To try to address current and future water shortage issues, some countries have implemented cloud seeding programs to induce rainfall. Such countries include: China, the United States of America, Dubai, India, Venezuela, the United Arab Emirates.
Many countries, over the years have experimented with cloud seeding, with varying degrees of success, such as in Australia, where it is success in some parts of the country, but not others.
Some jurisdictions have established water desalination plants to supplement existing supplies. Such schemes can be expanded.
In addition to such measures, water conservation programs, to reduce water consumption, form part of the strategies. Such programs include reducing domestic water usage in the bathroom & laundry,by reducing bathing times and the implementation of dual flush toilets. Redirecting rain water from household gutters to storage tanks so the water can be used on gardens.
Gray water systems have been used on an industrial scale in Mexico and are being introduced on a domestic scale elsewhere.
What strategy gets used where, will depend on what is most appropriate for each locality.
In 2018 the BBC reported on 11 cities most likely to run out of drinking water, London was one of them. The others were Sao Paulo, Bangalore, Beijing, Cairo, Jakarta, Moscow, Istanbul, Mexico City, Tokyo & Miami.
After enduring a drought, in which water levels started to decline in 2015, Cape Town nearly ran out of water in 2018, where dam capacity reached 15 to 30 percent. The city was 90 days away from having no water. Cape Town got lucky, heavy rains began falling in June 2018, averting the crisis and by September 2018 the dams were close to 70 percent full. In 2020, with successive rain the dams were 95 percent full.
As part of the strategy to ensure more water a desalination plant was built.
As a result of the Millennium Drought in Australia from 1997 to 2009, six major desalination plants were constructed between 2006 and 2012. These plants have a capacities ranging between 125 ML per day to 410 ML per day (45 GL/yr to 150 GL/yr). Another 18 additional smaller plants were also constructed and another 6 are planned or being constructed.
Britain is an island nation. It has easy and readily available access to sea water. If the will and money were there, desalination plants could easily be constructed to supply any part of Britain. The other problem that will need to be solved if such plants were to be construction is what energy source will be used to allow the plants to operate. The desalination plant in Perth, Western Australia initially had a dedicated wind farm. It may still be operating using renewable energy sources for its full production.
What happens with London's water supply issues will depend on what the government and water authorities do and how timely they are about it.