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开都河流域山区季节性土壤冻融过程对径流的影响
张飞云
学位类型博士
导师李兰海 ; 王权
2016
学位授予单位中国科学院大学
学位授予地点北京
学位专业自然地理学
关键词开都河流域 季节性冻土 冻融过程 径流过程
摘要干旱半干旱地区的河流多发源于高寒山区,补给源复杂多样,广泛分布的季节性冻土的存在会阻碍降水和积雪融水入渗,使得积雪融水对径流的补给更加复杂;加之新疆气象水文站点多分布于低海拔区,给研究高寒山区水文过程带来困难。为了研究季节性土壤冻融过程对径流的影响,本研究选取季节性冻土广泛分布的开都河流域山区产流区为研究区。开都河流域的径流受以冰川/积雪融水、降雨和地下水共同补给。本研究首先利用研究区临近站点观测得到的土壤温湿度数据来分析季节性土壤的融化过程;然后通过分析气象指标与春季洪峰的关系来确定季节性冻土对春季洪峰的重要性,分析季节性土壤冻融的影响因素;再通过改进基于系统动力学构建的水文模型模拟开都河流域山区的径流过程;最后分析了气候变化条件下径流的变化趋势。基于以上研究得到如下结论: (1)由于积雪的隔热作用阻止了地上空气与土壤间能量的传递,使得积雪较厚地区土壤冻结深度浅,积雪较薄地区土壤冻结深度厚。春季积雪融化期,有积雪覆盖地区土壤温度较低,无积雪覆盖地区土壤温度受气温的影响升温较快,土壤温度的升高会融化冻结的土壤增加土壤含水量。土壤温度在积雪消失后逐渐增加;土壤含水量则在积雪完全消失前达到最高值,随后减少。 (2)用通径分析的方法分析了开都河流域的巴音布鲁克气象站气象因子与大山口水文站春季洪峰的关系发现春季正积温和冬季降水对春季洪峰有显著的直接作用,同时以冬季负积温来表示的冻结土壤对春季洪峰的间接作用显著。对开都河流域时间序列较长且位于不同海拔高度的巴音布鲁克气象站、和静气象站及库尔勒气象站的土壤冻结深度和土壤融化日数的影响因素进行分析,发现不同海拔高度季节性土壤冻结深度和融化日数限制因子存在差异:随着海拔高度的升高,对土壤冻结深度影响最大的因子由低海拔处的负积温和最大积雪深度转化为中海拔处的负积温,再转化为高海拔处的相对湿度;对土壤融化日数影响最大的因子由低海拔处的风速和最大冻结深度转化为中海拔处的日照时数,再转化为高海拔处的相对湿度。其主要原因与各个海拔气象站点所在位置和实地的气候环境关系显著。 (3)结合开都河流域山区春季径流和春季洪峰主要由季节性积雪融水补给,且由于季节性冻土的广泛分布使得积雪融水对径流的补给过程更加复杂这一特点,对基于系统动力学原理构建的SDHydro水文模型进行改进改进来更好地模拟研究区的径流。通过用日有效正积温替代日平均温度来模拟积雪融化速率,并将土壤物理状态对水分入渗速率的影响由表层扩展到不同深度的土壤层来改进现有基于系统动力学模型构建的SDHydro水文模型模拟开都河流域的径流过程。本文通过敏感性分析,对比模拟径流和实测径流以及统计分析方法证明改进的SDHydro水文模拟不仅可以很好地模拟开都河流域的径流量,还准确地模拟开都河流域平水年,枯水年期和丰水年的径流量,且对平水年和枯水年径流的模拟能力高于丰水年径流。对比分析两处改进部分发现,在季节性积雪分布广泛且以积雪融水为重要补给源的开都河流域产流区,积雪融化模块的改进对径流的影响强于水分入渗模块的改进对径流的影响。 (4)通过分析开都河流域径流对气温和降水的敏感性发现开都河流域径流对降水的变化更敏感;而气温的变化对年内径流的分配影响显著。在未来气候变化条件下开都河流域春季径流量呈增加趋势,春季洪峰呈显著增加趋势。春季洪峰的开始时间在温室气体排放量最大的RCP8.5情景下有显著提前趋势。春季洪峰的发生时间并不像春季洪峰的开始时间一样对温室气温的排放有显著响应,主要原因是春季洪峰的发生时间受春季气温的增加速率和春季降雨量等共同限制,而与气温的变化关系不显著。春季洪峰的开始时间发生于3月中下旬到4月中下旬,春季洪峰的发生时间发生于4月初到5月中旬。
其他摘要Most rivers in arid and semi-arid areas originate from alpine regions with different water sources. The seasonal frozen ground widely exists in the area, which influences the water infiltration rate due to its preventing rainfall and snowmelt water from infiltration into soil layer. Most meteorological and hydrological stations in Xinjiang are situated in lowland areas. All of these bring difficulties for the study on hydrological process in alpine watershed in Xinjiang. This study chooses the Kaidu river watershed as the study area where the seasonal frozen ground widely is distributed with the rainfall, glacier/snow melt water and ground water as main water sources. The observed soil temperature and moisture data from closed station have been used for analyzing the seasonal frozen-thaw process, and path analysis method has been applied to determine the importance of the seasonal frozen ground on spring peak flow. An existing hydrological model, i.e. SDHydro, was modified to simulate the runoff and its responses to climate change in the Kaidu river watershed. According to the study, the main conclusions are as follows: (1) The thermal insulation of snow cover prevents the energy transformation between atmosphere and pedosphere, which results in the shallow frozen depth under thick snowpack and thick frozen depth under shallow snowpack. The soil temperature is lower under snow cover, and it will increase quickly with the influence of air temperature as snow disappeared. The increase of soil temperature resulting in snowmelt improves the soil moisture. Hence, soil temperature increases after snow cover disappeared, while soil moisture reach the maximum value before snow cover disappeared, and then decreases. (2) The results based on path analysis showed that> 0ºC accumulative temperature in spring and precipitation during winter have a significant direct influence on spring peak flow, while <0℃accumulative temperature in winter, representing the freezing status of soil, has the significant indirect influence in the Kaidu river watershed. The determining factors of the seasonal soil frozen depth and the thawing days are different with elevation enhancement after analyzing the influencing factors of the seasonal soil frozen depth and the thawing days in Bayinbuluk, Hejing and Kuerle stations using path analysis method. The determining factor of the seasonal frozen depth changes from <0℃ accumulative temperature and maximum snow depth in low elevation to <0℃ accumulative temperature in middle elevation, and to relative humidity in high elevation. The determining factor of the thawing days changes from wind speed and maximum frozen depth in low elevation to sunshine duration in middle elevation, and to relative humidity in high elevation. The difference depends on the locations and their environment in different elevation. (3) The SDHydro model which was developed on the basis of the principles of System Dynamics has been modified and used to simulate the streamflow in the Kaidu river watershed. The modification includes the estimation of snowmelt rate by replacing the daily mean temperature with the active >0℃ accumulative temperature, and the water infiltration calculation by expanding the influence of soil physical status on water infiltration from surface soil layer to deeper soil layers. Graphical comparison and statistical analysis on the simulated and observed streamflows indicated that the modified SDHydro model can efficiently simulate the streamflow including the low and high streamflow in the Kaidu river watershed, and the capability of the modified model to reproduce streamflow in low- and normal-flow years was better than that in high-flow years. The simulation tests also demonstrated that the modification of snowmelt estimation has a greater influence on snowmelt runoff than the modification of water infiltration calculation in different soil layers does. (4) The streamflow in the Kaidu river watershed is more sensitive to precipitation variation than that to temperature variation after analyzing the sensitivity of streamflow to climatic disturbance. Temperature variation has a great influence on intra-annual streamflow distribution. The spring streamflow has an increasing trend and the spring peak flow has a significant increasing trend under future climate change. The starting time of the spring peak flow brings forward significantly under scenario RCP8.5 with the maximum greenhouse gas emission. The response of the occurring time of spring peak flow to temperature variation is not as significant as that of the starting time of spring peak flow. The main reason is that the occurring time of spring peak flow is controlled by spring temperature increasing rate. The starting time of spring peak flow happens from middle and late March to middle and late April, while the occurring time of spring peak flow happens from the beginning of April to middle May.
学科领域自然地理学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14715
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
张飞云. 开都河流域山区季节性土壤冻融过程对径流的影响[D]. 北京. 中国科学院大学,2016.
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