**4.4 Water resource depletion**

 While the debate and study of how water quality may be impacted by UOG activities continues, there is clear evidence that water abstraction for hydraulic fracturing in water-scarce areas can lead to increased competition and shortages. A report by Ceres, a sustainability non-profit organization formerly known as the Coalition for Environmentally Responsible Economies, examined the relationship between water use by UOG and other sectors in water-stressed regions and found that water resources are negatively impacted [42]. Nationwide, Ceres looked at nearly 110,000 UOG wells and estimated that 57% of oil and gas wells hydraulically fractured between 2011 and 2015 were in water-scarce regions and where water is a subject of competition among farmers, towns and cities, and the oil and gas industry. Overall, fracking-related water use during the 5-year study period totaled 358 billion gallons. Put into perspective, this amount of water is consumed by approximately 200 mid-sized U.S. cities. States with significant oil and gas production that are particularly impacted by the threat of increasing water competition are Texas, Colorado, and California. These states are also home of some of the leading shale plays, including the Eagle Ford and the Midland Play (part of the Permian Basin) in Texas. Other plays characterized by high water use are the Marcellus Shale and the Niobrara in Colorado, Wyoming, and Nebraska. The county with the highest number of UOG wells (~7000 wells) and water use for hydraulic fracturing (>16 billion gallons) is Weld County, CO [42].
