A giant project diverting water from the Xijiang River in the western part of the Pearl River to the cities of Shenzhen and Dongguan in Guangdong province began operating on Tuesday, benefiting millions of residents.

The Pearl River Delta Water Resources Allocation Project will provide emergency standby water for the Hong Kong Special Administrative Region, as well as Guangzhou's Panyu district, Foshan's Shunde district and other areas in the Guangdong-Hong Kong-Macao Greater Bay Area. It will benefit more than 32 million people, said Zhu Chaorong, director of the construction division of the Guangdong Provincial Department of Water Resources.

The water currently supplied to Hong Kong mainly comes from the Dongjiang River in the eastern part of the Pearl River.

"The project will support a water demand of approximately 1.7 trillion yuan ($23 billion) in GDP, and gradually return ecological water in the Dongjiang River Basin, further ensuring water supply and ecological security in the GBA," he said.

Construction of the project — the largest water conservancy project in Guangdong and one of the top five water conservancy projects in the country — took four years and eight months, he added. It stretches 113 kilometers, includes 48 tunnels and costs more than 35.4 billion yuan.

The project will be able to annually divert more than 1.7 billion cubic meters of Xijiang River water from the Xingtan township in Foshan's Shunde district to the Dongjiang basin in Shenzhen's Guangming district, playing an important role in alleviating the pressure of drinking water shortages in Shenzhen and Dongguan in the eastern part of the Pearl River.

Shenzhen consumes about 1.8 billion cubic meters of water annually, while Dongguan consumes another 1.8 billion cubic meters.