长武塬区降雨入渗特征

为了深入理解深厚黄土层的降雨入渗机制,在黄土高原塬区的长武试验站,应用TDR监测天然降雨下大型土柱土壤含水率的动态变化,并结合土柱底部出流量测定数据,分析天然降雨的入渗特征。结果表明:降雨对土壤含水率的影响主要集中在160 cm深度以上,且随深度增加而递减,至240 cm土层降雨峰值信息几近消失;湿润锋运移速率与降雨强度呈正相关关系,与土壤初始含水率成负相关关系,湿润锋运移深度同降雨量和降雨强度正相关;降雨对300 cm土壤水的补给行为普遍存在,入渗补给以活塞流方式为主;降雨入渗补给土壤水的滞后作用表现出对100～200 cm土壤水的补给滞后时间为15～18 d,对300 cm深度土壤水的补给滞后时间为30～45 d。研究结果对明确黄土塬区水循环机制具有一定参考意义。

Characteristic of rainfall infiltration on Changwu Tableland

In order to deeply understand the mechanism of rainfall infiltration in thick soil layer on Loess Plateau, at Changwu experiment station, dynamic of soil water content in a large-scale loess columns was monitored by using TDR （ time domain reflectometry） , the amounts of seepage water collected at the bottom of the loess columns was also measured. The results showed that the impact of rainfall on soil water content was mainly concentrated in the depth less than 160 cm, and the impact decreased with depth. In the depth more than 240 cm, the information of rainfall peak almost disappeared. The velocity of wetting front was positively correlated with rain intensity, and negatively correlated with initial soil water content. The depth of wetting front movement was positively correlated with the rainfall and rainfall intensity. Soil water at the depth of 300 cm could be supplied by rainfall, piston flow was the main mechanism of soil water recharge in loess. The time lag of rainfall infiltration recharge to the soil water in 100 -200 cm soil layer was about 15 - 18 d, and the time lag for 300 cm soil layer was about 30 -45 d. The results could provide some useful references for understanding the mechanism of water cycle in Loess Tableland.