The influence of water level changes on sand bodies at river-dominated delta fronts:The Gubei Sag,Bohai Bay Basin

Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie Formation(Es3)on the gentle southern slope of the Gubei Sag,Bohai Bay Basin and draw some conclusions that,for complex sand bodies,with the increase in water level the distributary channels bifurcate frequently,from a simple branching shape to a network shape along with the increase in the development of crevasse splays,mouth bars and sheet sands.For single sand bodies,with an increase in water level in the slope zone of the lake basin close to the source area,the superimposition style transitioned from vertical cutting-stacking and lateral isolation to vertical stitching,isolation and lateral stitching.However,in the central zone of the lake basin far from the source area,the superimposition style transitioned from vertical stitching and lateral stitching to vertical isolation and lateral isolation.When water level stays stable,the greater the distance from the source area the greater the disaggregation ratio of a single sand body.At the same distance from the source area,higher water level tends to result in greater disaggregation ratio of a single sand body.

The World’s Largest Lakes Water Level Changes in the Context of Global Warming

The article is focused on the assessment of changes in the average annual water levels of large lakes of the planet in the changing climate conditions characteristic of the recent decades. Eight large lakes, i.e.Baikal, Balkhash, Superior, Issyk-Kul, Ladoga, Onega, Ontario, and Erie, located on the territory of Eurasia and North America, were chosen as the research objects. They were selected because of the availability of a long-term observations series of the water level. As is known, long-term changes in the lakes water level result from variation in the water volume. The latter depends on the?ratios between the water balance components of the lake that have developed during a given year, which, in turn, reflect the climatic conditions of the respective years. The features of the water balance structure of the above-mentioned?lakes and the intra-annual course of the water level are considered. The available long-term records of observational data on all selected lakes and their stations were divided into two periods: from 1960 to 1979 (the period of stationary climatic situation) and from 1980 to 2008 (the period of non-stationary climatic situation). The homogeneity and significance of trends in the long-term water level series of records have been estimated. It has been established that over the second period the nature and magnitude of the lakes water levels variations differ significantly. For lakes Balkhash, Issyk-Kul, Ladoga, Superior, and Erie, there is a general tendency for a decrease in water levels. For the remaining three lakes (Baikal, Onega, and Ontario), the opposite tendency has been noted: the levels of these lakes increased. Quantitatively, the range of changes in water levels on the lakes in question over the period of 1980-2008 ranged from -4 cm to +26 cm.

Relationship Between Changes of River-lake Networks and Water Levels in Typical Regions of Taihu Lake Basin,China

The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.

Impact assessment of climate change and human activities on annual highest water level of Taihu Lake

The annual highest water level of Taihu Lake （Zm） is very significant for flood management in the Taihu Basin. This paper first describes the inter-annual and intra-annual traits of Zm from 1956 to 2000. Then, using the Mann-Kenall （MK） and Spearman （SP） nonparametric tests, the long-term change trends of area precipitation and pan evaporation in the Taihu Basin are determined. Meanwhile, using the Morlet wavelet transformation, the fluctuation patterns and change points of precipitation and pan evaporation are analyzed. Also, human activities in the Taihu Basin are described, including land use change and hydraulic project construction. Finally, the relationship between Zm, the water level of Taihu Lake 30 days prior to the day of Zm （Z0）, and the 30-day total precipitation and pan evaporation prior to the day of Zm （P and E0, respectively） is described based on multi-linear regression equations. The relative influence of climate change and human activities on the change of Zm is quantitatively ascertained. The results demonstrate that： （1） Zm was distinctly higher during the 1980-2000 period than during the 1956-1979 period, and the 30 days prior to the day of Zm are the key phase influencing Zm every year; （2） P increased significantly at a confidence level of 95% during the 1956-2000 period, while the reverse was true for E0; （3） The relationship between Zm, P and E0 distinctly changed after 1980; （4） Climate change and human activities together caused frequent occurrences of high Zm after 1980; （5） Climate change caused a substantially greater Zm difference between the 1956-1979 and 1980-2000 periods than human activities. Climate change, as represented by P and E0, was the dominant factor raising Zm, with a relative influence ratio of 83.6%, while human activities had a smaller influence ratio of 16.4%.

Modeling the Pressure Distribution and the Changes of Water Level around the Offshore Platforms Exposed to Waves, Using the Numerical Model of Flow 3D

The humans’ need to use the oceans for exploration and extraction of oil has led to the development of engineering science in the field of offshore structures. Since it’s important to examine the offshore structures from different aspects and perspectives, we would have to evaluate many different parameters about them. So categorizing these parameters can help to perform their related analysis with more accuracy and more details. Due to the efficient force it exerts on the structure, the pressure distribution around every marine or hydraulic structure has a significant importance, and it even accounts for one of the dominant issues in designing and building of such structures. In the present study, an oil platform located in Phase 15 of South Pars oil fields, located in the Persian Gulf waters, has been analyzed using the FLOW 3D software. The outputs indicate that the pressure of water is distributed almost hydrostatically with the depth, and its maximum reaches 0.6 MPa at the bottom.

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.

A new theoretical solution of the effect of atmospheric pressure on water level

Based on the partial differential equation governing the effect of atmospheric pressure on water level of confined well,deriving the boundary condition and considering the seepage water between well and aquifer,the author obtained the analytical solution of water level change in time domain under the action of an atmospheric pressure history with the Laplace transform method.This solution is composed of two terms:stable and retarded terms.The stable term is the multiplication of barometric efficiency and simultaneous atmospheric pressure,and it implies the value of water level after infinite time when the atmospheric pressure is a constant from the time in question.The retarded term is the transient process due to the time lag of water exchange between well and aquifer.From the solution,it is obtained that the interference of atmospheric pressure on water level is the integral superimposition of the contribution of all atmospheric pressure changes before the time in question.So that,we further found out the response function of pulsive atmospheric pressure history.Calculation shows:① The pulsive response function starts from zero and tends to a steady value,which is proportional to the barometric efficiency,when the time tends to infinity;② The retarded time depends on the mechanical property of aquifer and the radius of well.The larger the seepage coefficient,the smaller the radius of well and the thicker the aquifer,then the shorter the retarded time gets.This solution can be used as the theoretical basis for further analysis of the atmospheric effect and practical correcting method in the future.

THE STUDY ON CLIMATIC CHANGES AND LAKE LEVEL FLUCTUATIONS OF OINGHAIB LAKE IN HOLOCENE

According to loess and palaeosol climatic record, field observation, analysis data and 14C dating, we discuss the climatic changes and the water level fluctuations of Qinghai Lake. It is pointed out that there were four relatively warm and moist stages in Qinghai Lake basin during the Holocene. They formed in the periods from 10,300 yr.B.P. to 8,500 yr.B.P., 7,000 yr.B.P. to 3,500 yr.B.P., 2,800 yr.B.P. to 2,000 yr.B.P. and from 1,300 yr.B.P. up to now. The climate in the Holocene optimum period, from 7,000 yr.B.P. to 3,500 yr.B.P., was much warmer and moister than that today. Polypodium plant grew luxuriantly around Qinghai Lake. The annual temperature was 2.5℃ higher than that today, but there was no forest at Qinghai Lake shore. It is found that there was a good relationship between precipitation and water level fluctuation. In warm and moist period water level was high and in the cold and dry period it was low in the Holocene. There were four high water level periods for Qinghai Lake in the

Climate Change, Regional Water Balance and Land Use Policy, in the Watershed of Lake Kinneret (Israel)

Long term data record (1944-2018) of climatological conditions in the Lake Kinneret and its watershed ecosystems was statistically evaluated and the impact of Anthropogenic operations was included as well. Precipitation input source is obviously uncontrolled natural component whilst the other three regional water outflows pathways are under anthropogenic control: Evapo-transpiration (ET), Runoff and underground flows. Indications for climate change expressed as air warming with consequences on regional (watershed and the lake) water resources and consumption capacities policy in the drainage basin and in the Lake are discussed. The decline of air temperature from 1940 to 1970s is probably due to a change in the Albedo effect. After the decline air temperature was twisted towards elevation. Climate change caused a decline in rainfall, followed by a reduction of Jordan and other river discharges and underground flows, accompanied by a decline of WL. With respect to climate change, water allocation for agricultural consumption was shrunk.

Water Intrusion in the Chesapeake Bay Region: Is It Caused by Climate-Induced Sea Level Rise?

Sea level rise due to climate change is a contentious issue with profound geographic and economic implications. One region in the USA identified as being particularly susceptible to seal level rise is the Chesapeake Bay region, and it has been estimated that by the end of the century Norfolk, Virginia could experience sea level rise of 0.75 meters to more than 2.1 meters. Water intrusion is a serious problem in much of the Chesapeake Bay region. The question addressed here is whether this water intrusion is the result of climate-induced seal level rise or is being caused by other factors. Our findings indicate that the water intrusion problems in the region are due not to “sea level rise”, but primarily to land subsidence due to groundwater depletion and, to a lesser extent, subsidence from glacial isostatic adjustment. We conclude that water intrusion will thus continue even if sea levels decline. These findings are critical because the water intrusion problems in the Chesapeake Bay—and elsewhere—cannot be successfully solved unless their causes are correctly identified and appropriate remedies are devised. For the Chesapeake Bay region, the required remedy is the reversal of groundwater withdrawal rates, which has been used successfully elsewhere in the USA and other nations to solve water intrusion problems.

近60年洞庭湖水位演变态势研究

辨析洞庭湖历史水位演变态势对保护湖泊生态系统健康运转以及确保长江中下游防洪安全和水资源利用均至关重要。为了定量评估洞庭湖近60年来水位变化特征、程度及规律,基于洞庭湖鹿角、杨柳潭和南咀水文站19612020年逐日水位监测数据,应用Mann-Kendall检验法、小波分析法、累积距平法、滑动t检验法等方法对洞庭湖水位变化趋势性、周期性、突变性进行分析,进而采用IHA-RVA法综合评价洞庭湖突变年前后各站点水位改变度和整体水位改变度。研究结果表明:(1)19612020年,鹿角站和杨柳潭站年均水位呈上升趋势,南咀站年均水位呈下降趋势;3个站点水位周期性变化较为明显,呈现4~5个时间尺度的周期变化规律,第一主周期为55~56年;鹿角站水位突变年份为1979、2003年,杨柳潭站水位突变年份为1978、2003年,南咀站水位突变年份为2003年,综合确定2003年为3个站点突变年份。(2)通过分析突变前后3个站点的水位、时间、频率、延时和改变率5组32个水位指标改变度,发现杨柳潭站水位改变度大于鹿角站和南咀站,鹿角、杨柳潭、南咀站的整体水位改变度分别为43%、48%、42%,均属于中度改变。该研究可为进一步解析洞庭湖水文情势演变规律以及为长江中下游通江湖泊水资源合理利用和水生态环境保护提供参考依据和数据支撑。

某水库水位变化对库区围堰坝体边坡稳定性的影响

为查明水库围堰边坡设计的合理性及水位变化对边坡稳定性的影响,基于FLAC3D数值模拟软件,针对百色市某水库建立三维模型,模拟了围堰边坡在水位下降、水位上升和基坑排水3种情景下的变形情况,分析了水位变化对边坡稳定性的影响。结果表明,围堰边坡上游一、二级台阶及下游二级台阶区域易发生较大变形;库水位下降引起各监测点水平位移为40~230 mm、竖向位移为260~390 mm,库水位上升引起各监测点水平位移为60~360 mm、竖向位移约为150 mm,基坑排水引起各监测点水平位移为580~600 mm、竖向位移为21~57 mm,对围堰边坡变形的影响大小依次为基坑排水>库水位下降>库水位上升;边坡安全系数与水位变化呈正相关关系,安全系数增量随水位上升先增大后减小。研究结果为边坡设计和防护提供了理论依据。

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。

湖泊与河流水文连通量化计算模型及其应用

湖泊与河流水文连通的量化是指导河湖保护与治理的关键之一,也是当前河湖生态复苏研究的热点问题。本文提出了一种湖泊与河流水文连通的量化计算模型,仅需少量实测或水动力模拟数据进行校验,即可量化计算单一或多个连通水道的河湖水文连通度。水位变化率与水位是决定水文连通的主控因子,水体交换强度与水位变化率呈线性正相关,且其增长速率与水位呈正相关。提出的水体交换流量计算方法可估算湖泊与长江水体交换流量。同等水位及水位变化率条件下,湖泊向长江输出水流的效率大于长江向湖泊灌入水流的效率。水文连通度峰值一般出现在整体上升或下降区间内的变异点,通过改变水位抬升或下降过程,可有效提升水文连通度均值及峰值,指导面向湖泊水生态环境改善的生态调度等。

三峡水库运行后汉口—九江河段水位变化特征及成因

大型水库的修建引起坝下游的水位调整,进而对河势、航运、防洪及生态等产生显著影响。为探究汉口—九江河段水位变化特征及成因,采用M-K分析法分析1988—2022年汉口、黄石港和九江站的水位变化趋势,并使用基于距平残差的水位变幅分析方法和一维水动力模型,分析河道冲淤、下游水位和阻力变化对不同特征流量下水位变化的影响。研究结果表明:①三峡成库前,除九江站枯水位呈显著性下降趋势,各级流量下的水位均没有显著性变化趋势。②三峡成库后,九江站的水位变化趋势与建库前相同;汉口站、黄石港站在12000 m^(3)/s和20000 m^(3)/s下的水位呈显著性下降趋势,12000 m^(3)/s时降幅分别为0.072、0.045 m/a,20000 m^(3)/s时降幅分别为0.048、0.027 m/a;水位变化的临界转换流量约为30000 m^(3)/s,在该流量附近水位未出现明显变化;当流量大于30000 m^(3)/s时,水位呈非显著性上升趋势,45000 m^(3)/s下的升幅分别为0.037、0.049 m/a。③临界转换流量以下水位下降的主导作用为河道冲刷,临界流量附近的水位未出现明显变化源于阻力增大作用接近抵消了河道冲刷的影响,临界转换流量以上的水位上升源于阻力增大作用更加明显,个别年份的洪水位上升显著源于下游水位顶托作用明显。

基于逐步回归分析的峡江水库对吉安水位顶托作用量化分析

峡江水库建设对赣江干流水位的顶托作用主要影响着上游吉安河段的水文情势变化,分析回水顶托作用下引起的水位变化以及解析河段水位抬升成因机制对研究水利工程修建改变河道水力特点的防洪减灾工作具有重要意义。基于历史实测水位和流量数据,构建计算水位顶托效果的逐步回归预测模型,利用皮尔逊相关分析定量评估水位顶托效果与各因素之间的相关性和影响程度,随后援用逐步回归方法量化分析了峡江水库运行对吉安水位顶托作用,即建立水位顶托效果与各因素之间的多元回归方程并验证方程的可靠性。结果表明:①基于逐步回归分析的预测模型模拟精度高,水位和流量要素模拟效果均良好,模拟水位过程与实测过程基本保持一致,在模拟流量方面也能够较好地再现实测过程且水位预测模型的各项评价指标优于流量预测模型;②水位顶托效果与峡江水库实测水位存在极强正相关性,与吉安实测水位和吉安水位落水过程存在中等正相关性,与吉安实测流量存在中等负相关性,与吉安水位涨水过程存在微弱负相关性;③多元逐步回归方程的修正后决定系数R2为0.892,表明方程拟合度较高且通过了后续的准确性检验,可表征吉安实测水位、吉安实测流量、峡江水库实测水位、吉安水位涨落过程的多重驱动作用。

西藏富锂盐湖-班戈错未来水位变化趋势预测

利用2016—2020年班戈错水位观测资料,采用ARIMA季节乘积模型、Winters线性模型及时间序列分解模型建立针对该湖的水位预测模型。通过对比时间序列分解模型在班戈错水位预测精度较高,运用时间序列分解模型对2022—2024年水位进行了预测,确定未来3年将会出现水位的明显升高,水位增幅达到0.97 m。研究结果能为LiCl矿的开采提供精度较高的水位预测,并通过水位监测来指导班戈错矿田建设。

The response of lake change to climate fluctuation in north Qinghai-Tibet Plateau in last 30 years

According to the analysis of the climate materials including the topographic map in 1975, the TM and CBERS satellite remote sensing materials from the 1980s to 2005 as well as the air temperature, precipitation, evaporation rate, maximum depth of snow and the biggest depth of frozen soil in the past 45 years, the water level area of four lakes at the southeast of Nagqu, Tibet including Barn Co, Pung Co, Dung Co and Nuripung Co show a distinct trend of expansion in the past 30 years. In 2005, the water level area of the above four lakes increased by 48.2 km^2, 38.2 km^2, 19.8 km^2 and 26.0 km^2 respectively compared to 1975, with the respective increase rate of 25.6%, 28.2%, 16.2% and 37.6%. That is closely related to the warming and humidified climate change in the recent years such as rise of the air temperature increase of the precipitation, decrease of the evaporation rate and permafrost degradation.

基于ICESat/ICESat-2卫星测高数据的黄河中上游水库水位监测

精确地提取出内陆水库水位高程数据以及分析其变化特征,对气候和生态环境变化、水资源管理等方面的研究具有重要的意义。利用ICESat卫星2003年10月至2009年4月期间的全球地表测高数据与ICESat-2卫星2018年11月至2022年6月期间的全球内陆水体高程数据,对黄河流域龙羊峡、刘家峡、三门峡、小浪底水库多期历史水位变化数据进行提取,并结合水文站实测数据对其准确度加以检验。结果显示:龙羊峡、刘家峡、三门峡与小浪底水库在水位变化上相互调节水位,确保了水库的安全运行和水资源的合理利用;通过与实测水位对比分析,龙羊峡、小浪底水库ICESat卫星测量水位与实测水位相关性系数分别为0.996、0.997,均方根误差分别为0.323 m、0.4567 m,平均误差分别为0.195 m、0.248 m;龙羊峡、刘家峡、三门峡以及小浪底水库ICESat-2卫星测量水位与实测水位相关系数分别为0.996、0.987、0.977、0.999,其均方根误差分别为0.6308 m、0.9606 m、0.7077 m、0.1354 m,平均误差分别为0.5046 m、0.7684 m、0.5661 m、0.11 m。此外,ICESat数据在一定程度上弥补了数据的缺失,表明全球地表测高数据与全球内陆水体高程数据在内陆水体水位变化监测方面具有很高的可行性。