干旱区平原水库坝后农田土壤水盐运移的规律研究

The Effect of Water and Salt Transport in Farmland Soil Behind Reservoir Dam in Arid Plains

干旱区的平原水库造成坝后农田地下水位抬升,加剧了土壤盐渍化的程度,厘清干旱区平原水库对坝后农田土壤水盐运移规律,便于制定有效的措施来控制地下水位,进而抑制土壤盐渍化的发生。因此采用试验监测和数值建模,利用Hydrus软件模拟出坝后农田土壤水盐运移规律。结果表明:水库水位的变动影响下游农田地下水位的变化,水库水位越高,上下游水位差越大,渗流量就越大,地下水补给量增加,水位上升越快;土壤地下水位与含水率呈正相关,地下水位越高,含水率就越高;土壤的含水率与含盐量呈负相关。通过蒸发量的增大,水分被蒸发速度加快,含水率逐渐降低,将水中的盐分留在土壤中,地表聚盐速度增加,从而含盐量增加。土壤的深度越浅,变化越明显;因此地下水位的变化对水盐动态影响较大,是诱发盐渍化的内因。而气象因素的蒸发是水盐运移的原始驱动力,是诱发土壤盐渍化的外因。通过合理的措施有效的控制地下水位,可以降低或防止坝后土壤的次生盐渍化问题。

The plain reservoir in the arid area causes the groundwater level of farmland behind the dam to rise,which intensifies the degree of soil salinization.It is convenient to take effective measures to control the groundwater level,and then to control the occurrence of soil salinization.Therefore,in this paper,the test monitoring and numerical modeling is used to simulate the law of water and salt movement of farmland soil behind the dam by using hydrus software.The results show that the change of water level of the reservoir affects the change of groundwater level in the downstream farmland.The higher the water level of the reservoir,the greater the water level difference between the upstream and downstream,the greater the seepage flow,the increase in groundwater supply,and the faster the water level rises.The soil groundwater level is positively related to the water content.The higher the groundwater level is,the higher the water content is.The water content of soil is negatively related to the salt content.With the increase in evaporation,the speed of water evaporation is accelerated,the water content is gradually reduced,the salt in the water is left in the soil,the speed of surface salt accumulation is increased,so the salt content is increased.The shallower the soil depth is,the more obvious the change is.Therefore,the change of groundwater level has a greater impact on water and salt dynamics,which is the internal cause of salinization.The evaporation of meteorological factors is the original driving force of water and salt transport and the external cause of soil salinization.Through reasonable measures to effectively control the groundwater level,we can reduce or prevent the secondary salinization of the soil behind the dam.