Bad news for you, it's not authentic but a copy of a famous painting (山高水長圖 lit. "painting of tall mountains and long(-flowing) waters") by the Qing dynasty painter Shi Xi (Shih-hsi, 1611-1673) (石谿 - his name is written on the strip of paper on the back of the scroll).

The original is in the collections of the National Palace Museum in Taipei.

http://painting.npm.gov.tw/npm_public/System/View.jsp?type=1&ObjectID=30986 (National Palace Museum catalogue)

From the NPM site:

Shixi (originally surnamed Liu, style name Jieqiu, sobriquet Kuncan) was a native of Wuling, Hunan. At the age of 27 he took the tonsure and became a Buddhist monk, going to Nanjing and studying under Juelang daosheng. He first lived at the Baoen Temple and then at the Youqi Temple on Niushou Mountain. The brushwork in Shixi's landscapes is free and natural; his scenes reveal a realm of profound depth. Along with the monks Jianjiang, Shitao, and Bada shanren, Shixi is known as one of the "Four Great Monk Painters" of the early Qing. This painting (donated by Mr. Chang Chun) depicts Tiandu Peak at Huangshan. The mountain soars to the sky with colors to express the hanging waterfall. In the thatched pavilion at its foot are two men leisurely enjoying the scenery. Veils of clouds swell up and mists twist through the vast valley, as compelling and awesome as the billows of a storm.