典型黄土灌区土壤水分零通量面变化特征研究

Study on Movement of Soil Water Zero Flux Plane in Typical Loess Irrigated Area

摘要: 黄土灌区土壤水零通量面动态对作物生长状况和水生态稳定性有着重要的影响作用，研究其运动变化特征对灌区地下水合理利用和水生态稳定意义重大。本文以宝鸡峡灌区作为研究区，基于钻孔资料，以灌溉水入渗和降雨入渗为供水条件，运用Hydrus软件，探讨黄土中水分的运动特征和土壤水分零通量面位置的变化，构建多层黄土条件下水分入渗和土壤水分零通量面位置变化模型，探索维持土壤水分含量稳定(零通量面下移极限)的途径。主要结论：1) 人工灌溉下发散型零通量面大多出现在距土壤表面20~30 cm之间，天然降雨下发散型零通量面大多出现在距土壤表面10~20 cm之间；2) 天然降雨情况下缺失中更新统下部黄土层会使发散型零通量面的厚度增大，变化更剧烈。人工灌溉条件下地层结构对零通量面的影响较小；3) 供水时段的合理分配对于维持土壤水分含量稳定有较大的影响。研究可为黄土灌区地下水运动参数的确定、作物需水预测和地下水农业污染研究提供理论基础。

Abstract: Dynamic of soil water’s Zero Flux Plane (ZFP) in loess irrigation area has important influence on crop growth status and water ecological stability, and study on its movement is of great significance to the ra-tional utilization of groundwater and water ecological governance and stable restoration in irrigated area. Taking Baojixia irrigation area as the research area, based on the borehole data, and setting irrigation water and rainfall infiltration as the water supply conditions, using the Hydrus, this paper discusses the seepage movement characteristics of water in loess and the position changing of soil moisture ZFP, and constructs a model of water infiltration and soil moisture’s ZFP position in multi-layer soils. Suggestions are put forward to maintain the stability of soil moisture content (downward shift limit of ZFP). Main con-clusions are as follows: 1) Most of the divergent ZFP under artificial irrigation occurbetween 20~30 cm from the soil surface, and most of the divergent ZFP under natural precipitation appear between 10~20 cm from the soil surface, 2) The absence of the lower mesopleistic loess layer under natural precipitation increases the thickness of the divergent ZFPand change more drastically. Under artificial irrigation condi-tions, the substructure has little influence on the ZFP, and 3) The reasonable allocation of water supply period has a greater impact on maintaining the stability of soil moisture content (downward shift limit of the ZFP). This study can provide a solid theoretical basis for the determination of groundwater movement parameters, the forecast of the water demand of crops, and the research of groundwater agricultural pol-lution in loess irrigation area.