The construction of a desalination plant in Hong Kong designed to expand water supplies in the special administrative region is expected to be finished and put into operation in 2023, the project engineers said on Tuesday.

The Tseung Kwan O desalination plant, built with a water production capacity of 135,000 cubic meters per day, can meet 5 percent of Hong Kong's current fresh water demand, said Lee Kwun-chung, chief engineer of Hong Kong's Water Supplies Department.

After its entry into service, it will be the first desalination plant using seawater reverse osmosis technology in the city, the most advanced and efficient technology for producing drinking water from seawater, Lee said.

The department commissioned three companies in 2019 for the project under a design-build-operate arrangement worth about HK$9 billion ($1.2 billion).

China State Construction International Holding, a State-owned company based in Hong Kong, is the major contractor of the project.

Zhang Baoping, manager of the project, said construction began in December 2019 and will end in March 2023.

"Although affected by the COVID-19 epidemic, the project is expected to be completed as scheduled," he said, adding that many construction materials are from cities in Guangdong province, which helps to save time.

Environmental protection is highlighted in the project, Zhang said, adding that many temporary components on the construction site will be recycled, including concrete and solar panels.

The desalination plant is part of a wider strategy of the SAR to diversify its water sources in the face of various challenges, including increasing local demands due to population and economic growth and occurrences of extreme weather.

Surrounded by the sea on three sides, the city of Hong Kong has faced a lack of fresh water resources in the past.

Before the 1960s, the water use of residents mainly depended on rainfall.

Lee, the engineer from the water supplies department, who is in his 40s, said, "When I was a child, I often heard the elders say that the water supply was once every four days and could only be used for four hours at a time."

There was an old saying at that time in Hong Kong that when you used water upstairs, you had to shout to your neighbors downstairs to turn off the faucet due to low water pressure, he said.

To solve the water shortage, Hong Kong has been importing water from the Dongjiang River, which runs through southern Jiangxi province into Guangdong province, since 1965, with the full support of the central government.

Currently, the daily consumption of water in Hong Kong is 2.7 million cubic meters.

About 75 percent of the fresh water comes from the Dongjiang, and 25 percent from local reservoirs and rainwater, official data showed.

"With the support of the country, Hong Kong has now achieved a stable water supply," Lee said, adding that there are also potential worries, including climate change and the increasing demand for water in cities along the Dongjiang.

"The plant is very important for Hong Kong's long-term development, so it has won the support of the public," he said, adding that space is reserved next to the first phase of the project for the second stage of construction to expand production capacity.