基于SPEI和SDI指数的云南红河流域气象水文干旱演变分析

本文基于红河流域43个气象站1961-2012年逐月降水、气温数据以及干支流2个水文站1956-2013年逐月流量数据,采用标准化降水蒸散指数(SPEI)和径流干旱指数(SDI)分析流域气象水文干旱的演变特征,并探讨水文干旱对气象干旱的响应。结果表明：①1961-2012年期间,流域总体上表现出干旱化的趋势,季节变化上春季有变湿的趋势,而夏、秋、冬三季有变干的趋势,但趋势并不显著。干旱频率季节空间分布差异较大,春旱和冬旱发生频率较高。从干旱范围来看,春旱范围呈缩小的趋势,夏旱、秋旱和冬旱范围表现出不同程度的增大趋势;②1956-2013年期间,流域水文干旱表现出加剧的趋势,其中1958-1963、1975-1982、1987-1993、2003-2006和2009-2013年为水文干旱多发期,近10年来频率明显增加;③流域水文干旱滞后于气象干旱1~8个月,气象和水文干旱事件的干旱历时、严重程度和强度之间具有紧密的相关性,流域气象干旱是水文干旱的主要驱动力。     

基于HY-1C的红海滩翅碱蓬提取与近5年变化趋势研究

为掌握红海滩翅碱蓬（Suaeda salsa）群落分布现状及修复情况,本文采用2018−2022年HY-1C卫星海岸带成像仪（CZI）数据,基于现场实测光谱特征分析,构建翅碱蓬遥感提取模型,获得了5期翅碱蓬群落空间分布数据,提取精度优于87%;基于提取结果,开展了红海滩翅碱蓬群落时空分布及类型水平上景观格局的变化分析,结果显示：近5年来,翅碱蓬群落分布面积总体呈显著增加趋势,斑块类型面积（CA）、斑块所占景观面积比例（PLAND）、最大斑块指数（LPI）、有效网格大小（MESH）、平均斑块面积（AREA_MN）等指标呈先减小后上升趋势,破碎化指数（SPLIT）先增大后减小、聚集指数（AI）总体呈上升趋势,可见翅碱蓬群落在红海滩景观构成中占比逐年增大,景观形状复杂度提升,破碎化势头得到逆转,聚集性分布趋势较为明显,这说明自2019年开始实施的翅碱蓬规模化修复工程成效显著;另一方面,翅碱蓬群落生境在总体持续向好的同时又表现出恢复水平空间不均衡的特点,大致为中、东部好于西部,南部好于北部。本文结果可为修复工程的效果评估工作提供基础数据,并为今后修复施工的空间布局规划提供决策参考。     

Downstream trends in sediment size and composition of channel-bed, bar, and bank deposits related to hydrologic and lithologic controls in the Llano River watershed, central Texas, USA

The downstream fining of fluvial sediments is a fundamental tenet of drainage systems and, for decades, has been the subject of considerable research. Most of this research has focused on variability in channel-bed material. Other sedimentological components such as channel bars and banks, however, represent distinctively different processes occurring at various flow magnitudes and durations and thus provide an opportunity to examine a more comprehensive set of controls on the larger fluvial system. This study analyses downstream patterns of sediment size and composition for channel-bed material, bars, and banks in the Llano River watershed (11,568 km²) in central Texas, USA.Fluvial deposits in the study area were characterized through field, laboratory, and statistical analyses and standard sedimentary indices (d₁₆, d₅₀, d₈₄, sorting) were computed. Two hundred thirty-eight sediment samples were collected at 15 sites along the main-stem channel with sampling occurring at the low-flow channel (thalweg), lateral bars, banks, and overbank locations. Channel-bar deposits are characterized by a downstream reduction in particle size, but low-flow-channel deposits have a substantially weaker trend, a discrepancy possibly attributed to uniformity and continuity of hydraulic sorting mechanisms during moderate and high flows. Channel-bar deposits reveal an abrupt downstream reduction in gravel size in the upper watershed, which is attributed to an increase in drainage area. Further, an abrupt gravel-to-sand transition occurs immediately downstream of a distinct lithologic change from mostly carbonate rocks to igneous and metamorphic rocks. The downstream decrease in channel-bar particle size occurs despite an increasingly constricted alluvial valley, commonly associated with greater unit stream power and relatively coarse sediment. Contrasting with channel-bed material, particle size of channel banks increases downstream, which is attributed to the addition of sand-sized sediment from igneous and metamorphic rocks. The consideration of distinctive sedimentological components of a dynamic fluvial system represents a more comprehensive and nuanced study of the topic of downstream sediment trends than prior studies, which is important to a range of engineering, biological, and planning issues at the watershed scale.     

Upscaled modeling of well singularity for simulating flow in heterogeneous formations

Subsurface flows are affected by geological variability over a range of length scales. The modeling of well singularity in heterogeneous formations is important for simulating flow in aquifers and petroleum reservoirs. In this paper, two approaches in calculating the upscaled well index to capture the effects of fine scale heterogeneity in near-well regions are presented and applied. We first develop a flow-based near-well upscaling procedure for geometrically flexible grids. This approach entails solving local well-driven flows and requires the treatment of geometric effects due to the nonalignment between fine and coarse scale grids. An approximate coarse scale well model based on a well singularity analysis is also proposed. This model, referred to as near-well arithmetic averaging, uses only the fine scale permeabilities at well locations to compute the coarse scale well index; it does not require solving any flow problems. These two methods are systematically tested on three-dimensional models with a variety of permeability distributions. It is shown that both approaches provide considerable improvement over a simple (arithmetic) averaging approach to compute the coarse scale well index. The flow-based approach shows close agreement to the fine scale reference model, and the near-well arithmetic averaging also offers accuracy for an appropriate range of parameters. The interaction between global flow and near-well upscaling is also investigated through the use of global fine scale solutions in near-well scale-up calculations.     

Bed load transport in an obstruction-formed pool in a forest, gravelbed stream

This paper examines channel dynamics and bed load transport relations through an obstruction-forced pool in a forest, gravel-bed stream by comparing flow conditions, sediment mobility, and bed morphology among transects at the pool head, centre, and tail. Variable sediment supply from within and outside of the channel led to a complex pattern of scour and fill hysteresis. Despite the large flood magnitude, large portions of the bed did not scour. Scour was observed at three distinct locations: two of these were adjacent to large woody debris (LWD), and the third was along the flow path deflected by a major LWD obstruction. Bed material texture showed little change in size distribution of either surface or subsurface material, suggesting lack of disruption of the pre-flood bed. Fractions larger than the median size of the bed surface material were rarely mobile. Sediment rating relations were similar, although temporal variation within and among stations was relatively high. Relations between bed load size distribution and discharge were complex, showing coarsening with increasing discharge followed by fining as more sand was mobilized at high flow. Lack of local scour in the pool combined with bed load fining and net fill by relatively fine material implied that the dominant sources of mobile sediment were upstream storage sites and local bank collapse. Patterns of flow, channel dynamics, and sediment mobility were strongly affected by a LWD flow obstruction in the pool centre that created turbulent effects, thereby enhancing entrainment and transport in a manner similar to scour at bridge piers.     

山西朔州井水位的前驱波记录及其讨论

在山西省朔州井水位动态观测的原始记录图中,发现很多远强震前的水位慢波动现象,称其为井水位的前驱波记录．本文介绍了典型的前驱波记录图象,初步分析了该井水位对前驱波的记录特征,发现38％的远大强震前有这种记录,波动周期为数分钟至数十分钟,多在震前两天内出现;讨论了前驱波的成因与传播及其井水位的响应条件,研究了井水位前驱波的科学意义及在地震预测探索中的实用价值．      

川西南地区五峰—龙马溪组黑色页岩古气候及物源特征: 来自新地2井地球化学记录*

晚奥陶世—早志留世之交是地球历史时期中的关键时段,该时段伴有全球生物大灭绝、冈瓦纳冰川以及火山事件。晚奥陶世末期的冰川事件历时相对较短,在中国尚未找到冰川存在的直接证据。为了更好地研究奥陶—志留纪交替时期是否存在古气候的变化,选取了川西南地区新地2井岩心中新鲜的上奥陶统五峰组—下志留统龙马溪组泥页岩样品,通过其主量、微量及稀土元素特征分析,采用多种化学风化指数判定源区风化作用强度及古气候条件。新地2井五峰—龙马溪组所有岩石样品成分变异指数(ICV)均大于1,表明源岩成分成熟度低,属构造活动时期的首次沉积。稀土元素表现为轻稀土富集、重稀土平坦并伴有明显的负Eu 异常,配分模式与花岗岩相似,表明源岩以亲花岗岩、长英质为主;A-CN-K图解、主量元素Al₂O₃/TiO₂值、微量元素Cr/Zr值和Th/Sc值也体现长英质成分为主的物源特征。化学蚀变指数(CIA)、化学风化指数(CIW)和斜长石蚀变指数(PIA)等多种化学风化作用指标均指示,晚奥陶世—早志留世古风化作用强度经历中等—低等—中等、古气候温暖湿润—寒冷干燥—温暖湿润的变化过程。CIA指数的低值指示的五峰组顶部(平均值64.14)、观音桥组(平均值61.7)和龙马溪组底部(平均值64.61)即赫南特期存在短暂的寒冷气候,间接证实了冈瓦纳冰川作用在中国华南地区存在相应的地球化学记录。     

论滇东北二叠纪玄武岩型铜矿(BC)找矿——美洲火山红层型铜矿(VRC)的启示

火山红层型铜矿表现为火山岩序列中断裂控制的整合或大致整合分布、纵横交错的脉状铜硫化物和/或自然铜矿床。本文详细介绍美洲火山红层型铜矿地质特征,剖析其成矿规律以及找矿方法、思路。系统研究滇东北地区玄武岩铜矿,并与北美火山红层型铜矿进行对比。在此基础上,提出滇东北地区火山红层型铜矿新的找矿思路与找矿方法。     

基于卫星重磁资料的南海深部构造研究

南海深部构造对研究南海构造演化和油气勘探具有重要意义.本文对南海地区的自由空气重力异常进行布格校正、海水层校正和沉积层校正,得到布格重力异常,再对布格重力异常进行区域异常和局部异常分离,利用位场界面反演方法对区域布格异常进行反演计算得到研究区域的莫霍面深度分布;采用全变倾角化极方法对研究区域的卫星磁异常数据进行化极处理,并进一步对化极磁异常作向上延拓,得到延拓后化极磁异常结果.分析布格重力异常、莫霍面深度及化极磁异常特征,结合天然地震层析成像的证据,得到以下结论：推测南海北部陆缘的古俯冲带位置是从118.5°E,24°N沿北东向延伸至109°E,15°N;红河断裂入海后经过莺歌海盆地在海南岛南部转为南北向与越东断裂相接并延伸至万安盆地;推测中特提斯洋的部分闭合位置是从110°E,2°N到101°E,21°N.