Let’s start thinking about water!

Determining the Primary Sources of Fecal Pollution Using Microbial Source Tracking Assays Combined With Land-use Information in the Edwards Aquifer

I accidentally crossed paths with this paper while researching something else and decided to include it here even though (cough, cough) it is “old” for this column. Fecal coliform is a growing issue in the Hill Country with an increasing population and more and more septic systems.

In this study, these folks from The University of Texas at San Antonio tested water from Leon and Balcones creeks in the recharge and contributing zones of the Edwards Aquifer. As that child’s book proclaims on its cover, “Everyone Poops,” and it seems everyone poops on the Edwards. The authors found evidence of dog (prominent in Leon Creek) and cow (prominent in Balcones Creek) poop with evidence of chicken/duck and human poop as well. Human fecal matter was greatest after rainfall events in Leon Creek and higher in areas with greater septic tank density.

PFASs Pollution in Galveston Bay Surface Waters and Biota (Shellfish and Fish) Following AFFFs Use During the ITC Fire at Deer Park (March 17th–20th 2019), Houston, TX

Galveston bay with big cargo ship on the background by Natalia Kuzmina.

Sadly, it seems that every generation has its own water contaminant, and the one for Generation Z is PFASs: per- and polyfluoroalkyl substances. Following a March 2019 petrochemcical fire alongside Galveston Bay where the firefighters used aqueous film forming foams that contained, you guessed it, PFASs, these good folks tested the water and the nearby biota for evidence of said PFASs.

The authors found PFAS levels in nearby water to be 4 to ~300 times higher than those measured in later months (which may or may not be background). The most prominent PFAS was perfluorooctanesulfonic acid (aka Scotchguard), which busted the Texas’ regulatory limit of 0.6 micrograms per liter in 3% of the samples analyzed in March and April 2019. They also found perfluorooctanesulfonic acid in eastern oysters, red drum, gafftopsail catfish, and spotted seatrout. Google gave me blanks for “What does perfluorooctanesulfonic acid taste like?” but the authors calculated that, if you fished near the fire, you shouldn’t eat more than one to two meals per week for gafftopsail catfish and red drum and two meals per week for spotted seatrout to be protective for human exposure. Oysters were all you can eat!

Storage and Regulation of River Flows by Dams and Reservoirs

Longhorn Dam in Austin, Texas by Zac Zeinert.

In this paper, the legendary Wurbs provides an overview of reservoirs in the state. He notes that the water availability models, which cover the entire state, include over 3,400 reservoirs (all with water rights), of which 82 with storage capacity greater than 50,000 acre-feet comprise 92% of all the permitted storage in the state.

The top three reservoirs by way of conservation storage capacity are Toledo Bend (4,453,000 acre-feet), Amistad (2,977,000), and Sam Rayburn (2,888,000). When conservation and flood control are included, the top three are Texoma (5,101,000), Amistad (4,721,000), and Toledo Bend (4,453,000). Wurbs also discusses evaporation versus precipitation (ranging from annual precipitation of 54.7 inches with 45.5 inches of evaporation in East Texas to precipitation of 13.5 inches with 70.9 inches of evaporation in Far West Texas). Not surprisingly, reservoirs have smoothed out a lot of flow variability in the state’s rivers, reducing flooding but also reducing downstream flows.

Wurbs also provides numerous analyses in this paper, including a total reservoir evaporation of 10.4 million acre-feet per year with 17.4 million acre-feet provided for diversions with a reliability of 87%. If you are looking for a general reference of salient facts on Texas reservoirs, head on over to the Texas Water Journal to get some.