South Africa's city of Cape Town is instructing people to severely restrict water use because of the area's worst drought in more than a century.

The city, a major international tourist destination, said it is experiencing the impact of climate change and predicts little rain in the next three weeks. It wants daily water usage to be reduced to 100 liters (26 gallons) per person and recommends taking two-minute showers and flushing the toilet only when necessary.

Cape Town residents worried about sediment from dams with low water levels are starting to boil tap water, said Justin Friedman, founder of For Love of Water , a non-profit group that promotes conservation. Some people are worried that the city might turn off the taps at some point, he said Tuesday.

The city of nearly four million people is in its low tourist season. Tour operators hope eventual rains will improve the situation before the high season toward the end of the year.

The drought-stricken Western Cape province, which includes Cape Town, was declared a disaster zone on Monday by Premier Helen Zille. The designation gives more power to the province to direct resources to the water crisis.

The levels of dams that supply Cape Town are at 20.7 percent, down by 0.7 percent from a week ago, the city said. It noted that the last 10 percent of a dam's water is mostly unusable because of mud, weeds and debris. Municipal repair crews are also struggling to attend to hundreds of leaks and faults that cause water loss.

As dam levels drop, the city said in a statement , authorities will "start to implement a lifeline supply which entails reducing the water pressure to a very low level across the metro."

The last time the Western Cape experienced a drought of the same severity was in 1904. South Africa is still struggling to overcome a drought that began in 2015. Experts attribute the drought to El Nino, a climate cycle in the Pacific Ocean, which has caused a massive heat wave throughout Southern Africa, with rainfall drastically decreased.