【作者】 霍雨；

【导师】 王腊春；

【作者基本信息】 南京大学 ， 自然地理学， 2011， 博士

【摘要】 鄱阳湖是长江干流重要的调蓄性湖泊,在我国长江流域中发挥着巨大的调蓄洪水和保护生物多样性等特殊生态功能。鄱阳湖湿地是我国七个国际重要湿地之一,也是世界自然基金会划定的全球重要生态区之一,在全球生态系统中起着举足轻重的作用,鄱阳湖研究对于维系区域、国家乃至世界生态安全具有重大意义。洞庭湖和鄱阳湖为长江中下游的两个仅有的大型通江湖泊,洞庭湖自上世纪50年代以来,湖泊萎缩速率大大增加,鄱阳湖与洞庭湖相比,虽然面积、容积萎缩速率小于洞庭湖,但仍具有明显的缩小趋势。因此,本文在分析近50年来鄱阳湖湖泊形态变迁,以及鄱阳湖流域土地利用、降水蒸发及径流泥沙变化趋势及持续性特征的基础上,通过建立径流模型、输沙模型以及湖泊形态对水沙变化响应的模型,对未来土地利用和降水蒸发条件发生变化时,鄱阳湖面积和容积做出的响应进行定量分析和预测,以期弥补对鄱阳湖形态特征变化研究的不足,为改善鄱阳湖面积缩小、湖容锐减的现状,维持鄱阳湖对长江洪水的调蓄能力,以及协调、处理流域河湖关系与江湖关系提供一定的科学依据。对近50年来鄱阳湖面积、容积以及低水位下岸线形态特征变化的分析表明,鄱阳湖在高程14m以上面积减小较为明显,16m以上湖容减小较为明显,岸线长度缩短,几何形态趋于简单,1990s之后湖泊面积容积基本处于稳定状态,但岸线形态变化特征更为明显；湖区部分对鄱阳湖形态的影响因素主要包括水土流失和围垦两个方面,除湖区外的鄱阳湖流域对其影响则主要通过人类活动和自然条件直接影响入湖径流量和泥沙量,从而间接地使鄱阳湖形态发生变化,降水、蒸发的变化是影响径流量的主要因子,降水、径流和土地利用方式则对输沙量的变化起主导作用。以流域蒸发、降水、土地利用等资料数据为基础,分别采用C++环境下基于不同下垫面产汇流原理的模型以及由小波支持向量机和自适应正态变异粒子群算法组成的模型对鄱阳湖流域进入6个水文控制站的径流量、输沙量以及鄱阳湖形态对流域水沙变化的响应进行模拟,结果表明模拟后的日流量过程变化趋势与实测值基本一致,年径流量模拟的精度相对较高,模拟误差的主要来源为原始数据本身的误差以及对复杂的自然条件变化的忽略,输沙量及形态响应的模拟结果相对误差范围为±1%,小波支持向量机和自适应正态变异粒子群算法相结合的模型的拟合能力明显强于传统的BP神经网络和多元线性回归两种方法。从鄱阳湖流域土地利用转移矩阵来看,从1990-2000年,流域内各种土地利用类型之间转换频繁,大面积、大比例的土地利用类型转换主要发生在草地、水田、林地、旱地和建设用地5种类型之间,水体总体面积变化最小,建设用地总体面积变化最为明显,未利用地主要向林地、旱地和建设用地转换,其中向建设用地的转换面积最大；在平水、枯水两种气候条件下,未利用地向这3种土地利用类型转换均可能导致鄱阳湖的面积和容积减小,但转化为林地时变化幅度最小,转化为耕地和建设用地均使湖泊大面积萎缩,且后者引起的萎缩更为明显。采用MK非参数检验法与R/S法分别对近50年来鄱阳湖流域年、主汛期降水量和年蒸发量的变化趋势及持续性特征进行分析,结果表明各站点年降水量均呈上升趋势,大部分站点在3年、5年、10年3种时间尺度上表现为持续性特征；各站点主汛期降雨量变化趋势不一致,在3种时间尺度上均表现为持续性特征；各站点年蒸发量呈明显的下降趋势,3种时间尺度上均表现为持续性特征,但不同时间尺度的持续性强度变化较小。根据近50年来降水量和蒸发量的极端变化确定各时间序列不同的持续性/反持续性等级所对应的具体变化量,将变化后的降水、蒸发数据输入以上3个模型,结果表明在未来3年和10年两个时间尺度上,湖口站水位21m时对应的湖泊面积和容积均可能有所扩大,在2009年的土地利用背景下,未来3年面积的变化范围可能为3441.69-4330.22km2,容积的变化范围可能为253.37-280.69×108m3,未来10年面积的变化范围可能为3974.37-4450.07 km2,容积的变化范围可能为262.17～290.71×108m3。本文研究结果表明土地利用变化对湖泊形态的影响主要体现在对输沙量的影响,降水蒸发条件的变化对湖泊形态产生的影响主要体现在径流量方面,且未来自然条件的变化可能不会造成湖泊萎缩,土地利用方式的变化可能成为导致湖泊萎缩的主要原因。更多还原

【Abstract】 Poyang Lake is one of the important lakes in the mainstream of Yangtze River. It plays a large part in flood storage, biodiversity protection of Yangtze River basin and so on. Poyang Lake wetland is one of the 7 wetlands of international importance in China, and one of the global important ecotopes demarcated by World Wildlife Fund as well. Poyang Lake is an essential part of global ecosystem. Therefore, study on Poyang Lake is significant to guarantee the regional, national and even international ecological security.Dongting and Poyang Lake are the only two lakes still linked with the Yangtze River in the middle and lower reaches, and are playing a very important part in the regional flood storage. The area of Dongting Lake has decreased rapidly since 1950s. Compared with Dongting Lake, Poyang Lake is shrinking slowly but still getting small obviously. Therefore, this paper simulates the runoff, sediment load and the response of lake area and volume to them, based on the morphological characteristics change of Poyang Lake, the trend and persistence/antipersistence of land use, precipitation and vaporation of Poyang Lake basin in recent 50 years. Then the lake area and volume in the future are predicted quantificationally, when land use and climate condition changes. All these works could provide scientific references for improving the decrease of lake area and volume, maintaining its flood storage capacity, coordinating and handling the relationship among the five rivers, Yangtze River and Poyang Lake. They also could make up the deficiency of the research on morphological characteristics of Poyang Lake.The area and volume are decreasing gradually in recent 50 years, especially the area above 14m and volume above 16m reduce obviously. The shoreline has become shorter and simpler. After 1990s, the change of area and volume gets stable, while the shoreline changes more significantly. The impact factors on lake morphology of Poyang Lake region mainly include soil erosion and inning. The other part of Poyang Lake basin changes the lake form through the direct influence of natural conditions and human activities on runoff and sediment load getting into the lake. Precipitation and vaporation are the primary factors affecting the runoff, and rainfall, runoff and land use dominate the sediment load changes.On the basis of vaporation, precipitation and land use in Poyang Lake basin, runoff output-and-affluence theory-based C++ program, wavelet v-support vector machines and adaptive and normal mutation particle swarm optimization are used to simulate the runoff, sediment load getting into the 6 hydrological stations and the response of lake form to their change. It shows that the daily flow simulated is consistent with the observed values. The annual runoff simulation is high in precision and the error principally comes from the original data itself and the ignorance of complicated natural conditions. The relative error ranges of sediment load and form response simulation are±1%. Model composed of wavelet v-support vector machines and adaptive and normal mutation particle swarm optimization fits much better than BP neural network and multiple linear regression.Land use transition matrix of Poyang Lake basin shows that cover areas of different land use types convert frequently from 1990 to 2000. The most obvious transition occurs among grassland, paddy, forest, irrigated field and built-up land. The area change amplitude of water is smallest and that of built-up land is greatest. Unused land mainly coverts to forest, irrigated field and built-up land and the area converted to built-up land is largest. The transition of unused land to all the three types will result in decrease of lake area and volume either in dry year or normal year. When it converts into forest, the area and volume change slightly; when it converts into irrigated field and built-up land, especially the latter, the lake area and volume decrease significantly.Mann-Kendall test and R/S method are used to analyze the change trends and persistence/antipersistence of annual vaporation, annual and flood season precipitation in Poyang Lake basin. As a result, in recent 50 years, the annual precipitations of all the stations have increased and most of the stations show persistence on 3 different time scales of 3,5 and 10 years; the flood season precipitation of the stations change differently and all of them show persistence on 3 time scales; the vaporation has decreased obviously and all the stations show persistence on 3 time scales. The persistence levels of vaporation are similar on 3 time scales. The daily variations of different persistence/antipersistence classes are determined based on the extreme change of precipitation and vaporation in recent 50 years, and then the new data are input into the 3 models. It indicates that the lake area and volume may increase either in the next 3 or 10 years. In the land use conditions of 2009, Poyang Lake area at Hukou station’s water level of 21m will vary between 3441.69 and 4330.22km2, and the volume will vary between 253.37 and 280.69X 108 m3 in the next 3 years; in the next 10 years, the variance of area will range from 3974.37 to 4450.07 km2, and that of volume will range from 262.17 to 290.71 X 108m3.The conclusions of this paper indicate that land use type changes the lake form mainly in terms of the sediment load, while the impact of precipitation and vaporation on Poyang Lake morphology primarily comes from the direct influence of runoff. Besides, the variation of natural condition in the future will not lead to the decrease of lake area and volume. It is the change of land use types that may make the lake get smaller.更多还原