Tapping into water security: a Tale of Two Cities
How two cities in emerging economies are responding to disaster reveals why water security is an urgent issue, and what other cities can do to build resilience.
Urbanisation is transforming the way we live, but failing to plan for water security could leave cities increasingly fragile.
Most cities weren’t designed for this kind of growth. Ageing infrastructure and unplanned expansion poses a danger exacerbated by climate change and limited freshwater. This lack of water security – reliable supply and resilience to risk – leaves cities at greater risk of floods, drought and economic damage. How do we overcome this?
How Chennai is answering its water crisis
Chennai – the ‘Detroit of India’ – is a thriving automotive hub. The IT, petrochemicals and manufacturing industries have flocked here. So do those looking for jobs: the current population of 11m expands by a quarter of a million people every year.
But unplanned expansion by industry and informal settlements has swallowed floodplains, green spaces and bodies of water. This has dire consequences for a city buffeted by heavy, unpredictable rains. In 2015, floods killed more than 400 people.
One solution is a return to Chennai’s ancient temple tank system: restoring or building tanks at temple sites to filter and store rainwater. These can recharge groundwater, too – which, without action, is expected to be 60% depleted by 2030.
And therein lies another issue. For all its excess water, the city can’t cope with demand. In 2019 Chennai reached Day Zero: it ran out of drinking water.
Bringing water in by truck and train is a costly fix for water scarcity. With climate change threatening less rainfall and higher temperatures, the long-term strategy is about future proofing the city’s infrastructure.
Measures include building two extra desalination plants, which would increase capacity by 550m litres a day. There’s also been investment in wastewater reclamation plants at Nesapakkam and Perungundi. Here, recycled wastewater will be blended into lakes, then pumped into the plants for treatment before re-entering the drinking water supply.
Making Marrakesh water resilient
With its population of 1m and arid desert environment, Marrakesh may seem far removed from Chennai. But like cities everywhere, Marrakesh has grown rapidly. The population increased by 300,000 between 1997 –2020 (23 years), but is projected to gain the same number by 2034 (14 years).
Until the 1950s, the city siphoned water from the Atlas Mountains via khettaras (man-made underground tunnels). Then came the tourist boom, its rising demands competing with the needs of residents and farmers. By the 1970s the city was almost entirely reliant on groundwater from the Tensift aquifer.
By the 1990s the khettaras were dried up and the water table dropping – yet the city was approving water-intensive golf resorts.
As in Chennai, wastewater has been key to resolving these tensions.
Rather than continuing to return minimally treated wastewater to the Tensift, sewage now passes through the city’s treatment plant. From there, it enters the irrigation system – servicing those verdant golf resorts. The process allows 30m cubic metres of water to be reused in this way. Importantly, the resorts are billed for at least 80% of their projected water needs, regardless of actual use. This stops them using cheaper water drawn from the aquifer.
A second strategy has tackled a global problem: water loss. Local water authority RADEEMA was losing close to 40% of the city’s water supply to leaks in the early 2000s. In the following decade that was reduced to 27%, with even lower goals set for the future.Cities from Malta to Las Vegas are battling these same issues – and a predicted 1.9bn city dwellers face living with water scarcity by 2050 as a result. Cities yet to be built are in a prime position to plan for resilience. In the meantime, Marrakesh and Chennai offer creative solutions to an increasingly urgent problem.
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