浅层地下水对玉米根区水分及根系吸水影响的数值模拟

Effects of Shallow Groundwater Table on Root Zone Water and Root Water Uptake of Maize Using Numerical Model

运用实测数据校准并验证模型,采用Hydrus-1D模型模拟了无灌溉、无浅层地下水以及浅层地下水波动对玉米根区水分动态及根系吸水的影响。结果表明,校准后的Hydrus-1D模型能够较为准确地模拟土壤非饱和区水分动态;浅层地下水可以将土壤剖面水分维持在较稳定的范围内。当无浅层地下水时,观测节点水分波动较大,尤其是40-100cm的砂土层水分在灌溉后迅速降低。浅层地下水在影响根区水分的同时影响着根系吸水,CK、无地下水、无灌溉下玉米生长季累积根系吸水量分别为58.2、53.9、57.4cm。累积根系吸水量随地下水埋深的降低而呈先增加后降低趋势,且均高于CK。累积根系吸水量随着地下水埋深的升高而总体呈逐渐降低趋势,当地下水埋深增加40cm时,累积根系吸水量仅为50.7cm,相对于2013年降低了13%。适宜的地下水位对于维持根区水分和促进根系吸水具有重要作用。

On the basis of calibration and validation of Hydrus-1D model,root zone water dynamics and root water uptake were simulated under no irrigation,no shallow groundwater table and different groundwater table.The results showed that hydrus-1D model could successfully simulate soil water dynamics.Shallow groundwater table could maintain soil water content in a relatively stable range.Soil water content fluctuated dramatically without shallow groundwater,especially for the sand layer from 40 cm to 100 cm.Cumulative root water uptake were 58.2cm,57.4cm,53.9cm under CK,no irrigation and no shallow groundwater scenarios,respectively.With the increase of groundwater table,cumulative root water uptake increased first and decreased then,but the value was always higher than CK.In general,cumulative root water uptake decreased with the decrease of groundwater table.When groundwater depth increased by40 cm,cumulative root water uptake was only 50.7cm,decreasing by 13% compared with that in 2013.Appropriate groundwater table played important roles in maintaining root zone water and root water uptake.