Water consumption on Rand Water supplied areas has shot up substantially over the past week, placing risk on sustainability of supply.

This was announced by Rand Water CEO Sipho Mosai on Monday as Gauteng was engulfed with serious high temperatures with no rain in sight in the next weeks.

"Water consumption has become unsustainable," said Mosai.

Mosai told journalists in Johannesburg that demand for water had increased from an average of 4,368 mega-litres a day to 5,000 mega-litres a day.

This, he adds, has prompted Rand Water to impose water restrictions to municipalities.

"At this stage we cannot be using water for anything than drinking... If we reduce the demand, we should be fine," said Mosai.

Gauteng has been having high temperatures for weeks, which has put water demand high.

Two years ago, the province faced a similar drought which had a negative impact to households and businesses.

Human settlement, water and sanitation Lindiwe Sisulu said despite high demand, there was no need to panic.

"There is no need to panic but there is a need to use water sparingly," Sisulu said.

Rand Water supplies Gauteng, parts of Mpumalanga, North West and Free State.

Sisulu said the other provinces facing high temperatures with no rain were Eastern Cape and Limpopo.