The most powerful salt tide since last autumn hit the Pearl River in Guangdong province yesterday, a senior local astronomer¹ said.

Li Jianji, director of the Guangdong astronomical² society, said that despite its force, the tide should recede³ on Saturday and, thanks to the preemptive measures taken, the water supply in the Pearl River Delta⁴ (PRD) region should not be affected⁵.

Salt tides are caused by astronomical events, Li said.

On Saturday, the moon will be at its closest point to the Earth, while on Sunday, the sun, Earth and moon will be in alignment⁶, he said.

However, thanks to the plentiful⁷ rainfall last summer and autumn, the impact of the tide is not expected to be serious, he said.

Salt tides are a perennial⁸ problem for Guangdong, generally striking during the comparatively dry months of January and February.

The province is now in its low-water season, following a marked lack of rainfall at the end of last year.

Last month, rainfall in the provincial⁹ capital Guangzhou was just 60 percent of the average for the time of year.

The provincial climate center has forecast rainfall to be down 10 to 20 percent on seasonal¹⁰ averages in the first quarter of the year, increasing the risk of salt tides.

Following a series of heavy tides between 2004 and 2006, authorities introduced several measures to minimize their impact, including the development of an integrated water supply network in the PRD.

A key element of the plan is the construction of the Zhuyin Reservoir in Zhuhai, work on which began last month.