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. Subsidence in the area of Burnett, Scott, and Crystal Bays near Baytown is becoming critical because much of the area is now subject to inundation by high tides.

Production of oil and gas from the Goose Creek Field on the southeast edge of Baytown had caused as much as 3.25 feet (1 meter) of subsidence by 1925. The subsidence due to oil and gas production 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 280 feet (85.3 meters) of artesian-head decline has occurred in the Evangeline aquifer, and as much as 320 feet (97.5 meters) of artesianhead decline has occurred in the Alta Lorna Sand of Rose (1943). Significant subsidence of the land surface probably began about 1920 or later and as much as 8.2 feet (2.5 meters) of subsidence had occurred in the area by 1973.

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 head in both the Alta Lorna Sand and Evangeline aquifer would continue to decline at a rate of 6 feet (1.8 meters) per year until 1980 and then cease. Case II provided that artesian head in the Alta Lorna Sand would continue to decline at a rate of about 6 feet (1.8 meters) per year until about 1995, when the potentiometric surface would reach the top of the Alta Lorna Sand. The artesian head in the Evangeline aquifer would also decline about 6 feet (1.8 meters) per year until 1995.

The ultimate subsidence expected for the assumed conditions of case I and case II is 11.4 feet (3.47 meters) and 15.1 feet (4.60 meters), respectively. However, only 1.4 feet (0.43 meter) of subsidence below present land surface would occur if artesian heads were maintained at their present levels.

To halt subsidence in the near future, artesian head must be increased, either by decreasing pumpage or by repressurization by artificial recharge.