Knowledge Resource Center for Ecological Environment in Arid Area
| 干旱区包气带水-汽-气-热耦合模拟及潜水蒸发估算—以额济纳三角洲为例 | |
| 其他题名 | Simulation for coupled water-vapor-air-heat flow transport in vadose zone and estimation of groundwater evaporation in arid region - A case study of Ejina delta |
| 杜朝阳 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 于静洁 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 黑河下游的额济纳三角洲位于我国的西北极干旱区，具有重要生态屏障作用。该地区地下水埋深小，蒸发能力大，潜水蒸发是主要消耗项，包气带地下水排泄的重要媒介。研究包气带水汽运移物理机制及建立水汽热耦合运移模型，对揭示干旱区潜水蒸发规律和深化干旱区包气带对潜水蒸发的影响认识有重要的学术价值。本论文以额济纳三角洲主要景观戈壁带和河岸带为研究对象，基于野外观测试验，利用Saito模型分析温度对戈壁带和河岸带包气带水汽运移的影响；并考虑土壤空气运动对包气带水汽的影响，建立了包气带二相水汽（气）热模型；运用该模型估算了日潜水蒸发速率，并与研究团队改进的地下水位波动法、作者改进的水热平衡方法进行了月尺度上的比较。主要研究结论如下： （1）利用观测期连续同步数据（2014年6月1日-6月15日）分析，温度梯度变化在研究区包气带有明显的上下分层，上层土壤温度梯度大，下层温度梯度小。最大土壤温度一般在地表以下50 cm以内，且存在水汽传输的零通量面。上层土壤中，温度梯度是水汽热运移的主控因素。戈壁带和河岸带包气带剖面温度梯度引起的水汽通量主要集中于埋深20-50cm范围内， （2）分析了包气带土壤空气、水汽传输机制，土壤空气流动对水汽热耦合运移过程不可忽略；建立了二相包气带水汽（气）热耦合模型，模型验证表明新模型能很好描述干燥土壤水汽热的运移过程。而模型的敏感性分析表明土壤水分对参数比较敏感，而温度不敏感。 （3）基于包气带水汽热耦合模型与改进水热平衡法、改进的地下水波动方法对2014年5-7月三角洲河岸带、戈壁带潜水蒸发计算结果进行了比较。结果显示，三种方法对月蒸发动态描述具有一致性，但绝对数值有所差异。本研究建立的水汽热耦合模型与改进的水热平衡计算结果整体上接近但略有偏高，其中戈壁带偏高24.5%~33.2%，河岸带偏高0.8%~11.1%；而与团队改进的地下水位波动法计算结果相差较大，整体上偏低，戈壁带月值偏低53.6%~55.6%，河岸带偏低37.5%~44.4%。 结果表明，改进后的水热平衡法相比地下水位波动法在月尺度上定量三角洲植被生长旺季潜水蒸发具有更高的可信度。 |
| 英文摘要 | Ejina Delta, located in the downstream of the Heihe River- an extremely arid northwest region, is an important ecological barrier. In the area, the groundwater table is low and groundwater evaporation is high. Groundwater evaporation is the main consumption, as well as an important medium for the vadose zone of groundwater discharge. Study on the mechanism of water and vapor movement in vadose zone and the establishment of water-vapor-heat coupled model are important to reveal groundwater evaporation process in arid region and to deeply understand the influence of vadose zone on the groundwater evaporation process. In this paper, Ejina Delta landscape with Gobi desert and riparian zone is selected as research site. First, the effect of soil temperature gradient on water-vapor movement in vadose zone was analyzed using the Saito model and the field observation in Gobi desert and riparian zone. Second, considering the effect of soil air movement on the vapor transport through vadose zone, the new coupled water-vapor(air)-heat transfer model was built by adding the soil air movement equation. Finally, the new model was used to estimate to the groundwater evaporation in Gobi desert and riparian zone during the growing season. The results by new model was compared the results by the improved water table fluctuation by our team member at daily scale and water and energy balance method by the author at monthly scale. The main conclusions are as follows: (1) Based on the analysis of continuous observation of synchronous data on soil temperature during June 1-15 2014, it was found that soil temperature gradient along the soil profile has very clear layered distribution. The soil temperature gradient in the upper layer is larger, and that in lower layer is smaller. The maximum temperature gradient along soil profile is located in less than 50 cm below the surface, and there is zero flux plane of vapor transport in the same layer. In the upper soil layer, the soil temperature gradient is the main influence factors of water-vapor-heat transfer in vadose zone. The vapor fluxes caused by soil temperature gradient of vadose zone in Gobi desert and riparian zone mainly distribute the depth with 20-50cm. (2) Based on analyzing the mechanism of soil air and vapor transport through vadose zone, it was understood that the effect of soil air flow water-vapor-heat transfer in vadose zone on cannot be ignored. The paper established a new coupled water-vapor(air)-heat model based on the traditional water and heat transfer model by adding the soil air movement equation. The new model has been verified by the published data about the vapor movement in very arid soil. The verification shows the new model can well simulate the process of vapor transport in arid soil. The sensitivity analysis about the parameter of water retention curve shows that the simulated soil moisture is more sensitive than the simulated soil temperature. (3) The groundwater evaporation in Gobi desert and riparian zone during May and Junly were estimated using the new coupled water-vapor(air)-heat model, improved water and energy balance method and water table fluctuation method. The comparison of the results by the three methods shows that the three methods have a certain consistency to describe the monthly groundwater evaporation dynamic for Gobi desert and riparian zone but represent some difference for the absolute value of monthly groundwater evaporation. The groundwater evaporations by the new model are higher 24.5%~33.2% in Gobi desert and 0.8%~11.1% in riparian zone than those by the improved water and energy balance method. Compared with the results by improved water table fluctuation method, the results by the new model are lower about 53.6%~55.6% in Gobi desert and 37.5%~44.4% in riparian zone. These results show that for quantitative estimation of groundwater evaporation in the delta during growing season, the performance of improved water and energy balance method are better than water table fluctuation method at monthly scales. |
| 中文关键词 | 包气带 ; 土壤空气 ; 水汽热耦合模拟 ; 潜水蒸发 ; 额济纳三角洲 |
| 英文关键词 | Vadose zone Soil air Simulation of coupled water-vapor-heat transport groundwater evaporation Ejina delta |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287650 |
| 推荐引用方式 GB/T 7714 | 杜朝阳. 干旱区包气带水-汽-气-热耦合模拟及潜水蒸发估算—以额济纳三角洲为例[D]. 中国科学院大学,2016. |
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