The most serious salt tide that struck the Pearl River estuary in south China last winter is gradually receding as a result of increased rainfall in late February.

The Guangdong Provincial Astronomers Society monitoring the Xiaoying Watergate near the Hengmen Waterway in the estuary gave the all-clear from February 28 to March 5, the longest salt tide-free period since last autumn. The waterway empties into the South China Sea. 

Salinity levels last Friday were 290 grams per liter at the Dayongkou Watergate near the Modaomen Waterway, in the same estuary, also a record low since last autumn. The chlorine content at the same site was above 5,080 milligrams per liter between February 17 and 28.

The Pearl River estuary fell victim to repeated salt tides as a result of reduced rainfall in autumn and winter, especially in and around Guangdong Province, the worst in recent years.

The salt tide gravely affected drinking water supplies in the densely populated Pearl River Delta, where major cities such as Zhuhai, Zhongshan, Panyu, Dongguan and Shunde are located.

However, heavy rainfall in the drainage area of the Pearl River on February 18 and February 27 increased water levels and reduced salinity content in the Xijiang, Beijiang and Dongjiang, all tributaries of the Pearl River.

Salinity concentrations are expected to continue to drop throughout March.

(Xinhua News Agency March 6, 2006)