(Yicai Global) Aug. 19 -- China's three major mainland stock indexes edged down by midday while shares related to the irrigation sector surged amid the Yangtze River's large-scale flooding.

The Shanghai Composite index fell 0.3 percent to 3,440.71. The Shenzhen Component Index decreased 1.05 percent to 13,623.06. The ChiNext index was 2.22 percent lower at 2,641.00.

Pipeline firms and irrigation project contractors, such as Qinglong Pipes Industry [SHE:002457], Guotong Pipeline [SHE:002205], and Dayu Water-Saving Group [SHE: 300021] all rose by the 10 percent daily limit.

The sectors of agriculture, as well as food and beverage, were also amongst the best performers, while vaccine makers and chip manufacturers tumbled.

Editor: Emmi Laine