内蒙河套灌区咸淡水交替灌溉模拟及预测

Simulation and prediction of rotational irrigation with salty and fresh water in the Hetao irrigation area of Inner Mongolia

为探索一种适合内蒙河套灌区特点、对区域土壤及地下水环境影响最小的咸淡水轮灌模式,预测长期微咸水灌溉条件下区域环境的变化,在田间试验及土壤水盐信息空间结构性分区的基础上,构建了描述非饱和—饱和水盐运动的耦合模型及其算法。通过对耦合模型的率定检验表明,模型计算值与实测值拟合较好,耦合模型能进行较好的循环计算,误差在允许范围以内,表明耦合模型具有较高的可靠性。基于耦合模型的咸淡水灌溉模式的数值模拟研究发现,"淡水-咸水-咸水"的咸淡水交替灌溉模式对区域土壤及地下水环境的影响在所有方案中最小;采用"淡咸咸"灌溉模式进行长期微咸水灌溉,整个研究区在非生育期的脱盐量大于生育期的积盐量,并且盐分主要通过排水沟系统排出区域外,土壤总体呈脱盐趋势;在模拟期内地下水位只有微小幅度的下降,地下水矿化度及含水层中的盐分呈下降趋势。在黄河水量逐年减少的形势下,"淡咸咸"灌溉模式为河套灌区提供了一条使区域环境可持续发展的开源途径,耦合模型的构建将为内蒙古河套灌区节水改造工程实施后及开发利用微咸水后的区域水土环境的预测预报提供参考及简便实用的途径。

For exploring a rotational irrigation model with the salty and fresh water which fits the feature of the Hetao irrigation area in Inner Mongolia and affects the regional soil and underground water enviroment most lightly,with the prediction of the regional enviroment variety with long-term salty and fresh water irrigation,coupling model and algorithm described unsaturated-saturated soil water and salt movement is established,based on the field experiment and spatial structural zone by soil water and salt information.The verification of calibration results to the coupling model turns out that the values calculated by model and the measured actual fit well.Coupling model can make circulation calculation smoothly,with error below allowable range,as shows the great reliability of the coupling model.Numerical simulation study of irrigation model with the salty and fresh water,based on the coupling model,indicates that ＂fresh-salty-salty＂Rotational Irrigation pattern minimizes the effect environmental impact to regional soil and underground water environment to other patterns.Adopting＂fresh-salty-salty＂pattern as long-term light salty water irrigation,the desalting amount in growth period is larger than that in non-fertile period.The salt mainly drains away the region via ditch system.The soil is desalting generally.The level of underground water declines little in the stimulating period.Salinity of underground water and salt in the aquifer are downtrend.With the reduction of the Yellow River water, ＂fresh-salty-salty＂pattern provides a way to maintain the sustainable development of regional environment.The coupling model provides reference and simple practical way for the implement to the region where the water-saving improvement project is implement and the prediction of the regional water and soil environment with utilization of the brackish water.