The world has witnessed unprecedented urban growth since the beginning of the twenty-first century. Much of this growth is concentrated in the less-developed countries of Asia. Asia is home to 54% of the world’s urban population, and the percentage share is expected to increase to 66% by 2050. Ninety-three percentage of the growth is expected to be in the less-developed countries with more than 60% in the cities of Asia. It is also the million-plus cities that are witnessing the most phenomenal urban growth under the impact of rural-to-urban migration. Along with climate change impacts, the rapid pace of mass urbanization is putting cities under increasing water insecurity and water stress. There is also an increased demand for water in order to maintain the intense pace of activities and a high standard of living in urban areas. Cities also concentrate on anthropogenic carbon emissions that accelerate global warming and impact the hydrological cycle to further increase water stress in cities. Increase in impervious surface and consequent depletion of groundwater reserves, increased water pollution from city waste, and industrial affluent decrease the availability of finite water resources. Choked water bodies and urban drainage systems increase the vulnerability to floods. Cities thus spatially concentrate the water demand of millions into a small area and also increase the frequency and intensity of water-related disasters like floods and droughts under climate change impacts, hindering development prospects.

自二十一世纪初以来，世界目睹了前所未有的城市增长。这种增长主要集中在亚洲欠发达国家。亚洲拥有全球54%的城市人口，预计到2050年，这一比例将增至66%。预计增长的93%将在欠发达国家，其中60%以上在亚洲城市。在农村人口向城市迁移的影响下，百万以上的城市也见证了最显著的城市增长。伴随着气候变化的影响，快速的大规模城市化使城市面临越来越严重的水资源不安全和水资源紧张。为了维持城市地区紧张的活动节奏和高生活水平，对水的需求也在增加。城市还集中于人为的碳排放，加速全球变暖，影响水文循环，从而进一步加剧城市的水压力。不透水表面的增加和随之而来的地下水储量的枯竭，城市垃圾造成的水污染加剧，以及工业的富裕，使有限的水资源的可用性降低。堵塞的水体和城市排水系统增加了洪水的脆弱性。因此，城市在空间上将数百万人的用水需求集中在一个小区域，同时也增加了气候变化影响下水灾和旱灾等与水有关的灾害的频率和强度，阻碍了发展前景。