Abstract: Located at Shuiche Town, Xinhua County of Hunan Province, Ziquejie Terrace is a newly discovered heritage of ancient rice farming. The natural gravity irrigation process in Ziquejie Terrace is analyzed in terms of flow movement and circulation, based on which the influencing factors on the process are summarized and studied. The gravity irrigation consists of two coupled processes, the SIP (surface irrigation process) and the UIP (underground irrigation process), of which the former dominates in rainy seasons while the latter prevails in dry seasons. The gravity irrigation process is mostly influenced by vegetation, geological and geomorphic condition, human activity and climate, all of which are indispensible for the natural gravity irrigation. Water source of the SIP, which comes from rainfalls intercepted and stored by vegetation, and water source of the UIP, which is offered by the underground “ stealthy reservoir ” formed by the terrace ' s special geological condition, hand in hand reallocate the water resources in the terrace region to ensure the irrigation in dry seasons. And the supplies of input water sources for the irrigation are increased by perpendicular change of climate characteristics in the terrace region. Moreover, the local farmer ' s careful cultivation on the terraces contributes to the storing and saving of irrigation water resources. The UIP speed is limited by the special geological condition, while is accelerated by the middle mountain landform and the steep slope. They interact, and result in an equilibrium, which finally guarantees the underground irrigation time in dry seasons.

Key words:  Ziquejie Terrace  ,  gravity irrigation ,    influencing factors  ,   stealthy reservoir  ,   water resources allocation