华南丘陵地区典型流域的土壤水分时空变化及其驱动机制  

Spatiotemporal Variation of Soil Moisture Profile and Its Driving Mechanism in a Typical Watershed of South China Hill Region

作　　者：刘远[1] 李思颖 周买春[1] 姜俊红[1] LIU Yuan;LI Si-ying;ZHOU Mai-chun;JIANG Jun-hong(College of Water Conservancy and Civil Engineering,South China Agricultural University,Guangzhou 510642,China;Guangdong Hehai Engineering Consulting Co.Ltd,Guangzhou 510610,China)

机构地区：[1]华南农业大学水利与土木工程学院,广州510642 [2]广东河海工程咨询有限公司,广州510610

出　　处：《节水灌溉》2022年第4期83-88,93,共7页Water Saving Irrigation

基　　金：广东省自然科学基金项目(2020A1515010914)。

摘　　要：流域土壤水分分布是水文学研究重要课题之一,采用地统计学半变异函数分析广东省泗合水流域旱季和雨季2 m深土壤剖面含水率,结果表明:流域土壤剖面水分可划分为表土层(0~20 cm)、根系层(20~70 cm)、基质势层(70~120 cm)、地下水位影响层(120~200 cm)和地下水位层(>200 cm)5个土层区间。表土层直接受降雨和大气蒸发强烈作用,同时受枯枝落叶持水和林下植被根系吸水影响,土壤水分季节和层间变化剧烈。林木根系主要分布在20~70 cm,这层的土壤水分补充主要为根系边隙流,消耗主要为根系吸水,土壤基质势梯度起调整分配作用,土壤水分季节和层间变化都较大。基质势层根系分布较少,大孔隙流较少,土壤水分主要受土壤基质势梯度影响,季节变化比上层土壤小,且随深度变化减小;在120 cm深基质势梯度作用消失,土壤水分季节间及土层间都不再变化,形成零通量层。山坡下部、山坳和低洼地区,地下水位季节变化,对120~200 cm区间的土壤水分产生影响。流域有效包气带厚度是从地面到土壤水分零通量面的深度,在泗合水流域约为120 cm;流域土壤蓄水容量即为这一区间土壤剖面含水量的季节差,计算结果为42 mm;该结果为华南丘陵地区无资料流域的水文模拟提供参数支持。Soil moisture distribution at a catchment scale is an important topic in hydrology.In this study,geostatistical semi-variograms were used to analyze the soil moisture profiles in a depth of 2 m sampled during dry and wet season over Siheshui catchment of Guangdong province.The results show that:at a catchment scale,soil moisture profile can be divided into 5 layers as top surface zone(0~20 cm),root zone(20~70 cm),matric potential zone(70~120 cm),groundwater affected zone(120~200 cm)and groundwater zone(>200 cm).Driven by rainfall and evaporation directly and also affected by interception of forest litter and water uptake of undergrowth roots,soil moisture in the top surface zone changes promptly seasonally and along depth.The roots of forest trees are mainly distributed in 20~70 cm soil depth.In this zone,soil moisture is replenished mostly by rainfall flow in gaps between roots and soil substrate,water consumption is mainly caused by root water absorption,soil matrix potential gradient plays a role of adjustment and distribution,and soil water changes greatly in season and between layers.There are few roots and little gap flow in 70~120 cm depth.Soil moisture in this depth is driven mainly by matric potential gradient and changes seasonally much less than that in upper zones and the change becomes less and less with the increase of depth.At 120cm depth,the matrix potential gradient disappears,and soil moisture does not change between seasons or between soil layers,forming a zero flux layer.In the lower part of the slope,mountain depression and low-lying areas,the seasonal variation of groundwater level affects the soil moisture in the range of 120~200 cm.The effective vadose zone thickness is the depth from the ground to the zero flux surface of soil water,which is about 120 cm in Siheshui Basin.The soil water storage capacity of the basin is the seasonal difference of soil profile water content in this region,and the calculated result is 42 mm.The results can provide parameter support for hydrological simulatio

关 键 词：华南丘陵地区 土壤水分剖面 驱动机制 时空变化 季节变化 半变异函数 

分 类 号：S271[农业科学—农业水土工程] S152.7[农业科学—农业工程]