Knowledge Resource Center for Ecological Environment in Arid Area
| 科其喀尔高寒草甸水量平衡试验研究 | |
| 其他题名 | Experiments on water balance of alpine meadow in the middle of Tianshan Mountain |
| 郭淑海 | |
| 出版年 | 2015 |
| 学位类型 | 硕士 |
| 导师 | 杨国靖 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 高寒山区典型下垫面水文过程是研究寒区流域水分循环和水量平衡特征的重要基础和关键环节，对于理解高寒草地生态过程与水资源的再分配有着重要作用。高寒山区是流域中下游干旱区重要的水源涵养区，而寒区生态与水文对气候变暖的响应较为敏感，目前寒区生态与水文研究已经成为全球变化研究的重要方向之一。但由于高寒山区自然条件相对较差，给寒区水文的长期观测和研究造成了一定的困难，高寒山区水文过程研究较少。高寒草甸作为高寒山区一种独特的下垫面，其涵养水源、调节水文过程的作用较强，在流域水文过程中有着重要作用。明确坡面尺度的高寒草甸水量平衡，对于理解高寒山区整个流域的水循环过程和生态变化有着极其重要的意义。 本论文依托天山科其喀尔冰川综合考察站，在其附近小流域高寒草甸分布区，选择典型的样地，布设了3种坡度的径流场，通过对2013年、2014年植被生长期内的水文观测数据进行分析，探讨了不同坡度下高寒草甸径流场的水量平衡特征。初步结论如下： （1）高寒草甸区，研究期（5―10月）降水特征明显，＜5 mm的小降水事件出现的频率最高，降水间隔期以＜2 d的间隔期为主。在143次降水中，＜ 5mm的小降水事件占总降水事件的78.3%，＞5 mm的降水事件出现的次数较少，但降水量比例大。＜2 d的降水间隔期占比达到了54.5%，这种时间间隔短且以小降水为主的降水特征，有利于土壤水分的积累和地下径流的形成。 （2）在高寒草甸区，不同深度的土壤水分对降水事件产生不同的响应。受降水量级、降水强度、土壤深度和土壤初始含水量等因素的影响，0~40cm各层土壤含水量对降水的响应比较复杂，各层土壤含水量的变化趋势与降水的变化趋势基本一致，但随着土层深度的增加，土壤含水量对降水的响应显著减弱，响应的滞后性越明显。 （3）高寒草甸全年降水量的84.1%以蒸散的形式耗损，最小二乘支持向量机（LS-SVM）能够较好的估算蒸散发。试验期间（2012年10月―2013年9月），研究区高寒草甸年内实测蒸散量为511.3 mm，日均蒸散量为1.4 mm·d-1。在不同时期，蒸散量变化剧烈，非生长期、生长前期、生长中期和生长后期的蒸散量分别占全年蒸散量的10.5%、6.4%、75.3%和7.8%，LS-SVM模型能够较好的反映蒸散发同气象要素之间的非线性关系，模拟精度较高（R2≧0.6），对观测资料相对缺乏的高寒山区来说，不失为一种较好的估算蒸散发方法。 （4）高寒草甸坡面产流主要以超渗产流为主。研究区植被生长期主要以﹤5 mm的小降水事件为主，﹥10mm的大降水事件对坡面产流起到了关键作用，但大降水事件出现的概率很小，高寒草甸地表几乎不产流，10°、17°、25°径流场地表径流仅观测到了6次、14次、15次，地表产流系数均﹤0.5%，且并未观测到明显的壤中流产生，高寒草甸对降水的拦蓄作用强。地表径流量与降水量之间存在明显的二次抛物线回归关系，且相关性显著。 （5）高寒草甸涵养水源、调蓄水资源作用明显。高寒草甸的存在减少了地表径流和浅层壤中流的产生，观测期径流场蒸散量占同期降水量的64.0%，但仍有20.2%的水分通过下渗到达深层土壤（40 cm以下），形成深层壤中流，10.8%的水分直接保存在上层土壤中（0~40 cm），从而起到涵养水源的作用，在流域水资源形成过程中起到了重要作用。 （6）坡面坡度是高寒草甸坡面流形成的重要因素之一。坡面坡度的改变导致雨水的重新分配，土壤的下渗量受到影响，地表径流、壤中流的比例发生改变，进而影响到坡面出口断面的流量过程。在本试验中，随着坡面坡度的增加，草甸蒸散量、下渗量及土壤蓄水量均减少，地表径流量、侧向流量呈增加趋势。 关键词：高寒草甸；水文过程；LS-SVM模型；水量平衡；阿克苏河上游 |
| 英文摘要 | Alpine meadow plays an important role in hydrological process in the high altitude regions of western China. It can change the soil interception and tend to different evapotranspiration and runoff. Alpine mountain area is the water source region for the middle and lower reaches of some rivers, and also the alpine regions are very sensitive to climate warming. Eco-hydrological process research in cold regions has been a focus in the effects of global changes. Due to poor natural conditions, it is very difficult to get long-term field observation, and which induced little study on hydrological research of alpine meadow. As an important part of landscape in alpine mountains, alpine meadows played a major role in conserving water and regulating water. The experiments on hydrological process in slope scale will provide better understandings of the water balance and water cycle in alpine mountains. Three runoff plots with different slope of alpine meadow in a little watershed near the Koxkar glacier had been set up in June of 2012. Based on the observation data of precipitation, evapotranspiration, and runoff from May 1st to Oct 31th (growing season) in 2013 and 2014, we analyzed the characteristics of hydrological processes and water balance in different runoff plots of alpine meadow, and the conclusions followed: (1) The minor precipitation events (< 5 mm) in alpine regions was major, and the inter-rainfall period was <2d. The number of times of <5mm precipitation events occupied 78.3% of the total rainfall events, and the large rainfall events (>5 mm) was few, but it contributed to the total precipitation largely. The number of times of inter-rainfall period (<2d) occupied the most of the total number, and which was conducive to the formation of runoff and sub-surface runoff. (2) The response of soil moisture to precipitation in alpine meadow is different. Because of rainfall intensity、soil depth and soil initial moisture, the responses of soil moisture (0~40cm) to precipitation differed significantly, yet the variation trend is almost consistent. With the increase of soil depth, the differences of soil moisture response were getting weaker, and the hysteresis was more obvious. (3) Evapotranspiration accounted for 84.1% of the precipitation. The total actual ET of the alpine meadow was 511.3 mm, and the daily average was 1.4 mm?d-1. The values of ET varied significantly in different seasons. The values of ET in non-growing stage, early growing stage, middle growing stage, last growing stage were 53.9 mm、32.6 mm、384.8 mm and 40.0 mm respectively, and they occupied about 10.5%、6.4%、75.3% and 7.8% of the annual ET values respectively. In this paper, we also discussed the applicability of the least squares support vector machine (LS-SVM) estimating the actual ET of alpine meadow, and the results showed that LS-SVM can better estimate actual ET with high accuracy, which will be a good and useful method for estimating actual ET in the high-cold mountainous region. (4) The infiltration excess runoff was the primary way of runoff yield in alpine meadow. The major precipitation type was <5 mm rainfall events in study area, though the precipitation﹥10mm rainfall events serve an important role in the process of surface runoff, the frequency of which was so less. There was almost no surface runoff in alpine meadow. Our observations results showed that the runoff coefficient was very low, and the shallow reel mid-stream was also rarely because the interception of alpine meadow played a greater part, our results also indicated that there was an obvious quadratic regression relationship between surface runoff and rainfall. (5) Alpine meadows played an important role in conserving water and regulating water in mountains, which reduced surface runoff and shallow reel mid-stream, and the evapotranspiration accounted for 64.0% of precipitation during observation period. The amount of water by infiltration accounted for about 20.2% of precipitation, and which would produce deep runoff. The alpine meadow had good water conservation function in growing season, and played an important role in the formation of watershed water resources. (6) Slope was one of the key factors influencing the flow formation. Different slope would lead to different runoff, and which redistributed the precipitation. The capacity of soil infiltration, proportion of surface runoff and shallow reel mid-stream would be changed because of the different slope. It would finally affect the flow outlet of the slope. The evapotranspiration、infiltration and soil water storage reduced with the increase of slope in study area, yet the surface runoff 、lateral water flow increased. Keywords: alpine meadow, hydrological process, LS-SVM, water balance, upper reaches of the Aksu River |
| 中文关键词 | 高寒草甸 ; 水文过程 ; LS-SVM模型 ; 水量平衡 ; 阿克苏河上游 |
| 英文关键词 | alpine meadow hydrological process LS-SVM water balance upper reaches of the Aksu River |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287554 |
| 推荐引用方式 GB/T 7714 | 郭淑海. 科其喀尔高寒草甸水量平衡试验研究[D]. 中国科学院大学,2015. |
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