World Water Day on 22 March 2018 provides yet another timely reminder that water is humanity’s most precious resource – and that we must strive ceaselessly to ensure access to it for as many people as possible.
In January 2018, the journal Nature sounded the alarm about the growing difficulties that communities in many areas of the world will face supplying their people with high-quality water. The water shortages problem will be particularly acute in large cities. According to the article’s authors, urban demand for water is expected to grow by 80% by 2050, while, at the same time, climate change is altering the geography of where water is found.
This study in Nature echoes the recent problems experienced by large cities, including Rome and Cape Town, in providing their populations with a regular supply of water. In late July 2017, the municipal government of Rome narrowly avoided imposing rationing and switching off the taps for eight hours a day. The issue is two-fold: climate change (about 75% less rainfall during the first six months of 2017 compared to 2016) as well as the poor quality of the water supply system, with a leakage rate of around 45%.
The study’s conclusions are not reassuring. Taking into account 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 and the 233 million people living in them.
Furthermore, populations in 19% of these 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 (i.e. quite a number more than 27.6% of them) will likely experience water shortages by 2050 and thus resort to large-scale storage and recycling measures. As a result, colossal investments at a variety of levels will be needed 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 reasons.
The same will hold true in the future. It is projected that cities, which currently have a cumulative population of 3.9 billion – 54% of the world total – will be home to two billion more people by 2030.
Against this disturbing backdrop, climate change could well worsen the scenario 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 end up lacking enough water.
This is a chilling prospect! Because of flows between interconnected groundwater sources, 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 communities living far from cities.
However, solutions do exist, and they need to be implemented as quickly as possible because changes in climatic conditions can be sudden and unexpected.
The most effective response would to use water more efficiently in agricultural irrigation. Measures that can reduce farming’s huge impact on urban water supplies include replacing traditional immersion-irrigation methods with drip irrigation; reducing 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 233 million inhabitants threatened with water shortages could be spared. In some 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 such solutions. In view of the immense and complex problems they are tackling, they should see exceptional growth over the next 20 years.
 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.