Seasonal changes of abiotic and biotic gradients downstream a multiple use reservoir in a Mediterranean River

The effect of regulated flow regimentation on hydrogeomorphological variables, autochthonous and allochthonous trophic sources and macroinvertebrates communities of the Mucone River, Calabria (Italy) were studied in May, August and November 2005 at three study sites. The first site (M1) was located close to the impoundment, the second one (M2) immediately upstream from the first permanent tributary (Cerreto stream) and the third one (M3) about 1 km downstream from the Cerreto confluence. Our results suggest that hydrogeomorphological gradients already exist in spring but their strongest development, with major consequences for the lotic biota, take place only with the beginning and ending of the dry season. Reduction of river width, shading due to well preserved riparian alder trees and marked sand deposition in November, were the variables negatively affecting epilithic microalgae biomass at site M1. These factors partially relieved at M2 site and became much less important at M3 resulting in the highest levels of autotrophic periphyton production. Coarse particulate organic matter accumulation exhibited an opposite trend due to the lack of discharge peaks at M1, whereas in November, litter fall removed most differences between stations. In May macrozoobenthic communities of the three stations were relatively similar (reophilous gatherer and scraper taxa). In November sand accumulation reduced spatial heterogeneity and habitats density close to the Cecita dam promoting settlement of shredder sand tolerant taxa (Plecoptera: Leuctridae) and a drop of community biodiversity. Flow reactivation, especially after Cerreto confluence, hindered sand accumulation, favoured autochthonous primary production and increased energy sources for macroinvertebrates. Copyright © 2010 John Wiley & Sons, Ltd.     

季节性冻土对风电场杆塔基础稳定性影响研究

本文分析了风电场架空输电线路的特点以及季节性冻土对线路基础的危害,并结合风电场中35 kV直流输电线路杆塔基础的稳定进行分析.计算结果表明,在季节性冻土地区,特别是对冻深较大的地区,在基础埋深达到要求的同时,切向冻胀力也会对基础的稳定造成不利影响.因此,对季节性冻土地区的输电线路基础工程除按一般地区的要求进行设计施工外...     

清流河流域水文气象要素历史演变特征

利用清流河流域1961-2012年的降水、气温、蒸发和径流量资料,采用数理统计方法系统诊断了不同尺度水文气象要素的历史演变特征。结果表明,近50年,清流河流域夏季气温呈非显著升高趋势,年与其它季节气温呈显著性升高趋势,在2007年之后,年和季节气温均存在下降的态势。年降水量和夏、冬季降水量呈增加趋势,春、秋季节降水量呈非显著性减少趋势。年水面蒸发量和除春季之外的季节水面蒸发量呈减少趋势,在清流河流域蒸发悖论现象突出。径流量的演变趋势与降水的演变特征总体一致,年和季节径流量均呈增加趋势,其中冬季径流量增加趋势显著;年和季节降水径流量之间的相关系数均在0.65以上,降水是径流量变化的主要驱动要素,因此,未来气候变化特别是降水变化对水资源的影响应引起足够的重视。     

玛纳斯河流域水质变化趋势分析

在玛纳斯河流域1991~2000年实测水质监测资料的基础上,选择肯斯瓦特断面、红山嘴断面以及蘑菇湖水库、大泉沟水库为代表性站点,采用季节性肯德尔(Kendall)检验方法进行玛纳斯河流域地表水水质变化趋势分析。结果表明:对地表水污染源必须进行有机污染物和含氮有机物的总量控制;对蘑菇湖水库水质管理应加强污染负荷消减力度,进行污染物总量控制;对大泉沟水库应该首先考虑控制挥发酚浓度。     

基于改进降水输入模块的融雪径流模拟:以拉萨河为例

降水是自然界物质循环和水循环的重要组成部分,是高寒地区径流的重要来源,水文模型中降水数据的输入精度对提高高寒地区融雪径流模拟效果具有十分重要的作用。青藏高原地区气象站点较少,站点数据无法全面反映流域内降水时空分布的真实情况,传统的融雪径流模型在地形、风向和水汽等要素对降水垂直分布的影响考虑不够全面,制约了模型在山区融雪模拟以及预测中的应用,因此有必要对模型的降水输入项进行改进,以期提高半干旱高寒地区融雪径流模拟效果。本文基于改进的遥感卫星数据校正理论,开发了适用于半干旱高寒地区的降水输入模块,将其与度日因子模型进行耦合,利用高程分带将降水组合成半网格半站点的降水输入数据驱动模型,并在拉萨河流域进行试验研究。结果表明:降水输入模块能够显著提高降水卫星反演地面降水精度,改进后的融雪模型在率定期和验证期的NSE(Nash-Sutcliffe efficiency coefficient)分别为0.741和0.770,高于原融雪模型的模拟效果,表明改进后的模型能够在流域各个分区获得较为精确的降水数值,融雪径流模拟精度比原模型精度得到提高。总之,耦合降水输入模块的融雪模型可以有效提高降水输入精度,对缺资料半干旱高寒地区融雪模拟具有重要的参考价值。     

SRM融雪径流模型在疏勒河流域上游的应用

疏勒河是西北典型的干旱区内陆河流域,其冰雪融水是春季径流补给的重要来源之一。本文结合MODIS积雪产品MOD10A2、DEM数据和气象台站数据,构建了疏勒河流域上游SRM融雪径流模型,模拟结果的拟合优度确定系数Nash-Sutcliffe系数R2=0.834和体积差DV=1.63%。结果表明:该模型能基本上把握疏勒河流域融雪径流的趋势,达到了较好的模拟效果,可用于该流域春季径流的预测,为预防春季融雪型洪水灾害和减轻春季旱情提供了基础。     

半干旱区季节性水源实时调度模型

漳卫南水系地处海河流域南沿,大部分属于半干旱半湿润地区,下游区年产流深仅数十毫米,使得季节性洪水资源利用的意义尤为突出,采用模型计算分析,可模拟季节性各种洪水资源利用方案的利用效率,通过比选便于制定合理的利用方案。根据漳卫南运河中下游水文气象特征,建立实时调度数学模型,并对所采用的数学模型方法及模型河网中的各类节点处理方法进行介绍,该模型可用于汛期实时调度,能为合理蓄存洪水资源提供辅助决策支持。     

含跨季节储热的多能互补分布式能源系统容量配置优化

为了满足我国对环保及能源的需求,多能互补分布式能源系统成为了分布式能源系统的发展的趋势。文章针对北京地区某办公建筑构建了含跨季节储热的多能互补分布式能源系统,以年总成本最低为目标函数,在满足全年负荷的情况下利用PSO算法(粒子群算法)对该系统中的跨季节储热系统关键设备(储热水箱和基岩储热设备)的容量进行优化,得出了其最佳的容量配置。     

Research on seasonal correlation of wavelet packet energy spectrum and temperature of Runyang Suspension Bridge

In order to establish an environmental-condition-normalized structural damage alarming method, the seasonal correlation analysis of wavelet packet energy spectrum (WPES) and temperature of Runyang Suspension Bridge is performed by means of the 236-day health monitoring data. The analysis results reveal that the measured WPES has remarkable seasonal correlation with the environmental temperature. The seasonal change of environmental temperature accounts for the variation of the damage alarming parameter I _p of the dominant frequency bands with an averaged variance of 200%. The statistical modeling technique using a 6th-order polynomial is adopted to formulate the correlation between the WPES and temperature, on the basis of which the abnormal changes of measured damage alarming parameter I _p are detected using the mean value control chart. It is found that the proposed method can effectively eliminate temperature complications from the time series of WPES and exhibit good capability for detecting the damage-induced 10% variances of the damage alarming parameter I _p . And the proposed WPES-based method is superior the modal frequency and hence is more suitable for online real-time damage alarming for long-span bridges. Supported by the National Natural Science Foundation of China (Grant Nos. 50725828, 50808041) and the Natural Science Foundation of Jiangsu Province (Grant No. BK2008312)     

Modelling seasonal influenza: the role of weather and punctuated antigenic drift

Seasonal influenza appears as annual oscillations in temperate regions of the world, yet little is known as to what drives these annual outbreaks and what factors are responsible for their inter-annual variability. Recent studies suggest that weather variables, such as absolute humidity, are the key drivers of annual influenza outbreaks. The rapid, punctuated, antigenic evolution of the influenza virus is another major factor. We present a new framework for modelling seasonal influenza based on a discrete-time, age-of-infection, epidemic model, which allows the calculation of the model''s likelihood function in closed form. This framework may be used to perform model inference and parameter estimation rigorously. The modelling approach allows us to fit 11 years of Israeli influenza data, with the best models fitting the data with unusually high correlations in which r > 0.9. We show that using actual weather to modulate influenza transmission rate gives better results than using the inter-annual means of the weather variables, providing strong support for the role of weather in shaping the dynamics of influenza. This conclusion remains valid even when incorporating a more realistic depiction of the decay of immunity at the population level, which allows for discrete changes in immunity from year to year.