A general multi-objective programming model for minimum ecological flow or water level of inland water bodies

Assessment of ecological flow or water level for water bodies is important for the protection of de- graded or degrading ecosystems caused by water shortage in arid regions, and it has become a key issue in water resources planning. In the past several decades, many methods have been proposed to assess ecological flow for rivers and ecological water level for lakes or wetlands. To balance water uses by human and ecosystems, we proposed a general multi-objective programming model to determine minimum ecological flow or water level for inland water bodies, where two objectives are water index for human and habitat index for ecosystems, respectively Using the weighted sum method for multi-objective optimization, minimum ecological flow or water level can be determined from the breakpoint in the water index-habitat index curve, which is similar to the slope method to de- termine minimum ecological flow from wetted perimeter-discharge curve. However, the general multi-objective programming model is superior to the slope method in its physical meaning and calculation method. This model provides a general analysis method for ecological water uses of different inland water bodies, and can be used to define minimum ecological flow or water level by choosing appropriate water and habitat indices. Several com- monly used flow or water level assessment methods were found to be special cases of the general model, including the wetted perimeter method and the multi-objective physical habitat simulation method for ecological river flow, the inundated forest width method for regeneration flow of floodplain forest and the lake surface area method for eco- logical lake level. These methods were applied to determine minimum ecological flow or water level for two repre- sentative rivers and a lake in northern Xinjiang of China, including minimum ecological flow for the Ertix River, minimum regeneration flow for floodplain forest along the midstream of Kaxgar River, and minimum ecological lake level for the Ebinur Lake. The results illustrated the versatility of the general model, and can provide references for water resources planning and ecosystem protection for these rivers and lake.

Online dynamic measurement of saturation-capillary pressure relation in sandy medium under water level fluctuation

An online dynamic method based on electrical conductivity probe, tensiometer and datataker was presented to measure saturation-capillary pressure （S-p） relation in water-light nonaqueous phase liquid （LNAPL） two-phase sandy medium under water level fluctuation. Three-electrode electrical conductivity probe （ECP） was used to measure water saturation. Hydrophobic tensiometer was obtained by spraying waterproof material to the ceramic cup of commercially available hydrophilic tensiometer. A couple of hydrophilic tensiometer and hydrophobic tensiometer were used to measure pore water pressure and pore LNAPL pressure of the sandy medium, respectively. All the signals from ECP and tensiometer were collected by a data taker connected with a computer. The results show that this method can finish the measurement of S-R relation of a complete drainage or imbibition process in less than 60 min. It is much more timesaving compared with 10-40 d of traditional methods. Two cycles of water level fluctuation were produced, and four saturation-capillary pressure relations including two stable residual LNAPL saturations of the sandy medium were obtained during in 350 h. The results show that this method has a good durable performance and feasibility in the porous medium with complicated multiphase flow. Although further studies are needed on the signal stability and accuracy drift of the ECP, this online dynamic method can be used successfully in the rapid characterization of a LNAPL migration in porous media.

Effect of Nitrogen on Water Content, Sap Flow, and Tolerance of Rice Plants to Brown Planthopper, Nilaparvata lugens

Water content (WC) and sap flow from leaf sheath of rice plants with varying nitrogen levels at different growth stages, and fluctuations in relative water content (RWC) of rice plants being damaged by brown planthoppcr (BPH), Nilaparvata lugens were determined in the laboratory, and the tolerance of rice plants to BPH at different nitrogen regimes was evaluated in the greenhouse at International Rice Research Institute (IRRI), the Philippines. The results indicated that both WC and RWC were increased significantly, as the amount of sap flow from rice plants was reduced statistically, with the increase of nitrogen content in rice plants. RWC in rice plants applied with high nitrogen fertilizer decreased drastically by the injury of BPH nymphs, while the reduced survival duration of rice plants with the increase of nitrogen content was recorded. These may be considered to be one of the important factors in increasing the susceptibility to BPH damage on rice plants applied with nitrogen fertilizer.

Modeling of unsteadiness of fluid flows and level fluctuations in thin slab continuous casting moulds

Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.

Using Ambient Noise to Study the Seismic Velocity Changes Caused by the Rise and Fall of the Water Level in the Zipingpu Reservoir Region

We study the feature of media changes beneath the Zipingpu reservoir and discuss the process of permeation with the water level rise and fall of the reservoir from January 2005 to January 2008 from ambient noise cross correlation by using continuous seismic data recorded by the stations of Zipingpu seismic network and YZP station. A moving-window cross-spectrum technique has been used to calculate the relative seismic velocity changes between station pairs. Results revealed an obvious relationship between relative seismic velocity, and the water level changes with a time delay that may be caused by permeation during three main impoundments and two large scale disemboguements. Impoundment generates a fast and large impact on the superficial layer, and the changes of seismic velocity is the result of increased pressure and permeation during the impoundment. At the first impoundment, the main effect factor is pressure. During the next two process of impoundment, permeation becomes the main effect factor, affecting the fault at a depth of about 8kin.

Monitoring models for base flow effect and daily variation of dam seepage elements considering time lag effect

Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.

Investigation on Water Pollution of Four Rivers in Coastal Wetland of Yellow River Estuary

[Objective] The study aimed at analysing water pollution of four rivers in coastal wetland of Yellow River estuary. [Method] Taking four seriously polluted rivers (Guangli River, Shenxian Ditch, Tiao River and Chao River) in coastal wetland of Yellow River estuary as study objects, water samples were collected from the four rivers in May (dry period), August (wet period) and November (normal period) in 2009 and 2010 respectively, then pollution indices like nutritive salts, COD, chlorophyll-a, petroleum, etc. were measured. Afterwards, the status quo of water pollution was assessed based on Nemero index and comprehensive trophic level index (TLI), so as to find out the integral status quo of water quality of wetland rivers and damages to aquatic ecological environment. [Result] On the whole, water pollution of four rivers in coastal wetland of Yellow River estuary was serious, in the eutrophication state, and the main pollutants were TN, TP, NH+4-N and petroleum. In addition, excessive N and P in the four rivers resulted in water eutrophication of Bohai Bay, so further leading to ride tide, which destroyed the coastal ecological environment of Bohai Sea. Moreover, compared with historical data, water pollution by nitrogen and phosphorus became more serious, while there was no obvious aggravation in the water pollution by petroleum. In a word, water pollution wasn’t optimistic on the whole. [Conclusion] The research could provide theoretical bases for the protection and utilization of river water in coastal wetland of Yellow River estuary and its coastal sea area.

Study of Water Flow in a Single Clay Crack

A model has been constructed to study water flow in a single clay crack, and a new concept of the critical rise rate of water level in the crack has been put forward. When the water level rises faster than this critical rate, the flow in a crack will increase, and vice versa. The flow in a crack is not in proportion to the water level. The maximium water flow in clay is 30-40 times smaller than that in a rock fissure under the same condition. In the process of water discharge, the flow in a crack will lessen gradually, and the crack will grow narrower by 3.0-4.0cm, with its depth reducing by over 50%.

两坝间河道高含沙水流驱动的下游船闸阀门井水位异常特征分析

葛洲坝船闸充水阀门井与输水廊道进水口水体相连,1993年洪季期间曾发生过阀门井水位异常升高,影响船闸设备设施安全等问题。为分析葛洲坝一号船闸充水阀门井水位异常升高的根本原因,基于Mike三维水沙数值模型,模拟分析了不同流量和含沙量级别下的河道水流和含沙量垂向分布结构特征,进而计算阀门井水位异常升高值与河道水流和含沙量的关系,反演1993年洪季葛洲坝一号船闸两个阀门井出现的水位异常现象。研究结果表明,葛洲坝一号船闸阀门井水位异常超过阈值0.5 m的流量和含沙量条件分别约为(30 000 m^(3)/s, 2.85 kg/m^(3)),(40 000 m^(3)/s, 1.42 kg/m^(3)),(50 000 m^(3)/s, 1.23 kg/m^(3))。受三峡水库及上游梯级水库蓄水拦沙、退耕还林政策等因素的影响,未来葛洲坝船闸出现高含沙水流导致阀门井水位异常升高>0.5 m的可能性极小,但在三峡水库排沙泄洪期间仍应引起重视。研究成果可为葛洲坝一号船闸安全营运和科学管理提供参考依据。

稻田控制排水对高邮灌区河道洪水过程的影响

以高邮灌区为例,采用水文-水动力模型,研究稻田控制排水措施对河道洪峰流量、水位和洪水过程的影响。结果表明,雨前通过控制灌溉适当降低田间水位可减轻稻田出流峰值,随着稻田控制水位的增加,稻田径流峰值逐渐降低。通过稻田控制排水,可降低田间出口峰值流量,改变灌区河道洪水过程,降低河道洪峰流量和水位,减轻灌区内部以及附近河道的防洪压力。

鄱阳湖水利枢纽工程施工和运行对湖区及尾闾洪水动力的影响

鄱阳湖是长江水系中的两大通江湖泊之一,在调节长江水位、涵养水源、改善当地气候和维护周围地区生态平衡等方面都起着巨大的作用。鄱阳湖水利枢纽的修建可能导致湖泊水文情势和水动力的变化。本文基于MIKE 21构建鄱阳湖二维水动力模型,选取1954年和1998年特大洪水年以及1991年长江倒灌年作为运行期的典型年,选取1995年作为施工期典型年,按照规划中的鄱阳湖水利枢纽工程施工及运行调度方案,计算水利枢纽修建前后鄱阳湖水位和流量的变化,定量分析枢纽工程对长江干流、鄱阳湖湖区及尾闾附近洪水动力的影响。结果表明:不同典型年鄱阳湖水利枢纽对长江干流、湖区及尾闾的洪水动力影响相似,其中洪水期、倒灌期及施工期一期对长江防洪、湖区及尾闾附近的影响较小,施工期二期湖区水位壅高幅度最高达0.237 m,对鄱阳湖湖区及尾闾附近防洪有一定影响;枢纽工程对星子、都昌、康山等湖区水文站水位影响幅度较为接近,且越靠近尾闾,影响越小。整体而言,鄱阳湖水利枢纽的修建会导致洪水年鄱阳湖湖区水位壅高,倒灌期湖区水位降低,湖区流速降低,但变化幅度均较小,故枢纽工程施工期和运行期对汛期行洪影响不大。

污水管道水位流速检测装置设计

在线实时监测市政污水管道内污水的水位和流速能帮助市政管理部门精准掌握污水流动情况,及时了解管道出现的问题,提高工作效率。该文依据绕流理论设计并制作了一种基于浮球的水位和流速检测装置,通过测量浮球随水位变化的相对位移实现水位测量;通过测量流体对浮球的推力实现流速测量。装置的GSM/GPRS模块接收水位和流速的检测数据并传输至远程监控端,实现远程在线监测。在明渠标准实验台对该检测装置的水位和流速测量值进行标定和精度实验,实验结果表明:测量水位的偏差在±3 mm内,误差不大于其满量程的0.5%;流速测量偏差值在±0.04m/s内,误差不大于其满量程的5%。将该检测装置安装在实际的污水管道内,对污水水位和流速进行了为期三个月的实验监测,检测值的远程传输结果符合预期。

根-土复合体岸坡渗流及稳定数值模拟

植物护岸中根系力学效应可显著提高岸坡浅层稳定性,但对降雨和水位变化等条件下,根系水力效应与力学效应之间相对关系变化对岸坡浅层稳定性影响的研究较少。采用数值分析方法模拟了岸坡根-土复合体从非饱和到饱和(降雨工况和水位上升工况)、从饱和到非饱和(水位下降工况)过程中根-土复合体水力效应对岸坡渗流场的影响,进一步分析了不同水力特性条件下根-土复合体对岸坡浅层稳定性的影响。模拟计算结果表明:(1)在设定的3种降雨强度下,根-土复合体的优先流入渗作用与降雨强度和降雨时间均呈正相关,而排水作用与降雨强度和降雨时间均呈负相关。在长历时的小降雨或短历时的强降雨情况下,由于降雨影响深度增大,根-土复合体水力效应带来的消极影响占主导地位。(2)在水位下降工况下,根-土复合体排水作用有滞后性,力学效应仍占主导地位;在水位上升工况下,根-土复合体增渗作用随水位上升速率增加而增强,根-土复合体的力学效应逐渐被水力效应所掩盖。研究结果对植物护岸工程应用具有借鉴意义,即使采用植物生态护岸,也应加强坡面排水和坡体排水措施。

多开发主体梯级电站实时负荷控制模型研究

由于多开发主体下梯级水电站间不能共享实时负荷数据,上一级电站发电负荷变动常导致本级电站非正常弃水或低水位运行问题。为解决这个问题,提出了基于预测控制的多开发主体梯级电站实时负荷控制模型来控制水位。模型分为实时跟踪、预测控制和厂内负荷分配3部分。实时跟踪每1 h进行一次入库流量反推计算来推算预测入库流量序列;预测控制根据标准差选择不同流量递推模型推算入库流量;厂内负荷分配以耗水量最小进行负荷分配优化,实现上游电站负荷及发电流量未知情况下的梯级电站实时负荷分配并保持水位稳定。所提出的实时负荷控制模型应用于木里河梯级电站实时负荷分配,对多开发主体下流域梯级水电站实时负荷分配,维持水位稳定具有一定的指导意义。

甘蔗生物质炭在界面太阳能海水淡化中的应用

太阳能驱动的界面水蒸发作为环保、高效、可持续的海水淡化技术,在近年来受到广泛关注。快速的水运输、高效的光热转换是实现持续、稳定蒸发的关键。多级孔道的生物质衍生蒸发器在太阳能水蒸发应用中展示出高效、环保、可持续的应用潜力。以废弃的甘蔗节为原料,利用冷冻干燥和高温碳化工艺制备了具有天然多级孔道结构的生物质基蒸发器,并研究了材料的光吸收、水运输和蒸发性能以及不同风速下对流空气对蒸发器的蒸发性能和热损失的改善作用。结果表明:具有发达的多级孔道结构的生物质基蒸发器展示出了高达92.8%的太阳光吸收率。在一倍太阳光强下展示出1.55 kg/(m^(2)·h)的蒸发速率和77.6%的光热转换效率。此外,在风速2 m/s的条件下,蒸发器的蒸发速率展示出了高达2.27 kg/(m^(2)·h)的蒸发速率和91.6%的光热转换效率,显示了对流效应对淡水产出速率的增强和对热损失的抑制作用。

明渠非标准断面法测流水位流量关系的率定及影响因素分析

为探究明渠非标准断面法测流的水位流量关系曲线的率定问题,以新疆第三师某团场25处渠道量水断面为研究对象,利用FlowTracker 2手持式声学多普勒流速仪进行了水位流量关系率定工作.根据实测结果,率定了各渠道量水断面的水位流量关系曲线,并对所率定出的曲线进行了符号检验、适线检验和偏离数值检验及误差分析,在此基础上,对流量拟合参数的影响因素进行了分析.结果表明:所率定的25处渠道量水断面中,14处具有稳定的水位流量关系,5处受回水影响、6处受渠道淤积影响为不稳定的水位流量关系;在渠道粗糙系数Ra、边坡系数m及坡降i相同的条件下,流量拟合参数与渠道底宽b总体上呈正相关;在渠道粗糙系数Ra、边坡系数m及底宽b相同的条件下,流量拟合参数与渠道坡降i总体上呈负相关.研究结果可以为灌区自动化量水设备测流准确性的校核提供参考依据.

莲阳河生态水位(流量)核定研究

受气候变化与经济社会快速发展影响,生活生产用水与生态环境需水的矛盾日益突出,河湖生态流量保障具有重要意义。受限于长系列水文资料的缺乏,中小河流的生态流量保障研究相对较少,而生态环境健康对生态流量保障要求日益增大,开展缺乏长系列资料的河湖生态水位(流量)研究具有重要现实意义。本文以莲阳河为研究对象,明确了生态水位(流量)控制断面,梳理合适的计算方法,科学确定生态水位(流量)保障目标,可为莲阳河流域水资源优化配置提供科学支持,也能为缺乏长系列水文资料的河流核定生态流量指标提供借鉴。

伏龙大桥工程路线与阻水率设计总结

伏龙大桥受地理位置限制,有许多控制设计的关键因素需从方案阶段就开始充分考虑。为使防洪评价报告能顺利通过相关审批,在桥梁路线优化设计时,就要充分考虑关键因素阻水率的影响,规划路线经过局部优化,以避免大斜交。从方案设计到施工图阶段,阻水率这一指标在路线优化和总体方案确定的过程中,起到了决定性作用。防洪评价过程中的阻水率对设计路线和方案近乎有“一票否决权”。故从方案阶段开始关注阻水率,避免了方案返工。优化阻水率可从跨径、桥墩尺寸、与水流夹角等方面进行。

王甫洲电厂水文站水位流量关系单值化分析研究

王甫洲电厂水文站位于王甫洲电厂尾水渠内,研究分析汉江新集水利枢纽蓄水后对王甫洲水利枢纽电厂尾水渠的顶托影响。经过一年多的水文测验验证王甫洲电厂提供的实时水位流量数据可靠、精度较高,可作为水文站定线推流的主要依据。在排除其他外部影响因素后,在电厂发电期内,可利用其水位流量均稳定时的数据建立水位流量的单一线关系。经验证,关系线可以用于推算水文站的旬平均流量、月平均流量以及时段径流。

V型球阀的米浆流量实验研究

建立一种符合实际生产的米浆流量模型对提高米粉生产标准化至关重要。对比以往的一次函数、二次函数和指数函数孔口流量模型,提出一种幂函数孔口流量模型,利用软件Origin的LMA算法的非线性最小二乘法拟合4种函数流量模型。结果表明:4种模型均通过了卡方检验及F检验,幂函数的调整R平方最高且残差平方和最小,说明幂函数流量模型拟合效果最好。为孔口流量模型提供了一种新的幂函数参考。