Fracking vs faucets: balancing energy needs and water sustainability at urban frontiers.

N accessible shale deposits have dramatically increased global gas reserves and are touted as a bridge to a clean energy future. For example, in the U.S., where shale gas is projected to comprise 49% of national natural gas production by 2035, proponents argue that shale gas production can provide energy independence, create employment, and stimulate regional economies. Amidst this optimism, however, are growing concerns about the effects of shale gas extraction, and, in particular, hydraulic fracturing or “fracking”, on water resources−−concerns that are magnified in urban areas where human populations and extractive operations overlap. We believe that water conflicts arising from expansion of the U.S. shale gas industry foreshadow developments in other countries with cities situated over large shale-gas deposits, including Diyarbakir, Turkey; Ahmedabad, India; and Chongqing, China. While much recent controversy over fracking and water resources is directed toward potential contamination, here we use the Dallas-Fort Worth (DFW) Metroplex, Texas, to illustrate challenges associated with balancing energy needs and water sustainability in cities with semiarid to arid climates. Along with one of the highest urban population growth rates in the U.S. (23.4%), the Barnett Shale underlying DFW represents the largest staging ground for shale gas extraction in the world. Ninety percent of DFW’s drinking water is supplied by surface runoff captured in 34 reservoirs, with municipalities and gas extractors consuming ∼86% (∼1.87 billion m) and <3% of the total water supply, respectively. DFW also experiences recurrent drought, heightening anxieties over water availability. In 2011, we randomly surveyed 1000 DFW residents to evaluate public perceptions and knowledge of watersheds. Six questions dealt specifically with regional shale-gas extraction. Our survey reveals considerable public uncertainty regarding the effects of shale-gas extraction on fresh water availability: after drought, nearly one-third (27.7%) of respondents ranked gas drilling as the greatest hazard to the water supply in 2011. Unfortunately, public uncertainty diverts attention from the primary factor affecting water supply in expanding urban areas: increasing municipal water use. We believe that DFW’s situation holds important lessons for other cities faced with the prospect of expansive shale gas extraction, growing populations, and/or increasing aridity. First, in urban areas where municipal water use dominates water consumption, reduction in residential and commercial use has the potential to play a major role in urban water sustainability. Notwithstanding, strategies that figure prominently into plans to meet future water needs are often not sustainable (either for water provisioning or ecological systems) and merely increase resource capture rather than improve efficiencies or decrease per capita consumption. In Texas, water management strategies aim to add ∼2.96 billion m of water to the region’s supply by 2060, at a price of $21.5 billion (for comparison, China’s Three Gorges Dam cost ∼$25 billion). These include the construction of four new reservoirs, importation of surface water from other basins and districts, and water reuse (Figure 1). Together, these strategies are anticipated to comprise 87.5% of future water gains. Conservation initiatives account for just 12.3%, or 364 123 844 m of additional water in 2060. Second, although municipal conservation is key to water sustainability, most urban residents have a limited understanding of the urban water cycle. For example, when asked if they lived in a watershed, 9.7% of our survey respondents answered “yes”, 63.3% said “no”, and 27.7% said “do not know”. Respondents also were “not sure” (11.5%) or “did not know” (40.9%) the source of drinking water supplied to their home. This is likely due to “quality” rather than “quantity” of education: 54% of survey participants had a bachelor’s degree or higher and yet were unfamiliar with the watershed concept. Clearly, as long as residents do not understand how they fit into the urban water cycle and fully recognize their role in water