REFILE-UPDATE 1-China's Sinohydro rises 10 pct in Shanghai debut
* Sinohydro $2.1 bln IPO is biggest in mainland so far in 2011* Bodes well for upcoming major IPOsBy Soo Ai Peng and Samuel ShenSHANGHAI, Oct 18 (Reuters) - Shares of Chinese dam builder Sinohydro Group rose as much as 10 percent on their Shanghai debut on Tuesday, after it raised $2.1 billion in the mainland's biggest IPO so far this year, boding well for future mega-IPOs.Shares in the builder of the Three Gorges Dam opened at 4.78 yuan and extended gains to as high as 4.95 yuan, compared with its IPO price of 4.50 yuan. Many analysts had expected the shares to hover around the IPO price on their first day of trading."It shows that the market can still digest big IPOs and it's a good sign for other mega IPOs in the pipeline," said Chen Yi, an investment adviser with the sales department of Xiangcai Securities in Shanghai.The firm performance of Sinohydro shares also points to a slightly firmer outlook for the Shanghai stock market's benchmark index . Beijing announced measures last week to bolster banking stocks and support small- and medium-sized enterprises (SMEs), helping trigger a rebound from two-and-half-year lows.China's stock market, which has fallen 13 percent so far this year due to fears of an economic slowdown and the euro zone debt crisis, has forced many Chinese companies to postpone or downsize their IPOs. Weakness in the Hong Kong stock market has also pushed back some firms' fundraising plans.In one of the most high-profile cases, Sany Heavy Industry Co last month postponed its plan to raise as much as $3.3 billion via a Hong Kong listing.Sinohydro braved the weaker market, but slashed the size of its IPO by a fifth in response to weak investor demand, pricing the offer at the bottom of an indicative range and raising 13.5 billion yuan ($2.1 billion) last month, compared with an original target of up to 17.3 billion yuan.Sinohydro's encouraging debut performance bodes well for upcoming major IPOs, including those from China Communications Construction Co , Shaanxi Coal Industry and New China Life.China Communications Construction, the country's biggest port builder, plans to raise 20 billion yuan in a Shanghai IPO, while coal miner Shaanxi Coal also plans to raise about 17.3 billion.Sinohydro, the builder of the Three Gorges Dam, the world's largest hydropower project, has said it plans to use the IPO proceeds to upgrade its machinery, invest in some green energy projects and supplement working capital.China Securities Co and Bank of China International were lead underwriters for the offer. ($1 = 6.371 Chinese Yuan)