The Houston metropolitan region has plentiful water supplies available from several ground water aquifers and surface water reservoirs. Public supply, domestic, industrial and irrigation water wells are completed in fresh water sands in the Chicot and/or Evangeline aquifer or the deeper Jasper aquifer. Lake Livingston, Lake Houston, and Lake Conroe have been constructed to the north and northeast of Houston and provide surface water supplies from rivers to the region. The regional ground water pumping in the Houston District peaked at approximately 500 to 530 million gallons per day in the mid- to late 1970s. Since that time, the regional water demand has continued to increase. However, the ground water pumping has been declining and surface water supplies have been increasing in volume, areal distribution and overall importance. In 2006 and 2007, the ground water supply from water wells and the surface water supplies from reservoirs and rivers provided approximately ¼ and ¾, respectively, of the total water supply for Harris and Galveston counties. Ground water still provides the vast majority of the water supply for the adjoining counties in the region.

The hydrologic response of the aquifers to moderate to large ground water withdrawals is a reduction in the hydrostatic head in the aquifers and a decline in the static water level in wells. Large static water-level declines of approximately 130 to 300 feet were observed in some wells completed in the Chicot and Evangeline aquifers in east and southeast Harris County.

The Harris-Galveston Subsidence District was formed in 1975, and regulations by the Subsidence District have reduced ground water pumping and regional land subsidence in the east, southeast, and central parts of the Houston metropolitan region. The hydrostatic heads in the aquifers have recovered in these same areas and the static water levels in some wells have risen about 175 to 245 feet.

Ground water use has increased in the west and north sections of the Houston region, where growth has continued and surface water has not been available, at least until recently in some limited areas. The static water levels in wells in these areas have declined in response. Regulations will require reductions in ground water pumping in the north and west parts of the region within the next two to ten years and aquifer water levels should rise and well pumping rates increase in response in these areas.

Currently, the design and construction of new surface water pipelines and infrastructure to deliver surface water to areas presently served only by water wells are in progress. Planners, regulators, major water users and scientists should work to ensure that an adequate number of large-capacity wells are available in the proper locations in the future so that the ground water aquifers are able to help meet normal water supply needs and emergency requirements, if one of the limited number of surface water supplies is temporarily interrupted.