我国入海河流河口地区海陆分界线划分方法研究

目前我国大多数入海河口地区没有划定明确的海陆分界线 ,导致相关部门之间权责不清 ,不利于解决河口海岸存在的污染、湿地退化、海岸侵蚀等环境问题和加强河口海岸地区的综合管理 ,因此迫切需要划定明确的河口海陆分界线。根据我国主要入海河口的类型及特点 ,从合理性、实用性、稳定性等多个角度提出分析了关于河口海陆分界线划分的几种观点 ,总结其优缺点 。

洪潮水动力作用下闽江乌龙江大桥桥墩冲刷影响研究

闽江南港乌龙江大桥上下游300m范围内先后共建有五座桥梁,在径流和潮流双重水动力作用下,群桥建设使得乌龙江大桥桥墩周边水流结构发生变化,影响桥墩冲刷过程。文章通过建立数学模型,对群桥建设后乌龙江大桥桥墩附近流速及冲刷进行影响研究,可为闽江南港峡口段群桥桥墩及涉河建筑物的防护提供指导。

Mean properties of mesoscale eddies in the Kuroshio recirculation region

Using a 19-year altimetric dataset, the mean properties and spatiotemporal variations of eddies in the Kuroshio recirculation region are examined. A total of 2 001 cyclonic tracks and 1 847 anticyclonic tracks were identifi ed using a geometry-based eddy detection method. The mean radius was 57 km for cyclonic eddies and was 61 km for anticyclonic eddies, respectively, and the mean lifetime was about 10 weeks for both type eddies. There were asymmetric spatial distributions for eddy generation and eddy termination, which were domain-dependent. Mean eddy generation rates were 2.0 per week for cyclonic eddies and were 1.9 per week for anticyclonic eddies. Both type eddies tended to deform during their lifetime and had different propagation characteristics, which mainly propagated westward and southwestward with velocities 4.0–9.9 cm/s, in the Kuroshio recirculation region. Further discussion illustrates that the eddy westward speed maybe infl uenced by the combined effect of vertical shear of horizontal currents and nonlinearity of eddy. To better understand the evolution of eddy tracks, a total of 134 long-lived tracks(lifetime ≥20 weeks) were examined. Comparison between short-span eddies(lifetime ≥4 weeks and <20 weeks) and long-lived eddies is also conducted and the result shows that the short-span and long-lived eddies have similar time evolution. Finally, eddy seasonal variations and interannual changes are discussed. Correlation analysis shows that eddy activity is sensitive to the wind stress curl and meridional gradient of sea surface temperature on interannual timescales. Besides, the strength and orientation of background fl ows also have impacts on the eddy genesis.

Changes in Streamflow Regime Due to Anthropogenic Regulations in the Humid Tropical Western Ghats, Kerala State, India

Regulation of streamflow by a reservoir creates a flow regime much different from the preimpoundment period flow regime. Hydro-Electric Projects(HEPs) commissioned in the Western Ghat regions of the Kerala State, India during the last four decades caused considerable changes in the flow regimes of the rivers of the Kerala State in southwest India. In this paper, the Indicators of Hydrologic Alteration(IHA) approach proposed by Richter et al.(1996) is used to analyze flow regime changes in the Periyar and Muvattupuzha Rivers, due to the construction of the Idukki(1976), Idamalayar(1987) and Lower Periyar(1997) HEPs in the high ranges of the Western Ghats. Normal rainfall years(annual rainfall values within mean ± 0.75 standard deviation limits) are only considered in the analysis to focus on hydrologic alterations due to human activities. The mean hydrologic alteration in the Periyar River(deviation from the pre-development hydrologic indicator values) after commissioning of three HEPs is 35%. Inter-basin water transfer after power generation from the Idukki HEP resulted in a higher discharge in the adjacent Muvattupuzha River, leading to considerable changes in the hydroenvironment(mean hydrologic alterations varying between 57 to 63%). IHA parameters showing hydrologic alterations above the 67 th Percentile werefurther analyzed. For each of the pre-construction hydrologic parameters ± 1 standard deviation from the mean is set as the upper and lower management target limits. The values of each IHA parameter beyond these targets are considered as nonattainment. Considerable hydrologic alterations are observed, especially for low flows in both basins. Inter-basin transfer induced larger changes in flow parameters compared to intra-basin regulations. The study shows that under a proper water release and diversion scheme, the non-attainment of IHA parameters(values fall beyond the target limits) can be reduced. The findings of the study will be greatly beneficial to regional water management and restoration of an eco-environmental system in the humid tropical region.

长江口近口段水流挟沙力与径潮动力关系

该文在充分考虑径流和潮流水动力因素的基础上,建立了更适合于河口区域的水流挟沙力公式,并以长江口近口段为例,讨论了径流和潮流水动力差异对水流挟沙能的影响。结果表明:长江口近口段涨潮和落潮相同流速时洪季的悬沙浓度大与枯季;建立的考虑径流和潮流因素的水流挟沙力公式与传统公式相比,精度上有较大提高,该公式将不同季节和潮型下的水流挟沙力统一起来,有效反应了年内潮汐河口近口段的水流挟沙能力。对于水流挟沙能力的研究则表明:径流不变时,潮流增加,近口段涨潮和落潮水流挟沙能力增强;径流增加时,徐六泾以上河段潮差减小,涨潮水流挟沙能力减弱,而徐六泾及以下河段潮差表现为增加,这表明涨潮和落潮水流挟沙能力取决于径流和潮流的对比过程。