基于小波变换的汉江径流量多时间尺度分析

汉江上游丹江口水库是南水北调工程的水源地,研究其入库年径流量的多时间尺度变化具有十分重要的意义.以汉江丹江口站1933～2004年共72 a的年径流量过程为例,利用Morlet小波变换对水文序列的多时间尺度演变特性进行了分析.利用小波变换时频局部化功能, 将水文序列的频率特征在时间域上展现出来, 清晰地给出了各种周期的强弱和分布情况, 而且还分析出其主要周期,并对汉江2004年以后的年径流量变化趋势进行了预测.研究结果表明,汉江年径流量的年际及年代际时间尺度在时间域中分布很不均匀,具有明显的局部化特征.     

基于小波分析的浑河流域径流量周期分析

利用浑河流域北口前、抚顺、邢家窝棚三个水文站1954―2011年径流量资料,采用Morlet小波分析法对径流序列进行周期分析。结果表明:流域径流演变过程存在明显的多时间尺度特征,存在5―10年、15―20年、35―40年时间尺度的周期变化,且16年尺度的周期变化最明显。     

赣江外洲站近50年水沙变化规律

基于赣江外洲站年径流量时间序列(1957-2008年)和年输沙量时间序列(1966-2008年),采用肯德尔秩次相关检验法、有序聚类分析和秩和检验法、小波分析法对赣江水沙变化规律进行分析.结果表明:年径流量时间序列趋势变化不明显,不存在显著跳跃点,当时间尺度为17时,存在以10～12a为周期的丰枯变化.年输沙量时间序列下降趋势明显,在1984年和1998年附近发生跳跃,周期性变化可分为两段,1966-1986年间,在时间尺度为6时平均变化周期约为4a,1986年后,在时间尺度为1时平均变化周期约为3.7a.水土保持、人工采砂、万安水库拦沙等是影响赣江输沙量显著变化的主要因素.     

基于小波变换的漳卫南运河流域降水和径流周期分析

周期分析是水文序列变化特征研究中的一项重要内容。根据漳卫南运河流域1956-2005年间的年降水量数据以及元村、淇门和临清3个站点的年径流量数据,对水文序列进行趋势分析,采用Morlet小波进行周期分析。研究结果表明:自1956年漳卫南运河流域的年降水量和年径流量均呈现下降趋势;不同时间尺度具有不同的降水和径流结构;年降水量变化的主周期为准6a、12a和准16a;元村、淇门和临清站年径流量具有两个相同的主周期,分别为准5a和准16a。     

DFA在径流波动分析中的应用

运用距平、累积离差、非趋势波动DFA法,对长江上游寸滩水文站近50年来河流径流量的年内变化和年际变化时间序列进行了分析,根据DFA指数的变化特性,分析了不同时间尺度下流量序列变化的突变点和幂律关系.结果表明,近50年来寸滩站河流径流量汛期、非汛期的径流量呈下降的趋势,变化具有多层次的时间尺度结构,年径流量和汛期、非汛期流量均存在3～8年左右时间尺度的周期变化,经水量变化趋势分析,2006～2013年汛期年径流量会有不同比率下降,2006～2009年非汛期的径流量会有不同比率增加.     

宜昌水文站年径流量演变多时间尺度分析

水文时间序列往往在时域中存在多层次时间尺度结构和局部化特征。运用小波分析的多分辨率功能,对宜昌水文站1882-2006年年径流量时间序列资料进行了多时间尺度分析。研究结果表明：宜昌水文站年径流量存在明显的年际变化特征,主要存在30～40年、10～20年及10年以下3类尺度的周期变化规律,变化主周期为14年,第二周期为7年,第三周期为34年;自2006年以后的3年左右,宜昌站年径流量将处于一个相对偏枯期,之后又将进入一个丰水期。     

黄河上游高寒地区水文时间序列小波特征

基于黄河上游吉迈站年降水量、径流量和蒸发量实测资料，利用小波分析方法，探讨了黄河上游高寒地区年降水量、年蒸发量和年径流量的多时间尺度演变特征。结果表明：高寒地区年降水量、年蒸发量和年径流量序列均具有多时间尺度特征；年径流量序列具有4a,8a左右的主周期；年降水量序列存在4a,7a、16a左右的主周期；年蒸发量序列存在4a、8a、18a左右的主周期。此外，给出了高寒地区雨水一冰雪融水类河流的水文情势：径流过程曲线呈双峰型；秋季径流递减速度大于春季递增速度；6月份径流量递增速度最快，9、10月份递减速度最快，在解冻期和冻结初期径流量增减速度仅次于6、9、10月份。     

雅鲁藏布江河川径流变化的季节性规律研究

利用雅鲁藏布江干流奴下水文站1956~2008年实测径流序列资料,采用Morlet小波分析雅鲁藏布江干流径流年际变化和季节性变化的多时间尺度演变规律,揭示了不同尺度下径流变化周期。结果表明:雅鲁藏布江流域年径流和各季节径流存在8~10 a左右时间尺度的丰枯交替,表现出明显的周期特征,其次14~16 a左右时间尺度的周期特征也较明显。研究还发现,雅鲁藏布江夏季径流量占年径流量的53.62%,夏季径流变化趋势与年径流具有较大相似性,不同时间尺度的周期特征之间有不同程度的吻合,说明夏季径流较大程度的控制着年径流。     

黄河上游宁蒙河段水沙变化特征分析

基于黄河上游4个水文站点1950—2009年实测年径流量和年输沙量的数据,利用趋势分析法、Mann-Kendall趋势检验及突变检验、Morlet小波分析等方法,对黄河上游来水来沙的时空变化特征、突变特点和变化周期进行了分析。结果表明:①近60 a来,黄河上游年径流量和年输沙量均呈明显减少趋势,头道拐站年径流量减幅最大,下河沿站年输沙量减幅最大;②径流量和输沙量序列均存在显著突变,但突变时间存在差异性,且输沙量的敏感性更强;③黄河上游水沙序列存在多时间尺度变化,但变化尺度并不一致。     

黄河下游年径流量及输沙量变化的EMD分析

运用EMD方法对黄河下游花园口站1952—2009年年径流量及年输沙量的时间序列资料分别进行了多时间尺度分析,得到了各自具有不同周期的波动分量以及趋势分量。结果表明:黄河下游年径流量、年输沙量的变化过程具有复杂的多时间尺度特性,是多种波动成分共同作用的结果;年径流量和年输沙量变化过程均存在3个波动周期,而趋势项呈递减的态势;相同尺度下的水、沙分量之间具有显著的相关性,而不同尺度下的水、沙分量之间基本无相关性。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.