Abstract

Water quality-induced water shortage is emerging as one of the main threats for the growth of the world’s population and economic development, especially for coastal cities in developing nations. This paper discusses how to supply enough sufficiently clean water to such cities using the technologies of coastal reservoirs and wetland pre-treatments, as well as employing the SPP strategy. The so-called coastal reservoir is defined as a freshwater reservoir situated in seawater which sources its water from river runoff; to improve its water quality, a wetland is used to pre-treat the runoff that is potentially polluted by domestic, agricultural and industrial contaminants. Generally, the existing lakes in the urban-rural fringe are severely polluted; the Separation, Protection and Prevention (SPP) strategy can quickly restore the lakes’ water quality to a drinkable standard. In this study, we take Shanghai, the largest city in China, as an example to investigate the feasibility of the proposed strategies. This investigation shows that using the technology of coastal reservoirs in Shanghai, namely the Qingcaosha Reservoir, freshwater can be pumped from the sea without requiring the desalination process and if an agricultural wetland on Chongming Island is used to pre-treat the river water prior to its storage, its water quality will be improved to Class II. It is also found that Dianshan Lake, which has been polluted and had a water quality of worse than class 5 in 2015, can have its water quality improved to class II in a short period if the SPP strategy is applied. It is expected that it will be a cost-effective and sustainable water supply method for coastal cities.

Highlights

  • The primary renewable source of freshwater on earth is continental rainfall, which generates a global supply of 40,000 - 45,000 km3 per year

  • The water quality at river estuaries can be significantly improved by using agricultural wetlands

  • 4) For a lake, the external pollution can be controlled once the unwanted water is discharged out of the lake; the remaining clean water can be developed for use as potable water

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Summary

Introduction

The primary renewable source of freshwater on earth is continental rainfall, which generates a global supply of 40,000 - 45,000 km per year This more or less a constant water supply that must support the entire world population, which is steadily increasing by approximately 85 million per year; the availability of freshwater per. Similar tendencies can be seen in the distribution of world population; in 1950 only 30% of total population lived in coastal regions, but by 2050, this will change to about 70%. Almost all of the world’s water supply comes from inland reservoirs that are generally located in the remote upstream section of a catchment, but people on the other hand generally live in the lower/coastal regions of the catchment, leading to a mismatch between the water availability and the local water demand. The main advantage of coastal reservoirs is that all runoff from a catchment can be fully collected if needed, and subsequently the reservoir can pump freshwater from the sea without requiring a desalination process

Background of Shanghai’s Water Supply and Water Crisis
Feasibility of Improving Qingcaosha Reservoir’s Water Quality to Class II
Findings
Conclusions

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