Aquifer Data & Maps

J-17 Data

Water levels at the J-17 Index Well are provided here as raw data in 15-minute intervals. These are provisional readings and are subject to further qualitative review by the EAA.

How Does it Work?

To ensure accuracy, the EAA uses three different devices to measure water level.  The elevation of the water in the well—the potentiometric surface—is created by artesian pressure in the aquifer and is measured in feet above mean sea level (msl).  For example, since the ground level at J-17 measures 730.8 feet above msl, when the water rises to 70 below the ground's surface, subtracting 70 from 730.8 gives us an aquifer level reading in the San Antonio Pool of 660.8 feet above msl.


Every day, the highest water level recorded between the hours of 12:00 a.m. and 8:00 a.m.  is reported as the Daily High.  However, during periods of heavy rain, water levels in the well may rise throughout the day so the highest water level would then be recorded in the late evening and a correction would be made to the previous reading.  The EAA uses this information for official historical reporting and for determining and enforcing groundwater reductions during periods of high aquifer demand and/or drought.