Environmental Influences on Fish Migration in a Hydropeaking River

Fish have evolved traits and life history characteristics that enable them to survive, exploit and depend on the flow regime of rivers, particularly the timing and predictability of flows for spawning and rearing their young. It is unclear to what degree pulsed flows from hydropower facilities and other environmental variables influence migratory behaviours. We used Dual Frequency Identification Sonar in the Michipicoten River, Canada, to address the relationship between fish migration and environmental factors with a focus on flow magnitude and fluctuation. In both 2007 and 2009, the peak of the Chinook (Oncorhynchus tshawytscha) and pink salmon (Oncorhynchus gorbuscha) migration occurred on 8 September. Mean water temperature on this date was 18 °C and precipitously dropped afterwards. The photoperiod was roughly 12‐h long with sunrise at 700 h and sunset at 2000 h. Most fishes moved upstream during the hours of darkness between 2000 and 600 h. The lowest counts of fish occurred from noon to just before sunset, whereas highest counts commonly occurred from 1 to 2 h after sunset. Fish moved upstream during all magnitudes of flow; however, there was a slight preference for larger flows in 2007 but not in 2009. Changes in flow magnitude occurred both during the day and night, with flows typically increasing during the day to meet electrical demand and decreasing at night. Most fishes moved upstream during periods of little to no change in flow. High flows and changing flows may deter salmon from moving up the Michipicoten River but not likely in a significant manner to cause energetic stress or harm. Other adverse effects of pulsed flows, however, must still be considered for spawning, hatching and rearing success. Copyright © 2014 John Wiley & Sons, Ltd.     

Why do fish strand? An analysis of ten years of flow reduction monitoring data from the Columbia and Kootenay rivers,Canada

Stranding of fish due to flow reductions has been documented in the near shore of the Columbia and Kootenay Rivers, Canada, and can result in sub‐lethal or lethal effects on fish. Ten years (1999–2009) of monitoring data have been collected at sites below two hydro‐electric dams (Hugh‐L‐Keenleyside and Brilliant Dam) following flow reductions. A generalized linear mixed effects model analysed the probability of a stranding event in relation to environmental and operational variables including the rate of change in the water levels, the duration of shoreline inundation prior to a reduction (wetted history), the river stage, the magnitude of the reduction, distance downstream from the dam, time of day, day of year (season) and whether a site had been physically altered to mitigate stranding. The results demonstrated statistically significant effects on stranding risk from minimum river stage, day of the year and whether a site had been physically re‐contoured. The combination of investigated factors giving the highest probability of stranding was a large magnitude reduction completed in the afternoon in midsummer, at low water levels when the near shore had been inundated for a long period. This research is significant in its approach to assessing years of ecosystem scale monitoring data and using the modelling results to determine ways for these findings to be applied in regulated river management to minimize fish stranding. It also highlighted data gaps that require addressing and provides ecosystem scale results to compare with stranding studies carried out in mesocosms. © 2014 The Authors. River Research and Applications published by John Wiley & Sons Ltd.     

Combined Effects of Reservoir Operations and Climate Warming on the Flow Regime of Hydropower Bypass Reaches of California's Sierra Nevada

Alterations to flow regimes from regulation and climatic change both affect the biophysical functioning of rivers over long time periods and large spatial areas. Historically, however, the effects of these flow alteration drivers have been studied separately. In this study, results from unregulated and regulated river management models were assessed to understand how flow regime alterations from river regulation differ under future climate conditions in the Sierra Nevada of California, USA. Four representative flow alteration metrics—mean annual flow, low flow duration, centroid timing and mean weekly rate of decrease—were calculated and statistically characterized under historical and future unregulated and regulated conditions over a 20‐year period at each of the eight regulated river locations below dams across the Sierra Nevada. Future climatic conditions were represented by assuming an increase in air temperature of 6 °C above historical (1981–2000) air temperatures, with no change in other meteorological conditions. Results indicate that climate warming will measurably alter some aspects of the flow regime. By comparison, however, river regulation with business‐as‐usual operations will alter flow regimes much more than climate warming. Existing reservoirs can possibly be used to dampen the anticipated effects of climate warming through improved operations, though additional research is needed to identify the full suite of such possibilities. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of Habitat Suitability Criteria and In‐Stream Habitat Assessment for the Benthic Cyanobacteria Phormidium

Global demand for freshwater has led to unprecedented levels of water abstraction from riverine systems. This has resulted in large alterations in natural river flows. The deleterious impacts of reduced flows on fish and macroinvertebrate abundances have been thoroughly investigated; in contrast, there is a limited understanding of the potential for changes in the abundance of nuisance benthic algal/cyanobacterial blooms. In New Zealand, Phormidium sp. blooms are common in numerous rivers during summer low flows. In this study, an in‐stream habitat assessment is used to examine the relationship between Phormidium habitat availability and reducing flows. Over 650 observations of Phormidium mats, from seven sites (Hutt River, lower North Island, New Zealand), were used to construct habitat suitability curves for depth, velocity and substrate. Preference curves were fitted using both the ‘forage ratio’ and ‘quantile regression’ methods. Phormidium growth, observed at all seven sites, increased significantly from upstream (uppermost site, 5.2% mat cover) to downstream (63.5%). The habitat suitability curves revealed Phormidium had a large tolerance to velocity, depth and substrate type. Consequently, decreases in flow had only negligible effects on available Phormidium habitat. During periods of stable flow, Phormidium abundance positively correlated with increased nitrogen concentrations, potentially explaining the large variation in Phormidium cover from upstream to downstream. Quantile regression generated habitat suitability criteria were a more accurate predictor of available Phormidium habitat than the forage ratio criteria. Copyright © 2013 John Wiley & Sons, Ltd.     

有压输水管涵检修时的气液二相流瞬变研究

结合wylie的自由气体离散模型,构建了分段低压输水系统因检修操作导致检修箱涵进气的瞬变流数学模型,并结合实例对计算结果进行了分析。该研究可以为长距离有压输水系统的设计和运行管理提供理论依据和技术支持,同时也为二相流的气泡模拟提供一种可供借鉴的思路和方法。     

基于流场数值模拟的导流堤加固方案优化设计

流态和流速分析是导流堤设计的先决问题。以某沿海水利枢纽导流堤为研究对象,采用有限元数值模拟的手段及平面二维水流数学模型,对其加长加固方案进行对比分析,优选出合理的导流堤结构型式和长度,为工程设计提供理论参考。     

闸坝水力学特性的三维数值模拟

本文采用标准k-ε双方程紊流模型及基于水气两相流的VOF方法,运用FLOW3 D软件对闸坝进行数值模拟,得出不同水位下的闸坝泄流能力,以及不同部位的闸室及消力池水面线、流速、压力等重要水力学要素。结果表明数值计算在一定程度上可以达到模型试验的效果。     

Method of calculating the collision integral and solution of the Boltzmann kinetic equation for simple gases,gas mixtures and gases with rotational degrees of freedom

The conservative method of calculating the Boltzmann collision integral for simple gases, gas mixtures and gases with rotational degrees of freedom of molecules is presented. In all cases the common approach based on the projection technique of summing up the contributions in the collision integral is used. The method is applied for solving the Boltzmann kinetic equation for two fundamental rarefied gas flow problems: the heat transfer problem and the problem of shock wave structure. A comparison with experimental and numerical data of other authors is reported. It is shown that the considered numerical method allows one to solve the Boltzmann equation for real gases with high accuracy.     

基于Hadoop的云端异常流量检测与分析平台

Hadoop系统作为一种开源的分布式云计算平台已获得广泛应用,但其云端易受到各种威胁和攻击,基于此,开发了一种基于Hadoop的云端异常流量检查与分析平台。首先,使用Mapper周期性地从所有存储流量信息的文件中提取流量的部分信息;然后,通过Reducer将异常流量提取并保存。通过对流量数据的存储、检测与分析可成功地检测出有威胁的攻击,从而保障云端的安全。由于本平台基于开源的Hadoop实现,因此成本较低;同时,基于Java语言实现,可成功移植于各种主流操作系统,具有广泛适用性。基于局域网进行监控试验,结果表明本平台可成功地检测出异常流量,并输出友好的用户界面。     

一种基于视频的公交客流自动统计方法

为提高公交系统智能化管理水平,提出一种公交客流自动统计方法。采用直方图统计与多帧平均的方法提取视频背景,使用背景边缘去除算法得到乘客目标边缘轮廓信息。在此基础上,根据乘客头部轮廓的类圆特性,利用基于梯度信息的Hough变换圆检测算法完成乘客头部轮廓的识别,通过基于Kalman滤波预测的CamShift目标跟踪算法实现乘客的检测与计数。实验结果表明,该方法能有效消除背景图像中的噪声以及背景边缘,准确识别乘客目标并对其跟踪计数,从而提高城市公共交通运输效率。