Two-fifths of the people in Asia's cities do not have access to regular sources of water, let alone piped water. India is a glaring example. Quite exceptionally, we are confronted with the conundrum of insufficient water for an increasingly urban population, receding groundwater levels, and yet the peculiar incidence of unexpected flash floods.

 Unplanned development – rapid growth in urban sprawl, unwieldy (though not necessarily unjustified) urban migration, and densification have led to unwarranted groundwater extraction. Urban floods are due to the sanction of construction zones on land earmarked for drains and flood-plains, encroachments, and the use of impervious materials in building pavements, common areas, etc. Paradoxically, even cities short of water should suddenly face floods, or contrarily, places like Cherrapunji in Assam which have heavy rainfall should be short of good drinking water. Mumbai faces floods intermittently. In 2012 Beijing was flooded. A flood in Shanghai led Uber to change its logo from a car to a boat and led to Chinese cities being described as having “sea-views.”

 Chennai was estimated to once have hundreds of water bodies. Wuhan in China used to have more than 100 lakes, but it lost two-thirds of them to construction sites. In India, the common practice of rapacious builders is to argue with regulators that a dried water-body deserves to be liberated for development in the master plan to meet the huge housing needs.

 China learned its lessons early. India has yet to fully wake up despite it using 25% more water because of the hot weather. In 2013 the Chinese President Xi Jinping initiated 30 “sponge cities,” and to attract private partnerships for effective PPPs. Work on 16 sponge cities has commenced, targeting to reduce rainwater runoff by capturing 70% of it through a grid of absorption channels and underwater tanks, cover rooftops with plants, create wetlands for rainwater storage and make pavements with permeable materials so that excess water can be stored. Water thus stored will be used for street cleaning and firefighting. The water table under Beijing had been subsiding at an alarming rate because of pumping from wells. This has now slowed. The project has revived severely eroded ecosystems nearby which had earlier dried up.

 Another initiative brought more than one-third of Beijing’s water supply to be brought from 1400 km away under the South-North Water Diversion Project from the Danjiangkou reservoir in the south from where water is brought through a linkage of canals and pipelines. Bhopal also lifted water from the Narmada river 100 km away, to reduce its dependence on the Bhopal lake which used to cause problems every summer.

 Along with policies for reuse and recycling, we will also have to stress that municipalities value water appropriately. It should be both revenue-fetching (metering systems have to be installed – so that it is paid for, and appropriate tariffs have to be fixed) and accountable (not systemically leaked due to faulty mechanisms). It is critical that for urban water systems only proven quality of materials and pipes be deployed – municipalities are prone to making expedient choices as a result of which pipes keep bursting and leaking, thereby failing the best-intended schemes.

 Apart from decentralized rainwater harvesting, check dams, desalination technology, drip irrigation, crops that can tolerate saline water, solar panel research, greenhouses, and hydroponic technology, it is also important to ensure that industrial and domestic water is treated and recycled to the best possible international standards. In Europe, 80% of water in industrial processes is recycled. In China, the share is half that. In India it is negligible. Therein lies the way forward.