This year even the Nueces River celebrated St Patrick’s Day. 

UT geology professor Marcus Gary and his hydrology class turned a portion of the Nueces River green the week of St. Patrick’s in collaboration with the Edwards Aquifer Authority. Gary, who is also a hydrogeology supervisor for the authority, said the purpose of this experiment was to study the movement of the water.

“We conducted a dye trace to try to understand how the river interacts with springs and how it recharges the Edwards Aquifer,” Gary said.

Students added a non-toxic green dye, which is commonly used for medical procedures, upstream from where the river water enters the ground. The class then traveled to nearby springs to test for the dye.

Gary said the results of the experiment, which are currently being analyzed, should indicate how much spring water came from the Nueces. He added that ideally, the experiment should be reconducted during drought conditions, to see how rainfall affects aquifer levels.

The Edwards Aquifer provides domestic, agricultural and industrial water for much of the greater San Antonio area. Steven Johnson, the hydrogeology manager at the Edwards Aquifer Authority, helped conduct the experiment. He said the authority’s main focus is to measure how much water flows into the aquifer to recharge it.

“We are interested in the Nueces River because it is one of the biggest sources of recharge,” Johnson said. “The objectives of the tracer test are to refine our understanding of recharge and reduce uncertainty in recharge estimates.”

James Cornejo, a geology freshman, said that experiments like these are critical to protecting the environment. 

“I think it’s important to know where water comes from and where it goes,” Cornejo said. “The water can have certain impurities that (can be) transferred into the aquifer, determining whether or not it’s usable.”