That triggered geologic faults in The Woodlands, which damaged homes.
Woodlands home split in half when groundwater extraction led to subsidence that activated a fault-line.Steps in front of same house dropped so far, they had to be replaced and are now twice their original height.
It also damaged infrastructure.
Faulting damage exacerbated by subsidence due to excessive groundwater extraction at The Woodlands High School.
Two subsidence experts in The Woodlands gave me a tour of three fault lines. Street after street showed dips, cracks, and storm sewer damage aligned precisely with the fault lines. Some of the repairs reportedly cost hundreds of thousands of dollars.
Many Paid the Price
Excessive groundwater withdrawals are also tilting Lake Houston. The area near the dam is subsiding much slower than the area in the headwaters of the Lake near the Montgomery County Line.
I listed science as the last victim in the water war. At some point during this skirmish, subsidence deniers started trotting out their own studies claiming huge volumes of water from the aquifers above could be produced without adverse consequences.
The loss of groundwater storage capacity due to subsidence will also leave Montgomery County more vulnerable to future droughts. Groundwater backs up surface water supplies. And now there will be less groundwater storage volume.
Someday, this will become a cautionary case study for other areas that think of groundwater as an unlimited resource.
Posted by Bob Rehak on 8/19/25
2912 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2025/08/Subsidence-Plateau.png?fit=1460%2C1092&ssl=110921460adminadmin2025-08-19 21:12:282025-08-22 17:24:10MoCo Water War Leaves Unintended Casualties
8/17/2025 – Three scientists have summarized more than 100 years of studies about the relationship of groundwater and land subsidence in the Houston region. The study’s title: “A Century (1906-2024) of Groundwater and Land Subsidence Studies in Greater Houston Region: A Review.” The review revealed some stunning facts about past groundwater management practices in the Houston area and their implications for the future.
About the Study
The comprehensive 25-page review of scientific literature is essential reading for anyone interested in understanding the history of geologic subsidence in southeast Texas. The review examines its causes, impacts, regulatory remedies, and how it’s measured.
The authors are Michael J, Turco and Ashley Greuter of the Harris-Galveston Subsidence District, and Dr. Guoquan Wang of the University of Houston’s Department of Earth and Atmospheric Sciences. They published their copyrighted article in the July/August 2025 issue of Groundwater on behalf of the National Groundwater Association.
Stunning Facts
In the study, the authors relate some fascinating facts about subsidence in the Houston region. For instance:
Subsidence has impacted approximately 12,000 square kilometers, encompassing nearly all of Harris and Galveston Counties as well as parts of surrounding counties.
This led to the irreversible loss of 12 cubic kilometers of groundwater storage – equivalent to 60 times the volume of Lake Houston.
That equals 8 years worth of water usage for all of Harris and Galveston Counties (at 2023 consumption rates).
That’s significant because groundwater is our backup for surface water during droughts. And who can forget the three-year drought from 2011 to 2013 when you could virtually walk from one side of Lake Houston to the other in many places.
Due to groundwater regulations, the extent of subsidence rates has decreased significantly since 1990. By the early 2020s, the areas seeing subsidence of greater than 1 cm per year had shrunk to one twentieth of the Houston region (1500 square kilometers). And only 50 square kilometers have rates higher than 2 cm/year.
Today, most of the remaining subsidence exists in the fast growing areas to the region’s north and west, which were the last to be regulated.
History of Subsidence in Region
According to Turco et. al., the earliest documented instance of subsidence happened in Baytown’s Goose Creek Oil Field during the 1920s.
From the late 1940s to the mid-1970s, rapid subsidence, occurring at rates of up to a decimeter per year, became increasingly pronounced in the southeastern parts of Houston
Declining groundwater levels (GWLs), driven by rapid industrial expansion, resulted in over 2 meters of subsidence in the area along the Houston Ship Channel from the 1940s to the mid-1970s. By 1979, as much as 3 meters of subsidence had been documented in the Baytown area.
Since the 1990s, as Houston’s population expanded to the north and northwest groundwater pumping triggered subsidence. Areas around Katy, Jersey Village, and The Woodlands experienced subsidence rates of 1 to 3 cm per year as of the early 2020s.
Striking a balance between groundwater resource management, subsidence, urban development, and environmental sustainability is central to the Houston region’s future. The paper explores how regulatory initiatives have influenced current practices and policies as leaders seek to reduce and prevent subsidence.
Evolution of Regulatory Agencies
A large part of the paper deals with how regulatory entities have expanded their geographic scope to keep pace with population growth. The paper includes discussions of:
The Harris-Galveston Subsidence District (HGSD) in 1975
Updates to its groundwater regulatory plan in 1985, 1992, 1999, and 2013
Different regulatory areas within the Houston region
Fort Bend Subsidence District (FBSD) in 1989
Seven additional groundwater conservation districts covering most of the counties in the region.
Evolution of Monitoring Technology
Technology aficionados will appreciate the discussion of techniques used to monitor both groundwater levels and surface subsidence.
HGSD, in cooperation with the U.S. Geological Survey, monitors water levels and pumping rates in 650 wells throughout the region. HCSD also annually monitors groundwater pumpage from all permitted wells within the District (about 7500 wells in 2024).
As more water is extracted, clay layers in the soil become compacted. A former leader of the subsidence district once described it as “squashing a brownie.” Once compacted, it will not return to its former state.
The effects of subsidence are most notable closest to sea level. We can see them in the loss of highways, subdivisions, wetlands, vulnerability to storm surge, and more.
However, even areas a 100 feet or more above sea level can feel the impacts. Differential subsidence can trigger faults, disrupt pipelines, alter the gradient of streams, and create bowls in the landscape that increase flood risk.
Prior to the 1990s, subsidence was tracked through repeated spirit-leveling surveys and extensometers. However, since then, GPS has emerged as the dominant tool for measuring subsidence. It offers greater precision and more efficiency than conventional methods.
HGSD and FBSD operate approximately 114 subsidence measuring stations that use GPS. And they continuously add new stations to areas of interest.
They also use Interferometric Synthetic Aperture Radar (InSAR) to create detailed displacement maps over time. InSAR is especially good at filling in the gaps between the GPS measuring stations to create contour maps.
The scientists also use tidal gages and borehole extensometers to cross-reference data and extend the historical record of subsidence.
Major Discoveries
According to the authors, “Before the 1960s, the connection between groundwater extraction and subsidence was not immediately evident. Other factors, such as oil and gas extraction and local fault activity, were also considered significant contributors.”
They continue, “However, as evidence from ground-water-level measurements grew, and subsidence increasingly led to infrastructure damage and altered drainage patterns, it became clear that groundwater withdrawal was the primary driver of land subsidence.”
Oil and gas extraction and fault movement were also considered serious contributors at one time. “However, as evidence from groundwater level measurements grew, and subsidence increasingly led to infrastructure damage and altered drainage patterns, it became clear that groundwater withdrawal was the primary driver of land subsidence,” say the authors.
Another major discovery was that subsidence-induced compaction of the soil has led to the loss of groundwater storage capacity.
“The volume of total land subsidence directly correlates with the loss of groundwater storage capacity,” says the paper. “Groundwater is a crucial backup supply for maintaining water security in large cities, and with decreased storage, the risk of water shortages grows, potentially impacting agricultural productivity, industrial operations, and daily life for residents.”
New Focus on Sustainability
In conclusion, the authors state, “As Houston’s population continues to grow, the increasing demand for water underscores the urgent need for sustainable water sources that extend beyond the current groundwater and surface water capacities. To address this, HGSD, FBSD, and GCDs are intensifying efforts in water conservation and exploring alternative water solutions, actively engaging local stakeholders.”
Need for Performance Audits To Ensure Timely Flood-Plan Implementation
8/20/25 – Everyone understands the need for financial audits; they prevent fraud. But what about performance audits? They can prevent waste. Yet how many government agencies routinely audit the implementation of plans they adopt?
Vermont Failed to Implement Half of Priorities in Emergency Plan
In Vermont last year, the state audited its performance in achieving its five-year hazard-mitigation plan. According to the Associated Press story, the plan is developed by Vermont Emergency Management every five years to identify natural hazards facing the state and take steps to reduce risk, including flooding risk.
But an audit released last year after a major flood found that only a third of the 96 actions, and half of the priority actions in the 2018 plan had been completed. Had flood-mitigation measures been completed in a timely manner, the audit says, communities affected by the floods would have been better able to withstand them.
State lawmakers said they were gravely concerned over the lack of progress. “The findings in this report are shocking and deeply troubling,” one said.
The director of the State’s Emergency Management Department called the plan “aspirational.”
But the audit focused on missed opportunities that could have lessened the severity of the floods, such as improved building codes, that would have helped communities recover faster. That sounds pretty practical to me.
Improved Harris County Building Codes Reduced Flood Damage 20X
A study by a former Harris County Engineer John Blount found subdivisions built to new, higher building codes before Hurricane Harvey experienced 20 times less damage than those that weren’t. Building codes are updated internationally every year, but Texas last updated its building codes in 2021.
New Floodplain Maps Years Past Due
Everyone agrees on the need for updated flood maps based on Atlas 14. But Harris County’s are years behind schedule. And some counties still base their flood maps on data acquired in the 1980s. In the meantime, people keep building and buying in floodplains based on outdated information. And one in every five Texans lives in a floodplain. Are we creating the conditions for future disasters?
Plans Without Financial Pathways
Why do we continually build plans that are not actionable? That are so long, no one can read or remember them?
We Need More of a Business Mentality in Government
In my opinion, we need less nonsense and more commonsense. Who would accept a position with a job description that’s 3,600 pages long? Or a monumental list of deliverables without any budget?
It’s good to dream. But we need government leaders who know how to produce results on a budget. Just like business leaders do.
Perhaps performance auditors can help us turn that around.
Posted by Bob Rehak on 8/20/25
2913 Days since Hurricane Harvey and 6183 since Ike
MoCo Water War Leaves Unintended Casualties
8/18/25 – The Montgomery County (MoCo) water war has produced a number of unintended casualties in the last decade. They include:
Unfortunately, those who profited from excessive groundwater withdrawals aren’t the ones paying the price.
Subsidence problems in southern Montgomery County – once thought to be solved by the San Jacinto River Authority’s (SJRA) Groundwater Reduction Plan (GRP) – have recurred. And despite settlement of a long running lawsuit on 8/14/25, there’s still plenty of hurt to go around.
How It All Started
To comply with the Lone Star Groundwater Conservation District‘s (LSGCD) rules to reduce groundwater pumping in Montgomery County, the San Jacinto River Authority (SJRA) introduced its Groundwater Reduction Plan (GRP) in 2009. The plan addressed the need to ensure adequate water supply for the county’s rapidly growing population using surface water from Lake Conroe.
The LSGCD’s rules, adopted in 2006, mandated a 30% reduction in overall groundwater pumping. In 2010, LSGCD also capped groundwater use, starting in 2016, at 64,000 acre-feet per year.
That gave the SJRA time to sell bonds, complete a half-billion dollar surface-water-treatment plant at Lake Conroe, and build a 55-mile pipeline-distribution system.
Then, the water war erupted.
Defectors Undermine Success
When water rates went up to pay for surface water, the City of Conroe, City of Magnolia, Quadvest, and Woodlands Oaks sued to get out of their GRP contracts. That, in turn, led to:
Subsidence: Briefly Halted
Ironically, all this happened as the groundwater reduction plan started to reduce subsidence. Areas in The Woodlands that had subsided consistently for years saw subsidence virtually level off. But the success was brief.
The leveling off lasted between three and four years. Then subsidence accelerated again. The trigger this time: politics.
A movement to make the LSGCD board elected rather than appointed opened the door for privately held groundwater providers. They backed a slate of candidates that favored pumping cheaper groundwater. And the groundwater pumpers won. Soon thereafter, unrestricted groundwater pumping resumed.
The newly elected board was sworn in during November, 2018, shortly before the graph above turned down again.
Groundwater Levels Decline with Changes in Groundwater Regulations
The newly elected LSGCD board removed conservation rules from their regulatory plan, leading to a rejection of the plan by the Texas Water Development Board (TWDB). This introduced uncertainty regarding the regulatory framework for groundwater management and the GRP’s role within it.
The protracted legal battles, settled last Thursday, centered on the validity and enforceability of GRP contracts and the fees charged for surface water.
Several cities disputed the SJRA’s ability to raise rates for surface water. Conroe initially refused to pay a rate increase implemented in 2016, and Magnolia followed suit. The SJRA responded by suing the cities for breach of contract.
These legal challenges created significant financial strain for the SJRA and its other customers. Unpaid fees caused shortfalls that had to be covered by other GRP plan participants. The recent settlement has resolved the dispute between SJRA and Conroe. But legal battles may still continue with others.
Meanwhile, southern Montgomery County has experienced the steepest well declines in the entire region.
From 1977 to 2025, maximum water level decline in the Chicot-Evangeline (undifferentiated) aquifer occurred in The Woodlands where water levels fell more than 400 feet. Likewise, water levels in the Jasper aquifer declined more than 250 feet near The Woodlands during the same time period.
Every water well drilled into those aquifers that USGS monitors in Montgomery County with the exception of two experienced significant water-level declines since the LSGCD board became elected. See below.
Clearly, the trend is not sustainable.
Flooding Worsened
As subsidence worsened, so did flooding in many parts of The Woodlands, especially those near streams whose gradients changed and those who lived near down-thrust faults that created bowls in the landscape.
Water Capacity Crunch Led to Development Moratorium
The U.S. Census Bureau rated Conroe the fastest‑growing large city in America for the period from July 1, 2015, to July 1, 2016. However, within several years, Conroe experienced a water-capacity shortfall and imposed a development moratorium (Aug 29, 2024).
TCEQ later approved a temporary reduction in the required water-supply allocation per connection—from 0.60 to 0.46 gpm—so projects could restart under tighter per-lot assumptions. For a year, that pause reportedly stalled plats, permits, and site work citywide.
It even affected large commercial projects. The Conroe Courier reported that Kelsey-Seybold was considering pulling a $24 million medical facility. Construction could not move forward because of concerns about water infrastructure capability.
With the settlement announced last Friday, Conroe has ended the development moratorium for now, but projects must use the TCEQ-approved 0.46 gpm through Feb. 2029. But the City’s plan reviewers will reportedly press for conservation fixtures/phasing until new supply is online.
The Greater Houston Homebuilders Association said the moratorium had had “detrimental effects on every facet of our industry from concrete to roofers, to pools to developers and builders.”
Under the terms of last week’s settlement, SJRA will provide additional water to Conroe. Heather Ramsey of the SJRA said that, “The additional surface water should keep them from using additional groundwater to accommodate their growth.” But in the meantime…
Homes Near Fault Lines Damaged
Deregulation of aquifer groundwater withdrawal in Montgomery County by the LSGCD led to declines in area water wells.
As Conroe and surrounding areas pumped more and more groundwater, subsidence continued. That triggered geologic faults in The Woodlands, which damaged homes.
It also damaged infrastructure.
Two subsidence experts in The Woodlands gave me a tour of three fault lines. Street after street showed dips, cracks, and storm sewer damage aligned precisely with the fault lines. Some of the repairs reportedly cost hundreds of thousands of dollars.
Many Paid the Price
Excessive groundwater withdrawals are also tilting Lake Houston. The area near the dam is subsiding much slower than the area in the headwaters of the Lake near the Montgomery County Line.
I listed science as the last victim in the water war. At some point during this skirmish, subsidence deniers started trotting out their own studies claiming huge volumes of water from the aquifers above could be produced without adverse consequences.
The loss of groundwater storage capacity due to subsidence will also leave Montgomery County more vulnerable to future droughts. Groundwater backs up surface water supplies. And now there will be less groundwater storage volume.
Someday, this will become a cautionary case study for other areas that think of groundwater as an unlimited resource.
Posted by Bob Rehak on 8/19/25
2912 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.
Houston-Region Groundwater, Subsidence Studies Reveal Stunning Facts
8/17/2025 – Three scientists have summarized more than 100 years of studies about the relationship of groundwater and land subsidence in the Houston region. The study’s title: “A Century (1906-2024) of Groundwater and Land Subsidence Studies in Greater Houston Region: A Review.” The review revealed some stunning facts about past groundwater management practices in the Houston area and their implications for the future.
About the Study
The comprehensive 25-page review of scientific literature is essential reading for anyone interested in understanding the history of geologic subsidence in southeast Texas. The review examines its causes, impacts, regulatory remedies, and how it’s measured.
The authors are Michael J, Turco and Ashley Greuter of the Harris-Galveston Subsidence District, and Dr. Guoquan Wang of the University of Houston’s Department of Earth and Atmospheric Sciences. They published their copyrighted article in the July/August 2025 issue of Groundwater on behalf of the National Groundwater Association.
Stunning Facts
In the study, the authors relate some fascinating facts about subsidence in the Houston region. For instance:
That’s significant because groundwater is our backup for surface water during droughts. And who can forget the three-year drought from 2011 to 2013 when you could virtually walk from one side of Lake Houston to the other in many places.
Due to groundwater regulations, the extent of subsidence rates has decreased significantly since 1990. By the early 2020s, the areas seeing subsidence of greater than 1 cm per year had shrunk to one twentieth of the Houston region (1500 square kilometers). And only 50 square kilometers have rates higher than 2 cm/year.
Today, most of the remaining subsidence exists in the fast growing areas to the region’s north and west, which were the last to be regulated.
History of Subsidence in Region
According to Turco et. al., the earliest documented instance of subsidence happened in Baytown’s Goose Creek Oil Field during the 1920s.
From the late 1940s to the mid-1970s, rapid subsidence, occurring at rates of up to a decimeter per year, became increasingly pronounced in the southeastern parts of Houston
Declining groundwater levels (GWLs), driven by rapid industrial expansion, resulted in over 2 meters of subsidence in the area along the Houston Ship Channel from the 1940s to the mid-1970s. By 1979, as much as 3 meters of subsidence had been documented in the Baytown area.
Since the 1990s, as Houston’s population expanded to the north and northwest groundwater pumping triggered subsidence. Areas around Katy, Jersey Village, and The Woodlands experienced subsidence rates of 1 to 3 cm per year as of the early 2020s.
Striking a balance between groundwater resource management, subsidence, urban development, and environmental sustainability is central to the Houston region’s future. The paper explores how regulatory initiatives have influenced current practices and policies as leaders seek to reduce and prevent subsidence.
Evolution of Regulatory Agencies
A large part of the paper deals with how regulatory entities have expanded their geographic scope to keep pace with population growth. The paper includes discussions of:
Evolution of Monitoring Technology
Technology aficionados will appreciate the discussion of techniques used to monitor both groundwater levels and surface subsidence.
HGSD, in cooperation with the U.S. Geological Survey, monitors water levels and pumping rates in 650 wells throughout the region. HCSD also annually monitors groundwater pumpage from all permitted wells within the District (about 7500 wells in 2024).
As more water is extracted, clay layers in the soil become compacted. A former leader of the subsidence district once described it as “squashing a brownie.” Once compacted, it will not return to its former state.
The effects of subsidence are most notable closest to sea level. We can see them in the loss of highways, subdivisions, wetlands, vulnerability to storm surge, and more.
However, even areas a 100 feet or more above sea level can feel the impacts. Differential subsidence can trigger faults, disrupt pipelines, alter the gradient of streams, and create bowls in the landscape that increase flood risk.
Prior to the 1990s, subsidence was tracked through repeated spirit-leveling surveys and extensometers. However, since then, GPS has emerged as the dominant tool for measuring subsidence. It offers greater precision and more efficiency than conventional methods.
HGSD and FBSD operate approximately 114 subsidence measuring stations that use GPS. And they continuously add new stations to areas of interest.
They also use Interferometric Synthetic Aperture Radar (InSAR) to create detailed displacement maps over time. InSAR is especially good at filling in the gaps between the GPS measuring stations to create contour maps.
The scientists also use tidal gages and borehole extensometers to cross-reference data and extend the historical record of subsidence.
Major Discoveries
According to the authors, “Before the 1960s, the connection between groundwater extraction and subsidence was not immediately evident. Other factors, such as oil and gas extraction and local fault activity, were also considered significant contributors.”
They continue, “However, as evidence from ground-water-level measurements grew, and subsidence increasingly led to infrastructure damage and altered drainage patterns, it became clear that groundwater withdrawal was the primary driver of land subsidence.”
Oil and gas extraction and fault movement were also considered serious contributors at one time. “However, as evidence from groundwater level measurements grew, and subsidence increasingly led to infrastructure damage and altered drainage patterns, it became clear that groundwater withdrawal was the primary driver of land subsidence,” say the authors.
Another major discovery was that subsidence-induced compaction of the soil has led to the loss of groundwater storage capacity.
“The volume of total land subsidence directly correlates with the loss of groundwater storage capacity,” says the paper. “Groundwater is a crucial backup supply for maintaining water security in large cities, and with decreased storage, the risk of water shortages grows, potentially impacting agricultural productivity, industrial operations, and daily life for residents.”
New Focus on Sustainability
In conclusion, the authors state, “As Houston’s population continues to grow, the increasing demand for water underscores the urgent need for sustainable water sources that extend beyond the current groundwater and surface water capacities. To address this, HGSD, FBSD, and GCDs are intensifying efforts in water conservation and exploring alternative water solutions, actively engaging local stakeholders.”
Posted by Bob Rehak on 8/17/25
2910 Days since Hurricane Harvey