Knowledge Resource Center for Ecological Environment in Arid Area
| 黄河源区气候变化及其对径流的影响 | |
| 其他题名 | Climate change and its impacts on streamflows in the Source Region of Yellow River |
| MUDASSAR IQBAL | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 高艳红 ; 文军 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 在全球变化的背景下，不同地区的气候呈现出变暖的趋势，由此影响着区域水文循环和全球性水资源变化。高山地区是全球重要的淡水源地，但是由于气候变化，其功能性作用正在发生显著改变。由于空间异质性和气候特征差异，相对于同海拔其他陆地下垫面，高山地区对于全球气候变化更加敏感和脆弱。观测和模拟研究也显示一些高山地区的变暖与海拔高度有关，增暖速率随海拔高度上升。随着全球变暖成为不争的事实，气候变化对于高山地区水资源变化产生巨大影响，因此对其影响机制的研究具有非常重要的意义。被认为是水塔的黄河源区，只占黄河流域的面积的16%，却提供了为黄河流域35~40%的水量，这说明黄河源区在满足黄河下游地区1.1亿人口的农业、工业和城市水资源需求方面中的举足轻重的作用。在气候变化背景下，气候变化与土地利用之间反馈会对径流与蒸散发等水文过程产生影响。因此，本研究在在考虑黄河源区以及子流域中的土地利用变化的情况下分析了径流对气候变化的相应。这一研究中的具有不同地表利用类型子流域的分析结果对于子流域尺度水与生态环境发展具有重要意义，并且对于整个黄河流域水资源的持续利用具有重要意义。本研究将最适于表征气候变化且对水文过程影响最大的气温与降水的变化特征加以分析。首先，评估了1961-2014气温和降水的空间和时间变化特征。对黄河源区以及唐乃亥，玛曲，吉迈和黄河沿子流域气温在1965-1989, 1990-2014，1965 ~ 2014范围内的做时间变化趋势分析。利用黄河源区11个气象观测站观测资料及赛森多边形法计算了统计学温度变化的显著性及其变化趋势，主要包括季节尺度和年尺度最高（Tmax）、最低（Tmin）、平均（Tavg）空气温度和日变化时间序列，并分别利用参数和非参数检验进行分析。在进行统计检验之前，数据质量和同质性经过了标准统计程序的控制，特别地，在非参数检验中为了除去时间序列的相关性进行了预白噪声处理。结果显示，最高气温Tmax，最低气温Tmin和平均气温Tavg均表现出增加的趋势，其中最低气温受气候变暖影响更加显著。与第一阶段（1965-1989）相比，第二阶段（1990-2014）的量值变化和趋势更加明显。除了海拔较低的唐乃亥，海拔较高的子流域冬季时的气温增加更为显著。与其他子流域相比，黄河岩的增加趋势更为突出。吉迈和黄河沿子流域内的Tmin的增加幅度最大，为1.24和1.18℃（每年10年）。而低海拔的唐乃亥Tmin 的增温幅度最小，为0.23℃（10年）。唐乃亥海拔高较低可能是Tmin增加幅度较小的主要原因。在过去的十年中，所有温度变量的趋势小意味着该地区的冷却信号。总体而言，温度变量的变化具有显着的空间和季节变化，这意味着每个子流域径流的季节变化可能更大或不同。在全球气候变化背景下，全球水循环加强，降水量变化特征也因此发生改变。黄河源区作为青藏高原的一部分，因其复杂的地形和脆弱的生态系统，对全球气候变化非常敏感。降水特征的改变影响环境因子的变化，主要包括冰川退化，湖泊、湿地和径流量的减少，冻土消融，山体滑坡，植被退化，荒漠化加重，土壤盐碱化和草场生产力的退化。通过计算有效降水天数（日降水量大于0.1 mm）、统计不同降水等级下的降水总量以及降水事件和干旱事件的持续性，对黄河源区降水量特征及其对环境因子的影响进行研究。降水的等级划分为小雨（0.0–5.0 和 5.0–10.0 mm），中雨（10.0–15.0, 15.0–20.0, 和 20.0–25.0 mm），和大雨（≥25.0 mm）。分析结果显示，研究区域5月至9月的降水量占全年降水量的82.5％，年平均降水量增加趋势不显着（P> 0.05）。日降水量0.0-5.0 mm的降水事件每月均有发生，最大（100%）发生月份是5月-9月，最低概率月份为12月，仅为47%。0.0-5.0 mm降水等级的发生概率及其对于总降水量的贡献显著高于其他等级。与其他较高降水类型相比，0.0-5.0毫米弱降水事件占主导，但弱降水事件在快速减少。空间上，等低海拔子流域如玛曲，唐乃亥的降水量呈下降趋势，而高海拔子流域的黄河沿，吉迈降雨日数呈下降趋势。降雨日数呈下降趋势。 持续1~2日和2日以上的持续降雨事件呈增加趋势，其中持续1~2日降水事件更频繁。同时，短干旱期（≤10天）发生次数增加，而长干旱期（>10天）减少。由于0.0-5.0毫米的弱降水事件对草地生产力有巨大影响， 而5.0-10.0，10.0-15.0和20.0-25.0 mm降水事件对植被生长有积极作用，因为植被生长依赖于深层土壤水分; 降水量大于25.0毫米的降雨事件有助于洪水爆发；持续降雨事件和长期干旱事件减少对农业产生积极影响。这些结果表明研究区域的草地退化，洪水风险较小，对农业的积极影响。降水量的减少（特别是0.0-5.0 mm 等级）以及温度的上升与水平衡的减弱、植被生态系统的退化或改变有关，对于黄河源区生态系统的稳定产生严峻考验。此外，气候变化和土地利用覆盖度的变化作为双重关键因素直接影响着水文过程，特别对于干旱和半干旱地区，由于供水不足，生态系统脆弱，对气候变化更加敏感。因此，量化气候变化和土地覆盖变化对于黄河源区子流域流动规律的影响，对于阐明不同气候类型的水文响应和不同气候和土地利用综合条件下的流动规律非常重要。利用统计方法和水文模型对1974-2014年期间不同的土地利用下水文过程的分析，揭示气候变化和土地利用覆盖变化，当以单一因素起作用时各自对水文过程的影响。为了实现上述目标，使用吉迈，玛曲，唐乃亥子流域的气象驱动数据，水文数据，土地利用类型数据的长期（1990-2010）观测数据作为SWAT的驱动数据。对每个子流域，SWAT模型校正通过1977-1995年月径流数据与土地利用数据模拟结果与1996-2014年的月径流数据和2010年的土地利用数据模拟结果的比对实现。SWAT的模拟能力使用Nash-Sutcliffe系数以及确定系数加以评估。评估结果显示模式的表现能力介于“很好-好”之间，表明SWAT模型可以用于本研究。使用四个假设场景S1，S2，S3，S4和土地利用类型（1980s和2010s），两个气候时期（1976-1995和1996-2014）加以分析气候变化与土地利用对水文过程的影响。土地利用与气候变化的影响通过对比SWAT在四个场景下的模拟结果加以阐明。对土地利用和水文气候变化呈现出草地，林地和未利用地增加，草原稀少等特点。子流域吉迈地区未被利用的土地增加了2%；子流域玛曲地区稀疏草地和草地分别增加了11%和10%；子流域唐乃亥地区的林地增加了1%。基于各子流域地区土地利用类型的变化，土地覆盖的改变主要是由于黄河源区的人类活动导致。1974-2014年期间年平均气温和降水量显示出显著和非显著的增加趋势，而径流呈下降趋势。气候变化和LUCC的综合效应似乎导致了径流量的减少（-29.6mm）与ET的增加（27.9 mm），这分别占黄河源区总径流和ET的8％和19％。气候变化对径流量减少（-22.4mm）和ET增加（21.4 mm）的影响，超过了土地利用覆盖变化的影响。 LUCC分别为径流和ET提供约-5.5和8.3 mm的变化。气候变化比土地利用/土地覆盖变化对黄河源区水文过程的影响更大。子流域玛曲的水流量比其他流域大幅度减少，其原因为降水量减少，增加草地拦截和调节能力。然而，气候变化与土地利用改变对ET增加的影响在吉迈子流域更显著，显著程度超过了玛曲和唐乃亥。因此，气候变化和土地利用对径流和蒸散量（ET）的影响存在一定的差异，这取决于这些子流域特定流域的变化。作为一项重要的战略成果，这项研究为许多决策者提供了可能的重要途径，以便设计适应气候变化和土地利用的措施，并为规划黄河源区在次流域尺度上的生态系统的可持续发展作出规划。 |
| 英文摘要 | In the context of global change, the climate in different regions shows a warming trend, which affects the regional hydrological cycle and global water resources change. Mountain regions are important sources of freshwater for the entire globe, but their role in global water resources could be significantly altered by climate change. Mountains are expected to be more sensitive and vulnerable to global climate change than other land surfaces at the same latitude owing to the highly heterogeneous physiographic and climatic settings. Furthermore, there is also evidence from observational and modeling studies for an elevation-dependent warming within some mountain regions. With the increasing certainty of global climate change, it is important to understand how climate change these changes will impact water resources in these mountain regions. Regarded as a water tower, the SRYR contributes on average 35-40% of the total water yield in disproportion to its 16% area of the whole Yellow River basin and plays an important role to meet the downstream water resources requirements for the 110 million inhabitants in terms of water resources for agriculture, municipal and industrial uses. The impacting climate change and land cover changes in results of the feedbacks of climate change and land cover change have consequences in terms of a hydrological process including runoff and evapotranspiration of the region. Therefore, this study investigated the response of streamflows to climate change with considering the land-use change in the SRYR and its sub-basins. The presented results at sub-basins having the different feature of land have important implications for the development of water and eco-environmental resources management at sub-basin scale in the SRYR and could be significant with unknown consequences for water availability in the whole Yellow River basin.Changes in climatic variables were examined by temperature and precipitation which are most important climatological parameters to detect the climate fluctuations and affects the hydrological processes within a basin. Thus assessment of variation in air temperatures trends and precipitation characteristics within the period of 1961-2014 were evaluated to identify the significant changes in space (i.e. stations or sub-basins) and time. Air temperature absolute changes and trends from 1965-1989, 1990-2014 and 1965 to 2014, were assessed in the source region of Yellow River and its sub-basins named as Tangnaihai, Maqu, Jimai, and Huangheyan. Results exhibited that annual and seasonal Tmax, Tmin and Tavg for the SRYR were experiencing warming trends. In comparison with the 1st period (1965-1989), more absolute changes and trends towards increasing were observed during the 2nd period (1990-2014). Apart from Tangnaihai (a low altitude sub-basin), these increasing trends and changes seemed more significant in other basins with the highest magnitude during winter. Among sub-basins, the increasing trends were more dominant in Huangheyan compared to other sub-basins. The largest increase in of Tmin, 1.24 and 1.18°C (10 yr)-1, arose in high altitude sub-basins Jimai and Huangheyan, respectively, while the smallest increase magnitude of 0.23°C (10 yr)-1 occurred in a low altitude sub-basin Tangnaihai. The high elevation difference in Tangnaihai probably was the main reason for the less increase in the magnitude of Tmin. In the last decade, the smaller magnitude of the trend for all temperature variables signified the signal of cooling in the region. Overall, changes in temperature variables had significant spatial and seasonal variations that imply the seasonal variations of runoff might be greater or different for each sub-basin.The characteristics of Precipitation and its impacts on the environment in the region were then explored by rainy days and precipitation amount among different precipitation classed as well as the trends of persistent rainfall events and drought events. Results revealed that annual average precipitation has a non-significant (P>0.05) increasing trend, and 82.5% of the precipitation occurred from May to September. More pounced rainy days of the 0.0–5.0 mm precipitation class decreased significantly compared to the other higher precipitation classes. Spatially, the precipitation amount appeared to decrease at the station located in low altitude sub-basins Maqu and Tangnaihai whereas the rainy days found towards more decreasing at the stations of higher altitude sub-basins Huangheyan and Jimai sub-basins. The persistent rainfall events of 1- or 2-day and more than 2-day showed an increasing trend, with the 1- or 2-day events being more frequent. Meanwhile, the number of short drought periods (≤10 days) increased while long drought periods (>10 days) decreased. Since the 0.0–5.0 mm precipitation class has huge impact on the grasslands productivity; the 5.0–10.0, 10.0–15.0, and 20.0–25.0 mm precipitation classes have positive effects on vegetation which rely on deep soil water through moving nutrients and water into the root zone of the vegetation or through plant-microbe interactions; the ≥25.0 mm precipitation class contributes to the floods; and more persistent rainfall events and fewer long drought events infer positive effects on agriculture, these results indicate grassland degradation, less risk of floods, and the upgrading impact of climate change on agriculture.Climate change and land use cover change impacts on hydrological processes were revealed by applying the statistical methods and hydrological model during the period of 1974-2014 with different land-use maps. Land-use and hydro-climatic changes showed several characteristics, including increased grassland, woodland, and unused land and decreased sparsely grassland. Annual mean air temperature and precipitation showed significant and non-significant increasing trends while runoff exhibited decreasing trends between 1974 and 2014. The combined effects of climate change and LUCC seemed to have decreased the runoff and increased the ET by about 29.6 and 27.9 mm, respectively, covering of 8% and 19% of the total runoff and ET in the SRYR. The climate change impact on the decrease of runoff and increase of ET recognized respectively at 22.4 and 21.4 mm, outweighed the impact of Land-use cover change. The LUCC delivered changes of about ?5.5 and 8.3 mm for runoff and ET, respectively. The overall, influence of climate change had the higher impact than LUCC on hydrological processes in the SRYR. The great reduction of streamflows in the Maqu sub-basin than other basins is the cause of a reduction in precipitation amount and increment of canopy interception and regulation capability due to increased grassland. However, their impacts to increase the evapotranspiration (ET) appeared more in Jimai followed by Maqu and Tangnaihai sub-basin through significant reduction of precipitation events and the increase of unused land in the Jimai sub-basin. Thus, the climate change and land use on runoff and evapotranspiration (ET) had different effects depending on the changes of these variables in a particular basin. As an important strategic result, this study delivers possibly important paths to be considered by numerous decision makers for designing adaptive measures to climate change and LUCC as well and for planning the sustainable development of ecological systems of the SRYR at sub-basin scale. |
| 中文关键词 | 黄河源区 ; 气候变化 ; 子流域 ; 径流 ; SWAT模型 |
| 英文关键词 | the source region of the Yellow River climate change sub-basins streamflow SWAT model |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 气象学 |
| 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/2XILL650/288146 |
| 推荐引用方式 GB/T 7714 | MUDASSAR IQBAL. 黄河源区气候变化及其对径流的影响[D]. 中国科学院大学,2018. |
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