基于能量的鄱阳湖—长江相互作用表征指标研究

鄱阳湖与长江之间存在着复杂的相互作用关系,决定着江湖水沙交换,对整个区域的水资源、防洪、航运、生态环境等均具有重要影响。本文基于能量的观点,在从新的角度解释鄱阳湖和长江相互作用原理的基础上,构建了江湖相互作用的表征指标—能差F_e,对20世纪50年代以来江湖作用关系变化进行了研究。结果表明,自20世纪50年代以来,F_e值整体呈现增加趋势,说明长江作用减弱,鄱阳湖作用不断增强。三峡水库蓄水运用对江湖关系产生了重要影响,进一步削弱了长江作用。从年内变化来看,由于三峡水库的调节,枯水期长江作用略有增强,汛末长江作用减弱较大。江湖作用一定程度上影响着湖区旱涝灾害的产生,当五河来流较大且长江顶托作用明显时,易发生洪涝;当五河来流较小但又对长江有明显的补水作用时,易发生旱情,三峡水库蓄水使湖区9-10月更易发生干旱。     

近50年来长江与鄱阳湖水文相互作用的变化

通过分析1957-2008 年长江与鄱阳湖相互作用的基本特征及其与长江中游、鄱阳湖流域的径流量和气候变化的关系,并用2004-2006 年三峡水库蓄水、放水量的数据,定量地计算和比较了三峡水库运行和区域气候变化对长江与鄱阳湖相互作用的影响程度,得出如下主要结论：1)从年际、年代际尺度上来看,鄱阳湖流域的气候变化和五河入湖流量是鄱阳湖水位和水量变化的主要因素,同时也在很大程度上决定了长江与鄱阳湖相互作用关系及其强弱变化。2) 长江与鄱阳湖的相互作用强度是此消彼长的关系。从季节来看,鄱阳湖对长江的较强作用主要在4-6月,而长江对鄱阳湖的较强作用主要发生在7-9 月。3) 三峡水库运行并没有改变长江与鄱阳湖作用的基本特征,在多数季节三峡水库的影响不足以解释长江径流量变化的10%,但是水库在不同季节的蓄水或放水在一定程度上影响了江湖作用的季节变化和鄱阳湖流域的旱涝机率。4-6月的放水加强了长江作用,由于此时正值鄱阳湖流域的雨季,增强的长江作用在湿润气候的环境下可能增加初夏鄱阳湖流域发生洪涝的概率;7-9 月的少量蓄水则减弱长江对鄱阳湖的作用,降低了湖区洪涝的概率;而10 月份三峡水库的大量蓄水可能增加鄱阳湖流域的旱季干旱发生率。     

长江对鄱阳湖退水期洲滩出露特征的影响

采用具有物理机制的二维水动力模型MIKE 21,基于2006 年长江枯水与1953―2000 年长江平均来水条件（平均条件）2 种情景,模拟比较2 种情景下鄱阳湖退水期（7―12 月）洲滩出露过程,阐释长江来水变化对鄱阳湖洲滩出露特征的影响。结果表明：2006 年长江来水减少导致鄱阳湖洲滩出露开始时间提前,与平均条件相比提前1 个月;洲滩出露50%面积仅历时约0.5 个月,比平均条件缩短约1.5 个月;长江枯水对鄱阳湖洲滩出露分布影响最显著的时段为8―11 月,8 月上旬洲滩增加的出露面积主要分布在赣江入湖三角洲和东部湖湾,而8月中旬―11 月末增加的出露面积主要分布在中部开敞湖区和北部入江通道洲滩;长江枯水对鄱阳湖中北部洲滩出露天数的影响大于南部湖区,对修水和赣江北支入湖三角洲的影响大于赣江中支和南支入湖三角洲,对鄱阳湖国家级自然保护区的影响明显大于南矶山自然保护区;长江来水变化还显著影响洲滩出露速率,2006 年长江水情下洲滩自开始出露至到达最大出露面积（8 月初―10 月中旬）期间的平均出露速率（25 km²/d）,与平均条件下洲滩自开始出露至到达最大出露面积（9 月初―12 月末）期间的平均出露速率（14.5 km²/d）相比增大了72%。     

Effect of Three Gorges Dam on Poyang Lake water level at daily scale based on machine learning

Lake water level is an essential indicator of environmental changes caused by natural and human factors. The water level of Poyang Lake, the largest freshwater lake in China,has exhibited a dramatic variation for the past few years, especially after the completion of the Three Gorges Dam(TGD). However, there is a lack of more accurate assessment of the effect of the TGD on the Poyang Lake water level(PLWL) at finer temporal scales(e.g., the daily scale). Here, we used three machine learning models, namely, an Artificial Neural Network(ANN), a Nonlinear Autoregressive model with eXogenous input(NARX), and a Gated Recurrent Unit(GRU), to simulate the daily lake level during 2003–2016. We found that machine learning models with historical memory(i.e., the GRU model) are more suitable for simulating the PLWL under the influence of the TGD. The GRU-based results show that the lake level is significantly affected by the TGD regulation in the different operation stages and in different periods. Although the TGD has had a slight but not very significant impact on the yearly decline of the PLWL, the blocking or releasing of water at the TGD at certain moments has caused large changes in the lake level. This machine-learning-based study sheds light on the interactions between Poyang Lake and the Yangtze River regulated by the TGD.     

鄱阳湖流域水文变化特征成因及旱涝规律

本研究分析了1960-2008年鄱阳湖流域的气候和水文变化特征,用水量和能量平衡关系解释和印证了这些特征,并由此揭示了鄱阳湖流域水文变化特征的成因及干旱和洪涝发生的规律.得到以下主要结论:1)正常或偏湿年份鄱阳湖流域6月份容纳水量能力已达到饱和,若6-7月降水量超出正常年份,则流域超饱和,洪涝发生.长江中上游降水量7月份的异常偏多会对鄱阳湖流域的洪涝起触发和强化作用.2)鄱阳湖流域7-10月蒸发量大于降水量,特别是7-8月蒸发量大于降水量的一倍以上,所以若4-6月流域降水量少于平均年同期量的20％以上,则累积效应使秋旱发生.当初冬(11月)降水偏少时,秋旱可持续到来年的初春,形成严重的春旱.长江中上游降水量对鄱阳湖流域的春旱没有直接影响,但7-8月降水量偏少时则对秋旱起重要的强化作用.3)长江对鄱阳湖流域的水文过程和旱涝的发生、发展的影响主要在7-8月的“长江与鄱阳湖耦合作用”时期和9-10月的“弱长江作用”期.     

鄱阳湖水文节律变化及其与江湖水量交换的关系

在气候变化、人类活动导致流域水循环改变、极端水文事件频发的背景下,从江湖关系角度分析鄱阳湖水文节律变化规律,对于维护流域水安全具有重要意义。利用1951~2011年湖区4站及湖口站水文实测资料,采用统计分析及水文过程分析方法,对湖泊水文节律在2003~2011年与1980~2002年发生的显著变化及其与长江水量交换的关系进行研究。结果表明:2003~2011年,湖泊因涨、退水阶段水位均偏低,进而枯水阶段延长,同时丰水阶段缩短,湖泊水文节律整体呈现洪旱急转情势;近年来江湖水量交换的变化是造成湖泊水文节律变化的主要原因。     

三峡工程蓄水运行对鄱阳湖典型湿地植被的影响

以鄱阳湖1989～2009年10景秋季Landsat-TM影像为基础,对赣江主支口与饶河口交汇处三角洲和赣江南支口两处典型湿地进行了遥感解译,分析三峡工程运行后鄱阳湖典型湿地的演变趋势.结果表明:三峡工程蓄水运行之前,1989～2001年间鄱阳湖湿地草滩迅速蔓延,湿地正向演替趋势明显.距离湖口远近不同的湿地受三峡工程运...     

三峡地区城市与河流关系的时空演化研究

主要采用历史文献和城市沿革分析,对314BC-AD2013 年间三峡地区城市与河流关系的时空演变特征进行宏观分析,结果表明：从时间演变看,战国西汉时期,三峡地区城市主要沿长江干流缓慢增长;东汉隋唐时期,三峡地区城市由长江干流向支流迅速蔓延;宋元明清时期,三峡地区城市沿长江干流调整稳固;民国以来,三峡地区城市主要依托重庆、宜昌两市极化增长;唐代是三峡地区城市发展的分水岭,明清是三峡地区城市格局的成型期,现代则是三峡地区核心城市的极化期。从空间分布看,2300 年来,以城址论,三峡地区共出现过61 个城市,其中71%的城市分布于长江干流沿岸,73%的城市分布于两河交汇处,82%的城市分布于海拔300 m以下的河谷地带,小河流域城市多从河流下游向上游拓展。总体来看,三峡地区的城市发展体现了其由易到难、由低到高、溯江而上的区域开发时序。     

鄱阳湖水文特征动态变化遥感监测

鄱阳湖是中国第一大淡水湖,对鄱阳湖的水文变化进行持续监测可以为流域内生态环境变化提供基础数据,有利于研究其与长江和流域内河流的交互关系,更好地服务于陆面过程模式和水资源管理。本文利用卫星测高数据反演的鄱阳湖水位数据与MODIS数据结合,对鄱阳湖2000—2015年的水位、水域面积和水量变化进行研究,并通过水量平衡模型,推导出了同期长江—鄱阳湖的水量交互。研究发现,2000—2015年鄱阳湖面积呈现波动性变化,最大水域面积为3600 km ²,是最小水域面积482 km ²的7.5倍。2004年、2007年、2009年和2011年水域面积比较低,2012年后形势好转。每年1月、2月、12月份是鄱阳湖干季,水域面积低至500 km ²,湖口处水位可低至4.71 m,湖面从南往北倾斜,南北水位差异达2.59 m。相对于2000—2015年最低水量,干季时湖泊水量平均增加量为3 km ³。每年6—9月份是鄱阳湖的湿季,水域面积一般大于2670 km ²,水位高于15 m,南北水位差异不大,相对于2000—2015年最低水量,湿季时湖泊水量平均增加量为12 km ³。2000—2015年鄱阳湖流入长江的水量范围为-7~40.66 km ³,每年有93.33%的时间水流从鄱阳湖流入长江。流入长江的水量多少具有明显的季节性,通常5月、6月流入长江的水量高于7月、8月,主要因为7月、8月长江中上游降水增加,长江干流来水增多,对鄱阳湖湖水倒灌有一定的顶托作用。     

长江干流河道对流域输沙的调节作用

利用长江干流和主要支流上测站1956~2004年的输沙量资料,对干流未测区域的来沙进行了估计。根据泥沙平衡 (Sediment budget) 概念,对长江干流河道的冲淤对来水来沙的响应以及对入海泥沙的影响进行研究发现,长江干流屏山至大通河道平均淤积速率为88.58×10⁶ t/a,河道淤积占总的来沙量及大通站输沙量比例分别为14%与21%。由于河道淤积,大通站输沙量减少了17.5%。总体来说上游淤积较轻,宜昌至汉口区间淤积严重,汉口至大通区间为微冲。长江干流的河道冲淤与流域总的来沙具有显著的相关关系,但各段河道的冲淤对流域来沙的响应各不一样。上游的冲淤与流域的径流量和来沙量均没有很好的相关性,宜昌-汉口段河道冲淤的变化与宜昌站的来沙具有显著的相关性;影响汉口-大通间河道的冲淤变化的主要因素是流域的来水量,河道的冲淤与大通站径流量的存在显著的负相关关系。三峡水库蓄水后整个长江干流的冲淤形势发生了根本的变化。三峡水库的蓄水运用有效地减轻了洞庭湖的泥沙淤积,同时也降低了洞庭湖的对长江干流泥沙的调节作用;长江上游干流河道淤积增强,中下游河道出现冲刷,但不同的河段表现不一;中下游河道冲刷量小于预测值,三峡水库的蓄水运用直接导致了长江入海泥沙的减少。     

长江三峡水库消落区保护利用研究

阐述了长江三峡水库消落区概况及其保护利用的意义和目的,分析了消落区存在的主要问题,提出了三峡水库消落区保护利用的相应对策：尽快编制消落区保护利用规划,有序开展保护利用工作;尽快建立完善消落区保护利用法规,依法开展其工作;及时研究消落区保护利用作中出现的新情况及重大问题,进行理论突破、政策创新和管理创新;尽快开展消落区保护利用的科研工作,寻求科技支撑,提高其保护利用效益。     

Evolution characters of water exchange abilities between Dongting Lake and Yangtze River

By using field-survey hydrological data of the related control stations in Dongting Lake and the Yangtze River mainstream in 1951–2010, the evolution characters of water exchange abilities between the two water bodies and their response to the operation of the Three Gorges Reservoir (TGR) from different time scales are analyzed based on their hydraulic relations. The results are shown as follows. Firstly, during July-September, the replenishment ability of Three Outlets to Dongting Lake is stronger, and in January-March, the replenishment ability of Dongting Lake to Yangtze River is stronger. Secondly, there has been an obvious inter-decadal wave on the water exchange coefficient between Dongting Lake and Yangtze River. In 1951–1958 and 1959–1968, the replenishment ability of Three Outlets to Dongting Lake was stronger, but in 2003–2010, the replenishment ability of Dongting Lake to Yangtze River has been strengthened. Thirdly, the spill-division ability of Three Outlets weakens, and the water of Dongting Lake coming from Three Outlets decreases either in typical years or under different dispatching modes of the TGR after the operation of the Three Gorges Reservoir. Furthermore, the water of Dongting Lake coming from Four Rivers takes the dominant position, which obviously enhances the replenishment ability of Dongting Lake to Yangtze River. Fourthly, if the effect of the runoff fluctuation in the basin is not considered, the evolution characters of the exchange capacities and the exchange process between Dongting Lake and Yangtze River in different time scales are generally changed with the variation of the water exchange amount between them, although the factors influencing the water exchange capacities between them is very complex. These show that there is an in-line growth or decline relation between the river-lake water exchange ability and the river-lake water exchange amount.     

Acoustic Doppler current profiler surveys along the Yangtze River

An acoustic Doppler current profiler is used to characterize the river velocity against the morphology of the Yangtze River from Chonqing to the sea. High flow velocities occur in the Three Gorges section and lower velocities in the middle and lower reaches of the river. This is largely due to the change in river pattern from a high gradient deeply-cut valley to a flat fluvial plain. Flow velocities fluctuate in the middle Yangtze due to the presence of meander bends of different length. There are numerous smaller velocity fluctuations in the lower Yangtze channel that reflect multichannel pattern with numerous sand bars and a river morphology affected by bedrock outcrops. Water depths of 40–100 m occur in the Three Gorges valley but decrease to 15–40 m in the middle and lower Yangtze. At the Gezhou Reservoir, 30 km downstream of the Three Gorges damsite velocity drops to low (< 1.0 m s^− 1) 20 km reach. A second low velocity (< 0.5 m s^− 1) zone, about 20 km in length, is located in the lower Yangtze near the coast probably due to the tidal influence. The results from this research will serve as a datum for evaluating changes to the river once the Three Gorges dam is completed in 2009.     

Quaternary sediment in the Yichang area: Implications for the formation of the Three Gorges of the Yangtze River

Sediment data from the Yichang area in the Jianghan Basin of Hubei Province in China suggest deposition in a lacustrine environment prior to 0.75 Ma, B.P., followed by incision of the Yangtze River. The earliest Quaternary Yunchi Formation accumulated in an alluvial fan to fan-delta environment. The subsequent Shanxiyao Formation was deposited in an environment that changed from fan-delta to lacustrine. The distribution of sedimentary facies suggests the presence of a lake in the Yichang area prior to 0.75 Ma, B.P. The lack of sediments contemporaneous with the Yunchi and Shanxiyao Formations in other areas of the Jianghan Basin, suggests that this ancient lake was limited to the Yichang area. This lake predates the present Yangtze River in the Yichang area and the Jianghan basin. Provenance studies of gravels in the Yunchi and Shanxiyao Formations, as well as gravels in terraces and the channel of the Yangtze River indicate a variety of sediment sources, but suggest that no material from the area west of the Three Gorges had been carried into the Yichang area prior to 0.75 Ma, B.P. The Yangtze River cut through Three Gorges area only after 0.75 Ma, B.P.     

洞庭湖与长江水体交换能力演变及对三峡水库运行的响应

运用洞庭湖区与长江干流相关控制站1951-2010 年实测水文数据, 在分析江湖水力关系的基础上, 从不同时间尺度分析江湖水体交换能力的演变特征及其对三峡水库运行的响应。结果表明:① 7-9 月长江荆南三口对洞庭湖的补给能力较强, 1-3 月洞庭湖对长江的补给能力较强;② 江湖水体交换系数具有明显的年代际波动, 其中1951-1958 年、1959-1968 年荆南三口对湖泊的补给能力较强, 而2003-2010 年湖泊对长江的补给能力增强;③ 三峡水库运行后无论是典型年还是在水库不同调度方式运行期, 三口分泄能力减弱, 入湖水量减少, 而因四水入湖水量占绝对优势, 湖泊对长江的补给能力明显增强;④ 尽管影响江湖水体交换能力的因素极为复杂, 但从总体上讲, 除受流域降水波动影响外, 江湖水体交换能力在不同时间尺度上的演变特征及其过程均随着江湖水体交换量的变化而变化, 说明江湖水体交换能力强度与江湖水体交换量之间存在着彼此消长的关系。     

长江三角洲城市化效率与经济发展水平的耦合关系

本文利用DEA模型、层次分析法和耦合度模型分析了1980-2010 年长江三角洲16 个地级市的城市化效率、经济发展水平, 以及城市化效率与经济发展水平的耦合度, 并对其耦合关系进行了理论初探, 提出了概念模型。结果表明:① 30 年间, 长三角城市化效率与经济发展水平的耦合度总体经历了缓慢上升—急剧上升—缓慢下降—急剧下降的过程, 呈倒“U”型发展;② 不同发展阶段的经济发展水平和城市化效率耦合关系不同, 在一定时期, 提高城市化效率可以提升区域经济发展水平, 区域经济水平的发展也可提高城市化效率;但当城市化效率和经济发展达到一定的水平时, 城市化效率的提高不再成为提升区域经济发展水平的重要因素, 而区域经济发展水平的提升也不会过多地影响城市化效率;③ 城市化效率与经济发展水平存在动态耦合关系, 经济发展水平较高的城市会首先摆脱城市化效率带来的促进作用。     

长江三峡考古遗址文化断层研究

长江三峡考古遗址的地理位置、14C 测年数据及考古学文化年代、地面高程、文化层的连续性、文化层的埋深和厚度、文化断层的埋深和厚度等统计数据综合分析的结果表明长江三峡地区新石器时代到历史时期考古遗址沉积地层中有5 期文化断层: (1) 城背溪文化末期到大溪文化初期(7200~6000a BP); (2) 大溪文化关庙山类型三期(5800~5500a BP); (3) 夏代 (4000~3500a BP); (4) 春秋晚期至战国时期(2500~2200a BP); (5) 宋代以来(960A.D.以来)。探讨文化断层与灾变事件发生之间的关系, 从而揭示三峡地区史前和历史时期环境演变过程及其与人类活动的影响。     

Seasonal variations of sediment discharge from the Yangtze River before and after impoundment of the Three Gorges Dam

Over the past decades, > 50,000 dams and reforestation on the Yangtze River (Changjiang) have had little impact on water discharge but have drastically altered annual and particularly seasonal sediment discharge. Before impoundment of the Three Gorges Dam (TGD) in June 2003, annual sediment discharge had decreased by 60%, and the hysteresis of seasonal rating curves in the upper reaches at Yichang station had shifted from clockwise to counterclockwise. In addition, the river channel in middle-lower reaches had changed from depositional to erosional in 2002.During the four years (2003–2006) after TGD impoundment, ~ 60% of sediment entering the Three Gorges Reservoir was trapped, primarily during the high-discharge months (June–September). Although periodic sediment deposition continues downstream of the TGD, during most months substantial erosion has occurred, supplying ~ 70 million tons per year (Mt/y) of channel-derived sediment to the lower reaches of the river. If sand extraction (~ 40 Mt/y) is taken into consideration, the river channel loses a total of 110 Mt/y. During the extreme drought year 2006, sediment discharge in the upper reaches drastically decreased to 9 Mt (only 2% of its 1950–1960s level) because of decreased water discharge and TGD trapping. In addition, Dongting Lake in the middle reaches, for the first time, changed from trapping net sediment from the mainstem to supplying 14 Mt net sediment to the mainstem. Severe channel erosion and drastic sediment decline have put considerable pressure on the Yangtze coastal areas and East China Sea.     

鄱阳湖流域降水变化及其与太阳黑子的关系

基于鄱阳湖流域1961―2000年的降水栅格数据和太阳黑子相对数数据,采用滑动平均、一元线性回归、Mann-Kendall检验等方法对鄱阳湖流域1961―2000年降水特征进行了分析;采用小波分析方法探讨鄱阳湖流域降水变化规律与太阳黑子的可能联系。结果表明:1961―2000年鄱阳湖流域降水量呈增加趋势,并在1996年发生突变。通过小波分析发现鄱阳湖流域降水主周期为10 a,与太阳黑子活动周期相同,且两者的小波方差系数达到0.86。在1996年发生突变之前,降水量在太阳黑子活动的上升期比下降期小,鄱阳湖流域降水周期变化与太阳黑子活动有一定联系。