London ranked among world's most water-stressed cities
London is one of the most water-stressed cities in the world according to new research, which has mapped 500 large cities to determine how global urbanisation is affecting water supplies.
London is ranked as the 15th most water-stressed city, behind Tokyo (1st), Delhi (2nd), Mexico City (3rd), Shanghai (4th) and Beijing (5th). The most water-stressed city in the US is Los Angeles (8th) but the top spots are dominated by cities in India and China - developing countries with fast-growing rates of urbanisation.
The study, carried out by The Nature Conservancy, was undertaken by surveying the water infrastructure of the world's large cities and the results published in the Global Environmental Change Journal. Findings showed that these cities collectively move a total of 504 billion litres of water per day across an estimated distance of 27,000km.
According to researchers, one-quarter of the largest cities suffering from water stress account for a significant amount of economic activity - estimated at $4.8 trillion.
"This large amount of economic activity in large cities with insecure sources of water emphasises the importance of sustainable management of these sources, not just for the viability of individual cities but for the global economy," the study notes.
"Put another way, this $4.8 trillion in economic activity directly or indirectly depends on the supply of 167 billion liters of water per day to these cities. Finding ways to maintain this water supply over time is thus of considerable economic importance."
The research highlights the fact that while large cities only occupy 1% of the Earth's land surface, their source watersheds cover 41% of that surface so the raw water quality supplied into cities depends on the land use of this much larger area.
In addition, financial limitations on infrastructure leave poorer cities in greater water stress, as they have to survive on closer water sources. The study found that cities with low per-capita income rely on water sources on average 26km away, while cities with high per-capita income utilise sources on average 57 km away.
Looking ahead, regions which are geographically limited with regard to water availability, such as the western US and northern China, might have to coordinate better to ensure adequate water can be supplied to all cities.
"Essentially, this is a collective action problem, which requires a regional water management solution," the study states. "For water scarce regions, making more efficient use of available water, by decreasing leakage from urban water systems, increasing the use of recycled water, and increasing the efficiency of agricultural irrigation, may become increasingly important."
"Water shortages are more pressing than climate change... The impact of water stress is one of the most important business risks for the agri-food business globally."
The research comes less than a week after Paul Kelly, the vice president for corporate affairs at Asda, stressed that any businesses that isn't incorporating water scarcity issues into its business strategy is taking a 'very great risk' in terms of its sustainability and resilience going forward.