The Harris-Galveston Subsidence District (HGSD) was created in 1975 by the 64th Legislature to regulate the withdrawal of groundwater within Harris and Galveston Counties to end subsidence, which contributes to or precipitates flooding or overflow of the HGSD, including rising water resulting from a storm or hurricane.
HGSD has adopted five regulatory plans beginning in 1976. The initial plan focused on having an immediate impact in the area where the most subsidence had taken place and where surface water was available as an alternative to groundwater. The 1976 Plan regulated pumpage in all of Galveston County and much of southeastern Harris County in an area referred to as the “Area of Concentrated Emphasis” (ACE).
The 1985 plan divided the HGSD into eight Regulatory Areas so that subsidence could be addressed throughout the entire HGSD. This plan had an overall goal of changing primary water usage from groundwater to surface water in a series of steps.
The 1992 plan modified the 1985 plan based on a detailed re-analysis of regional population and water demand data. The 1992 plan divided HGSD into seven Regulatory Areas each with goals for the reduction of groundwater withdrawal by certain dates. The Regulatory Areas were based on surface water availability, geophysical characteristics and groundwater demand.
The 1999 Regulatory Plan divided HGSD into three Regulatory Areas. The Regulatory Areas were reconfigured from the 1992 plan to generally reflect converted versus non-converted areas. The requirements contained within the 1999 Regulatory Plan were based on the most current data and studies on water demand, aquifer levels and projected subsidence, and provided permittees organizational flexibility in meeting the regulatory goals.
In 2010, HGSD began a Regulatory Plan Update Project to 1) update population and water demand projections and 2) update and recalibrate the parameters in the groundwater models and subsidence models. The updated data and models were then used to evaluate the regulations in the 1999 Regulatory Plan and make any necessary changes to the regulations for the upcoming decades. The HGSD was able to use the conversion plans for Regulatory Area 3 contained within certified Groundwater Reduction Plans to more accurately represent where groundwater reductions would likely occur. HGSD was able to incorporate the 2010 U.S. Census data and more accurately project population growth. Once projected water demands were determined for the updated population growth, multiple scenarios of groundwater pumpage regulations were tested in the groundwater model and subsidence models. The results from the groundwater model and subsidence models for each scenario of potential regulatory changes were compared back to a baseline scenario that used the regulations from the 1999 Regulatory Plan. Consideration of the projected subsidence rates throughout the District were weighed against the feasibility of obtaining alternative water supplies necessary to meet the proposed groundwater reductions. This 2013 Regulatory Plan is the result of HGSD’s analysis and replaces the 1999 Regulatory Plan for all Regulatory Areas within the HGSD boundaries.
This 2013 Regulatory Plan is the result of HGSD’s analysis and replaces the 1999 Regulatory Plan for all Regulatory Areas within the HGSD boundaries.