The influence of relative sediment supply on riverine habitat heterogeneity

The diversity of aquatic habitats in streams is linked to physical processes that act at various spatial and temporal scales. Two components of many that contribute to creating habitat heterogeneity in streams are the interaction between sediment supply and transport capacity and the presence of local in-stream structures, such as large woody debris and boulders. Data from previously published flume and field studies and a new field study on tributaries to the South Yuba River in Nevada County, California, USA, were used to evaluate the relationship between habitat heterogeneity, local in-stream structural features and relative sediment supply. Habitat heterogeneity was quantified using spatial heterogeneity measures from the field of landscape ecology. Relative sediment supply, as expressed by the sediment supply/transport capacity ratio, which controls channel morphology and substrate textures, two key physical habitat characteristics, was quantified using a dimensionless bedload transport ratio, q. Calculated q values were plotted against an ecologically meaningful heterogeneity index, Shannon's Diversity Index, measured for each study reach, as well as the percent area of in-stream structural elements. The results indicate two potential mechanisms for how relative sediment supply may drive geomorphic diversity in natural river systems at the reach scale. When less mobile structural elements form a small proportion of the reach landscape, the supply/capacity ratio dictates the range of sediment textures and geomorphic features observed within the reach. In these settings, channels with a moderate relative sediment supply exhibit the highest textural and geomorphic diversity. In contrast, when less mobile structural elements are abundant, forced local scour and deposition creates high habitat heterogeneity, even in the presence of high relative sediment supply.     

储层非均质性研究--以葡萄花油层组PI1～PI4小层为例

储层非均质性对油气田的勘探和开发效果影响很大。结合测井资料二次解释的孔隙度(φ)、泥质含量(Vsh)、粒度中值(Md)、束缚水饱和度(Swi)等资料,借助BP网络对渗透率进行预测。对萨尔图油田中部葡萄花油层组的非均质性进行了定量半定量的研究,认为萨尔图油田中部葡萄花油层组PI2小层层内非均质性最严重,与沉积微相密切相关。单砂层垂向上渗透率的变化以正韵律和复合式韵律为主,局部发育反韵律模式。经对葡萄花油层组PI1—PI4系统研究,层内非均质性强弱依次为PI2a、PI3、PI2b、PI1、PI4;层间非均质性在PI3和PI4间表现得最强,其它相对要弱;各小层平面非均质性相差无几,整体表现为较强的非均质性。     

基于FME实现AutoCAD Dwg向Shape数据转换

数据转换是实现GIS(Geographic information system)数据间互操作的重要手段之一。详细阐述目前实现数据转换的几种方法及存在问题,并以AutoCAD dwg数据格式为例,介绍如何利用FME(FeatrueManipulate Engine)语义转换实现AutoCAD dwg数据向GIS shape数据格式转换,并利用脚本程序进行批量处理,这在很大程度上提高了地籍数据入库的效率。     

Scales of heterogeneity of water quality in rivers: Insights from high resolution maps based on integrated geospatial, sensor and ROV technologies

While the spatial heterogeneity of many aquatic ecosystems is acknowledged, rivers are often mistakenly described as homogenous and well-mixed. The collection and visualization of attributes like water quality is key to our perception and management of these ecosystems. The assumption of homogeneity can lead to the conclusion that data collection from discrete, discontinuous points in space or time provide a comprehensive estimate of condition. To counter this perception, we combined high-density data collection with spatial interpolation techniques to created two-dimensional maps of water quality. Maps of four riverine transitions and habitats - wetland to urban, river to reservoir, river to estuary and a groundwater intrusion - were constructed from the continuous data. The examples provided show that the most basic water quality parameters - temperature, conductivity, salinity, turbidity, and chlorophyll florescence - are heterogeneous at spatial scales smaller than those captured by common point sampling statistical strategies. The 2-dimensional, interpolation-based maps of the Hillsborough River (Tampa, FL) show significant influences of a variety of geographic features including tributary confluences, submarine groundwater inflow, and riparian interfaces. We conclude that many sampling strategies do not account for the type of patchy heterogeneity observed. The integration of existing in-situ sensors, inexpensive autonomous sampling platforms, and geospatial mapping techniques provides high resolution visualization that can adds a more comprehensive geographic perspective needed for environmental monitoring and assessment programs.     

Exploring the Effects of Microscale Structural Heterogeneity of Forest Canopies Using Large-Eddy Simulations

The Regional Atmospheric Modeling System (RAMS)-based Forest Large-Eddy Simulation (RAFLES), developed and evaluated here, is used to explore the effects of three-dimensional canopy heterogeneity, at the individual tree scale, on the statistical properties of turbulence most pertinent to mass and momentum transfer. In RAFLES, the canopy interacts with air by exerting a drag force, by restricting the open volume and apertures available for flow (i.e. finite porosity), and by acting as a heterogeneous source of heat and moisture. The first and second statistical moments of the velocity and flux profiles computed by RAFLES are compared with turbulent velocity and scalar flux measurements collected during spring and winter days. The observations were made at a meteorological tower situated within a southern hardwood canopy at the Duke Forest site, near Durham, North Carolina, U.S.A. Each of the days analyzed is characterized by distinct regimes of atmospheric stability and canopy foliage distribution conditions. RAFLES results agreed with the 30-min averaged flow statistics profiles measured at this single tower. Following this intercomparison, two case studies are numerically considered representing end-members of foliage and midday atmospheric stability conditions: one representing the winter season with strong winds above a sparse canopy and a slightly unstable boundary layer; the other representing the spring season with a dense canopy, calm conditions, and a strongly convective boundary layer. In each case, results from the control canopy, simulating the observed heterogeneous canopy structure at the Duke Forest hardwood stand, are compared with a test case that also includes heterogeneity commensurate in scale to tree-fall gaps. The effects of such tree-scale canopy heterogeneity on the flow are explored at three levels pertinent to biosphere-atmosphere exchange. The first level (zero-dimensional) considers the effects of such heterogeneity on the common representation of the canopy via length scales such as the zero-plane displacement, the aerodynamic roughness length, the surface-layer depth, and the eddy-penetration depth. The second level (one-dimensional) considers the normalized horizontally-averaged profiles of the first and second moments of the flow to assess how tree-scale heterogeneities disturb the entire planar-averaged profiles from their canonical (and well-studied planar-homogeneous) values inside the canopy and in the surface layer. The third level (three-dimensional) considers the effects of such tree-scale heterogeneities on the spatial variability of the ejection-sweep cycle and its propagation to momentum and mass fluxes. From these comparisons, it is shown that such microscale heterogeneity leads to increased spatial correlations between attributes of the ejection-sweep cycle and measures of canopy heterogeneity, resulting in correlated spatial heterogeneity in fluxes. This heterogeneity persisted up to four times the mean height of the canopy (h _c ) for some variables. Interestingly, this estimate is in agreement with the working definition of the thickness of the canopy roughness sublayer (2h _c –5h _c ).     

古河道储层构型层次分析法——以弧岛油田馆陶组曲流河为例

以胜利油区孤岛油田11J11密井网区曲流河储层为例,在曲流河野外露头和现代沉积原型模型研究成果的基础上,应用岩心、测井及动态等资料,探索了一套曲流河地下储层构型分析方法。在基于构型分析的精细等时地层对比及单井构型要素解释的基础上,采用“层次分析”和“模式拟合”的研究思路,按复合曲流带、单一曲流带、单一点坝以及点坝内部侧积体的4个层次进行模式拟合,对曲流河各级次构型单元内部结构进行系统分析。拟合结果既符合曲流河沉积成因理论,又与研究区动态资料吻合,说明研究成果是可靠的,由此建立了真正意义上的三维储层构型模型,再现了曲流河点坝内部泥质侧积层空间分布特征,为分析油田开发后期储层构型控制的剩余油分布规律提供了科学依据,该方法对类似油田精细储层研究有较好的借鉴作用,并能推广应用。
     

穿过青藏高原的面波传播路径与速度结构

利用时频偏振分析技术分析穿过青藏高原不同地区的基阶Love波的偏振方向,确定不同周期的Love波到达台站的入射方向对于大圆的偏离．结果表明,在青藏高原内部传播的Love波传播路径基本不偏离大圆路径,穿过青藏块体及川滇西部低速区边界的Love波明显偏离大回路径低速区（青藏高原及川滇西部）的边界区域速度变化梯度大,对路径影响大．低速区内部路径偏离不明显,内部速度变化梯度比边界区域速度变化梯度小．低速区内大约在青藏高原中部位置是面波速度最低的地方．面波路径对于大圆路径的明显偏离,是由于速度结构的横向不均匀性造成的．利用已知的相速度分布,采用射线追踪方法正演计算的结果与实测结果在偏离方向上是一致的,但偏离角的值则比实测值小．     

琼东南盆地崖13-1气田陵三段沉积微相对储层非均质性及流动单元划分的影响

崖13-1气田陵三段是河控与潮控的辫状三角洲,主要储层沉积微相为分流河道、水下分流河道、河口坝、远砂坝及席状砂,其中河口坝的储层物性比分流河道和水下分流河道微相好,席状砂与远砂坝的物性相对较差,而各类正韵律河道与反韵律的砂坝决定了各垂向流动单元储层韵律特征。气田内的隔夹层与不同规模的海泛面相关,隔层以前三角洲泥为主,分布稳定,而夹层以分流间湾与水下分流间湾泥为主,分布较局限。结合沉积微相分布、储层非均质性及断层的分布,可以把气田区分为两个大区及6个流动单元,而南II、南III区仍可有较好的储层,但由于构造上处于低部位,含气前景还需进一步论证。