Pumpage in Orange County from the lower unit of the Chicot aquifer averaged 21.2 million gallons per day (0.93 cubic meter per second) and pumpage from the upper unit of the Chicot averaged about 2 million gallons per day (0.088 cubic meter per second) from 1971-79. Annual pumpage increased in municipal areas and decreased in industrial areas with little net change in total annual pumpage during the report period. The major water-bearing unit in the study area is the Chicot aquifer, which overlies the Evangeline aquifer. The Evangeline aquifer is undeveloped in Orange County, but is developed at Evadale in Jasper County, Texas, and at Silsbee in Hardin County, Texas. Both aquifers consist of unconsolidated and discontinuous layers of sand and clay that gently dip toward the Gulf of Mexico.
Water levels in Orange County tended to stabilize or rise in areas where ground-water withdrawals decreased. Elsewhere in Orange County, most water levels continued to decline, generally at a slower rate than before 1971. Bench-mark elevations determined during 1973 show regional land-surface subsidence from 1918-73, generally attributed to ground-water development, to be less than 0.5 foot (0.15 meter). Locally, subsidence due to production of oil, gas, saltwater, or sulfur was about 15 feet (4.6 meters) at Spindletop Dome, Jefferson County, Texas, and as much as 3 feet (1.0 meter) near Port Acres gas field, Jefferson County, Texas.
Although saltwater encroachment is evident in parts of southern Orange County, the encroachment is not expected to be detrimental if the ground-water pumping remains stable and the projected increase in demands for water is met with surface-water supplies.
