Water shortages have been a problem for the country's oldest city since Jan van Riebeeck arrived.

Ten years after the Dutch ship's captain settled in Cape Town he was forced to build a reservoir to deal with the problem.

Professor Jenny Day, director of the Freshwater Research Unit at the University of Cape Town, said much has to be done to ensure that the Mother City does not dry up.

This could even include pumping water from under Table Mountain.

"The Table Mountain Series Aquifer stretches from Port Elizabeth to Cape Town and up to the Cederberg. We think there is an awful lot of water but we don't know what we can exploit without causing any damage. Or how much of it would be replaced by rainfall," she said.

The city is currently investigating this option.

Day's views have been backed up by the Department of Water Affairs which on Monday announced that the Western Cape could face dire water shortages within the next six years.

But these shortages will not bring the city to a grinding halt if Capetonians "use water more sparingly".

In the mid-1980s, Day co-authored Vanishing Waters, in which he predicted that, by about 2015, many of the country's larger cities will experience permanent drought conditions.

According to the department's latest Western Cape water supply system study, few surface water development options are available "for augmenting water supply to the City of Cape Town and surrounding towns".

"Population growth and the subsequent growth in the economy have been identified as major factors that are placing exponential strain on the water available for users," the department said in a statement.

"The users include the City of Cape Town, as well as municipalities of Stellenbosch, Drakenstein, Swartland and Saldanha as well as agricultural users."

But it is not all doom and gloom for the city. Millions have been invested in infrastructure upgrades and replacements, water metering and water pressure management among other measures to reduce water losses.

The city also plans next month to issue a tender for a feasibility study to build a "large scale" seawater desalination plant. And feasibility studies on a large-scale re-use programme are also on the cards.

Day said desalination, although expensive, was not far off.

"In my opinion it is going to have to happen in Cape Town not very long from now. But because it is so expensive, they have to look at other options first."

Phil Mashoko, director of water and sanitation for the city, said it was pivotal to start planning for the future supply of water.

"There is no reason for people to panic. We are being proactive by putting plans in place now to ensure that we don't run out of water six years from now," Mashoko said.

Last year the city embarked on a water conservation campaign which will be intensified.