Why is groundwater regulated in Harris and Galveston counties?

Back in 1918, areas in the Houston region began to display surficial cracks, which prompted research into what was causing the land to sink. By the 1940s, studies conducted by local universities, the State of Texas, and the United States Geological Survey identified the correlation between groundwater withdrawal and subsidence. Subsidence is the gradual sinking of the Earth’s surface due to substantial, long-term groundwater withdrawals and has been an issue for coastal cities worldwide, including Houston. It has caused damage to roads and bridges, problems with foundations and underground pipelines, changes in drainage patterns, and increased flooding.

With Houston’s booming growth in population, the demand for water increased, and the easiest way to meet this demand was to use groundwater. The increased use of groundwater resulted in hundreds of feet of water-level decline in the Gulf Coast Aquifer System, well infrastructure damage, and aquifer compaction that produced subsidence. Impacts from this subsidence were observed as increased flooding and coastal inundation from devastating storm surges. Local entities began to analyze the severe implications that subsidence could have on potential economic growth and determined that the region needed to reduce its reliance on groundwater to prevent future subsidence.

In 1975, the Texas Legislature created the Harris-Galveston Subsidence District (HGSD) to regulate groundwater withdrawal in Harris and Galveston counties to prevent subsidence. Since then, HGSD has successfully reduced subsidence within its jurisdiction and has become a recognized leader in effective groundwater regulation, subsidence research, and water conservation.

Watch the video to see estimated subsidence from 1906 to 2022, showing the reduction of subsidence since implementing groundwater regulation.

The red contour lines shown above are measured in feet. 

How has HGSD reduced subsidence rates?

HGSD has successfully reduced subsidence rates by implementing a regulatory plan based on the best available groundwater and subsidence data, population and water demand projections, and coordination with regional alternative water providers. This plan divides HGSD’s jurisdiction into three regulatory areas. These areas all have the same goal to prevent subsidence by reducing overall groundwater withdrawal; however, each regulatory area’s groundwater withdrawals will be reduced to a specific percentage of their total water demand by a designated date based on alternative water source availability, geophysical characteristics, and groundwater demand.

  • Area 1: No more than 10% of Total Water Demand (TWD) may be sourced from groundwater.
  • Area 2: No more than 20% of TWD may be sourced from groundwater.
    • A Groundwater Reduction Plan (GRP) may be approved with conditions.
  • Area 3: No more than 20% of TWD may be sourced from groundwater.
    • Permittees operating within an approved GRP have the following requirements:
      • By 2025 – reduce groundwater use to no more than 40% of TWD.
      • By 2035 – reduce groundwater use to no more than 20% of TWD.

Due to Houston’s strong economy and vast business opportunities, the greater Houston area continues to grow, especially in suburban areas. Therefore, HGSD’s regulatory plan is regularly reviewed to account for population growth and evolving water management strategies. HGSD collaborates with local, state, and federal agencies, such as the United States Geological Survey, the Texas Water Development Board, Flood Control Districts, Groundwater Conservation Districts, River Authorities, Regional Water Authorities, and University Research Programs, to obtain the most reliable data. These data are used to improve the understanding of groundwater use and to analyze its impact on aquifer water levels and subsidence.

In areas where HGSD has implemented groundwater regulation, and only a small percentage of the total water demand is supplied by groundwater, measured rates of subsidence have significantly decreased. Studies conducted by research programs, such as the University of Houston, have shown reduced subsidence rates within the boundaries of HGSD (fully converted) regulatory areas, while areas that rely on groundwater as their primary water source show higher subsidence rates.

If groundwater withdrawal is reduced, where will we get our water from?

The goal is to shift our region’s primary water supply from groundwater to sustainable alternative water supplies that do not cause further land subsidence. However, the transition from groundwater to alternative water supplies (surface water, reclaimed water, etc.) is complex and requires regional water planning, which is why the Texas Legislature created Regional Water Authorities to provide local control for these water infrastructure projects and are responsible for facilitating the conversion from groundwater to alternative water supplies to meet HGSD’s Regulatory Plan requirements.

Local and regional water providers have worked diligently to deliver sustainable solutions for their communities. For example, the West Harris County Regional Water Authority, the North Fort Bend Water Authority, and the City of Houston have joined efforts to construct the Surface Water Supply Project. Additional efforts were made at the Northeast Water Purification Plant Expansion near Lake Houston to increase treated water production from 80 million gallons per day to 400 million gallons per day.

What else can be done to reduce subsidence?

The answer is simple: reduce reliance on groundwater through regulation, alternative supplies, and conservation. Make every drop count by utilizing water conservation best practices, which is the driving force behind HGSD’s Water Conservation Program that includes:

  • Water Conservation School Program – Provides quality and locally-based water education to over 45,000 local 3rd-6th grade students.
  • Water Conservation Grant Program – Provides funding for local projects that implement water use efficiencies and reductions.
  • Smarter About Water – Provides online water conservation tools and resources for students, homeowners, businesses, and more.
  • Water My Yard – Delivers customized watering recommendations for yards in the Houston region to help increase irrigation and water efficiency, available free to the public on a website or smartphone app.

HGSD hopes to encourage water users to use less water and increase water efficiency whenever they can. Wasting water not only affects individual households and their budgets, but also puts a strain on our infrastructure and natural resources.