紫鹊界梯田原生态自流灌溉的环境因素探析

Preliminary Study on Environmental Factors Influencing Natural Gravity Irrigation in Ziquejie Terrace

紫鹊界梯田位于湖南省新化县水车镇,是一处新发现的我国古代农耕稻作文化遗存。从水流运动与循环角度对紫鹊界梯田原生态自流灌溉过程进行分析,并在此基础上对影响该过程的因素进行系统归纳与分析。梯田自流灌溉过程是地面灌溉与地下灌溉的耦合过程,雨季以地面灌溉为主,旱季以地下灌溉为主。影响该过程的因素主要有植被、地质、地貌、人类活动及气候等,这些因素对实现梯田的自流灌溉缺一不可。植被拦截和接纳降水,构成地面灌溉水源,特殊地质形成地下"隐形水库",构成地下灌溉水源,两者一道对梯田区水资源进行调配,保障梯田在旱季得以灌溉。梯田区气候特征的垂直性变化,增大了灌溉过程输入性水源的补给。当地农民对梯田精耕细作,实现了对梯田灌溉水源的"开源"与"节流"。特殊地质限制地下灌溉速度,而中山地貌和相对较陡的坡度,加快地下灌溉速度,两者在相互作用中取得平衡,从而保障旱季地下灌溉的时长。

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.