LONG-TERM EFFECTS OF THE GEZHOUBA PROJECT ON FLOOD PROPAGATION IN THE YANGTZE RIVER

A l-D numerical model of unsteady flow for river channel has been developed in the paPer. Based ontoPograPhy of l980 and field data of a flood occurred on July l2-25, l981 (,'8l.7" flood), caIculation ofthe "8l.7" flood rouhng has been imPlemented as calibration of the model. Using the same hydrographsof,'8l.7" flood and different toPograPhies of l980 and l993 respectively, processes and profiles ofhydrograps, variations and featores of flood traVel along the Yichang-Jianli river reaches h…     

A NOTE ON THE ESTIMATION OF THE PARAMETERS IN LOGARITHMIC STAGE-DISCHARGE RELATIONSHIPS WITH ESTIMATES OF THEIR ERROR

Abstract

Under certain assumptions the stage-discharge relationship of a channel cross-section can be approximated by a logarithmic relationship. Observational pairs of stage and discharge plotted on log-log paper often cluster around a straight line and this suggests that the assumptions involved are often approximately satisfied.

In such cases the parameters of the logarithmic relationship are usually estimated graphically from the position and slope of the straight line on the log-log paper. In this paper principles and methods are outlined for the estimation of the parameters with estimates of their standard error, via regression analysis. Because the water level of zero flows is usually one of the unknown parameters, the regression is non-linear and least squares optimal estimates can be obtained by a step-by-step approximation. The variances of the parameter estimates can be obtained from the dispersion matrix of the joint distribution of the least squares estimators via the likelihood function. An estimate of the error in predictions of the discharge depending on the corresponding stage may be obtained.     

Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period

Abstract

The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly.     

日本秋田地震(1983年7.7级)引起我国应力场的震时调整变化

本文通过水平分层承压含水层模型,推导出含水层的水头和含水层应力变化之间的定量关系.利用我国在日本秋田地震时有水位阶变的52口井孔的观测资料,通过水井水位的体应变固体潮系数,估算了震时引起我国应力场的调整变化.讨论了这种应力调整时应力增加区和降低区交替出现的可能原因.      

ON THE SHRINKAGE OF RIVER CHANNEL

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FLOOD FREQUENCY AND CHANNEL CROSS-SECTION OF A SMALL NATURAL STREAM

Abstract

Based on some special characteristics between the depths and the cross-sectional areas of a channel, and the use of the stage-discharge relationship, a promising simple method of establishing the runoff for a recurrence interval of about 10 years on the upper frequency curve for an ungaged small stream is presented. This method was tested quite successfully on a number of sample streams in the eastern part of the United States with drainage areas less than 400 square miles. This method applies only to stable natural streams without anyman-made deterrent to the natural development of the stream channel or flood plain.     

南四湖“三湖两河”洪水演算数值模型优化

南四湖是中国北方最大的淡水湖泊,由南阳湖、独山湖、昭阳湖和微山湖4个湖区串联而成,地形复杂,洪水易涨难消,与滨湖区涝水交换频繁,建立兼顾效率和精度的洪水演算模型复杂困难.基于1960s提出的用"三湖"和"两河"来概化模拟南四湖洪水的理念与"三湖两河"半图解法洪水演算模型,采用四阶龙格库塔法代替半图解法,改进"三湖两河"洪水演算模型,对比分析计算精度、效率和灵活性,"三湖两河"洪水演算数值解模型优于半图解法;分析了滨湖排水模数、"两河"传播历时等模型经验参数的敏感性,以及韩庄闸水位—流量关系变动对湖泊高水位的影响,据此提出了南四湖洪涝治理的若干建议.南四湖"三湖两河"洪水演算数值解模型可作为南四湖洪水管理的基础工具,因地制宜的建模思路对类似湖库具有重要参考价值.     

滨湖平原河段的水位预报方法

从洪水特性出发,提出了一种适合于滨湖平原河段的水位预报方法。经实例验证,证明方法是有效的。     

1950s以来洞庭湖调蓄特征及变化

针对洞庭湖区淤积、围垦和江湖关系变化对湖泊调蓄功能的影响,根据洞庭湖调蓄属于典型复合洪水波的实际情况,提出利用离散小波分解和计算入、出湖径流过程方差的方法揭示1950s以来洞庭湖调蓄特征及其实际调蓄作用的多年变化.结果发现:洞庭湖削减的洪峰主要是32 d以下的中短尺度洪水波,其全年整体削峰系数在0.13~0.56之间;从入、出湖径流方差多年变化体现的调蓄效果看,洞庭湖区近几十年淤积围垦虽然极大地改变了湖区面积和容积,但并未使湖泊调蓄作用发生大的变化.结合洞庭湖削峰系数与城陵矶-螺山段水位落差的对应关系,认为在整个江湖系统关系中洞庭湖的调蓄能力是被动的,其变化主要取决于城陵矶以下河段过水能力对洞庭湖泄流的制约.从整个江湖关系下的洞庭湖调蓄变化特征看,1990s以来湖区"小水大灾"的原因之一是入湖径流过程的短尺度方差和削峰系数较大,本质上是由荆江裁弯和三峡运行导致的江湖关系变化引起的长江螺山段出流使出湖径流方差减小造成的.     

THE INFLUENCE OF TOPOGRAPHY ON TIME AND SPACE DISTRIBUTION OF SOIL SURFACE WATER CONTENT

The distribution of water content in time and space at the soil surface has been investigated on a small farmland catchment (1.3 km² ) from four field surveys corresponding to different moisture statuses. For each survey, about 400 samples were collected at the soil surface at a depth of 5 cm along ten axes parallel to the greatest slope. The relationship between the measurements and the topography has been analysed. The structure of the data is well explained by a topographic index referring to the downslope conditions and defined as the elevation difference between the sample point and the stream point corresponding to the outlet of the water pathway derived from the digital elevation model (DEM). This index can be considered as an hydraulic head, at least for saturated conditions. A threshold for this index allows two domains within the catchment to be distinguished; an upper domain where the water content is nearly constant and varies slowly, and a lower domain where moisture status increases and is highly variable. The spatial distribution of these two domains is well correlated to the spatial distribution of the soils. Thus, both topography and the spatial distribution of soil appear to control the spatial distribution of surface water content at the 1-km² scale. © 1997 by John Wiley & Sons Ltd.     

季冻区砂性土堤防水分场温度场及水分迁移试验研究

以黑龙江干流堤防工程实际环境为研究基础,依托水分迁移试验装置,测试了干流堤防典型砂性土试样在冻融循环下的温度场、水分场、应力场的分布情况。结果表明：堤顶混凝土公路破坏与堤身不均匀沉降有关,温度变化引起堤基含水率出现梯度变化,从而出现应力场变化,且温度梯度含水率梯度呈线性关系。地基稳定冻结深度达到1.12 m。结合实测数据建立季节性冻土区堤防基础的水、热、力三场耦合模型,最后利用ANSYS有限元分析软件进行模拟分析,证明该模型在堤防工程上的实用性。     

INTEGRATION OF THE MODELS OF ANNAGNPS AND REMM TO ASSESS RIPARIAN BUFFER SYSTEM FOR SEDIMENT REDUCTION

The United States Department of Agriculture (USDA) Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) is used to help evaluate a watershed response to agricultural management practices to control water quality. However, AnnAGNPS version 3.5 does not contain features to estimate the effect of a riparian buffer (RB) system on water quality. The Riparian Ecosystem Management Model (REMM) is used to simulate the impact of riparian buffer systems on water quality. However, frequently the lack of measured upland loadings that are required by REMM simulation limits the application of REMM. To address this data gap, a study was conducted to integrate AnnAGNPS with REMM for RB system simulation. AnnAGNPS was used to simulate water and sediment loadings from an upland field into a three-zone RB system at the Gibbs Farm located in the Georgia coastal plain. These AnnAGNPS outputs were used as the inputs to REMM. REMM was used to simulate water and sediment movement along the riparian buffers. The AnnAGNPS simulated amount of annual runoff at the edge of the field was close to observed amounts (Nash-Sutcliffe efficiency of 0.92). It is believed that a substantial portion of sand was removed from the runoff one meter into the grass buffer where the samplers were located; therefore, sand was excluded from the AnnAGNPS simulation for comparison with observed sediment. Excluding sand, the AnnAGNPS predicted amount of annual sediment matches the observed amount fairly well (Nash-Sutcliffe efficiency of 0.46). In addition, based on evaluating the percent reduction of sediment at each zonal interface, the AnnAGNPS/REMM model well simulated the function of the RB system to reduce sediment.     

Bayesian power-law regression with a location parameter,with applications for construction of discharge rating curves

This paper presents a Bayesian approach for fitting the standard power-law rating curve model to a set of stage-discharge measurements. Methods for eliciting both regional and at-site prior information, and issues concerning the determination of prior forms, are discussed. An efficient MCMC algorithm for the specific problem is derived. The appropriateness of the proposed method is demonstrated by applying the model to both simulated and real-life data. However, some problems came to light in the applications, and these are discussed.     

A NUMERICAL MODEL OF SEDIMENT TRANSPORT IN HANDUN IRRIGATION DISTRICT

LABRIEFINTRODUCTIONOFRANDUNIRRIGATIONDISTRICTYellowRiverisoneofthemainWaterresourcesinNOrthChina.SincethefiftiesirrigationbydivertingwaterfromtheYellowforerdevelOPssteadily.AstheYdlowforerisaheavilysacmentsladenone,sedimentisdiVertedsimultaneouslywhenwaterisdiverted.HOwtoproperlytreatthedivertedsedimentboomesoneOfthekeyproblemsrestrichngthesustainingdevelOPmentofthCwaterresourcesinthatarea.LongchStanceconvopngsedimentisoneofthemainmeasuresfordealingwiththediVertedsedim…     

GEOPHYSICAL STUDIES OF WATER LEAKAGES FROM RESERVOIRS*

Considerable water leakages from reservoirs make it difficult to attain the planned storage capacity. In some cases water leakages give rise to suffusion followed by catastrophes. Until recently methods for locating water leakages were extremely imperfect. Geophysical methods offer good prospects in this direction. For solving these problems, it is effective to use streaming potential measurements, water flow rate observations and thermometry. Laboratory experiments were carried out in connection with the fact that water leakages from reservoirs are characterized by negative anomalies of natural currents; the more filtration discharge, the higher these anomalies are. As a result, the relationship governing the intensity of streaming potential and sand granulometric composition, electrolyte concentrations and other factors were revealed. To determine the velocity of water flowing to leakage sites, a special device, based on the relationship between the temperature of a heated body and its resistance, is applied. This device simultaneously makes it possible to measure the water medium temperature. Observations at reservoir sites were effected by moving along the reservoir non-polarizable potential electrodes and water velocity devices. Recordings were carried out automatically by the recording device of the logging apparatus. Under the conditions of ice cover on water surfaces, measurements were made through separate points by digging holes in the ice cover. Practical field observations were carried out at reservoir sites located in regions where fissured massive rocks as well as loose sediments predominate. In the first case field experiments were carried out in alpine reservoirs, in Armenia. The major water leakages were found to be concentrated on the right bank of the reservoir. In this connection it was not only possible to locate water leakage sites, but also to evaluate their relative intensity. These data were used for planning antifiltration measures. In the second case water leakages from a reservoir located in Uzbekistan in the submontane part of the Pamirs were studied. Streaming potential anomalies and high benthonic flow rates made it possible to discover high filtrations in the base and walls of the dam. Further perfection of these methods should not only permit the determination of water leakage sites and their relative intensity, but also filtration discharges in absolute units.     

Effect of observation errors on the uncertainty of design floods

This study investigates the uncertainty in the estimation of the design flood induced by errors in flood data. We initially describe and critically discuss the main sources of uncertainty affecting river discharge data, when they are derived using stage-discharge rating curves. Then, different error structures are used to investigate the effects of flood data errors on design flood estimation. Annual maxima values of river discharge observed on the Po River (Italy) at Pontelagoscuro are used as an example. The study demonstrates that observation errors may have a significant impact on the uncertainty of design floods, especially when the rating curve is affected by systematic errors.     

近30年洞庭湖季节性水情变化及其对江湖水量交换变化的响应

江湖水量交换的变化影响着通江湖泊洞庭湖的水情,进而影响湖区社会经济及生态的可持续发展.以洞庭湖城陵矶站、南咀站以及长江干流宜昌站、螺山站1981-2012年逐日水位、流量观测数据为基础,采用单位根检验、方差分析和水位-流量绳套曲线等方法对洞庭湖季节性水情变化特征进行提取,并探究江湖水量交换变化对其产生的影响.研究表明:近30年来洞庭湖水情呈阶段性特征,与相对稳定的1981-2002年相比,2003-2012年湖泊水位总体呈下降趋势,年均水位下降0.43 m;枯、涨、丰、退水期各季水情变化特征为:2003年以后洞庭湖丰水期水位平均下降0.60 m,呈现出"高水不高"现象;退水期水位平均下降1.49 m,退水加快;枯水期水位略有上升,平均上升0.18 m;涨水期水位变化不明显.湖泊退水期水位降幅最为明显,尤其是10月大幅下降,平均下降2.03 m,有提前进入枯水期的趋势.水情变化与江湖水量交换变化密切相关:丰水期,三口(松滋、太平和藕池)分流量减小在一定程度上降低湖泊水位;退水期,三口分流量减小叠加城陵矶出口长江水位下降对洞庭湖产生拉空作用,湖泊出流加快水位被拉低;枯水期,主要是1 3月,城陵矶出口长江水位上升对湖泊顶托作用增强,湖泊出流减缓水位略有抬升.     

RELATIONSHIP BETWEEN VELOCITY PROFILE AND DISTRIBUTION OF SEDIMENT CONCENTRATION

I. ON THE INFLUENCING FACTORS OF THE SEDIMENT~LADEN FLOW VELOCITY PROFILEThe influence of sediment on the water--now structures must be considered when thevelocity profile of the sediment--laden now (or turbid flow) is studied. widely usedparameters for reflecting thoses influences are the sediment concentrahon and theffichardson number, where Ri represents the variation of the concentration gradient.Generally, the vertical distributions of sediment concentration and th…     

由地下水位变化反演大同—阳高6.1级地震前后应力场的动态图像

分析研究了承压含水层应力应变与井水位变化之间的定量关系,得出了井水位变化与含水层应力应变之间的定量关系公式,给出了利用承压井水位变化反演含水层应力变化的两种新方法。利用大同地震前后井水位变化资料,反演了该地震前后大区域应力场的动态调整变化,并形成了时间与空间的演化图像。利用这些图像分析了大同地震前后大区域应力场的动态调整变化特征与可能的机制。     

FLOW MECHANISMS AND SEDIMENT TRANSPORT IN COMPOUND CHANNELS

IINTRODUCTIONCompoundortWo-stagechannelshavereceivedconsiderableattentioninrecentyearsduetotheirrelevancetofloodstudiesinnaturalrivers,theirsignificanceinunderstandingrivermol'phology,andtheiruseinsomefloodalleviationschemeswherethefloodplainshavebeenartificiallyloweredtoproduceengineeredchannels.ThispaperreviewsworkwhichhasbeenundertakenintheUKFloodChannelFacility(FCF)overthepastdecade.TheACewasbuiltatHRWallingfordin1986,asalargescalenationalfacilityforhydraulicengineeringstUdies.T…