Officials in Austin say the parking lot hole opened Jan. 25 after heavy rainfall, leading to discovery of a cave and a flow ultimately leading to the aquifer.
Scientist David Johns with Austin's Watershed Protection Department estimates several million gallons of water, mostly runoff, went into the sinkhole.
Researchers with the Edwards Aquifer Conservation District on Feb. 3 began tests using dye to trace the flow of water. Results are expected in a few weeks.
Hydrogeologist Brian Hunt says the district has been getting samples from different well monitors along the aquifer. The city has been monitoring water in Barton Springs and Cold Springs.