China aims to double the amount of water it transfers from the flood-prone south to arid northern regions, officials said Thursday, as the government prepares to launch the second phase of its controversial cross-country water diversion program.

The South-North Water Diversion Project was first proposed in 1952 to ease flooding in the south and drought in the north, but critics say its costs are too high and the diversion of polluted water to other regions could contaminate other lakes and rivers.

The first phase of the project, completed five years ago, linked the Yangtze and Yellow rivers through two main routes in eastern and central China, with a more challenging route in the far west still to come.