The Texas Water Development Board publishes hourly water levels from a changing set of wells, currently (November 2014) numbering 171. I wanted to see how levels have risen and fallen over time. How exceptional has the current Texas drought been?

Choosing the readings for midnight each day, on all the wells available that day, I kriged the data to interpolate away from the wells. Then I subtracted the interpolated field from that of a reference day. I used January 1, 2004, as a reference. To smooth the animation, I applied a ten-day lagging moving average filter to the difference fields, so that each image represents the current day's difference combined with the previous nine days. I made color images of these smoothed differences, one for each day. Blue areas have higher water levels than they had on the reference day; tan levels have lower levels. Finally, I used the excellent and free FFmpeg software to form those images into the frames of this two-minute movie.

The images from later years, where well coverage across the state is more extensive, are much more trustworthy than the earlier images. You can really see southeast Texas change around 2008, when new wells come on line around Houston.