China's earliest known water-harnessing facilities found in Hubei

WUHAN, Dec. 5 (Xinhua) -- A 5,100-year-old dam, complete with a reservoir and spillway, has been identified as China's earliest known water conservancy project.

Capable of flood control and irrigation, the Xiongjialing Dam is part of the Qujialing relics site in the city of Jingmen, central China's Hubei Province, where a rice-growing Neolithic culture once thrived.

It was initially built around 5,100 years ago on a tributary of the Qingmudang River and was later expanded in both height and width, said Tao Yang with the Hubei Provincial Institute of Cultural Relics and Archaeology.

The existing dam measures 2 meters in height and 180 meters in length. It has a reservoir to the east and an 8.5-hectare irrigation area to the west, with the latter found to have hosted a prehistoric paddy, according to Tao.

The dam was constructed with local earth, which was mixed with root plants to increase the structure's toughness, Tao added. A spillway lies at the northern side of the reservoir, which allowed for discharge of excess water during flood seasons.

The main purpose of the water project is believed to have been irrigating the rice paddy, which suggests that ancient people in the area had learned to harness water rather than simply implementing flood-defending measures, said He Nu, a researcher with the Institute of Archaeology, Chinese Academy of Social Sciences.

The Qujialing relics site is known for witnessing the first-ever discovery of carbonized rice along the midstream of the Yangtze River, China's longest waterway.

Researchers say the dam further illustrates that, in the Neolithic Age, the area had a mature rice-growing agriculture, as this relies heavily on irrigation.

"The Jianghan Plain has a dense river network and abundant water resources, as well as an occasional mismatch of rainy and hot seasons, so storing water for better use while preventing flood is of great importance," Tao said.