长江中下游阻隔性河段作用机理

阻隔性河段能够阻隔上游河势调整向下游的传递,对稳定河势起到关键性作用。本文以长江中下游34个单一河段为研究对象,在系统总结长江中下游河道演变规律的基础上,归纳出阻隔性河段控制要素包括：单一微弯的河道平面形态、河段中上部无挑流节点;河相系数小于4;河道纵比降大于1.2?;凹岸黏粒含量高于9.5%;床沙中值粒径大于0.158 mm等。从Navier-Stokes方程出发,推导出河湾水流动力轴线弯曲半径的表达式,进而分析了各控制要素对水流动力轴线摆动及阻隔性河段形成的作用。阻隔性河段的判别条件为：不同流量级下水流动力轴线摆动力与河道边界条件约束力的比值始终小于1;阻隔性河段作用机理在于：即便上游河势发生调整,本河段的河道边界始终能约束主流摆动幅度,归顺上游不同河势条件下的主流平面位置,为下游河道提供了相对稳定的入流条件,从而阻隔上游河势调整向下游传递。     

Assessment and exploitation of the waterfront resources in the middle and lower reaches of the Yangtze River

Waterfront resources are important and special kind of natural resources in the marginal area between land and water. The Yangtze River, the longest river in China, is not only rich in waterfront resources, but also has favorable development conditions with great potentiality. Aided by large-scale underwater topographic map, the major factors of the waterfront resources in the middle and lower reaches of the Yangtze River, such as the stability, the water depth and the natural conditions for port construction, are assessed in this paper respectively on the basis of the overall investigations. The results show that: (1) the waterfront resources are abundant in the middle and lower reaches of the Yangtze River, but lack of perfectly combined high grade waterfront; (2) there exists an obvious regional difference in the natural quality of the waterfront along the Yangtze; (3) the fore-bank water depth and waterfront stability are the main natural factors related to the waterfront quality in the middle and lower reaches of the Yangtze River; (4) the waterfronts along the Yangtze are mainly used for port, warehouse and industrial purposes; and (5) the waterfronts near important cities are highly used, especially the high-quality waterfronts. In addition, some suggestions for the development and utilization of the waterfront resources are presented in this paper.     

The mechanism of barrier river reaches in the middle and lower Yangtze River

Alluvial channel has always adjusted itself to the equilibrium state of sediment transport after it was artificially or naturally disturbed. How to maintain the equilibrium state of sediment transport and keep the river regime stable has always been the concerns of fluvial geomorphologists. The channel in the middle and lower reaches of the Yangtze River is characterized by the staggered distribution of the bifurcated river and the single-thread river. The change of river regime is more violently in the bifurcated river than in the single-thread river. Whether the adjustment of the river regime in the bifurcated river can pass through the single-thread river and propagate to the downstream reaches affects the stabilities of the overall river regime. Studies show that the barrier river reach can block the upstream channel adjustment from propagating to the downstream reaches; therefore, it plays a key role in stabilizing the river regime. This study investigates 34 single-thread river reaches in the middle and lower reaches of the Yangtze River. On the basis of the systematic summarization of the fluvial process of the middle and lower reaches of the Yangtze River, the control factors of barrier river reach are summarized and extracted: the planar morphology of single-thread and meandering; with no flow deflecting node distributed in the upper or middle part of the river reach; the hydraulic geometric coefficient is less than 4; the longitudinal gradient is greater than 12‰, the clay content of the concave bank is greater than 9.5%, and the median diameter of the bed sediment is greater than 0.158 mm. From the Navier-Stokes equation, the calculation formula of the bending radius of flow dynamic axis is deduced, and then the roles of these control factors on restricting the migration of the flow dynamic axis and the formation of the barrier river reach are analyzed. The barrier river reach is considered as such when the ratio of the migration force of the flow dynamic axis to the constraint force of the channel boundary is less than 1 under different flow levels. The mechanism of the barrier river reach is such that even when the upstream river regime adjusts, the channel boundary of this reach can always constrain the migration amplitude of the flow dynamic axis and centralize the planar position of the main stream line under different upstream river regime conditions, providing a relatively stable incoming flow conditions for the downstream reaches, thereby blocking the upstream river regime adjustment from propagating to the downstream reaches.     

1961-2010年长江中下游地区农业洪涝灾害时空变化

为揭示长江中下游地区农业洪涝灾害的发生、分布及时空演变特征,基于1961-2010年研究区内426个气象站点的逐日降水数据,以湖北省单站洪涝等级标准为初始指标,对该指标临界值在-50~100 mm范围内进行同步增减,结合该区7省（市）的洪涝历史灾情记载和农业洪涝受灾面积,采用逐步剔除的方法筛选指标,构建分省农业洪涝等级指标并验证指标的合理性,分析该区近50年农业洪涝灾害的时空变化。结果表明：① 近50年长江中下游地区的农业洪涝灾害发生总体呈增加的趋势,但不同区域和不同年代际差异明显;② 20世纪60年代至80年代农业洪涝发生次数相对平稳,90年代洪涝明显增多,21世纪初洪涝又相对减少;③ 区域农业洪涝灾害明显呈现出江南多、江北少的分布特征。农业洪涝多发区主要集中在江西中北部、江汉平原、浙江沿海,以及安徽、江西和浙江三省交界地带。     

Summertime temperature variations in the middle and lower reaches of Yangtze River and their related circulation anomalies in the past five decades

Using the daily data of temperature from China Meteorological Administration and the NCEP/NCAR reanalysis from 1960 to 2005, we have analyzed the relationships between the summertime high/low temperature events in the middle and lower reaches of the Yangtze River (MLRYR) and the related circulation anomalies in the Eastern Hemisphere. Our results have demonstrated that a significantly increasing trend is observed in daily minimum temperature in the past 50 years. And in some regions in the Northern Hemisphere, the opposite scenarios are observed in circulation anomalies in lower and upper parts of the troposphere in the years when the temperatures are higher than normal, as compared to those in the years when the temperatures are lower than normal in the middle and lower reaches of the Yangtze River (MLRYR). Additionally, the anomalous circulation structure in vertical direction in both the high and lower temperature years are barotropic. It is found that the emergence and maintenance of the aforementioned anomalous circulations are related to three kinds of wave train teleconnection patterns. Further more, influences of the long wave surface radiation on the air temperature are stronger in the nighttime than that in the daytime. While both the maximum and minimum temperatures have negative relationships with the sensible heat flux but positive relationships with the latent heat flux. To some extent, the anomalous dynamic heating (cooling) caused by the vertical thermal advection as well as the diabatic heating (cooling) caused by diabatic processes can explain the formation of the high (low) temperature events in the middle and lower reaches of the Yangtze River (MLRYR) in boreal summer.     

近50年长江中下游地区夏季气温变化与环流异常

Using the daily data of temperature from China Meteorological Administration and the NCEP/NCAR reanalysis from 1960 to 2005, we have analyzed the relationships between the summertime high/low temperature events in the middle and lower reaches of the Yangtze River (MLRYR) and the related circulation anomalies in the Eastern Hemisphere. Our results have demonstrated that a significantly increasing trend is observed in daily minimum temperature in the past 50 years. And in some regions in the Northern Hemisphere, the opposite scenarios are observed in circulation anomalies in lower and upper parts of the troposphere in the years when the temperatures are higher than normal, as compared to those in the years when the temperatures are lower than normal in the middle and lower reaches of the Yangtze River (MLRYR). Additionally, the anomalous circulation structure in vertical direction in both the high and lower temperature years are barotropic. It is found that the emergence and maintenance of the aforementioned anomalous circulations are related to three kinds of wave train teleconnection patterns. Further more, influences of the long wave surface radiation on the air temperature are stronger in the nighttime than that in the daytime. While both the maximum and minimum temperatures have negative relationships with the sensible heat flux but positive relationships with the latent heat flux. To some extent, the anomalous dynamic heating (cooling) caused by the vertical thermal advection as well as the diabatic heating (cooling) caused by diabatic processes can explain the formation of the high (low) temperature events in the middle and lower reaches of the Yangtze River (MLRYR) in boreal summer.     

长江中下游流域自然保护地空间分布及其与人类活动强度关系研究

以2015年土地利用类型数据为基础,计算长江中下游流域人类活动强度,采用最邻近指数、地理集中指数和不均衡指数分析研究区自然保护区、风景名胜区等六类国家级自然保护地分布特征,并定量揭示保护地空间分布与人类活动强度的关系,旨在为长江中下游流域建立基于人类活动强度的各类自然保护地管控策略提供科学依据。结果表明：1）人类活动高、较高、中、较低和低强度带在研究区的占比分别为3.74%、9.83%、14.98%、30.81%和40.63%;高等级强度带主要分布在长江三角洲平原、江汉平原等平原区,低等级强度带主要分布在秦岭山区、武陵山区等山地丘陵区。2）湿地公园、森林公园、风景名胜区和地质公园的空间分布类型为均匀型,水利风景区和自然保护区为凝聚型;六类保护地在各人类活动强度带空间分布不均衡。3）湿地公园、森林公园、水利风景区、自然保护区、风景名胜区和地质公园分别在中、较高、高、低、较低和低强度带密度最大;在高等级强度带“人地”矛盾更突出,应加强对自然保护地的保护力度和人类活动管控,尤其针对湿地公园、森林公园和水利风景区。     

都市区视角下长江中游城市群发展的思考

本文首先对都市区、城市群概念、标准进行界定,并将城市群建立在都市区基础上,从而为城市群的认定划分提供了具体的指标依据;进而用近两次人口普查和2011年区域经济统计年鉴数据,对社会经济意义上的长江中游地区湖北、湖南、江西、安徽四省进行实证研究。结果表明,2010年长江中游地区共有都市区22个,比2000年新增2个;长江中游城市群由四省内部相对独立的四个小城市群,沿东北-西南和西北-东南十字形轴向组合而成。最后根据长江中游城市群大分散、小集中的特点和区位价值的提升等提出四点发展建议。     

Characteristics of dry-wet abrupt alternation events in the middle and lower reaches of the Yangtze River Basin and the relationship with ENSO

During recent decades, more frequent flood-drought alternations have been seen in China as a result of global climate change and intensive human activities, which have significant implications on water and food security. To better identify the characteristics of flood-drought alternations, we proposed a modified dry-wet abrupt alternation index (DWAAI) and applied the new method in the middle and lower reaches of the Yangtze River Basin (YRB-ML) to analyze the long-term spatio-temporal characteristics of dry-wet abrupt alternation (DWAA) events based on the daily precipitation observations at 75 rainfall stations in summer from 1960 to 2015. We found that the DWAA events have been spreading in the study area with higher frequency and intensity since 1960. In particular, the DWAA events mainly occurred in May and June in the northwest of the YRB-ML, including Hanjiang River Basin, the middle reaches of the YRB, north of Dongting Lake and northwest of Poyang Lake. In addition, we also analyzed the impact of El Niño Southern Oscillation (ENSO) on DWAA events in the YRB-ML. The results showed that around 41.04% of DWAA events occurred during the declining stages of La Niña or within the subsequent 8 months after La Niña, which implies that La Niña events could be predictive signals of DWAA events. Besides, significant negative correlations have been found between the modified DWAAI values of all the rainfall stations and the sea surface temperature anomalies in the Nino3.4 region within the 6 months prior to the DWAA events, particularly for the Poyang Lake watershed and the middle reaches of the YRB. This study has significant implications on the flood and drought control and water resources management in the YRB-ML under the challenge of future climate change.     

长江中下游岸线资源的特征及其评价利用

Waterfront resources are important and special kind of natural resources in the marginal area between land and water.The Yangtze River,the longest river in China,is not only rich in waterfront resources,but also has favorable development conditions with great potentiality.Aided by large-scale underwater topographic map,the major factors of the waterfront resources in the middle and lower reaches of the Yangtze River,such as the stability,the water depth and the natural conditions for port construction,are assessed in this paper rspectively on the basis of the overall investigations.The results show that:(1)the waterfront resources are abundant in the middle and lower reaches of the Yangtze River,but lack of perfectly combined high grade waterfront;(2)there exists and obvious regional difference in the natural quality of the waterfront along the Yangtze;(3)the fore-bank water depth and waterfront stability are the main natural factors related to the waterfront auality in the middle and lower reaches of the Yangtze River;(4)the waterfronts along the Yangtze are mainly used for port,warehouse and industrial pruposes; and (5)the waterfronts near important cities are highly used,especially the high-quality waterfronts.In addition,some suggestions for the development and utilization of the waterfront resources are presented in this paper.     

长江中下游流域旱涝急转事件特征分析及其与ENSO的关系

基于长江中下游流域75个雨量站1960-2015年的日降水资料,通过对原有的旱涝急转指数加以改进,定义了日尺度旱涝急转指数（Dry-Wet Abrupt Alternation Index, DWAAI）,全面分析长江中下游流域夏季（5-8月）旱涝急转事件的时空演变特征,并讨论了旱涝急转事件与事件发生前太平洋海表温度的关系。结果表明：① 改进的DWAAI综合考虑了事件前后期旱涝差异与急转快慢程度,筛选事件更加全面。② 总体来说,自20世纪60年以来,流域内发生旱涝急转事件的区域范围越来越广,事件频率和强度均具有逐年增长趋势。旱涝急转事件主要发生在5月和6月,且汉江水系、中游干流区间、洞庭湖水系北部和鄱阳湖水系西北部地区为事件高发区。③ 旱涝急转事件与事件发生前Nino 3.4区域海温持续异常偏低存在一定关系。在发生时间上,La Ni?a现象具有一定的先兆作用,41.04%的事件发生在La Ni?a现象衰亡期或现象结束后8个月内;在事件强度上,流域内站点的DWAAI与事件发生前第1~6个月的Nino 3.4区域海温异常值存在显著的负相关性,尤其是在鄱阳湖水系和中游干流区间,二者负相关性最强。研究结果可以为长江中下游流域防洪抗旱工作提供一定的依据。     

长江中游新石器时代遗址规模的分布特征

运用ArcGIS软件建立了长江中游地区9.0~4.0 ka BP文化遗址的空间数据库,采用叠加分析和统计学方法,对文化遗址的规模、海拔分布、坡度、距河流远近等特征进行了系统分析。结果表明：① 由新石器时代早期到晚期,遗址的数量、规模和分布范围等均呈现增长或扩大趋势,叠置型遗址个数增加;② 遗址一般具有低海拔、平缓地形和距河流较近的选址倾向,晚期的文化遗址大体保持该倾向,但对海拔、坡度及距河流远近等的选择开始出现分化。③ 新石器时代晚期不同规模的文化遗址在选址上存在一定分异。小型遗址多分布在坡度为6°~15°的缓坡地,中型及以上规模的遗址更倾向于坡度为2°~6°平缓地;中小型至大型遗址的海拔分布均以30~50 m为主,特大型遗址的海拔分布以50~100 m为主;特大型遗址在距河流1000 m以内的分布比例高于其他规模遗址;④ 新石器文化在早中期受气候、水源、地形等自然环境因素影响较大,晚期文化的适应能力有所增强。     

基于Google Earth和MODIS陆地数据的农林地转换对地表温度的影响——以长江中下游及毗邻地区为例

揭示耕地与林地转换对地表温度的影响对于认识人类活动的气候与环境效应具有重要意义。基于卫星遥感数据的统计分析是揭示土地利用/覆盖变化对地表温度影响的重要手段。但是,在景观破碎度较高地区,混合像元问题成为使用这一技术手段的主要限制性因素,中国南方长江流域尤为典型。为突破这一限制,论文基于Google Earth高清影像,在1 km尺度上辨识了200对耕地与林地纯像元,进而利用MODIS陆地数据产品,对比分析了耕地与林地的地表温度(LST)、叶面积指数(LAI)、地表反照率(Albedo)之差。结果表明：耕地的LST高于林地,白天和夜间温度分别约偏高2.75 ℃和1.15 ℃,并且温差因季节而异,白昼温差呈双峰(分别是5月和10月,温差约3.18 ℃和3.33 ℃),夜间温差为单峰(7月,约2.46 ℃)。同时,温差因地而异,总体表现为西高东低,陕甘交界处的白昼温差最大,年平均约为3.83 ℃;安徽中南部温差最小,约为1.1 ℃。耕地与林地的LST之差主要由蒸散发的差异所致。林地的LAI较大,蒸散发较强,地表向大气的潜热通量较大,用于直接加热地表的感热相对偏少,因而LST相对偏低。上述结果表明近年来长江流域及毗邻地区的耕地转为林地通过增加蒸发产生了一定的致冷效应。     

长江中下游浅水湖泊表层沉积物潜在可交换性磷研究

利用无限稀释外推法 (IDE法 )和Hieltjes与Lijklema提出的H-L法对长江中下游浅水湖泊表层沉积物中可交换性磷进行测定,研究了IDE法测定的潜在可交换性磷 (IDE-P )与H-L法使用NH₄Cl测定的氯化铵磷 (NH₄Cl-P )在不同污染程度沉积物中的分布规律及二者关系,并对IDE-P和NH₄Cl-P与沉积物土壤测试磷 (STP)、磷吸附饱和度 (DPS)、总磷 (TP)和有机质关系进行讨论。结果表明,沉积物IDE-P和NH₄Cl-P分布遵循重污染沉积物>污染较轻沉积物的规律,IDE-P含量高于NH₄Cl-P含量;不同沉积物的(NH₄Cl-P/IDE-P)%变化较大;IDE-P和NH₄Cl-P与STP、DPS、总磷和有机质的相关性较好。     

疏勒河中下游土地荒漠化敏感性评估

土地荒漠化是疏勒河流域面临的关键环境问题,加强该区域的荒漠化敏感性评估对有效控制荒漠化至关重要。通过集成多源GIS与遥感数据,构建土壤、植被、气候和管理定量评估指标,利用地中海荒漠化与土地利用模型（MEDALUS）计算环境敏感性指数,识别荒漠化敏感区,在此基础上分析荒漠化敏感性的成因,并引入变异系数法确定荒漠化敏感性的主要影响因素。结果表明：目前疏勒河中下游荒漠化态势严峻,17.70%的区域属于极高敏感区,54.34%属于较高敏感区。荒漠化敏感性的空间格局是中部高、北部低,主要由与人类活动有关的管理质量指数决定。从绿洲内至绿洲外荒漠化敏感性逐渐升高,大致呈层状分布,表明人类活动对荒漠化影响显著,建议加强和巩固绿洲外围的防护体系建设。     

渭河中下游干流洪水资源化效益分析与测算

渭河流域中下游不仅水资源总量紧缺,而且配置型、工程型、水质型缺水问题突出,实施洪水资源利用在河道减淤和流域防洪等方面具有显著的经济和环境效益。通过分析河道冲淤特性、确定洪灾损失标准、统计堤防建设和使用现状,结合研究区经济发展现状和土地利用特征,采用效益分摊系数法,计算渭河中下游干流洪水资源化综合效益。主要结论：（1）洪...     

长江中游城市群创新平台空间分布及其影响因素分析

创新是引领发展的第一动力。创新平台作为区域创新体系的重要组成部分和集聚创新资源的核心支撑载体,是推动创新驱动发展的主要抓手。论文以长江中游城市群为研究区域,运用最邻近指数、核密度估计、Ripley's K函数、地理探测器等方法,探究2017年长江中游城市群省级以上创新平台的空间分布特征及其影响因素。结果表明：① 长江中游城市群创新平台整体呈现出集聚分布特征,以武汉、长沙和南昌为核心呈“品字形”的分布格局;② 基于不同等级和不同功能类型划分的各类创新平台均呈现出显著集聚的特征,但集聚强度和集聚状态存在一定差异;③ 创新平台总体和不同类型创新平台的空间集聚存在尺度效应,随地理距离的变化空间集聚趋势先增强后减弱;④ 创新平台的空间分异是多因素综合作用的结果,金融实力、信息化程度、利用外资水平、人力资本条件的影响最为显著,其次为交通可达性、城镇化水平、经济基础和创新氛围。     

长江中游城市网络结构韧性评估及其优化策略

城市网络结构韧性是国际上区域韧性（regional resilience,也译作区域弹性）研究领域正在兴起的概念,着眼于城市网络结构对区域应对冲击并恢复、保持或改善原有系统特征和关键功能的影响力,对区域空间的健康发展意义重大。以长江中游城市群为研究对象,在构建经济、信息、交通三类联系网络的基础上,借助于Gephi社会网络分析工具,尝试评估城市群城市网络的结构韧性能力及其空间特征。结果表明：长江中游城市群网络具有一定韧性能力,结构韧性的层级性和匹配性差异较大,传输性和集聚性差距不明显;在空间上呈现出总体形态模式差异化、分区形态模式错位化、网络联系特征多样化的特征。进而,对城市群空间结构在总体结构、片区结构和要素流动等方面的优化提出建议。     

长江中游城市群空间结构的多分形特征

在城市群越来越演化为多尺度、多区域复杂系统背景下,有必要引入多分形理论与方法研究其空间结构。本文基于2018年NPP-VIIRS夜间灯光数据,计算长江中游城市群整体及其局部的多分维谱,根据谱线分析不同尺度下长江中游城市空间结构的多分形特征。结果显示：① 长江中游城市群夜间灯光容量维在整体和局部都出现双标度现象。② q < -5.5时,整体广义关联维谱线突破理论上限2,在q > 0时,武汉城市圈和环长株潭城市群的分维显著较高。③ 整体的局部分维谱和武汉城市圈、环长株潭城市群、环鄱阳湖城市群、宜荆荆城市群局部分维谱表现为单峰偏右。根据上述结果,得到和验证了以下结论：① 长江中游城市群区域一体化程度较低。② 长江中游城市群不同层级和区域的空间结构差异显著,呈现出多尺度复杂特征。③ 长江中游城市群在不同尺度中均倾向于中心集聚式发展。研究揭示多分形模型能够从尺度依赖视角有效揭示巨型城市群空间结构的复杂性及其背后的问题,具有很好的理论探索和实践分析前景。     

实施流域生态管理的长江中下游湿地保护探讨

长江中下游地区湿地分布广泛且类型多样,是我国淡水湖泊分布最集中和最具有代表性的地区。为了从根本上解决长江中下游湿地利用面临的问题,实现湿地资源的可持续利用,保护湿地环境,解决区内上、下游用水的供需矛盾,实现水资源的优化配置,调动区域湿地保护的积极性和主动性,有必要遵循湿地流域分布规律,应用流域生态学最新理论与实践成果,进行流域生态管理。一方面,要从流域角度处理好几大江湖关系、蓄泄关系、湖垸关系和山湖(河)关系等;另一方面,在流域内建立统一协调机制,对流域湿地进行保护与合理利用、合理布局和统一规划;同时在保护的前提下,科学合理地利用长江中下游湿地资源,开拓新的生产力。