鄱阳湖水利枢纽工程关键技术研究

本文针对鄱阳湖水利枢纽工程修建后将发挥的作用和可能产生的影响,采用现场调研、实测资料分析和数学模型计算等研究手段,从鄱阳湖流域水资源演变趋势及开发利用状况,三峡水库运用对长江中下游河道冲淤变化及江湖关系的影响,枢纽工程对水资源、防洪、湖区水环境和鱼类的影响,枢纽工程合适的下闸蓄水时期和蓄水位,工程闸门型式及鱼道建设等方面进行了研究,试图为鄱阳湖水利枢纽工程项目立项和规划设计提供科技支撑。     

博斯腾湖矿化度影响因子的敏感度分析

水位,吞吐流,风场从不同机理不同程度影响着博斯腾湖的矿化度分布。本文在定性分析博斯腾湖矿化度分布的影响因子的基础上,建立水流-盐度数学模型,通过采用单因子影响的分析的方法,进行矿化度分布对各影响因子的敏感度分析。研究表明:风场对博湖矿化度分布的影响最为明显,水位和吞吐流对博湖矿化度分布的影响均不明显。该研究对博湖的水环境综合治理有一定的指导意义。     

基于遥感和GIS技术的青海湖环湖地区生态环境脆弱性评价

以青海湖环湖地区为研究区,从生态环境脆弱性的影响因子和脆弱性形成的结果表现入手,通过遥感与GIS技术提取出8项生态因子包括植被指数、土壤亮度和土壤湿度指数、高程和坡度以及气温降水和土地利用作为评价指标,利用层次分析法（AHP）计算各评价指标的权重,然后计算研究区综合脆弱度,并根据统计结果将脆弱度的大小划分为微度脆弱、轻度脆弱、中度脆弱和重度脆弱4个不同等级。结果表明：研究区轻度脆弱和中度脆弱所占面积比例较大,分别占到研究区陆地面积的35.2%和40.7%,说明该区总体环境质量较好。     

鄱阳湖出湖流量时序变化特征与驱动因子分析

长江中游与鄱阳湖及五河构成复杂的“江-湖”系统,研究阐明鄱阳湖出湖流量的时序变化特征与驱动因子,是调控改善江湖关系的关键所在。本文在初步选取12个潜在的出湖流量驱动因子基础上,有机结合相关系数判别和主成分分析方法,揭示了不同潜在驱动因子间的多重共线性;进而通过构建出湖流量数学模型,量化了不同潜在驱动因子对出湖流量的相对重要性排序及其影响程度。研究结果表明：（1）赣江、抚河、饶河、修水的入湖流量,湖区星子站水位,三峡出库流量等6个驱动因子间不存在多重共线性,可完整表征五河来流、湖区水位、长江干流的多重驱动作用;（2）运用基于随机森林回归方法的出湖流量数学模型,揭示了湖区水位、长江干流来流、赣江入湖流量是最为重要的驱动因子,并且其对出湖流量的影响呈现复杂的非线性特征。研究表明：影响出湖流量的众多驱动因子之间关系复杂但影响程度有所差异。这为科学调控典型通江湖泊江湖关系提供了重要参考依据。     

基于洞庭湖水沙模型的荆南三河冲淤变化研究

荆南三河起于荆江河段,水沙情势受上游来水来沙条件影响较大,荆南三河冲淤变化研究有助于认识洞庭湖地区防洪形势和江湖关系的演变。本文构建了洞庭湖水沙数值模型,计算了三峡工程运行后荆南三河各河段的冲淤变化,并结合实测冲淤数据探究了影响荆南三河冲淤的因素。计算结果表明,三峡工程运行后荆南三河河道发生普遍冲刷,冲刷趋势短期内不会变化,但冲刷强度逐渐下降。三峡工程运行后,荆南三河口门分流量、分流比和分沙比均无明显趋势性变化,分沙量大幅度减小,清水下泄改变了荆南三河冲淤状态。此外,采砂对荆南三河冲淤也有重要影响。     

A second-order analytic solution for oscillatory wind-induced flow in an idealized shallow lake

We present a second-order analytic solution to the nonlinear depth-integrated shallow water equations for free-surface oscillatory wind-driven flow in an idealized lake. Expressing the solution as an asymptotic expansion in the dimensionless wave amplitude (ζ/h), which is considered to be a small parameter, enables simplification of the governing equations and permits the use of a perturbation approach to solve them.This analytic solution provides a benchmark for testing numerical models. In particular, the main merit of this solution is that it accounts for advective effects, which are typically omitted from analytic solutions of two-dimensional free surface flow. In order to retain these effects in an analytic solution, we restrict our attention to forcing from a monochromatic wind stress, consider a constant depth rectangular lake, and simplify the governing equations by omitting the Coriolis and eddy viscosity terms and using a linearised friction factor. As such, the analytic solution is of limited use for considering real world problems. Due to the complexity of the analytic solution computer code for this solution is available online.Our solution is valid for cases where changes in the water surface level are small compared with the depth of the lake, and the advective terms in the momentum equations are small compared with acceleration terms. We examine the validity of these assumptions for three test cases, and compare the second-order analytic solution to numerical results to verify an existing hydrodynamic model.     

基于Landsat-TM影像的鄱阳湖典型湿地动态变化研究

利用分层分类法,通过对鄱阳湖典型湿地(蚌湖与赣江中支口三角洲)长序列秋季Landsat-TM影像进行解译分析,探讨了1991年~2008年间鄱阳湖典型湿地动态变化特征。结果表明分层分类方法能够有效地应用于Landsat-TM遥感影像的解译;从1991年到2008年蚌湖和赣江中支口三角洲湿地的植被面积分别增加18.56km2和6.01km2,其中赣江主支三角洲洲滩植被分布呈向湖体扩展态势。植被分布受水情影响比较大,蚌湖湿地的苔草面积与同时期水面积呈负相关性,而赣江主支三角洲湿地植被类型结构变化受水位影响也比较明显,苔草面积变化与秋季湖口水位表现为负相关,芦苇分布面积变化则与湖口水位变化趋势较为一致。     

Integration of MODIS-derived metrics to assess interannual variability in snowpack, lake ice, and NDVI in southwest Alaska

Impacts of global climate change are expected to result in greater variation in the seasonality of snowpack, lake ice, and vegetation dynamics in southwest Alaska. All have wide-reaching physical and biological ecosystem effects in the region. We used Moderate Resolution Imaging Spectroradiometer (MODIS) calibrated radiance, snow cover extent, and vegetation index products for interpreting interannual variation in the duration and extent of snowpack, lake ice, and vegetation dynamics for southwest Alaska. The approach integrates multiple seasonal metrics across large ecological regions.Throughout the observation period (2001-2007), snow cover duration was stable within ecoregions, with variable start and end dates. The start of the lake ice season lagged the snow season by 2 to 3 months. Within a given lake, freeze-up dates varied in timing and duration, while break-up dates were more consistent. Vegetation phenology varied less than snow and ice metrics, with start-of-season dates comparatively consistent across years. The start of growing season and snow melt were related to one another as they are both temperature dependent. Higher than average temperatures during the El Niño winter of 2002-2003 were expressed in anomalous ice and snow season patterns. We are developing a consistent, MODIS-based dataset that will be used to monitor temporal trends of each of these seasonal metrics and to map areas of change for the study area.     

Dust source identification using MODIS: A comparison of techniques applied to the Lake Eyre Basin, Australia

The impact of mineral aerosol (dust) in the Earth's system depends on particle characteristics which are initially determined by the terrestrial sources from which the sediments are entrained. Remote sensing is an established method for the detection and mapping of dust events, and has recently been used to identify dust source locations with varying degrees of success. This paper compares and evaluates five principal methods, using MODIS Level 1B and MODIS Level 2 aerosol data, to: (a) differentiate dust (mineral aerosol) from non-dust, and (2) determine the extent to which they enable the source of the dust to be discerned. The five MODIS L1B methods used here are: (1) un-processed false colour composite (FCC), (2) brightness temperature difference, (3) Ackerman's (1997: J.Geophys. Res., 102, 17069-17080) procedure, (4) Miller's (2003:Geophys. Res. Lett. 30, 20, art.no.2071) dust enhancement algorithm and (5) Roskovensky and Liou's (2005: Geophys. Res. Lett. 32, L12809) dust differentiation algorithm; the aerosol product is MODIS Deep Blue (Hsu et al., 2004: IEEE Trans. Geosci. Rem. Sensing, 42, 557-569), which is optimised for use over bright surfaces (i.e. deserts). These are applied to four significant dust events from the Lake Eyre Basin, Australia. OMI AI was also examined for each event to provide an independent assessment of dust presence and plume location. All of the techniques were successful in detecting dust when compared to FCCs, but the most effective technique for source determination varied from event to event depending on factors such as cloud cover, dust plume mineralogy and surface reflectance. Significantly, to optimise dust detection using the MODIS L1B approaches, the recommended dust/non-dust thresholds had to be considerably adjusted on an event by event basis. MODIS L2 aerosol data retrievals were also found to vary in quality significantly between events; being affected in particular by cloud masking difficulties. In general, we find that OMI AI and MODIS AQUA L1B and L2 data are complementary; the former are ideal for initial dust detection, the latter can be used to both identify plumes and sources at high spatial resolution. Overall, approaches using brightness temperature difference (BT10-11) are the most consistently reliable technique for dust source identification in the Lake Eyre Basin. One reason for this is that this enclosed basin contains multiple dust sources with contrasting geochemical signatures. In this instance, BTD data are not affected significantly by perturbations in dust mineralogy. However, the other algorithms tested (including MODIS Deep Blue) were all influenced by ground surface reflectance or dust mineralogy; making it impossible to use one single MODIS L1B or L2 data type for all events (or even for a single multiple-plume event). There is, however, considerable potential to exploit this anomaly, and to use dust detection algorithms to obtain information about dust mineralogy.     

Extreme value analysis of streamflow time series in Poyang Lake Basin, China

Extreme meteorological and hydrological events may cause major disasters and heavy social and economic losses.Therefore,more and more studies have focused on extreme hydro-meteorological events in various climates and geographic regions.Based on nearly 50 years of observed records of the Poyang Lake Basin,the occurrence and changing trends of extreme streamflow indices,including the annual maximum flow,annual peak-over-threshold flows,and low flows,were analyzed for ten hydrological stations.The results indicate that most annual maximum flows occurred from April to July,highly attributed to the Southeast Asian summer monsoons,whereas the annual minimum flows were concentrated between January and February.As for the low flow indices (the annual minimum flow,annual minimum 7-d flow,and annual minimum 30-d flow),a significant increasing trend was detected in most parts of the Poyang Lake Basin.The trends illustrate the potential effects of climate change and human activities on the hydrological cycle over the Poyang Lake Basin.