As part of China’s Sponge City Initiative, Shanghai’s Nanhui District (formerly Lingang District) has installed wetlands to store water, planted gardens, and created rooftop gardens to channel rainfall more efficiently and address urban flood management. Lingang is also laying down permeable pavement, which allows the soil underneath the pavement to absorb runoff water – not to mention reduce surface temperatures during hot weather.
Pavement is a major preventer of groundwater absorption, resulting in only 20-30 percent of rainwater infiltrating the ground in urban areas. This, according to Wen Mei Dubbelaar, Director of Water Management China at Arcadis, “breaks the natural water circulation and causes waterlogging and surface water pollution.” And while Lingang is able to easily adapt sponge city policies, other districts of Shanghai have not fared as well, with more buildings and developed concrete roads preventing a complete retrofitting of the city.
Shanghai is one of the most at-risk cities in the world when it comes to flooding, with predictions that the city could become completely submerged if global temperatures rise just 3°C. But Shanghai’s problem is hardly new. In fact, the city has been sinking since 1921, primarily due to groundwater depletion. And although China has over 87,000 dams, most of which have been built since 1978, the country suffers from groundwater depletion, drought, and flooding. More recently, the crisis has become more pressing, with flash flooding in China in 2010 resulting in over 700 deaths. As a result of repeated water-related crises, Chinese authorities have adopted strict policies to prevent global warming and aid resource renewal.
First launched in 2015, The Sponge City Initiative includes 30 Chinese cities and is a joint effort by the housing and rural-urban development, finance, and water resources ministries. The Initiative aims to reuse 70 percent of the rainwater in the cities by 2020, with that number rising to 80 percent by 2030, although it is unlikely that the cities will actually able to achieve that goal. Once completed, the initiative will equip cities like Shanghai with circular water systems.
One challenge is transforming the concrete jungles of China into sponge cities, which, unlike the planned district of Lilang, have developed rapidly over the past few decades. Older districts of Shanghai have adopted green rooftops and raised walkways to integrate urban water drainage systems, while other plans have attempted to integrate more permeable materials into the city.
One of the biggest challenges to the Initiative remains funding. The project is expected to cost $12 billion, but the central government will only provide 20-25 percent of the funding, leaving the cities responsible for raising the remaining 75-80 percent from local governments and private investors. Lingang’s city government has invested $119 million in retrofits, making it the poster child of the Sponge City Initiative.
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