monitored annual well and spring discharges since 1934. Annual well discharge - the sum of all well discharges in a year - ranged from 219,300 acre-feet to 542,500 acre-feet between 1955 and 2012. The average well discharge for this period was approximately 371,667 acre-feet, equivalent to 183 thousand Olympic-sized swimming pools. Annual spring discharge ranged from 69,800 acre-feet to 802,800 acre-feet between 1955 and 2012. The average spring discharge for this period was approximately 392,991 acre-feet. During dry years, more water is discharged from wells while during wet years, more water is discharged from springs. Annual total groundwater discharge from pumping and springs ranged from 388,800 acre-feet to 1,130,000 acre-feet, and the average total groundwater discharge for 1955 to 2012 period was approximately 764,431 acre-feet. Hydrologic modeling Scientists with the United States Geologic Survey have developed numerical groundwater flow models for the San Antonio and Barton Springs aquifer segments to determine the amount of water in the aquifer, the direction it is flowing, and its velocity. These are used to estimate the sustainable levels of groundwater withdrawal throughout the aquifer. Given ample data is needed for numerical simulations, yet often lacking, regional modeling of large aquifers is difficult, but modeling segments within an aquifer is common and provides useful information for water users throughout the aquifer. Aquifer storage is correlated with water levels recorded in the J-17 Bexar index well which serves as the sole official monitoring well in the Edwards Aquifer. The J-17 well, is located in the artisanal confined Edwards Aquifer at a location AY-68-37-203 based on the latitude and longitude. Water levels have been recorded in the J-17 well since the 1910s, and is used to generalize the entire aquifer system. Changes in aquifer storage are used to estimate recharge rates. In the Edwards aquifer, groundwater flow models have been developed for the San Antonio and Barton Springs aquifer segments in the San Antonio region of Texas. Two model simulations were conducted: steady state and transient. A steady-state groundwater flow model requires magnitude and direction of flow remain constant, whereas a transient model simulation allows for a change in water storage over time. Steady-state results suggest water leaving the aquifer occurs through springs (73.3 percent), water well pumping (25.7 percent), and to the Colorado River (0.6 percent). Inflow of water to the aquifer mostly occurs through natural recharge (93.5 percent) and water delivered through the aquifer's regional