【作者】 张小侠；

【导师】 王秀茹； 姚治君；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2011， 博士

【摘要】 雅鲁藏布江地处青藏高原腹地,受特殊的地形特点及高原高海拔的影响,流域空气稀薄、辐射强、气压低。因此,雅鲁藏布江流域对全球气候变化极其敏感和脆弱。雅鲁藏布江流域作为西藏最重要的经济区,其径流变化必将对青藏高原及其周围地区国民经济及人民生活带来重大的影响。因此,在全球气候变化的大背景下,研究青藏高原的水资源变化特征及其对全球气候变化的响应,有助于深入了解高寒地区水循环与水资源演变规律,对维持流域内的水土资源平衡有深远意义,同时亦对分析水资源开发利用中存在的问题、合理开发利用雅鲁藏布江流域的水资源有重要的现实意义和长远的指导意义。本文选择雅鲁藏布江流域作为研究区,通过对各气候因素、径流时空变化规律、土地利用／土地覆被变化的时空格局变化进行分析,并探讨了降水、气温、蒸散发等气候因子和LUCC等驱动因素对径流的影响。通过研究,得出了以下主要成果和结论：(1)流域1960-2009年年平均气温具有显著的上升趋势,升温趋势随海拔升高而增大的特点。此外,流域最低气温倾向率远远高于最高气温倾向率,最低气温上升的速率约为最高气温的2倍,表明青藏高原变暖主要是发生在夜间。流域多年平均气温总的分布趋势与地形大致吻合,具有从东南向西北递减的趋势。嘉黎为升温幅度最小地区,升温幅度为0.18-0.20℃/10a；拉萨为升温幅度最大区域,为0.55-0.58℃/10a。对流域平均气温时间序列进行突变检验,发现雅鲁藏布江流域平均气温序列先后于1987年和1997年发生气候突变,197年出现流域气温增暖突变信号,1997年出现气温快速增暖突变信号。(2)1960-2009年流域年降水呈上升的趋势,但趋势不显著,流域降水变化呈现复杂性。降水量空间分布趋势由东南向西北递减,与流域平均气温变化趋势一致。整个流域以波密为中心,降水量倾向率向外逐渐递减。波密为降水增多幅度最大区,河源区为降水减少幅度最明显区域。与流域平均气温突变的信号相比,降水变化的信号明显比平均温度的信号弱。经进一步分析认为,雅鲁藏布江流域降水量序列在缓慢上升过程中,于1982年和于1995年发生了2次突变,并经历了减少、增多和再次减少的3个阶段。(3)流域降水与气温具有协变性。利用标准化处理后气温、降水变化趋势Z值的乘积来描述两变量同步变化趋势显著的区域。结果发现,在年尺度上,流域中游大多数地区呈暖湿化趋势；干季尺度上,流域多呈暖湿化态势；雨季时,流域由于降水变化的空间分异性,气温、降水变化Z值的乘积分布很均匀,总体上流域以暖干倾向为王。(4)蒸散发具有明显的年内分配特征,年内变化呈双峰型。流域多年平均潜在蒸散发从东南向西北呈递增趋势,即从流域上游向下游递减趋势。对27个站点蒸散发的年序列进行了线性拟合并进行显著性检验分析,流域蒸散发减小具有普遍性,流域年ET0、干季ET0、雨季ET0分别以0.949mm/a、0.546mm/a、0.403mm/a的速率减小,流域年潜在蒸散发变化受干季、雨季共同作用影响。通过多元回归、K-means分类、偏相关分析,认为风速是雅鲁藏布江流域潜在蒸散发变化的主导性因子。(5)通过对流域天然径流进行线性拟合可知,雅鲁藏布江径流量总体上呈现减少的趋势,但趋势不是很显著。径流的代际变化存在一定的周期性波动,年内分配极不平衡。通过对径流进行M-K法突变检验得知雅鲁藏布江径流在70年代初期发生突变。经小波分析发现雅鲁藏布江干流4个水文站具有相同的周期性,4个水文站第一主要周期为19-20a,第二主要周期为5-6a。(6)流域土地利用主要类型以草地为主,其次是未利用地和林地,这三类面积的总和达到94%。采用土地利用动态度、土地利用转移矩阵等方法分析LUCC特征,结果表明10多年来流域土地利用变化速度很缓慢,属青藏稳定少动区。土地利用转换特征为：林地增加最为显著,其次是草地和水域减少,再次是建设用地的增加和耕地的减少。土地利用的转换方向为：草地、水域、未利用地向林地转化,耕地、草地向建设用地转化。(7)对流域径流影响因素分析表明：气温、降水的变化是影响雅鲁藏布江天然径流变化最直接的影响因素。降水变化是雅鲁藏布江天然径流最主要的影响因子,降水变化在一定程度上控制着河川径流的演变规律。另外,气温上升、蒸发量增大、冰川退缩也在一定程度上影响径流的演变。流域林地、裸岩石砾地及建设用地面积增加,在一定程度上促进径流的增长作用,但流域发生土地利用类型转换的面积相对较小,因而产生的水文效应相对较小更多还原

【Abstract】 Yarlung Zangbo River is located in the Qinghai-Tibet Plateau. The basin is extremely sensitive and fragile to the global climate change, due to the impact of special topographical features and high altitude plateau. As the Tibet’s most important economic region, the runoff change of Yarlung Zangbo River basin has a significant impact on the national economy around and people’s lives. Thus, in the global context of climate change, the study of water resources change characters and its response to the global climate change in the Qinghai-Tibetan Plateau will provide insights into the water circulation and the evolution law of water resources in the alpine area, has deep significance for the maintenance of water and land resources balance, but also has practical significance and long-term significance for the rational exploitation of water resources in the Yarlung Zangbo River basin.Choosing the Yarlung Zangbo River basin as the study area, through the analysis of hydrological elements change law and spatial and temporal patterns change of the land use/land over, in the paper, the impact of climatic factors such as the precipitation, temperature, evaporation and driver factor of LUCC on the runoff is discussed. The main results and conclusions of the study are drawn as follows:(1)The annual mean temperature of 1960-2009 in the Yarlung Zangbo River basin had a significant upward trend, which increased with the ascent of the altitude. In addition, the minimum temperature tendency rate was much higher than the maximum one, and the rising rate of minimum temperature was about two times more than the maximum one. It showed that the warming of temperature occurred mainly at night in the Qinghai-Tibetan Plateau. The general distribution trend of annual mean temperature in the Yarlung Zangbo River basin was approximately fit for the terrain, with a decreasing trend from southeast to northwest. Jiali was the smallest temperature boost area with the range of 0.18-0.20℃/10a. Lhasa was the largest temperature boost region with the range of 0.55-0.58℃/10a. Mutation testing for mean temperature time series of the basin showed that the abrupt change points of mean temperature series emerged in 1987 and 1997.(2)The annual precipitation of 1960-2009 in the basin had an upward trend, but not significant, and the precipitation change showed complex. The trend of precipitation spatial distribution was decreasing from southeast to northwest which was similar with the mean temperature change of the basin. With the center of Bomi, the precipitation tendency rate of the basin had a gradually decreasing outward trend. Bomi was the area with the largest increase range of precipitation, while Heyuan was the area with the most obvious decrease range of precipitation. Compared with the mean temperature mutation signals, precipitation in the basin was obviously weaker. After further analysis, it was shown that the precipitation of the Yarlung Zangbo River basin was in the process of slow rising with two mutations in 1982 and in 1995, and experienced three stages of decrease, increase and decrease again.(3)The precipitation was covariant with the temperature. Use the product of temperature and precipitation change trends Z values after standardization to describe the regions where the two variables had significant simultaneous change trend. It was shown that, the middle reach of the basin had a warm and wet in the annual scale. In the dry season scale, when the basin had a trend of warm and wet monsoon, the product distribution of temperature and precipitation change Z Values was even and with a main warm-dry trend as a whole, due to the spatial distribution difference of precipitation.(4) ETo has obvious characteristics of annual distribution, changes of a year showing a double peak.The mean ET0 of the basin was increasing from southeast to northwest trend. It also means the ET0 was decreasing from upstream to downstream. ET0 was in a universal decreases trend, with the reduced rate of 0.949mm/a for ET0(year),0.546mm/a for ET0(dry season) and 0.403mm/a for ET0(rainy),by the method of linear fitting for the ET0 of the 27 sites and significance tests. That was mainly to say, ETo(year) changes were impacted by the joint function of ETo(dry season) and ETo(rainy).By the analysis of multiple regression, K-means classification and partial correlation, a conclusion that the wind speed was the dominant factor for ET0 changes in the Yarlung Zangbo River basin was taken.(5)After the linear fit of natural runoff in the basin, it was shown that there was a decreasing trend as a whole in the Yarlung Zangbo River Basin, but not obvious. Decadal variation of runoff had cyclical fluctuations, and the annual distribution was extremely imbalance. Through the Mann-Kendall mutation, it was found that, there was a mutation in the early 1970s.The wavelet analysis showed that the four hydrological stations of Yarlung Zangbo River main stream had the same periodicity, the first main period of 19-20a, the second main period of 5-6a.(6) The main types of land use in the basin was grass, secondly unused land and forest land, and the sum areas of these three types reached 94%. Land use dynamic degree and land use transfer matrix were adopted to analyze the characters of LUCC, and it was shown that the land use changed relatively slowly in the past 10 years and the area belonged to the stable Qinghai-Tibet region. Land use types were characterized by transformation from grassland, water area and barren land to forest land, from arable land to construction land. The most significant conversion was the increase of woodland, secondly the reduction of grassland and water area, thirdly the increase of construction land and the decrease of arable land.(7)Through the analysis of the runoff affecting factors, it was shown that the changes of temperature and precipitation were the most direct factors affecting the natural runoff of the Yarlung Zangbo River. Precipitation change was the most important factor of the natural runoff, controlled the evolution of river runoff to a certain degree. In addition, the rising of temperature, increasing of evaporation and retreating of glacier affected the evolution of runoff to a certain extent. The increase of forest, barren lands and construction land area promoted the growth of runoff, but the hydrological effect was relatively small, resulting from the small conversation area of land use.更多还原