In late July I attended the 9th International Association of Hydrological Sciences (IAHS) Groundwater Quality Conference (GQ16), which this year was held in Shenzhen, China, a city that has grown from less than 30,000 residents to over 20 million in the last 40 years. The location and the conference theme of “Safeguarding Groundwater Quality in a Changing World” provided ample opportunity to ponder the looming water quantity and quality challenges that megacities such as Shenzhen, which have populations of 10 million or more, will face in the coming decades. Shenzhen has the advantages of relatively new infrastructure and a city government that prides itself on promoting an environmentally friendly lifestyle. An entire floor of the Shenzhen Industrial Museum is devoted to green city planning; interactive exhibits illustrate strategies to protect water quality and sustain the coastal marine environment. However, during my wanderings through the city, I saw numerous streambeds that were either almost dry or choked with sediment- and algae-laden water.
Several of the conference presenters made remarks that recognized these persistent problems, which are not unique to Shenzhen. Shiyi Chen, President of the South University of Science and Technology (SUSTech), used his introductory remarks to describe a major water quality improvement campaign that is underway in the city. Liu Zhiquan, Deputy Director General of the Chinese Ministry of Environmental Protection, noted Chinese cities’ heavy reliance on groundwater as well as the significant investments currently being made in water quality research and monitoring at the national level. Chunmiao Zheng, Dean of SUSTech’s School of Environmental Science and Engineering and Chair of the GQ16 conference, noted that despite the current priority being placed on water resources, nitrate contamination of groundwater persists throughout China. Citing a recent article in The New York Times [Buckley and Piao, 2016] that concluded that groundwater contamination, not smog, may be China’s most serious environmental problem, Zheng called for increased recognition of water quality challenges coupled with an emphasis on pollution prevention and on systems approaches that consider soil, surface water, and groundwater holistically. Looking ahead to looming water quantity shortfalls, Yan Zheng of SUSTech and Lamont-Doherty Earth Observatory argued that using reclaimed water for managed aquifer recharge needs to play a larger role in China’s water management strategies.
China is not the only country grappling with these issues, as other conference participants emphasized. Frank Schwartz of Ohio State used part of a keynote address to highlight the “ticking time bomb” of water-related health problems in megacities. Other presenters at the meeting described the development of national and regional monitoring networks and groundwater resource evaluation efforts in India, Korea, and the European Community. Presenters discussed emerging contaminants such as pharmaceuticals, nanomaterials, and caffeine both in terms of their potential impacts on health and as valuable tracers of the urban footprint on groundwater resources. The role groundwater exploitation plays in exacerbating urban populations’ exposure to high concentrations of naturally-occurring substances such as arsenic and iodine was another conference theme.
Many in the Water Resources Research (WRR) audience are already familiar with the water challenges associated with megacities, but the hydrologic community is still far from identifying viable, long-term solutions. In a pair of papers published in 2010, Srinivasan, Gorelick, and Goulder used simulation-optimization models to explore the evolution of a drought-driven water crisis in the Indian megacity of Chennai and to evaluate a variety of policies that could contribute to increased resiliency of the urban water supply [Srinivasan et al. 2010a, 2010b]. As part of a set of debate articles on the future of the hydrologic sciences, Lall  argued that we must move beyond our current understanding of local-scale hydrologic systems to develop a “planetary focus” to our science, in part because megacities create “hot spots” in the hydrologic flow field: “[The] surface and groundwater hydrology modifications by such cities require their own paradigm for understanding at a level that transcends a particular city.” A number of the articles published last year as part of a special issue celebrating the 50th anniversary of WRR recognized the need for new approaches to water management and protection in megacities. For example, Kumar  proposed a new framework, “hydrocomplexity,” that would take an integrated approach to water security threats posed by stressors such as the rapid expansion of urban and peri-urban areas. In the same issue, Cosgrove and Loucks  wrote a commentary about current challenges and research directions in water management, in which they highlighted problems of urban waste disposal and the cross-scale interdependencies of freshwater, wastewater, flood control, and stormwater in urban areas. They concluded that “there is a need to identify, and then implement, ways to rehabilitate urban ecosystems. This will require innovative institutional mechanisms, and a balance between autonomy and cooperation.”
While my visit to Shenzhen heightened my awareness of the water challenges posed by megacities, I am hopeful that collaborative efforts involving the hydrologic community along with other physical, biological, and social scientists and practitioners will yield the innovative strategies that are needed to sustain both water quantity and water quality in an increasingly urban world. I look forward to seeing those strategies explored further by my fellow hydrologists and the broader geoscientific community.
—Jean Bahr, Editor, Water Resources Research; email: email@example.com