The Edwards Aquifer is one of the most studied and most prolific aquifers in the United States. The aquifer is a heavily fractured and faulted carbonate aquifer with transmissivities in excess of 100 ft2/s. The City of San Antonio relies upon the Edwards Aquifer as its sole source for water. Much work has been done on quantifying recharge to the aquifer and discharge from wells and acquiring aquifer characteristics from pumping tests, specific capacity tests, and geophysical logs. Although the aquifer has been well studied in Bexar County, much less is known about the Edwards Aquifer in Kinney County. This is partly due to the lower population within the county (approximately 3,500 people) relative to the eastern counties (Uvalde, Medina, Bexar, Comal, and Hays) and the great distance of Kinney County from high profile discharge areas such as the City of San Antonio and Comal and San Marcos Springs. Three key products resulted from this study: (1) exploratory well drilling and the largest aquifer test in the county that were conducted to evaluate the well yields within a 10,000 acre study area in which a drawdown of 2.5 ft approximately 1.2 miles away was observed while pumping at approximately 4,600 gpm; (2) a recharge estimate for the Edwards Aquifer within Kinney County of approximately 71,382 ac‐ft/yr; and (3) locating the Brackettville Groundwater Divide from an evaluation of ground water flow direction and hydrograph analysis. These results help evaluate the complex hydraulics occurring within Kinney County and aid in development of ground water modeling that will be used in managing the Edwards Aquifer.

Land subsidence caused by groundwater withdrawal in the Houston–Galveston region is a well‐documented phenomenon. Subsidence of up to 3 m has been calculated in the region since 1905. Subsidence caused by hydrocarbon withdrawal is also a plausible cause of subsidence, where groundwater withdrawal has diminished and significant petroleum production has occurred for> 95 years. Sixteen fields were investigated by acquiring reservoir depressurization data near bore‐hole extensometers set up by the Houston–Galveston Coastal Subsidence District. All reservoirs were found to be well below hydrostatic pressure; a few of them were underpressured even before production began. Four oil and gas fields (the Mykawa, Satsuma, Dyersdale, and South Gillock) and three production zones (the Miocene, Frio, and Yegua) were used in a reservoir model and a boundary clay reservoir model to calculate subsidence. Subsidence under these fields is predicted to be as high as 0.44 m in a 19‐year period at the Satsuma field and as low as 0.02 m in a 22‐year period at the Dyersdale field. Implications of this study are (1) hydrocarbon production, although not the major contributor to most land surface subsidence in this area, does play a role; and (2) depressurization and, subsequently, subsidence from oil and gas fields may be regional and connected with other fields which is inferred from the fact that some fields were already underpressured before production began.

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