Oil and gas exploration in the United States is depleting some of the driest, most drought-prone states of water, a new report shows. The latest research by Ceres, a non-profit that promotes corporate sustainability, indicates that, since 2011, more than 55 percent of hydraulically fractured wells were located in areas experiencing drought.

Last year, the group released a similar survey, which found that nearly half of all oil and gas wells are located in “high to extremely high water-stressed areas.” The latest survey is based on hydraulic fracturing water-use data from 39,294 wells that were fracked between January 2011 and May 2013. Research shows that 97 billion gallons of water were used during that time. Nearly half that amount was used in Texas, followed by Pennsylvania, Oklahoma, Arkansas, Colorado, and North Dakota.

According to the EPA, 64 percent of the country was in drought in 2012. Oil-rich states such as Texas, Pennsylvania, Wyoming, and Colorado, water usage is of particular concern. The fracking process requires extremely large amounts of fresh water, up to 8 million gallons per fracking operation. A single well can be fracked up to 18 times.

Large portions of the state of Texas are experiencing “exceptional or extreme drought,” according to the Texas Commission on Environmental Quality. Prolonged dry conditions alone put a strain on water supplies. Fracking operations account for more than 20 percent of water usage in some counties in Texas and over half of wells in the state are found in high or extremely high water-stressed areas. In fact, the town of Barnhart, Texas temporarily ran out of water last year, about 2 years after fracking began in the town.

Earlier this month in California, Gov. Jerry Brown declared a drought emergency in the state, which is experiencing possibly the worst dry spell in a century. Ceres reports that 96 percent of wells in the state were found in high to extremely high water-stressed regions. According to the report:

Shale development in many regions is highly reliant on groundwater resources, which are generally less regulated than surface waters, thus increasing risks of water resource depletion and water competition. Over 36 percent of the 39,294 hydraulically fractured wells in our study overlay regions experiencing groundwater depletion.

Because fracking continues to progress, the demand for water will also increase. Rural counties can expect to be highly water-stressed in the coming years, the report notes.

Alisha is a writer and researcher with Ring of Fire. You can follow her on Twitter @childoftheearth.