沙地降雨入渗水分动态

DYNAMIC VARIATIONS OF SOIL MOISTURE CAUSED BY RAINWATER INFILTRATION IN BARE SANDY LAND

应用土壤水动力学基本原理，结合先进仪器的使用，从动力学角度，以能态观点定量研究沙地水分入渗动态。通过野外现场观测，分析不同深度含水率和吸力随时间变化过程，研究沙地降雨入渗水分传递过程，探讨入渗条件下沙地水分运动的动力学机制和特征。

Shapotou Desert Experimental Research Station is situated in the southeastern fringe ofTengger Desert,with an annual rainfall of 186.2 mm. Neutron probe, tensiometer and automaticrain gauge have been installed in bare sandy land to measure soil moisture, soil water potential , rainfall amount and its intensity. Based on the otherved data, the processes rain water of infiltrationand redistribution were analyzed.The results are as followings:(1)Volume water content and suction power reflected the characteristics of quantity and energyof soil moisture respectively. The observed data showed that the change process of soil moisture contentwas consistent with the energy transmitting process,and the moisture sorption process was faster thanthe desorption one in sandy land.Volume water content and suction power varied from high to lowfrom top to bottom during the rainwater infiltration process. From the obervations one might concludethat 0.6 m depth was a dividing line indicating the brisk extent of soil moisture.(2)Vertical transimission speed of soil moisture under rainfall condition varied from 0.35 to2.29 cm/h. The initial infiltration speed of rainwater was low due to the existence of the dry sandlayer at the surface.However, as a whole , the soil water transmitted fastly at first , then slowed downand finally tended to be stable.(3)The boundary condition of rainwater infiltration was controlled by water supply, Theinfiltration rate was equral to rain in tensity, and cumulative infiltration was equal to rainfall. Othervations of soil water pontential showed that zero flux plane was atbove 0.2 m depth, and soilmoisture moved down constantly below 0.2 m depth in the rainy season. The redistribution ofrain water played a key role in the dynamic variation process of soil moisture.