'36% cities to face water crisis by 2050'

How will expansion of cities affect global water demand?

With global urban growth set to add more than 2 billion additional people by 2030, our cities will expand. Today, approximately 54 per cent of the global population, or 3.9 billion people, live in cities. This is likely to grow between 60 and 92 per cent by the end of the century. Historically, as urban population increased by leaps and bounds, domestic water use almost quadrupled in the past 60 years. Factors such as wealth and access to drinking water infrastructure contributed to high water usage. The worrying point is this trend will continue with domestic water use forecast set to increase by another 80 per cent by 2030.

Which cities risk facing water crisis?

In a recent research published in the online journal, Nature Sustainability, my colleagues and I found that 16 per cent of the cities featured in our sample experienced water shortage. These cities witnessed at least one month of surface water deficit during the 1971-2000 baseline period. This happened even after they prioritised water over agriculture. According to the study, by 2050, Los Angeles, Jaipur and Dar es Salaam are predicted to witness the greatest surface-water deficit. On an average, this will exceed 100 million cubic metre (m3) per year. It also says that urban surface-water deficit of the top 20 cities is currently about 2,338 million m3, which is around 35 per cent of the total deficit.

How will climate change hit supply?

While growth in urban population is leading to increased water demand, climate change will make supply more variable. In some places, it will lead to a reduction of availability. It is likely that by 2050, 36 per cent of the world's cities will face water crisis. The common opinion of various studies is that water shortage will increase in the years to come. In future, one in six large cities is likely to be at the risk of water deficit.

Increased demand for urban water supply will put pressure on groundwater resources. We investigated urban groundwater stress by calculating the urban groundwater footprint of regional aquifers. Climate change and socio-economic factors like urbanisation will lead to an increasing urban groundwater footprint. Historically, many cities in less developed countries had systems that were inadequate to provide 24X7 water access to its people, a goal that will become even harder to reach in the future.

Are we heading towards a dry future?

Everyone is talking about Cape Town. Prior to this, droughts hit Sao Paulo and California. As weather varies, it is impossible to predict which cities may face drought in the future. However, what we can say with certainty is that increased water demand and less regular supply due to climate change will make events like the Cape Town drought frequent.

How can we avoid more Cape Towns?

There are two solutions. One is expanding water supply and increasing storage. This will ensure that cities survive under drought. This can be done by long-distance water transfers, but can also come from groundwater or desalination. When cities appropriate more water, they impact the freshwater ecosystem. Sometimes urban water usage is more than in agriculture. Also, society should make more efficient use of water. This can be done by fixing leaky pipes, which causes wastage. Steps must be taken to make farmers efficient in use of irrigation water. Water reuse is an option too.

(This interview was first published in the 16-31st March issue of Down To Earth as part of this cover story).

India

India Environment Portal Resources :

• Water competition between cities and agriculture driven by climate change and urban growth
• Order of the Delhi High Court regarding supply of water to Delhi, 13/03/2018
• Urban water systems in India: a way forward
• Urban water supply and sanitation in Indian cities: compendium of good practices