Evaluating the relationship between spatial heterogeneity and temporal variability of larval fish assemblages in a coastal marine ecosystem (Haizhou Bay,China)

In coastal marine ecosystems, spatial patterns of larval fish assemblages (LFAs) tend to exhibit geographic stability because of relatively stable spawning site selection and predictable oceanographic phenomena such as eddies. To evaluate the relationship between spatial heterogeneity and temporal variability of LFAs, we conducted a high spatiotemporal resolution ichthyoplankton survey from April to July in 2013 in the shallow waters (<20 m) of Haizhou Bay, China. Our analysis indicated three distinct assemblages, which were stable geographically but exhibited a gradual and directional change of species composition and abundance over our study period. Sea surface temperature was the most important environmental co‐variate for determining temporal variability of LFAs, likely owing to temperature effects of species composition and spawning period selection of adult fish, along with known temperature‐dependent survival rates of larval fish. Study of LFA spatiotemporal dynamics is essential for improved understanding of adult fish spawning behavior, and has potential to inform design and implementation of conservation and management measures (e.g. marine protected areas) in coastal systems.     

Watershed delineation using hydrographic features and a DEM in plain river network region

Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight‐neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector‐based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi‐direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the ‘stream burning’ approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd.     

深水声学拖曳系统

介绍了我国自主设计和研制的深水声学拖曳系统,它的最大工作水深4000m,安装有高分辨率测深侧扫声纳,可在近海底工作获得高分辨率的海底地形地貌和温盐深等数据.它的测深覆盖范围600m,侧扫覆盖范围800m,垂直航迹分辨率5cm,最小可检测高度10cm,测深分辨率高于目前的多波束测深系统.该系统已进行了湖试和海上锚泊试验.该系统的研制成功将对开展大陆架勘查,探测和开发国际海底资源发挥重要作用,拖曳系统中高分辨率测深侧扫声纳还可装船安装,在大陆架水域进行高分辨率海底地形地貌测绘.     

Historical aspects of soil erosion in the Mejerda catchment,Tunisia

Abstract

Agricultural use and related water erosion may lead to significant changes in the sedimentological and hydrological characteristics of watersheds, and therefore negative consequences for rural development. This research aimed to put present-day soil erosion of the important Mejerda catchment into a historical context. The catchment of Wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impacts for thousands of years. We used historical texts and results from archaeological research that go back to 1000 BC, as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analysed together with information on the soils' production potential, the hydrographic network and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain by as much as 15 km²/century. However, soil productivity has decreased significantly. Moreover, due to in channel sedimentation and river choking, the number of flooding occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings should be considered for better water and soil management in the context of semi-arid areas.

Editor Z.W. Kundzewicz

Citation Jebari, S., Berndtsson, R., Lebdi, F., and Bahri, A., 2012. Historical aspects of soil erosion in the Mejerda catchment. Hydrological Sciences Journal, 57 (5), 901–912.     

海洋测绘成果在港口与航道维护保障中的应用

详细介绍了海洋测绘成果在港口与航道疏浚工程水下挖槽量、回淤量和航道边坡土方量及超宽量计算中的应用,探讨了维护疏浚工程效益分析方法,提出了扩大海洋测绘成果在港口与航道通航保障应用范围的建议.     

海洋测绘国际标准S-100的空间模式

S-100——《通用海洋测绘数据模型》是IHO颁布的海洋测绘最新国际标准,其中的空间模式是描述几何类型及其相互关系的框架,在描述、存储、应用海洋测绘地理空间数据方面起着基础和关键性作用。从拓扑学的角度对S-100空间模式的几何构造理论进行了总结,对几何类型的基本框架、继承关系、用途和构造方法进行了分析,将其与现行国内外标准的空间模式进行了对比,进而得出它具有数学严密性、灵活性和可扩展性等优点,同时也发现了一个类型继承错误以及无法描述线群和面群的不足。     

Several significant hydrographic characteristics and their formation mechanism in the South China Sea during the spring and summer of 1998

INTRODUCTIONTheSCSisthelargestmarginseainthewestoftheNorthPacificOcean .Theprevailingwindinwinterisnortheast,whileinsummeritissouthwest .Itisstilluncertainthathowthecirculationandtemperature -salinityfieldassociatewiththemonsoonforcingandaccompanywithseveralkindsofvariationsbeforeorafterthesummermonsoonburst .DuringSECMEXin 1 998,twointensiveobservationperiods (IOP)havebeencarriedoutntheSCS (Fig 1 ) :IOP1 ,from 1 0Aprilto 5May ;IOP2 ,from 1 2JunetoJuly 6 ,inordertounderstandthe…     

11年《海洋测绘》论文综述

针对2011年《海洋测绘》刊载的论文情况,从海洋测绘学科发展角度,通过对各专业论文发表情况的统计分析,对海洋大地测量、水深测量、潮汐观测与水位控制、海洋遥感应用、海图制图、卫星定位与导航等专业的发展现状,进行了归纳总结和简要评述。旨在为广大测绘工作者提供参考。     

海洋测绘资料综合数据仓库的设计

在介绍了海洋测绘资料综合数据仓库的存储对象、体系结构和建设目标的基础上,从实际需要出发,阐述了海洋测绘数字化生产对海洋测绘综合资料科学化和自动化保障的需求,以及系统的总体设计原则、安全需求、软件的设计思路、系统的功能模块和网络化安全的建设方案,并且重点介绍了系统建设中的各种关键技术。     

地磁日变数据幅值关系分析与应用

基于多项式模型的地磁日变改正值幅值关系分析,旨在提供一种站间日变数据互补方法,通过数据的内插和外推,采用加权平均值算法求取插补时段的最优改正数。算例分析表明,利用站间幅值关系重建日变改正值可以达到相当高的精度。