Austin Chalk as an alternative supply for Brackettville?

With flows in Las Moras Springs failing recently (and seemingly more commonly and for longer), someone has suggested that Brackettville (and others) pull water from the Austin Chalk instead. Lowering groundwater production so close to the springs is not a bad idea for helping the springs as there is likely a one-to-one benefit to the springs. In other words, a gallon not pumped or produced close to the springs is a gallon that will flow out of the springs.

How much might that benefit springflow?

Municpal water use for Kinney County as reported to (and estimated by?) the Texas Water Development Board is about 1,100 acre-feet per year for the few years before and including 2021, the most recent year posted. That 1,100 acre-feet per year converts to about 1.5 cubic feet per second. Based on springflows measured daily since September 30, 2014, through September 5, 2024 (with some days with no data early in the record), the median daily average flow is 12.2 cubic feet per second. That means reducing all muni production in the county (the vast majority in Brackettville, I reckon) amounts to about 12 percent of the median flow of the springs.

Would eliminating all municipal production from the Edwards have kept the springs flowing over the past year? Probably not. They would have probably flowed longer before going dry, but I think they still would have gone dry. Is that an argument against moving production from the Edwards to somewhere else? No. Just trying to put things into perspective.

Back to the chalk!

The Texas Water Development Board’s Groundwater Data Viewer only shows a few wells in the immediate Brackettville area completed in the Austin Chalk in their Groundwater Database. One (70-45-607) is located about a mile southeast of downtown Brack off Joe York Road, is 80-feet deep, and, at the time of its survey in 1957, used for domestic and stock purposes. A water sample pulled in 1938 shows total dissolved solids of 473 milligrams per liter (solids less than 1,000 is generally considered fresh; less than 500 is recommended for drinking water for aesthetic reasons). Sulfates (as SO4) in this well came in at 4 milligrams per liter.

Another well about half a mile west of downtown (70-45-508) close to West Lackey Street and Ranch Road 2804 is 73-feet deep and was used for domestic and livestock purposes when it was first surveyed. This well has a higher salinity with total dissolved solids of 694 milligrams per liter as measured in 1938. This well differs from the Joe York well in that sulfates (as SO4) are much higher at 194 milligrams per liter. The water here (Ole Smelly?) is probably odiferous (to put it politely).

About a mile and a half east of town is another well in the Austin Chalk used for stock (70-45-608). This well is 80-feet deep with a water level 39.5 feet below land surface in 1938. Total dissolved solids in this well amount to 428 milligrams per liter as measured in 1938. Sulfates (as SO4) in this well were 12 milligrams per liter.

None of the files at the Board have information on well yields, so we don’t know how productive these wells are. However, unless cracked up by local faulting, wells in the Austin Chalk don’t tend to produce a lot of water, at least according to my experience (my Ph.D. research was focused on Austin Chalk, albeit up south of Dallas).

Some deeper non-Edwards wells in Brackettville tap into the Eagle Ford Group. Four wells in Brackettville have depths of 90, unreported, 183, and 300 feet with wells getting deeper toward the south following the slow dive of the formations into the subsurface. These wells have total dissolved solids of 831, 581, not reported, and 298 milligrams per liter with concentrations of sulphate (as SO4) of 293, 206, 500, and 13 milligrams per liter, respectively. Again, no well yields for these wells.

Could wells in the Austin Chalk and Eagle Ford Group replace water pumped from the Edwards Aquifer? Based on what I’m seeing in TWDB’s database and based on my experience, the odds are extremely low.