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1.
宜昌水文站年径流量演变多时间尺度分析   总被引:6,自引:0,他引:6  
 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。  相似文献   

2.
为了分析宜昌水文站径流演变规律,利用宜昌站1950~2007年实测日均径流量资料,采用MATLAB编程,运用复Morlet小波方法对其径流年际变化和洪枯季节变化进行多时间尺度分析,并剖析了不同尺度下的变化周期。计算出了宜昌水文站年均径流量、汛期与枯水期丰枯交替的时间尺度和主周期。结果表明,1950~2007年不同时间尺度下的演变规律较显著,但其水文规律的长时间尺度结构和记忆有待于进一步分析与探讨。  相似文献   

3.
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.  相似文献   

4.
近60年来长江干流水沙特征分析   总被引:3,自引:0,他引:3  
根据长江干流宜昌站、汉口站、大通站1950-2013年的年径流量和1954-2013年的年输沙量数据,采用小波分析、相关分析和双累积曲线分析等方法,分析三个水文站的水文序列的周期性特征及水沙关系的变化。分析结果显示:三个水文站的水沙序列存在多时间尺度变化特征,大尺度波动中有小尺度震荡,年径流量变化存在着16~17年、7~9年和2年的主要周期,年输沙量变化存在17~18年、9年、2~3年的主要周期;长江干流年径流量和年输沙量存在一定的相关关系,但受水利工程建设等人类活动的影响,相关关系不断变化。研究结果对研究气候变化和人类活动对长江干流水沙特征的影响有一定的参考价值。  相似文献   

5.
东江流域汛期降雨序列的小波分析   总被引:4,自引:1,他引:3  
为了揭示流域汛期降雨变化的多时间尺度的复杂结构,采用Morlet小波函数,对东江流域1956~2005年汛期降雨时间序列进行了小波分析,找出了不同时间尺度下降雨序列变化的周期和突变点,并根据降雨主周期对未来汛期降雨变化进行了预测。研究结果表明,汛期降雨序列呈现微弱的减少趋势,倾向率为每10 a12.08 mm,近50 a汛期降雨量减少了约60.4 mm;汛期降雨量变化的特征时间尺度为2、4、7、12 a与19 a,其中4、7 a左右的周期振荡最强,为汛期降雨量变化主周期;依据主周期的变化趋势,预测2006年前后东江流域汛期降雨将偏少,在2008~2010年汛期降雨将偏多。  相似文献   

6.
运用Morlet连续复小波函数分析鄱阳湖星子水文站1953年~2012年历年年均水位变动的多时间尺度演变特征,并在水位变动的小波方差分析结果的基础上运用surfer8.0绘制出控制鄱阳湖历年年均水位演变的主周期趋势图。结果表明,鄱阳湖历年年均水位在不同时间尺度的分辨率条件下,其序列显现出不同的周期交替现象,演变过程中存在着25~32、19~23、8~15年以及3~7年4类时间尺度的周期变化规律;其变动存在3个较为明显的峰值,依次对应着28、22、5年的时间尺度;3类时间尺度具有较明显的局部化特征,前两个时间尺度上,年均水位变动的平均周期为19、15年左右,在5年时间尺度上,历年年均水位变动的频率变化较快,同时振荡行为也较明显。  相似文献   

7.
雅鲁藏布江河川径流变化的季节性规律研究   总被引:2,自引:0,他引:2  
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。  相似文献   

8.
岷江上游年径流变化的多时间尺度分析   总被引:3,自引:0,他引:3  
水文时间序列通常包含了多层次时间尺度结构和局部化的特征.针对岷江上游紫坪铺水文站1937~2004年的径流实测资料,本文将小波分析理论应用于水文序列的多尺度分析中.研究结果表明,岷江上游的地表水资源具有多时间尺度的变化,具有6~7年、13年、16年左右的周期变化,利用小波变换可以准确分析它的变化阶段和序列特征.  相似文献   

9.
运用Mann-Kendall法分析长江中下游河流水文变化特征,并应用生态水文指标变动范围法(RVA)综合分析了三峡水库蓄水对长江中下游河流生态水文指标改变程度及其生态效应。研究结果表明,1952年~2014年长江中下游年均流量呈现减少趋势,其中宜昌水文站减少趋势显著;长江中下游宜昌、汉口和大通水文站整体水文改变度属于中度改变,其中宜昌站和汉口站的整体水文改变度分别为61%和63%,接近于高度改变;三峡水库蓄水引起长江中下游河流水文情势发生了较大改变。  相似文献   

10.
利用1951-2007年月平均水沙通量资料,采用Morlet小波函数,对汀江上杭水文站近60年来的年际和年代际变化特征进行小波分析,揭示了汀江水沙通量的多时间尺度变化特征和突变点,并根据小波能量谱(能量集中区)所对应的主周期进行了趋势分析.计算结果表明,洪季水沙通量的多时间尺度振荡趋势和位相与水沙通量的年变化特征相一致;洪季(4-9月)和年径流量均存在18年左右时间尺度的主振荡周期,6 -9年时间尺度的次主周期;洪季(年)沙通量均存在28年左右时间尺度的主振荡周期,16年时间尺度的次主周期;经小波趋势分析,未来10 -20年,汀江水沙通量与正常值相比呈降低趋势.  相似文献   

11.
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。  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).  相似文献   

16.
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.  相似文献   

17.
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.  相似文献   

18.
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。  相似文献   

19.
岩石动态拉伸断裂特性的实验研究   总被引:1,自引:0,他引:1  
采用新近发展起来的拉伸式Hopkinson冲击装置(SHTB),对岩石切口圆柱断裂试样进行了动态拉伸断裂特性的实验研究。同时,利用MTS试验机进行了岩石的静态拉伸断裂实验,成功地获得了岩石试样的断裂韧度及断裂能随加载率而变化的实验结果。对静态和动态破坏后的试样断口进行的扫描电镜观察进一步表明,试样断口形貌的复杂程度与其断裂耗能有着十分密切的联系。  相似文献   

20.
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.  相似文献   

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