基于人工示踪方法的河套灌区根系层净淋滤水量研究

Using Tracer to Study Salt Leaching from Root Zones in Hetao Irrigation District

【目的】获取河套灌区作物根系层的净淋滤水量,对灌区根系层进行盐分平衡分析。【方法】兹利用溴离子作为人工示踪剂,研究了河套灌区根系层净淋滤水量,并采用简化的盐分平衡方程估算盐分达到平衡时根系层的平均土壤含盐量。【结果】河套灌区根系层年净淋滤量为40.8 mm,与水均衡法计算结果(41.6 mm)相互验证良好;不同灌溉方式的净淋滤量之间存在明显差异;地下水埋深和秋浇水量是决定净淋滤水量的关键因素。灌区若采用矿化度为1.0~2.5 g/L的地下水进行灌溉并维持现有灌溉制度,盐分平衡时的根层土壤溶液质量浓度将接近作物耐盐极限。【结论】灌区引黄水渠灌可维持现状灌溉制度不变;若采用矿化度较高的地下水进行灌溉,需适当加大淋盐水量,以保证长期利用条件下根系层盐分能满足作物正常生长的要求。

【Objective】The overarching objective of this study is to calculate water percolation and salt leaching from the root zone in Hetao Irrigation District.【Method】Bromide tracer experiment was conducted in Hetao Irrigation District in attempts to estimate the movement of water and salts in the root zone.【Result】The average water percolation rate estimated from the tracer experiment for the bottom of the root zone was 40.8 mm per annum,close to 41.6 mm estimated from water balance analysis. The percolation rate varied considerably between different irrigation methods, affected profoundly by the depth of groundwater table and the amount of irrigation. When groundwater with salt content of 1.0～2.5 g/L was used for irrigation, the root-zone salinity was just tolerable by plants after slats moving into and out of the root zone reached balance.【Conclusion】The current conjunctive use of groundwater and canal water in Hetao irrigation district is safe in terms of soil salinity, but the amount of irrigation needs to be increased if groundwater with high salt content is to be used for irrigation.