Opportunities for water ­companies are booming around the world because of looming shortages and decades of underinvestment, a conference in Barcelona heard on Tuesday.

China, Saudi Arabia and Algeria, where water shortages have become acute, are placing billions of dollars of contracts out to tender to improve water supplies for their growing populations. The trend is expected to grow, as 40 per cent of the world’s population will suffer water shortages by 2050, according to the United Nations Development Programme. Global warming is expected to exacerbate the problem.