Beijing and neighboring Hebei Province will jointly plant 100,000 mu (66.7 square km) of forest in 2015, in a step to guarantee the capital city's water security and improve local eco-systems, authorities said on Monday.

According to the program, the forests will cover areas along Beijing's Miyun Reservoir, the city's major source of drinking water, and the upper reaches of Guanting Reservoir on the Beijing-Hebei border.

The project, initiated in 2009, will also cover eight counties under Hebei's Zhangjiakou and Chengde, Beijing's main barrier against sandstorms from northwestern China and an important water source, said Yuan Shibao, an official with Beijing Municipal Bureau of Landscape and Forestry.

The joint project is expected to realize 500,000 mu of forests by the end of 2014, with further plans to reach one million mu.