吉尔吉斯斯坦楚河过去407年径流量重建     

高志鸿  张合理  陈峰  Rysbek Satylkanov  Bakytbek Ermenbaev  Zulfiyor Bakhtiyorov  张瑞波  喻树龙  岳伟鹏  赵晓恩 《第四纪研究》2022,42(1):288-301

紧邻丝绸之路经济带核心区的中亚地区跨境河流众多,水资源分配极不均衡.揭示中亚跨境河流径流变化规律,对水资源调配管理,缓解区域水资源紧张局面有深远影响,对促进东西方经济文化交流和"一带一路"建设具有重大的战略意义.文章选取中亚重要跨境河流——楚河为研究对象,利用吉尔吉斯斯坦天山山区雪岭云杉(Picea schrenkia...  相似文献   

Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana     

Isaac Boateng  Malcolm BrayJanet Hooke 《Geomorphology》2012,138(1):100-110

Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 10⁶ m³/a before 1964 (pre-Akosombo dam) to about 7 × 10⁶ m³/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast. There is the need, therefore, to ensure that catchment management plans and coastal management plans are integrated or interconnected.  相似文献   

塔里木河流域中游渭干河-库车河绿洲盐渍土水盐信息光谱特征研究   总被引：2，自引：0，他引：2  

张飞  塔西甫拉提·特依拜  丁建丽  买买提·沙吾提  桂东伟  韩桂红  孙倩 《地理与地理信息科学》2012,28(1):65-70

土壤水分、盐分时空变异强,是影响土壤光谱特征的两个重要因素。土壤水分与盐分之间的关系以及土壤水分、盐分与土壤光谱特征间的关系直接关系到利用遥感光谱信息监测土壤盐渍化的精度。该文运用多元统计学及可见光-近红外反射光谱分析方法对2010年10月渭干河-库车河三角洲绿洲盐渍土水分、盐分数据和盐渍土野外光谱数据进行分析,探讨该绿洲盐渍土表层(0～10cm)水盐信息与野外光谱特征间的关系。结果表明:1)土壤水分和土壤电导率可用Cubic曲线拟合,相关系数R=0.8503,土壤盐分和土壤电导率也可用Cubic曲线拟合,相关系数R=0.842,但土壤水分与盐分之间的显著性较弱,相关系数R=0.74。2)与原始野外光谱相比,包络线消除后光谱波段与土壤水分和土壤电导率之间的Pearson相关性都有不同程度的提高,利用包络线消除法后的波段分别建立盐渍土土壤水分、土壤电导率后向回归预测方程,为动态水盐条件下的盐渍土遥感监测提供了理论依据。  相似文献   

Diagnosis of a new species of neolithodes (Crustacea: Anomura: Lithodidae) from New Zealand (note)     

Elliot W. Dawson  J. C. Yaldwyn 《新西兰海洋与淡水研究杂志》2013,47(2):227-228

A new stone crab, Neolithodes brodiei sp.nov., known from an ovigerous female taken in 455 fm (832 m) on the Campbell Plateau, is characterised and distinguished from the five species previously recognised. It is morphologically close to the North Atlantic N. agassizii and the South African N. asperrimus.  相似文献   

The river continuum concept — reply to Barmuta and Lake     

M. J. Winterbourn 《新西兰海洋与淡水研究杂志》2013,47(2):229-231

Spectral analyses of water‐level oscillations in Wellington Harbour during the 1960 Chilean and 1964 Alaskan tsunamis are given. The results are used to define the periods for the three longest‐period characteristic oscillation modes. Some implications for future tsunamis are discussed.  相似文献   

Morphological characterization of cluster microforms     

K. B. STROM  A. N. PAPANICOLAOU 《Sedimentology》2008,55(1):137-153

A field study was conducted on two mountain streams in the Cascade Mountains of Washington State on the morphological characterization of cluster microforms. Morphological characterization of clusters is presented in terms of: (i) cluster shape; (ii) cluster geometric properties; and (iii) the spatial arrangement of clusters in the horizontal plane. Clusters were differentiated from other microtopography features such as reticulate structures and transverse ribs, and identified clusters were categorized by shape as being of pebble, line, comet, heap or ring type. The complex spatial arrangement of clusters at the sites was characterized by using a two‐dimensional correlation function, which allowed for measurement of the average cluster‐spacing properties. For the rivers examined, pebble‐shaped clusters were the most frequently observed cluster shape. Cluster geometric properties were found to be controlled by particles of the largest size fraction in the bed and the projected frontal width of the cluster – with cluster length being linearly related to cluster width for cluster width‐to‐height ratios <3·5. Results of the cluster‐spacing analysis suggest that cluster spacing increases with cluster size and decreases with local slope. Application of this principle to the available spacing data shows that cluster spacing λ scales with the ratio of S/d₀ such that λS/d₀ = constant, where S is the local slope and d₀ the diameter of the largest particle in the cluster.  相似文献   

Calibration studies concerning a one-dimensional numerical tidal model with particular reference to resistance coefficients     

Stephen G. Wallis  Donald W. Knight 《Estuarine, Coastal and Shelf Science》1984,19(5):541-562

Since the hydrodynamics of flow in most shallow estuaries is dominated by the boundary resistance, the selection of appropriate values for the roughness coefficients in any numerical tidal model is important. The paper describes studies involving the intra-tidal variation of resistance coefficients in twelve reaches of the Conwy estuary in North Wales. Resistance coefficients are evaluated for six water level data sets covering the neap to spring tidal variation by cubature based and parameter estimation techniques. Results from these two inverse methods are shown to agree well despite somewhat different schematizations for the estuary. A direct check on the intra-tidal variation of resistance coefficients at one particular reach is made possible by specifically gathered field data described in an earlier paper by Knight. In general the resistance coefficients exhibit three basic trends—a strong stage dependence, a flow directional dependence due to flood or ebb dominated bed forms, and a high variability with location along the estuary, especially where sand banks are oxposed at low water. The optimized resistance coefficients are then used in a one-dimensional numerical tidal model in order to ascertain the effect of particular modes of calibration. Estuary mean errors in water levels are of the order of 2,5 and 16 cm for the three calibrations tested.  相似文献   

Hydraulic modelling of fish habitat in urban rivers during high flows     

D. J. Booker 《水文研究》2003,17(3):577-599

In urban rivers, flow regime and channel morphology are the drivers of physical habitat quality for aquatic species. Peak discharges are increased at high flows as a result of impermeable catchments and channel engineering for flood protection schemes. Hazardous conditions and flashy hydrographs mean that measurement of velocities at high flows is a difficult task. This research uses a three‐dimensional computational fluid dynamics (3D‐CFD) model to simulate hydraulic patterns in two urban river channels. A 3D‐CFD code, called SSIIM, was used to simulate hydraulic conditions in two engineered river reaches of the River Tame, Birmingham, UK. These two sites represent channels with different levels of engineering. Models were calibrated and tested using field measurements. Results show that modelled water surface levels and velocity profiles are well simulated. Calibrated roughness heights are compared with those derived from field measurement of sediment size. Numerical experiments are used to assess the relationship between grid resolution in the vertical dimension and the form of the modelled velocity profiles. Biologists have used laboratory experiments to determine maximum sustainable swimming speeds (MSSS) of fish, often in order to assess what level of a particular pollutant may be tolerable. In this work, simulations of high‐flow hydraulic patterns are used to compare velocity patterns with fish MSSS. Results show that when the water levels rise to fill the first channel of the two‐stage channels at the sites, which occurred 16 times in 2000, MSSS are surpassed in the majority of available habitat, suggesting that excessive velocities at high flows are one factor that limits fish habitat. A comparison between the two reaches shows that there is less available habitat in the more modified reach. Conclusions suggest that an approach that integrates water quality issues and physical channel characteristics must be taken in river rehabilitation schemes, as improvements to water quality alone may not be sufficient to improve habitat quality to the desired level. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Estimation of canopy drying time after rainfall using sap flow measurements in an emergent tree in a lowland mixed‐dipterocarp forest in Sarawak,Malaysia     

Tomonori Kume  Koichiro Kuraji  Natsuko Yoshifuji  Toshiyuki Morooka  Shinji Sawano  Lucy Chong  Masakazu Suzuki 《水文研究》2006,20(3):565-578

This study emphasizes the importance of canopy drying time (CDT) after rainfall in a lowland tropical rain forest. In this study, we estimate CDT using sap flow velocities measured by a heat‐pulse method in an emergent tree in a lowland mixed‐dipterocarp forest. Estimated CDT (ECDT) for each rain event has been defined as the time from rainfall cessation to the specific time derived from the difference between diurnal courses of sap flow velocities on a rainy day versus bright days. ECDT could be derived for 22 rain events that were grouped into two types, depending on whether rainfall ceased before or after noon. The ECDTs were distributed more widely and with greater values when rainfall ceased before noon (Type 1) than after noon (Type 2). The ECDTs of both Type 1 and Type 2 decreased with increases in net radiation (Rn) and vapour pressure deficit (VPD) after rainfall. This result shows that ECDT is determined mainly by post‐rainfall evaporation rates. The sap flow velocity as a detector of canopy wetness worked out well because of the specific rainfall characteristics at this site. The practical limitations of the method using sap flow velocities are discussed in relation to rainfall characteristics and time lags between transpirations and sap flow velocities. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

长江中游地区第四纪河湖演变及其对环境的影响   总被引：8，自引：1，他引：8  

龚树毅  陈国金 《地球科学》1997,22(2):199-203

第四纪以来，区内长江水系的演化和变迁经过了４个阶段，形成了丰富的资源，同时也是区内主要环境地质问题产生的根本原因，未来演变的趋势是湖群的进一步衰亡和荆江河段地上河继续抬升，这对区内环境潜伏着巨大威胁。  相似文献