Welcome to the inquiry from the BBC World Service with me,

Helena Merriman.

Each week we bring you four expert witnesses,

answering one pressing question from the news. It's morning in Cape Town and the phone call comes in, the one everyone's been dreading. Engineers spread through the

city cutting off the water to most of its homes. The next call goes to South

Africa's defense force.

Thousands of soldiers go out on the streets and the police are on standby.

200 water collection points then spring into action and soon there are long cues at each one.

Thousands of people stand in line clutching plastic bottles surrounded by armed guards. This is not science fiction. It's the

scenario that the authorities in Cape Town are preparing for, the apoglyphically named Day Zero, when the city runs out of water.

It's currently projected for the 4th of June.

Everyone's hoping it won't get this far but things aren't looking good.

We are now entering a phase where we start anticipating the very real possibility of a day zero scenario.

Unless everybody commits fully to saving every possible drop of water, we might well see a scenario where people

start collecting water from water distribution points.

It's a bleak situation, one which other cities are watching with interest.

Because Cape Town isn't the only city in the world that's got water problems.

Around a quarter of shortages.

Cape Town is just an extreme example

of what's now a global phenomenon of water scarcity.

We want to know how it got to this point and whether there's anything that other cities can learn.

So in this week's inquiry we're asking, why is Cape Town running out of water. Part 1.

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