Water flow is lowest in seven decades of tracking

A drought that has negatively impacted local water sources has area officials concerned.

Senior Director of Aquifer Science and Modeling Paul Bertetti said that the Edwards Aquifer San Antonio pool, of which water is discharged in San Marcos, is currently in Critical Period Management Stage 2 which means that there are reductions in pumping across the San Antonio pool of the system.

The rate of flow is significantly slower than it should be at this time of year and hasn’t been like this in approximately 70 years.

“We recovered a little bit from this spring,” Bertetti said. “We were down in Stage 3 for the better part of a year or so, and then the reset rainfall in the last couple of months moved us up into stage 2, but we’re still about 20 feet or so below normal levels.”

Bertetti said it would take more than one rain event to recharge the aquifer.

“We would probably need multiple events. We had a couple of years where we had maybe 20 inches below normal rainfall for the San Antonio area, so I think it probably would take subnormal or above average rainfall over a period of about - a year's worth of rain to get the system to recover,” Bertetti said.

Bertetti said that 2022 was the second driest year on record–the main contributing factor when it comes to low aquifer levels. “That's significant. We’re talking about rainfall amounts that are low enough that we really haven't seen those kinds of levels and flow since the 1950s or so,” Bertetti said. “Obviously there’s an ever increasing demand on usage, but the Aquifer permitting system was capped. The amount of pumping is always restricted and limited, and that really hasn’t changed since the mid 2000s when those management strategies were put in place.”

Meadows Center Executive Director Robert Mace, also the Chief Water Policy Officer, said in order to bring the levels back to normal we would need two things.

“For the rain we would need longer sustained rains over a longer period of time. It’s been nice that we’ve been getting rain, but you’ll notice we’ll get rain then it will be dry for a long time. The soil ends up soaking up a lot of that rain and then it gets evaporated into the atmosphere, and we don’t see the maximum impact versus if we got a month of rain. The soil would get full of water and then subsequent rains would then recharge the Aquifer,” Mace said. “The second thing is that it needs to rain in the right place, so flows here in the springs and in the river– there’s a local component of flow. So, the rains that happen locally can cause little spikes in flow, but the baseline flow is from the regional system. That requires rain in the Western part of the Aquifer, west of San Antonio.”

Bertetti said the region hit the hardest by the drought is the Central Texas region North of San Antonio.

“A similar set of conditions occurred back in around 2006. San Marcos Springs seemed to have very low flows and was really sort of the driver for Aquifer restrictions. Even though the … area in San Antonio had relatively high levels. It seems like when the Blanco and all those surrounding areas dry up, particularly, then you get these low flow positions, and it's because of the extent of the drought and the dry out period.

'It will likely take a little bit of time to recover even with the recent rains,” Bertetti said. “I think that’s kind of what’s happening now.”

The springs in town that flow into the San Marcos River are fed by Edwards Aquifer.

Bertetti said the headwaters are currently flowing at 77 cubic feet per second. “Typically in the June timeframe you’ve got 190 cubic feet per second,” Bertetti said. “So, it's less than half –close to about a third–of what it normally would be this time of year.”

Mace said the original reading was 77 cubic feet per second as of Thursday, but the United States Geological Survey recalibrated the gauge on the San Marcos River. “The flow is now suddenly 88 cubic feet per second. Even at this higher rate, this flow is still the lowest flow since 1956,” Mace said. He said in 1956 the rate was 64 CFS.

Bertetti said it's plausible that such a low flow rate could lead to higher amounts of algae in the water.

“Things are not moving along as well. Typically what happens is you have a little more stagnant water then that algae is able to build up because it's essentially not being washed away,” Bertetti said.

Mace said the low flow rate creates a prime condition for algae growth.

“When the water is flowing slower, it can get warmer,” Mace said.

He said the low rate of flow does create concerns for the endangered species of fish and plants in Spring Lake and down the river. “When flow gets below 80 CFF then there’s certain things that we’re not allowed to do and need to be careful about to protect those endangered species,” Mace said.

According to the Incidental Take Permit for the Edwards Aquifer, when spring flows decline to 120 CFS or lower, the permittees will suspend activities such as habitat restoration and riparian restoration that may result in disturbance of the substrate, water quality, plants and animals, including invertebrates, of the San Marcos Springs, Spring Lake and the San Marcos River.

Mace said that lower water levels can lead to human-related damage to endangered plants.

“When there’s less flow in the river, it’s not as full in the bank. That can have consequences for the plants that are along the edges.

'With Texas wild rice, which is one of the endangered species, it just becomes easier for people to get into those dams of wild rice and pull them up and cause damage to their habitat. It’s a combination of low flow and increased access,” Mace said.

Bertetti said there was a recent chemical sampling approximately a month and a half ago.

“The chemistry of the water coming out of the springs hasn’t been affected. It’s what I would describe as normal - of good quality right now,” Bertetti said.