Balancing Urban Growth with Environmental Protection

Birds Eye view of Jiaxing city
Mar 31 2023

Shanghai, Beijing, Chongqing, Guangzhou—China’s mega-cities are well-known to urban researchers. But smaller, lower-tier cities and towns, where much of China’s population lives, are less understood. While big cities may outshine small cities in terms of investment, the Chinese government has identified the development of small towns and cities as a priority. As cities develop, close attention needs to be paid to infrastructure development, including clean water supply, concluded a recently published study.

The study, by NYU Shanghai Assistant Professor of Urban Science and Policy Guan Chenghe and NYU Shanghai – ECNU Joint Graduate Training Program PhD student Cheng Tong, published in Environment and Planning B: Urban Analytics and City Science, evaluates water infrastructure protection. The paper, "Evaluating the impact of water protection policy on urban growth: A case study of Jiaxing,” looks at the relationship between urban development and impact on water resources, including wetlands, rivers, and reservoirs for standard drinking water.

With five million residents, Jiaxing has a number of natural water resources including many canals, but they are threatened by development and pollution.  “Jiaxing is facing some very serious water problems because there is a quality-induced shortage,” said Cheng, the corresponding author on the paper. “Much of the water was not drinkable ten years ago.” The government has tried to improve the drinking water quality with many measures, she said, including protecting the wetland and filtering the drinking water. The scarcity of safe drinking water for residents is an issue that sustainable development can address. 

The study looked at urban development and assessed how it impacts water resources. The researchers used two urban growth models, machine learning model and SLEUTH cellular automata model, to simulate urban growth under several different water resources protection buffer scenarios for future urban development and population distribution between 2020 and 2040. 


Population distribution, binary footprint of ML and SLEUTH models for the base scenario by year.
Population distribution, binary footprint of ML and SLEUTH models for the base scenario by year.

Binary footprint of ML and SLEUTH models in 2040 for each scenario.
Binary footprint of ML and SLEUTH models in 2040 for each scenario.

Through modeling, the researchers determined that a no-infrastructure buffer zone of 400 meters around water resources would safeguard the area’s ecology while also promoting a convenient and efficient city life for residents. A wider buffer zone of 500 meters would lead to an inaccessible city, making daily life inconvenient for residents. A narrower buffer zone of 300 meters would not offer enough protection for the ecological environment and the encroaching infrastructure would adversely affect water quality.

Guan said that there are lessons that can be taken from the study. “We are applying this method from other fields into water policy intervention to tackle this kind of urban issue,” he said. “This can definitely be translated for other cities and towns that have water issues.”

Cheng said that combining the two models could also be used to assess small cities with other ecological environments and socioeconomic problems caused by urbanization, for example cities in mountainous regions. It can also be used to evaluate larger regions, she said. “In the next stage, maybe we will focus on larger integrated developing areas. We want to study the small cities' performance in the big regional picture,” she said, adding that future research might focus on Turkey or China’s Yangtze River Delta. 

The study, which took over three years to complete, involved researchers in four countries over four continents. Guan said that the contributions of NYU Shanghai Assistant Professor Li Ying, an author on the paper who is from Zhejiang Province, were invaluable. Guan said that he and Li have been traveling to Zhejiang Province for a decade to inform their research, and Li provided local expertise and context for local policy interventions. 

Guan said that mentorship has been crucial to the research as Cheng learned to manage the research from start to finish. “I wanted to push Cheng to go through the whole process, not just the modeling part,” he said. “Through this collaboration, she learned from so many different scholars, managed the study, and learned how to deal with journal editors.”

Cheng said that Professor Guan’s guidance has taught her how to manage a research study. “I learned how to write a scientific, academic paper and how to collaborate with scholars with different backgrounds; how to organize our research; how to meet a deadline,” she said, adding that he introduced her to many resources but pushed her to take the lead.  “I think that trust has been very important for our collaboration.”