The South African 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, says 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.

The drought-stricken Western Cape province, which includes Cape Town, was declared a disaster zone on Monday by Helen Zille, the province’s premier.

Cape Town authorities say area dam levels are at 20.7 %, down by 0.7 % from a week ago. They note that the last 10 % of a dam’s water is mostly unusable because of mud, weeds and debris at the bottom.