XINING - China has spent 4.55 billion yuan ($713 million) on conservation work to preserve the source of the Yellow, Yangtze and Lancang rivers, a local conservation official said Wednesday.

The ecological conservation program, initiated in 2005 and with 7.5-billion yuan earmarked, aims to halt degradation of the three-river region in Northwest China's Qinghai province, said Chen Yongle, chief of Qinghai office three-river sources conservation program.

The investment has funded grazing bans, pasture conservation projects, inhabitant resettlements and artificial weather control, Chen added.

The lake area in the targeted region increased by 245 sq meters, water yields increased by 18.3 percent compared to those of in 2004, according to Li Xiaonan, deputy chief of the conservation office.

Li said since the efforts to repair the fragile plateau wetland, the rivers are able to hold more water and the pasture in the area is improving.

The lakes sprawling on the Qinghai-Tibet plateau that serve as source of China's three major rivers are hailed as the "water tower" of Asia. Covering an area of 395,000 sq km, the area also is the habitat for many endangered species, such as the Tibetan antelope, yak and snow leopard.