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22.03.2018 | 09:05

BNP Paribas AM: Cities at risk of severe water shortages

World Water Day, which will take place on 22 March 2018, provides yet another timely reminder that water is humanity’s most precious resource and that we must relentlessly focus our efforts on ensuring access for the largest number of people.

In January 2018, the journal Nature[1] sounded the alarm about the growing difficulty communities will face supplying their populations with high-quality water in many areas of the world, especially large cities.

According to the article’s authors, urban demand for water is expected to grow 80% by 2050 while, at the same time, climate change is transforming the way water is geographically distributed.

This Nature study echoes the recent problems experienced by large cities, including Rome and Cape Town, in providing their population with a regular supply of water.[3] In late July 2017, the municipal government of the Eternal City, once known as the Queen of Water, had to impose rationing (cutoffs for eight hours a day on a rotating basis, among other measures).

The issue is two-fold: climate change (about 75% less rainfall during the first six months of 2017 compared to 2016[4]) as well as the poor quality of the water supply system, with a leakage rate of around 45%[5]).

The study’s conclusions are not reassuring. Considering the effects of urban population growth and global warming alone, water demand in 2050 is projected to exceed the available supply in 27.6% of the cities studied[2] and the 233 million people living in them.1 Furthermore, populations in 19% of cities will compete for access to water with the surrounding countryside and its farmers, each with their respective claims. If priority is given to rural areas for food production, among other needs, 38.9% of cities (up from 27.6%) will likely experience water shortages by 2050 and thus resort to large-scale storage and recycling measures. As a result, colossal investments in a variety of areas will be necessary to address this threat.

Over the past 60 years, household water consumption has quadrupled as a result of natural population growth, rising living standards and increasing access to drinking water. This trend was more pronounced in cities due to urban population growth, among other factors. The same will hold true in the future. It is projected that cities, which currently have a population of 3.9 billion – or 54% of the world total – will grow by 2 billion people by 2030. Against this disturbing backdrop, climate change could well act as a major aggravating factor by affecting water resources, raising temperatures, altering rainfall patterns and increasing evaporation. All of these problems are compounded by the need, often neglected in the past, to set aside enough of the available water to protect the environment and biodiversity; if this need were fully met, 46.6% of cities rather than 27.6% (see above) would eventually lack a sufficient supply of water.

This is a chilling prospect! Because of flows between interconnected aquifers, problems could spread from one basin to another if some of them are overused. On a global scale, this could deprive more than 1.4 billion people of water, including certain populations living far from cities.

Solutions, however, do exist. Because changes in climate can occur suddenly and without warning, these solutions must be implemented as quickly as possible. The most important response is the more efficient use of water in agriculture. Measures that can reduce farming’s huge impact on urban water supplies include replacing traditional immersion-irrigation methods with drip irrigation; decreasing leakage from pipes; growing crops that are less water-intensive; and watering only when and where necessary.

If these measures were adopted, 78% of vulnerable cities and their 236 million inhabitants threatened with water shortages could be spared. In certain areas, more radical steps will have to be taken, such as wastewater recycling, rainwater storage and the systematic replacement of defective water pipes.

Companies worldwide are working to design and develop appropriate solutions. Due to the ongoing problems, they should enjoy exceptional growth over the next 20 years.

1 https://www.nature.com/articles/s41893-017-0006-8

2 A total of 482 cities with 736 million inhabitants were studied. The cities most likely to suffer water shortages are Los Angeles, Jaipur, Dar es Salaam, San Diego, Karachi, Harbin, Phoenix, Monterrey and Lima.

3 http://www.novethic.fr/actualite/environnement/eau/isr-rse/le-chiffre-los-angeles- san-diego-lima-ou-caracas-font-partie-du-top-20-des-villes-qui-vont-manquer- d-eau-ces-prochaines-annees-145456.html

4 http://www.ompe.org/secheresse/

5 http://codacons.it/siccita-roma-codacons-affonda-nellemergenza-acqua-la- montagna-esposti/

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