Most locals know that one of the most important citizens in our environmentally conscious city is the salamander. The Barton Springs salamander and Austin Blind Salamander are US endangered species that only live in the habitat of Barton Springs, Zilker Park in Austin, Texas. The city goes to great lengths to protect the water quality of this amphibian habitat as well as many other environmentally sensitive watersheds.
The Barton Springs salamander was given the taxonomic name Eurycea sosorum in honor of the citizens of Austin, who initiated and passed the SOS (Save Our Springs) Ordinance in 1992 to protect the Edwards Aquifer. Both of these rare and tiny (average length is 6.35 cm) salamanders require clean and consistent water flow in order to survive. As stream salamanders, they are ecological indicators – they provide readily quantifiable metrics of ecosystem health and integrity
This is where water resources engineer and Associate Professor Ben Hodges enters the picture. He is developing recommendations that will impact the Barton Springs Pool’s preservation and improvement in collaboration with the City of Austin. Hodges’ expertise on hydrology, hydraulics and fluid mechanics landed him on the Hydrodynamic Design Team for the Barton Springs Pool Master Plan.
The project was also the thesis topic for master’s student Abby Tomasek (MS 2013). Tomasek spent two years working alongside Hodges, collecting data and developing a model of Barton Springs Pool.
As part of the city’s master plan, a detailed bathymetry survey, hydrodynamic modeling, and redesign of the pool’s dams are three components of a larger effort to improve the pool. The Hydrodynamic Design Team is looking at ways to modify the lower dam with new gates to improve water flow for the salamander habitat and reduce the build-up of gravel behind the dam during floods.
Hodges and his team produced a detailed bathymetric study of the pool. For this study, a cost-effective, custom survey instrument was constructed using an off-the-shelf “fish finder” sonar with GPS, which was mounted inside a 5-gallon bucket and supported with an inflatable swim tube.
“In the past, a similar survey would have required instruments costing tens of thousands of dollars,” says Hodges.
The team has created a three-dimensional hydrodynamic model of the pool under different discharge conditions in order to better understand the flow conditions for the salamander’s habitat. The model analyzes flow speed and direction and the influence of wind on water circulation in the pool.
To calibrate the model, the team measured the water velocity using an acoustic Doppler current profiler (ADCP), which was mounted on the pool bottom with the help of a diver from the City of Austin. The ADCP uses high-frequency sound waves to measure the water velocity, a concept that is similar to the way Navy submarines use sonar.
In 2013, this instrument was placed close to the springs in two different deployments. Data collection in 2014 focused on areas further away from the springs in order to get a better understanding of the mean flow through the pool.
The ADCP data collection continued around the clock for several weeks, including when occupied by swimmers. Fortunately, the speed of a swimmer gliding over the top of the instrument is much greater than the actual pool water, so the swimmer’s effects are easily removed from the final data set.
In the next year, the team will be using the model to provide the city with recommendations on new gate placement for the downstream dam, which will allow the city to examine either modifying or replacing the aging downstream dam. The new gates should enhance the flow habitat for the salamanders, as well as decrease the gravel accumulation behind the dam during floods.
“In the long run, improved flow conditions will make the pool a better place for endangered species and reduce the periodic costs of closing the pool to remove gravel accumulations,” says Hodges.
This is one of many ways in which UT CAEE is providing innovative solutions to problems surrounding the nexus of cities, water, and energy. Read more about our strategic vision.
