The threat of Day Zero, which is an increasing reality for Cape Town, is gaining ground, according to data on the latest dam levels released on Monday.

It indicates that dam levels for Cape Town are 26.3% as at January 29, 2018, from 26.6% at January 26, 2018.

The average daily water production of all water sources is at 580 ml/d compared to the target of 450 ml/d.

If Day Zero does arrive on April 12 as predicted - though not mentioned in Monday's weekly update - taps will be cut off, except in the CBD and commercial and industrial zones.

The City of Cape Town and the national Department of Water and Sanitation measure dam levels to check how much water is available for the region and whether water restrictions are necessary for residents and businesses.

The dam levels are critical for Cape Town's water supply and are a key contributor to the Day Zero water dashboard.

When levels drop to 13.5%, the city will begin to shut down its reticulation system in residential areas.

Residents will have to queue for water at about 180 communal water collection sites, according to the City of Cape Town's contingency plans for Day Zero.

Meanwhile, retailers are cashing in as panic-stricken Capetonians are buying bottled water in bulk.