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This article summarizes land subsidence and groundwater level changes that have occurred in the Houston metropolitan area during an eight-year period (2005-2012). The Chicot and Evangeline aquifers are the major aquifers that underlie the Houston metropolitan area. Subsidence measurements from 95 permanent global positioning system (GPS) stations and 11 borehole extensometers, as well as groundwater level measurements from 170 wells screened in the Chicot aquifer and 320 wells screened in the Evangeline aquifer, were investigated. The Evangeline aquifer is currently the primary source of municipal, agricultural, and industrial water for urban and rural areas in the western and northern regions of the Houston area. Global positioning system and extensometer observations indicate that the overall subsidence rate in the Houston area has been decreasing since 2005. This decrease is a result of groundwater withdrawal regulations enforced by the Harris-Galveston Subsidence District, the Fort Bend Subsidence District, and other local agencies. Currently, subsidence in downtown Houston and in the southeastern region of the Houston metropolitan area has nearly ceased (< 3 mm/year). Slight land rebound has been observed at several GPS and extensometer sites along the Houston Ship Channel area since 2005. However, subsidence is occurring at a rate as rapid as 2.5 cm/year in the western and northern regions of the Houston metropolitan area. This study indicates that the local preconsolidation heads, the groundwater levels of the Chicot and Evangeline aquifers before human pumping of groundwater began, were approximately 30-40 m below the land surface. Presently, the water level of the Chicot is close to the preconsolidation head throughout most parts of the Houston metropolitan area. However, the Evangeline water level is approximately 70 m below the preconsolidation head in the northern region and 50 m below the preconsolidation head in the western region. The land subsidence rate is decreasing in the areas where the water level is rising, but is still below the preconsolidation head. Some such areas include Addicks and Jersey Village. The rate of land subsidence is steady in the areas that groundwater head is declining and below the preconsolidation head, such as in The Woodlands area. It will take a long period of time (e.g., > 50 years) for the current groundwater level to rise to the preconsolidation level in the northern and western regions of the study area and for subsidence to cease. In general, groundwater and aquifer systems respond slowly to human actions. Therefore, a long-term perspective is needed to manage groundwater resources and control land subsidence. (C) 2015 American Society of Civil Engineers.
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