青海湖湖东沙地不同沙丘降雨入渗研究

Rainwater Infiltration at Dunes under Various Rainfall Events in Sandy Land to the East of Qinghai Lake

降雨入渗对干旱、半干旱区土壤水分的影响很大,降雨量、降雨强度、土壤前期含水量等要素都会影响水分的入渗过程。本文通过监测青海湖湖东沙地3种类型沙丘的土壤水分和降雨情况,对区内降雨特征以及不同要素对沙丘水分入渗的影响进行了分析。结果表明:降雨量只有达到某一临界值才发生下渗,流动沙丘、固定沙丘、经治理(人工植被+麦草方格沙障)的流动沙丘发生下渗的临界降雨量分别为5.6mm、1.6mm、0.2mm。水分累积入渗量随降雨量增大而增加,降雨量相同的情况下,入渗量大小表现为经治理的流动沙丘>固定沙丘>流动沙丘。当降雨量和土壤前期含水量相近时,入渗量随降雨强度的增大而增加,尤其在小降雨事件下,降雨强度是影响入渗的关键因素,大降雨事件下降雨量则成为影响入渗的决定因素。降雨量和降雨强度相近的情况下,入渗量与土壤前期含水量呈负相关关系。随着降雨量增大,入渗水分全部消耗所需要的时间逐渐增加,尤其当降雨量大于10mm时,入渗水分消耗所需时间将随着降雨量的增大迅速增加。

In arid and semi-arid areas, rainwater infiltration has significant effect on the soil moisture. Many factors such as precipitation, rainfall intensity, and antecedent soil moisture play important roles in the rain-water infiltration. Based on the monitoring data from 08/2009 to 12/2010, we analyzed the rainfall charac-teristics and its infiltration at dunes under various rainfall events in sandy land to the east of Qinghai Lake. The results showed that infiltration took place only when precipitation reached a critical value. The critical value for active dune, fixed dune and active dune with artificial measurement （artificial vegetation and straw checkers） were 5.6 mm, 1.6 mm and 0.2 mm, respectively. In the case of same rainfall, the cumulative in- filtration of the active dune with artificial measurement was the largest, followed by the fixed dune and the active dune, and it increased with increasing rainfall. When the precipitation and antecedent soil moisture was similar for a certain sand dune, its infiltration would increase with increasing rainfall intensity, especially in the small rainfall event, whereas in the large event the precipitation became the determinant factor. For the similar precipitation pattern, infiltration had inverse correlation with antecedent soil moisture. The time for the infiltration of water to be consumed grew with increasing rainfall, particularly after rainfall exceeding 10 mm it increased rapidly.