灌水量对包气带水分运移与滞留影响过程研究

Research on impact process of irrigation amount on moisture migration and retention in vadose zone

包气带水是支持植被生长的关键因子,也是联系地表水与地下水、以及补给地下水的重要水源,为了解地表灌溉量和历时对包气带水分运移和滞留过程的影响,在陕西省泾惠渠试验站开展了夏玉米和冬小麦畦灌试验,应用实测数据和Hydrus-1D模型模拟包气带0~6 m土壤水分运移滞留过程,并对其水分平衡进行定量分析计算,结果表明：不同的灌水量、进水流量和灌溉历时会引起明显土壤水分运移滞留变化。夏玉米模拟期采用大流量、快速灌溉,剖面底部的渗漏量大,占地表总入水量的24.88%;冬小麦模拟期灌溉流量小、历时长,底部渗漏量小,占地表灌溉量的2.29%;夏玉米试验期内蒸发蒸腾量大于冬小麦,分别占地表总入水量的32.32%和27.33%,棵间蒸发量占蒸发蒸腾量的比例分别为18.15%和16.92%;夏玉米与冬小麦试验期内包气带土壤水分滞留比例分别为42.8%和70.38%,灌溉进水流量和历时是控制包气带水分滞留和进入地下水的关键因素。

In vadose zone,soil water is the key factor supporting vegetation growth,the connection between surface water and groundwater,and the important water source for groundwater recharge. In order to understand the impact process of moisture migration and retention by surface irrigation amount and duration in the vadose zone,field irrigation experiments were conducted on the summer corn and winter wheat in the Jinghuiqu Experimental Station. By sample collection and moisture determination using Hydrus- 1 D model,the process of soil moisture migration and retention at underground 0 ~ 6 m depth was simulated,and the water balance was analyzed quantitatively.The results showed that different irrigation amounts,influent flows,and durations caused obvious changes of soil moisture migration and retention in the vadose zone. In the corn test,big influent flow and rapid irrigation were adopted,and there were large amount of seepage at the bottom of boundary,accounted for 24. 88 % of the total infiltrated water. In the winter wheat test,small irrigation flow and long duration were used and the leakage quantity at the bottom was small,accounted for 2. 29 % of the surface irrigation quantity. The winter wheat test had a much longer moisture retention time than the core one. The evapotranspiration during summer corn experiment period was greater than that during the winter wheat,accounted for 32. 32 % and 27. 33 % of the infiltrated water,respectively,and 18. 15 % and 16. 92 % of the evapotranspiration,respectively. The soil water retention ratios during the summer corn and winter wheat experiment periods were 42. 8 % and 70. 38 %,respectively. Thus,this indicates that in vadose zone the irrigation influent flow and duration time are the key factors leading the soil water retention and entry into the groundwater.