Journal of Sustainable Urbanization, Planning and Progress

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Next to air, fresh water has been always considered as the most important resource, central to economic development as well as to human physiological needs. Currently the total world population is about 7 billion, and, by 2050, it is projected to be 9 billion. By that time an additional 40 Nile Rivers will be needed. Historically, inland dams have successfully solved the water deficit problems in many places, but more and more countries are resorting to emerging technologies like desalination, wastewater recycling and rainwater tanks which are needed to replace inland dams for a number of geomorphological, environmental and societal reasons. These new technologies require a paradigm shift in the water supply industry: global water consumption is only 5~6% of annual runoff—as it is in Australia—so the coming shortage is not of water, but of storage.

A coastal reservoir is a reservoir designed to store floodwaters in a seawater environment. The first generation of this technology has been successfully applied in China, Singapore, Hong Kong and Korea, but the water quality is generally not as good as that from inland reservoirs. The second generation of coastal reservoirs has been developed and its water quality is comparable with the water available from conventional urban water supply reservoirs. The conceptual design of coastal reservoirs for Australia’s capital cities is outlined.

Qingcaosha Reservoir (QR) is typical fresh water storage and salty water avoidance featured coastal reservoir, which is located in south branch of Yangtze River Estuary, China. Due to the location of QR, pollutants and short-term salt tides have threatened the clean fresh water intake of the reservoir. There are 289 km² shoal wetlands in upstream of QR. After the continuous purification of wetlands, water quality of raw water has been improved. Qingcaosha shoal, Zhongyangsha shoal, Beixiaohong shoal and Dongbeixiaohong shoal are on the circumference. From the water quality monitoring data after the reservoir operation, the average value of NH₄⁺-N, NO₃^--N, TN, TP in the outlet are 81%, 65%, 77% and 66% of the inlet respectively after flowing through the natural wetland in the reservoir. The wetlands can solve two major problems facing the coastal zone reservoirs that enhance intake water quality and stabilize water quality. In the design of coastal reservoirs, we suggest that we should make the full use of existing wetlands, enhance the function of wetland water purification through ecological engineering methods, and construct artificial wetlands as a supplement.