Spatial variations of tidal water level and their impact on the exposure patterns of tidal land on the central Jiangsu coast

The exposed area of intertidal zone varies with tidal water level changes, If intercomparisons of satellite images are adopted as a method to determine geomorphological changes of the intertidal zone in response to accretion or erosion processes, then the effect of water level variations must be evaluated. In this study, two Landsat TM images overpassing the central Jiangsu coastal waters on 2 January and 7 March 2002, respectively, were treated by the changing detection analysis using Image Differencing and Post-classification Comparison. The simultaneous tide level data from four tide gauge stations along the coast were used for displaying the spatial variations of water levels and determining the elevations of waterlines. The results show that the spatial variations of water levels are highly significant in the central Jiangsu coastal waters. The huge differences of tidal land exposure patterns between the two imaging times are related mainly to the spatial variations of tidal water levels, which are controlled by the differences in tidal phases for different imaging times and the spatial variations of water level over the study area at each imaging time. Under complex tidal conditions, e.g., those of the central Jiangsu coastal waters, the tide-surge model should be used to eliminate effectively the effects of water level variations on remote sensing interpretation of geomorphological changes in the intertidal zone.

New Understanding of Variation Characteristics of Well Water Level in Majiagou Mine,Tangshan City,Hebei,China

Based on the well water level data in Majiagou Mine in Tangshan City since 2000,it is suggested that the water level rise from 2008-2014 is possibly associated with reduced infiltration caused by less precipitation,together with the effect of less groundwater exploitation. However,the water level rise from 1992-1998 cannot be interpreted properly if we extend the data source back to 1991. After comparing the data with long-term water level data of five wells with different hydro-geological units in Tangshan and Qinhuangdao, the study indicates that the long-term water level variation cannot be only attributed to the effect of less precipitation and the control of groundwater exploitation,but also with the influence of regional stress field change.With the support of regional geological and tectonic information,combined with the comprehensive analysis of CBM data obtained from the coal field,new understandings of the dynamic characteristics of annual variation are obtained.

Effective groundwater level recovery from mining reduction: Case study of Baoding and Shijiazhuang Plain area

The effective recovery of water level is a crucial measure of the success of comprehensive groundwater over-exploitation management actions in North China.However,traditional evaluation method do not directly capture the relationship between mining and other equilibrium elements.This study presents an innovative evaluation method to assess the water level recovery resulting from mining reduction based on the relationship between variation in exploitation and recharge.Firstly,the recharge variability of source and sink terms for both the base year and evaluation year is calculated and the coefficient of recharge variationβis introduced,which is then used to calculate the effective mining reduction and solve the water level recovery value caused by the effective mining reduction,and finally the water level recovery contribution by mining reduction is calculated by combining with the actual volume of mining reduction in the evaluation area.This research focuses on Baoding and Shijiazhuang Plain area,which share similar hydrogeological conditions but vary in groundwater exploitation and utilization.As the effect of groundwater level recovery with mining reduction was evaluated in these two areas as case study.In 2018,the results showed an effective water level recovery of 0.17 m and 0.13 m in the shallow groundwater of Shijiazhuang and Baoding Plain areas,respectively.The contributions of recovery from mining reduction were 76%and 57.98%for these two areas,respectively.It was notable that the water level recovery was most prominent in the foothill plain regions.From the evaluation results,it is evident that water level recovery depends not only on the intensity of groundwater mining reduction,but also on its effectiveness.The value of water level recovery alone cannot accurately indicate the intensity of mining reduction,as recharge variation significantly influences water level changes.Therefore,in practice,it is crucial to comprehensively assess the impact of mining reduction on water level recovery by combining the coefficient of recharge variation with the contribution of water level recovery from mining reduction.This integrated approach provide a more reasonable and scientifically supported basis,offering essential data support for groundwater management and conservation.To improve the accuracy and reliability of evaluation results,future work will focus on the standardizing and normalizing raw data processing.

Effect of Sea Level Variation on Tidal Characteristic Values for the East China Sea

Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is compared with the harmonic analysis result of hourly sea level data from 19 tide gauges for more than 19 years. It is indicated that the long-term mean sea level variation affects notably tidal waves in this region. Generally, the tidal amplitude increases when the mean sea level rises, but this relationship may be inverse for some sea areas. The maximal variation of tidal amplitude takes place in the zones near the Fujian coast and the Zhejiang coast, rather than the shallowest Bohai Sea. The maximum increase of M2 amplitude can exceed about 15 cm corresponding to the 60 cm rise of the mean sea level along the Fujian coast. The other regions with large variations of tidal amplitude are those along the Jiangsu coast, the south-east coast of Shandong, and the south-east coast of Dalian. The propagation of tidal waves is also related to mean sea level variation, and the tidal phase-lag decreases generally when the mean sea level rises. Almost all the regions where the tidal phase-lag increases with rising mean sea level are close to amphidromic points, meanwhile the spatial area of such regions is very small. Because the influence of mean sea level variation upon tidal waves is spatially marked, such spatial effect should be considered in calculation of the tidal characteristic value and engineering water level. In the region where the amplitudes of the major tidal constituents increase, the probable maximum high water level becomes higher, the probable maximum low water level becomes lower, and both design water level andcheck water level increase obviously. For example, the design water level at Xiamen increases by 13.5 cm due to the variation of tidal waves when the mean sea level rises 60 cm, the total increase of design water level being 73.5 cm.

Reassessing the contributions of terrestrial waters to sea level variations in the South China Sea and its response to alternating ENSO events

Regional sea level variability is linked to regional terrestrial water and the El Ni?o-Southern Oscillation(ENSO).This study assessed the relationships between the sea level variations in the South China Sea(SCS)and ENSO,the impact of terrestrial water storage(TWS)on non-steric sea level(NSSL),and the contributions of steric sea level(SSL)and NSSL to sea level anomaly(SLA),respectively.From 2003 to 2015,the SLAs exhibited a long-term trend of 6.65±0.78 mm/yr,which was primarily attributed to the SSLs.Additionally,during 2003-2015,ENSO events alternating with varying intensities might also be responsible for the unusually high SLA trend.Compared to the SSLs,the NSSLs contributed the seasonal signals to the SLAs,while the NSSLs changes were largely explained by the TWS in the Mekong River Basin at the seasonal scale and in the Pearl River Basin and Red River Basin at other time scales.In contrast to the TWS,the contributions of precipitation and evapotranspiration were relatively minor.A negative correlation between the sea level variations and ENSO was also found,with cross-correlation coefficients between the oceanic Ni?o index and SLAs/SSLs/NSSLs of -0.36/-0.37/-0.62 with lags of 2/3/2 months,respectively.These findings systematically reassessed the contributions of different components to the sea level variations.This study provided a benchmark for in-depth analysis of the impacts of terrestrial water and other potential causes on sea level rise in the SCS.

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.

Characteristics of coseismic water level changes at Tangshan well for the Wenchuan MS_8.0 earthquake and its larger aftershocks

Coseismic water level changes which may have been induced by the Wenchuan Ms8.0 earthquake and its 15 larger aftershocks （Ms〉5.4） have been observed at Tangshan well. We analyze the correlation between coseismic parameters （maximum amplitude, duration, coseismic step and the time when the coseismic reach its maximum amplitude） and earthquake parameters （magnitude, well-epicenter distance and depth）, and then compare the time when the coseismic oscillation reaches its maximum amplitude with the seismogram from Douhe seismic station which is about 16.3 km away from Tangshan well. The analysis indicates that magnitude is the main factor influencing the induced coseismic water level changes, and that the well-epicenter distance and depth have less influence. Ms magnitude has the strongest correlation with the coseismic water level changes comparing to Mw and ML magnitudes. There exists strong correlation between the maximum amplitude, step size and the oscillation duration. The water level oscillation and step are both caused by dynamic strain sourcing from seismic waves. Most of the times when the oscillations reach their maximum amplitudes are between S and Rayleigh waves. The coseismic water level changes are due to the co-effect of seismic waves and hydro-geological environments.

Dynamic analysis of water level in the Wanquan Well and the precursory anomalies of earthquakes

According to the characteristics of frequent water level step-variation in the Wanquan Well, the step-variation frequency change on the time axis can be regarded as a sequence of step-variation. A study of the relationship between the process of development and evolution of the sequential step-variation and the regional seismicity indicated that the sequential step-variation anomalies are rather better in coincidence with the time, magnitude and frequency of regional seismic activities, which may predict the seismicity trend in months. Furthermore, on this basis, if the water level changes in a characteristic manner, the seismic regime during the time period from several days to 20 days or more may be evaluated. By using the method presented in this paper we had a prediction about the Baotou ML=6.6 earthquake on May 3, 1996. This event occurred within the predicted time span but with a less magnitude and a little location deviation.

Water-Level Fluctuations of Urmia Lake: Relationship with the Long-Term Changes of Meteorological Variables (Solutions for Water-Crisis Management in Urmia Lake Basin)

Urmia Lake in northwest of Iran, through the recent years has been extremely faced with the water crisis. Climate variations and anthropogenic impacts could be two main affiliated factors in this regard. We considered the long term data series of precipitation, temperature and evaporation in monthly and yearly scales in order to compare to water-level values of Urmia Lake. The statistics approaches such as: standard deviation, trend analysis, T test, Pearson and Spearman correlations, liner regression are used to analyze all variables. The results released that the water-level of Urmia Lake along with the precipitation and temperature of the lake’s basin have experienced the periodic changes through 1961 to 2010, as there are some gradual dryness trends on the study area according to precipitation and temperature variations. Urmia Lake periodic water-level fluctuations show more significant correlation to temperature than the precipitation. Whiles, the water-level’s decreasing behavior especially through 1998 to 2010 is more harsh and different than the rate that is considered for precipitation’s decrease and temperature’s increase. Thus, there could be some anthropogenic factors in the basin which produced some supplementary causes to shrink Urmia Lake. Extracting the double precipitation over the basin through introducing and categorizing of atmospheric synoptic systems in order to cloud seeding operation could be one of urgent and innovative solutions to mitigate water crisis in the basin.

降雨和库水位变动联合作用下滑坡位移加权反分析及监测预警方法

降雨和库水位变动是诱发大型库岸滑坡体持续变形甚至失稳的主要外在因素。针对以上两种因素联合作用下滑坡体的变形特征,本文提出一种基于多源数据的“反演-评估-融合-预警”四步式滑坡监测预警方法。该方法采用趋势项位移进行力学参数反演,有效避免了降雨、库水位变动等外在因素对反演结果的影响。同时,采用熵权值构建了反演目标函数,借此考虑了不同位置监测点对反演结果的影响程度。此外,考虑了滑坡体自身的地质条件和坡体结构对监测预警的影响,综合运用安全系数和综合变形速率构建了具有地质和力学基础的预警模型。采用本文方法对贵州三板溪水电站东岭信滑坡体进行了力学参数反演和监测预警,结果表明:该滑坡体整个监测期间的安全系数在1.25~1.70之间波动,整体状态呈下降趋势,基于安全系数的角度判断其尚处于稳定状态;综合变形速率呈现上、下波动趋势,与安全系数在变化规律上具有高度的相关性,两者可以从整体上表征该滑坡体在降雨和库水位变动联合作用下稳定性的演进过程;当前监测时刻点的综合变形速率是0.0599,根据分级预警模型判断此滑坡体当前处于稳定变形阶段(Ⅰ级预警),与安全系数的判断结果具有一致性。

雅鲁藏布江大拐弯地区河流水位日变化时空分异特征

径流(或水位)日变化是反映河流水文情势的重要方面,解析径流(水位)日变化特征有助于明晰河流水文动态过程和规律,揭示径流来源和产汇流机制。以藏东南雅鲁藏布江大拐弯地区的易贡藏布、帕隆藏布、曲宗藏布、拉月曲、金珠曲和白马西路河为对象,基于典型河段2022—2023年小时分辨率实测水位数据,采用数理统计和表征参数分析河流水位日变化时空分异特征,并结合降雨、冰川/积雪数据探究河流水位日变化影响因素。结果表明:研究区河流水位日变幅在汛期多高于非汛期,日水位数据分布在汛期多呈正偏(均值大于中值),汛后多呈负偏(均值小于中值);除白马西路河外,各河段水位日涨落过程在非汛期相对于汛期有所延迟,且汛后延迟趋势更明显;汛期各河段日水位上涨历时均小于回落历时,非汛期则多相反(拉月曲和金珠曲除外);白马西路河水位日变化主要受降雨过程扰动,而其他河流水位日变化主要受冰雪消融过程影响。

水库水位的VMD-CNN-GRU混合预测模型

水库水位预测为其运营、防洪、水资源调度管理提供了重要决策支持.准确可靠的预测对水资源的优化管理起着至关重要的作用.针对水库水位数据的非线性、不稳定性以及复杂的时空特性,提出一种融合自适应变分模态分解(VMD)、卷积神经网络(CNN)和门控循环单元(GRU)的混合水库水位预测模型.VMD通过对水位序列进行分解消除噪声,CNN用于有效提取水位数据的局部特征,GRU用于提取水位数据的深层时间特征.以葠窝水库日水位为例,与多个相关模型对比分析,结果表明:精度方面,新模型在选取的评价指标上均表现最佳;运算效率方面,本文选择的GRU与长短时记忆网络(LSTM)相比,运算效率显著提高.新模型预测的高精度、高运算效率更能满足实际水库水位实时调度的需求.

青藏高原中部班戈错富锂盐湖水位月际变化与驱动因素分析

锂在新能源领域的独特优势使其需求规模呈爆发式增长,世界各主要经济体将其列为关键矿产。西藏盐湖锂资源丰富,水位变化是锂资源动态评价的重要环节,班戈错是典型富锂盐湖,极具代表性。本文以2016—2023年班戈错现场实测水文及气象观测资料为基础,分析了水位月际变化特征及驱动因素。主要结论如下:(1)以2018年6月、2021年12月为界,2016年1月至2023年7月,班戈错水位月际变化剧烈,经历下降—上升—下降波动变化过程,且水位上升速度远大于水位下降速度。(2)蒸发量增大是班戈错两次水位波动下降的主要原因;而蒸发量降低和温度升高是驱动水位波动上升的动力。(3)温度及降水是控制湖泊年内变化的主导因子,且温度主要通过控制蒸发来实现影响。研究结果为青藏高原月际尺度气候变化的盐湖区域响应和班戈错将来开采过程中锂资源保障程度研究提供数据基础。

降雨-波浪-水位对库岸崩滑泥沙空间分布影响

库岸崩滑对库区含沙量有显著影响,掌握崩滑泥沙与水文因素的关系有助于分析库区泥沙的淤积过程和输移规律.通过降雨-波浪-水位多因素耦合模型试验分析了崩滑泥沙在不同水文因素作用下的空间分布规律.结果表明,降雨能减弱含沙量的变化幅度,促使悬移质泥沙颗粒细化.降雨后含沙量平均变异系数降幅为22%,极细砂粒含量降幅为53%.波浪可加大离岸方向库区含沙量,同时降低此方向含沙量变异系数.波浪作用下离岸方向的平均含沙量增幅为78%,含沙量平均变异系数降幅为67%.水位升高促使离岸方向和水深方向的含沙量降低,悬移质泥沙颗粒粗化.离岸方向和水深方向的平均含沙量在水位升高时降幅分别为14%和20%,极细砂粒含量增幅为15%.

濒危物种疏花水柏枝残存种群有性繁殖的时空变化

本文以分布于枝江关洲岛的濒危物种疏花水柏枝(Myricaria laxiflora(Franch.)P.Y.Zhang et Y.J.Zhang)为研究对象,调查其种群开花和结果性状沿高程的变化,分析该残存种群有性繁殖的时空变化规律;同时结合三峡大坝-葛洲坝水利水电工程修建所引起生境地水位消涨节律的变化,分析其对残存种群有性繁殖的影响。结果显示,残存疏花水柏枝种群的有性繁殖在不同高程之间存在显著差异。消涨带上部植株的每株花枝数、每枝花朵数、每株花朵数分别比消涨带中部植株高66.09%、50.14%和98.63%,比消涨带下部植株高79.50%、283.33%和461.05%。消涨带上部植株的每株果枝数、每枝结果数、每株结果数、每果种子数和种子发芽率分别比消涨带中部高60.17%、25.26%、88.05%、6.96%和30.69%,比消涨带下部高97.39%、82.45%、208.31%、19.12%和45.91%。相关性分析结果表明,植株的开花结果特性与高程、出露时期、土壤含水量以及温度变化极显著相关。环境因子对有性繁殖的影响强度依次为出露时间>高程>日均温度>土壤含水量。上游水利水电工程对疏花水柏枝残存种群的有性繁殖具有一定的影响。

基于Landsat影像的鄱阳湖面积监测及其与水位关系研究

湖泊是陆地生态系统的一个重要的组成部分,湖泊水域的变化对环境和人类的生产活动都有着重大的影响。鄱阳湖作为中国第一大淡水湖,近年来多次出现洪旱灾害现象,因此对鄱阳湖进行动态监测意义重大。文章以2000—2021年鄱阳湖175期Landsat影像作为数据源,对比分析了归一化差异水体指数(normalized difference water index,NDWI)、改进的归一化差异水体指数(modified normalized difference water index,MNDWI)、自动水体提取指数(automated water extraction index,AWEI)、谱间关系法(spectrum photometric method,SPM)这4种水体提取方法,优选最适宜鄱阳湖的水体提取模型;利用175期面积数据分析了鄱阳湖2000—2021年面积的年际变化趋势,分析年内季节变化特征,同时结合2009—2013年和2017—2018年同时期的50组水位数据,建立面积-水位关系模型。结果表明:①AWEI模型提取水体精度优于其他3种,该文最终选用AWEI进行鄱阳湖水体提取;②鄱阳湖面积存在明显的季节性变化,且丰水季面积年际波动大,枯水季较平缓;③棠荫水位站湖泊面积-水位分段线性模型为最佳模型,从而可以根据鄱阳湖区域的实时水位观测值对水体覆盖面积进行预测,以弥补云雨天气时利用可见光遥感手段难以监测到湖泊水体淹没情况的不足。

土工织物加固土质坝堤加高工程的离心模型试验研究

土工织物是一种广泛用于边坡加固的合成材料,但土工织物在土质坝堤加高工程中尚未得到合理应用。针对水位变动条件下土工织物加固的加高土质坝堤进行了离心模型试验,观测了加高坝堤的变形破坏响应过程。试验结果表明,土工织物加固的加高土质坝堤的破坏呈现出新旧坝堤各异的特点,新旧坝堤呈现出不同的破坏特性,离土工织物较远的旧坝堤先发生破坏,土工织物加固的新坝堤的破坏发生较晚,且呈现从上到下渐进发展的特性;加高坝堤的最终破坏是由变形局部化和局部破坏相互耦合渐进发展导致的;土工织物分为加固段和约束段,在约束段坝堤给土工织物提供约束力,在加固段土工织物限制了坝堤的变形,土工织物的加固机理是将坝堤深部的约束力传递到坝堤表面,从而增强了坝堤浅层的抗滑能力;水位变动引起坝堤的变形增加,土工织物的加固作用也随之增强。

袁河龙尾洲枢纽施工期及运行期水位变化研究

龙尾洲枢纽工程施工拟采用分期导流的方式,一期围堰围左侧8孔泄水闸及相应的鱼道,利用右侧滩地开挖导流明渠进行导流;二期围堰围船闸进行施工,利用右侧已建8孔泄水闸进行导流。为满足龙尾洲枢纽运行期时的通航水流条件,同步实施切滩和疏浚工程。采用数值模拟方法研究施工期围堰、航道疏浚、切滩等工程实施以及龙尾洲枢纽运行引起的水位变化。结果表明,一、二期围堰分别引起围堰上游水位壅高0.28、0.20 m,下游水位降低0.08、0.12 m,且围堰上游断面内水位的横向比降较大;运行期上下游航道区的疏浚和航道区外的切滩工程有效扩大了河道过水断面面积,增加了槽蓄量,导致沿程水位明显下切,减弱了枢纽工程引起的上游水位的壅高作用。

适应高水位变幅的鱼道进口流速调节数值模拟

鱼道进口布置受多种因素影响,当下游河道水位变幅较大且鱼道进口数量布置受限时,鱼道进口难以承受较大水位变幅,诱鱼水流条件差。为此,提出了设置流速调节浮箱对鱼道进口结构进行优化设计,并采用三维数值模拟对鱼道进口流速调节浮箱布置进行了优化研究。研究结果表明:鱼道进口段浮箱尺寸确定与下游水位变化密切相关,鱼道进口布置适当高度的浮箱,可以明显改善进口区域的流速条件;浮箱长度和鱼道进口段长度对鱼道进口段水流条件的影响不大,当浮箱长度取值为2~4倍进口宽度、鱼道进口段长度取值为5~8倍进口宽度时,鱼道进口段均可获得利于鱼类上溯的水流条件;浮箱尺寸一定,当浮箱布置位置距离鱼道池室段为1.0~2.5倍进口宽度时,流态较优。

人类活动影响下洪泽湖水位变化特征分析

研究洪泽湖水位变化规律及动态特征,为流域防洪、供水和生态调度提供科学依据。基于洪泽湖主要水文站长系列实测水位数据,采用曼-肯德尔法分析过去71年洪泽湖水位的变化趋势,判断是否存在水位突变,识别洪泽湖水位周期性变化特征。结果表明:洪泽湖水位只在1954年之前呈下降趋势,在1954—2020年间均呈上升趋势,1968—2020年水位上升趋势非常明显。进一步分析可知,由于工程调控的不断加强,洪泽湖水位总体呈“稳中略升”的态势,年最高水位和年平均水位的波动幅度趋于减小,年内水位变动长期呈“反季相”态势,水位波动频率变高。