A new study published today estimates that fracking dangerously depletes water levels in up to 51 percent of streams in Arkansas, where water is taken and pumped deep underground (along with sand and chemicals) to frack a well to access natural gas.

Each well uses approximately 5 million gallons of freshwater from small streams over a two-to-five-day period when the frack is done, said lead author Sally Entrekin, a biologist at University of Central Arkansas. That’s enough water to fill every bathtub in a city of 250,000 people.

“Little is known about how much water can be withdrawn from these streams without impacts on fish and other aquatic species,” Entrekin said in an interview. While the researchers didn't look at drinking water specifically in this paper, most of the state’s drinking water comes from streams, rivers, and lakes.

Between 2004 and 2014, over 5,000 gas wells were fracked in Arkansas’ Fayetteville Shale play, primarily using water from streams and impoundments created by over 150 dams on those streams. “We don’t know if there has been an impact on the streams because there isn’t any site-specific monitoring,” she said.

Read More: Hydraulic Fracking Is Behind Thousands of Earthquakes in the Midwest This Year

Nor could researchers obtain detailed data on how much water was pumped from which stream and when. Time of year makes a huge difference. One frack well sucking 5 million gallons out of small stream over a few days in a dry summer is likely to have a significant impact on stream temperatures and stream flow affecting aquatic insects, fishes, and bottom-dwelling mussels, the study said.

Some of this wastewater is reused, but the majority is pumped deep underground, where it has been linked to a wave of earthquakes that have rocked the state starting in 2010. However, recent research out of Stanford University suggests that fracking itself was responsible for most of Arkansas’ quakes.

Fracking has also been linked to low-birth weight babies. A child born within a mile or two of a fracked well is likely to be smaller and less healthy than a child born farther away, according to the largest study ever conducted on the health effects of fracking.

In that paper, published last month in Science Advances, researchers looked at 1.1 million births in Pennsylvania from 2004 to 2013, comparing infants born to mothers living at different distances from active fracking sites. The largest health impacts were seen in newborns whose gestation period occurred while the mother was living within 1 km (0.6 miles) of a fracking site. Air pollution, not water pollution, is the suspected cause.

This adds to the growing evidence that living near oil or gas fracking sites is associated with a wide range of health impacts, from higher rates of asthma and migraines, to more hospitalizations for cardiovascular disease, neurological disorders, and cancer. About 17.6 million Americans live within one mile of an active oil or gas well.