Removal of water, oil, and gas from the subsurface in Harris County has caused declines in fluid pressures which in turn have resulted in subsidence of the land surface. One critical area of subsidence is in the area of Burnett, Scott, and Crystal Bays near Baytown. Much of this area is now subject to inundation by high tides.
Production of oil and gas from the Goose Creek Field at the southern edge of Baytown had caused as much as 3.25 feet of subsidence by 1925. The subsidence bowl is restricted to the area of production and has not extended to the area of Burnett, Scott, and Crystal Bays.
Withdrawals of water from large-capacity industrial wells, which resulted in declines in artesian pressure, began about 1918; as much as 250 feet of water-pressure decline has occurred in the Evangeline aquifer, Significant subsidence of the land surface probably began about 1920 or later. Possibly as much as 7.5 feet of subsidence had occurred in the area by 1971.
The study of subsidence in the area of the three bays included the collection of undisturbed clay samples for laboratory analyses, collection of water-level records, and installation and monitoring of pressure transducers in clays and of observation wells in sands.
Probable future subsidence was calculated for two loading situations. Case I provided that the artesian pressure in both the Alta Loma Sand of Rose (1943) and Evangeline aquifer would continue to decline at a rate of 6 feet per year until 1980 and then cease. Case II provided that artesian pressure in the Alta Loma Sand would continue to decline at a rate of about 6 feet per year until about 1995, when the potentiometric head would reach the top of the Alta Loma Sand. The artesian pressure in the Evangeline aquifer would also decline about 6 feet per year until 1995.
The ultimate subsidence expected for the assumed conditions of case I and case II is 11.2 feet and 14.5 feet, respectively. However, only 1.8 feet of subsidence below present land surface would occur if artesian pressures were maintained at their present levels.
To halt subsidence in the near future, artesian pressure must be increased. The most logical method of increasing artesian pressure is by decreasing pumpage rather than repressurization by artificial recharge.
