Under the scorching sun, Wang Jihu and dozens of villagers clean dust and earth from a section of the Great Wall in Gansu province.

To help protect the ancient cultural relic, Wang and more than 50 other villagers are building a channel to catch floodwater.

Stretching 88 kilometers in Ximen, the section of the wall where Wang works was built during the Ming Dynasty (1368-1644). More than 400 km of the Great Wall can be found in Gansu.

Wang, 50, said he and his friends used to climb the wall during their childhood.

"We didn't know the significance of the Great Wall," he said. "We just played there for fun.

"Things have changed. People who live around here now know it is a cultural relic and may not be damaged."

Gansu began its flood prevention project in 2011 with an investment of 30 million yuan ($4.8 million).

Two phases of the project have been completed. The third phase involves constructing a 658-meter-long support structure on either side of the wall and a 1,340-meter-long flood discharge channel.

"When this phase is finished, the Great Wall won't fear for floods anymore," said Song Chang, director of the cultural relics bureau in Shandan county, which administers Ximen.

Each villager involved in the project is paid about 100 yuan per day, and they help out when not carrying out duties on their farms.

"It's a good way to increase their income as well as protect the Great Wall," Song added.

According to research released by the State Administration of Cultural Heritage, Gansu has the longest length of the Great Wall built in the Ming Dynasty, and it has the second-longest length of wall built in the Qin (221-206 BC) and Han (206 BC-AD 220) dynasties.

Unlike eastern parts of the Great Wall in Beijing and Hebei, which were mostly built with stones and bricks, sections in Gansu were made with earth. They have become extremely fragile after centuries of erosion from wind and sandstorms.

Gansu has undertaken more than 10 consolidation and flood prevention projects in recent years, said Xiao Xuezhi, deputy director of the provincial cultural heritage department.

The central government has spent more than 500 million yuan to protect sections of the structure under the 11th Five-Year Plan (2006-10).

Construction of the Great Wall began during the reign of China's first emperor, Qin Shihuang (259-210 BC), to keep out invaders.