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.

Anthropogenic activity,hydrological regime,and light level jointly influence temporal patterns in biosonar activity of the Yangtze finless porpoise at the junction of the Yangtze River and Poyang Lake,China

Under increasing anthropogenic pressure,species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations.The critically endangered Yangtze finless porpoise(Neophocaena asiaeorientalis asiaeorientalis),once commonly observed in the Yangtze River-Poyang Lake junction,is now rarely seen in the river-lake corridor.In this study,static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor.Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation,as well as environmental variables,including hydrological conditions and light levels.Over approximately three consecutive years of monitoring(2020–2022),porpoise biosonar was detected during 93%of logged days,indicating the key role of the corridor for finless porpoise conservation.In addition,porpoise clicks were recorded in 3.80%of minutes,while feeding correlated buzzes were detected in 1.23%of minutes,suggesting the potential existence of localized,small-scale migration.Furthermore,both anthropogenic and environmental variables were significantly correlated with the diel,lunar,monthly,seasonal,and annual variations in porpoise biosonar activities.During the pandemic lockdown period,porpoise sonar detection showed a significant increase.Furthermore,a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity.In addition to water level and flux,daylight and moonlight exhibited significant correlations with porpoise biosonar activities,with markedly higher detections at night and quarter moon periods.Ensuring the spatiotemporal reduction of anthropogenic activities,implementing vessel speed restrictions(e.g.,during porpoise migration and feeding),and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.

Elevation of basal lacustrine sediments along the mid-lower reaches of the Yangtze River and its implications for the reconstruction of Holocene water levels

The middle and lower reaches of the Yangtze River,a primary region for freshwater lakes in China,have undergone significant transformations throughout the Holocene.These changes,driven by factors such as sea-level rise,climate change,and human activities,have led to the progressive elevation of water levels in this area.As a result,a floodplain has emerged,characterized by the formation of numerous shallow lakes along the river course.However,the pattern of water-level changes in the main channel of the Yangtze River during the Holocene remains unclear.This gap in knowledge poses challenges for understanding sediment transport dynamics,the interactions between the river and its adjacent lakes,and the prevention and control of flood disasters in the Yangtze River basin.To shed light on these issues,our study compiled data on the surface elevation and water depth of 81 lakes in the mid-lower reaches of the Yangtze River basin.Additionally,we analyzed historical water-level records from the 1900s to the 1970s at eight gauging stations from Shashi to Jiangyin along the river’s main stream.Our findings reveal that,particularly along the Jingjiang section,the basal elevation of most lakes is lower than the Yangtze River’s water level during the dry season.Conversely,the water level of the main stream exceeds that of both the floodplain and the lakes enclosed by the Jingjiang embankment.In the tidal reach,especially within the Taihu Lake basin,the basal elevation of lakes typically falls below sea level.Meanwhile,lakes located along the section from Chenglingji to Wuhu exhibit basal elevations that correspond with the Yangtze River’s annual average and dry season water levels.Given the widespread presence of lakes along the middle and lower reaches of the Yangtze River,our study introduces a new proxy for reconstructing the mean water level of the mid-lower Yangtze River in the Holocene.By analyzing sediments from Nanyi Lake and Chenyao Lake in the lower Yangtze River,we attempted to reconstruct the water level of the Yangtze River’s main channel since 8 ka BP.

Variation of Floods Characteristics and Their Responses to Climate and Human Activities in Poyang Lake, China

The Poyang Lake is one of the most frequently flooded areas in China. Understanding the changing characteristics of floods as well as the affecting factors is an important prerequisite of flood disaster prevention and mitigation. The present study identified the characteristics variations of historical floods in the Poyang Lake and their tendencies based on the Mann-Kendall(M-K) test, and also investigated the related affecting factors, both from climate and human activities. The results revealed that the highest flood stages, duration as well as hazard coefficient of floods showed a long-term increasing linear trend during the last 60 years with the M-K statistic of 1.49, 1.60 and 1.50, respectively. And, a slightly increasing linear trend in the timing of the highest stages indicated the floods occurred later and later during the last six decades. The rainfall during the flood season and subsequent discharges of the Changjiang(Yangtze) River and runoff from the Poyang Lake Basin were mainly responsible for the severe flood situation in the Poyang Lake in the 1990 s. In addition, the intensive human activities, including land reclamation and levee construction, also played a supplementary role in increasing severity of major floods. While, the fewer floods in the Poyang Lake after 2000 can be attributed to not only the less rainfall over the Poyang Lake Basin and low discharges of the Changjiang River during flood periods, but also the stronger influences of human activity which increased the floodwater storage of the Poyang Lake than before.

Phytoplankton Communities in a Coastal Site of Natural Reserve “Lake of Tarsia-Mouth of River Crati”-Northern Ionian Sea, Calabria (Italy)

Our work was aimed to study the phytoplankton communities in two coastal sites placed in Natural Reserve “Lake of Tarsia-Mouth of river Crati” in Northern Ionian Sea-Calabria (Italy). This zone represents a wetland area of high natural interest populated by different organisms (animals and plants) living in a transitional ecosystem characterized by a great biodiversity. The sampling was performed in two different seasonal periods (summer and autumn 2012) and in two different sites (marine site vs fluvial one). Different algal genera/species were recognized and analyzed by Utermohl inverted microscope method and also qualitative and quantitative measures of biomass were performed. The results showed that the dominant group was the Diatoms with exclusive species in such periods in both the sampling sites;we also observed the presence of genera and/or species of potentially toxic algae (Pseudo-nitzschia sp., Alexandrium taylori, Prorocentrum micans, Skeletonema sp.), mostly in summer. Complessively, the phytoplankton biomass was always higher in marine site than in the fluvial site. The results were also processed considering the context of the chemical-physical parameters (such as temperature, pH, salinity, nutrients). The high concentration of the nutrients N and P in such periods indicated a state of meso-eutrophic waters both in the proximity of river site as well as in the marine zone. The data represent the first contribution to the knowledge of the phytoplankton structure in this area, which results in a very variable environment with a high recovery capacity.

江苏省平原水网区河湖生态水位确定探索与实践

保障河湖生态流量,事关江河湖泊健康。本文在分析江苏平原水网区域特点的基础上,选择生态水位作为河湖生态流量的表征指标,根据水利部确定的江苏省26条全国生态流量保障重点河湖名录,科学选定控制断面,采用1990—2020年水文序列资料,选用Qp法分析计算90%、95%、99%保证率下的水位,同步对比分析近10年最枯月水位、最低通航保证水位,最终确定了26条河湖的生态水位。通过制定保障措施方案、开展监测预警评估、强化统一调度管理等措施,全面保障区域河湖生态水位,为平原水网地区河湖生态水位的确定与保障提供了经验。

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。

大湖演算模型在裕溪河流域的适用性分析

为探究大湖演算模型在裕溪河流域是否适用,采用大湖模型和误差自回归模型,对2020年汛期裕溪河闸闸上水位一次涨水过程进行模拟研究,发现大湖模型对该流域的洪峰模拟精度较高,对水位的整体涨落过程预测较好,经过实时误差修正后,模型精度进一步得到提升。结果表明,大湖模型在裕溪河流域有一定的适用性,可为裕溪河流域今后防洪调度预报工作提供参考。

曲流河沉积模式及演化规律研究——以渤海湾盆地L油田明下段为例

【目的】L油田明下段发育多种曲流河模式,其沉积模式和演化规律尚不明确。【方法】综合利用古生物资料、岩心、壁心、测井、地震等资料,对明下段各时期的曲流河特征、古地质背景进行了系统分析,并进一步总结了明下段曲流河的演化规律。【结果】明下段沉积时期,研究区先后发育了五种曲流河模式;L_(4)油组底部L_(4)^(4)小层为辫曲共生模式;L_(4)^(2)~L_(4)^(0)小层为高弯度曲流河模式;L_(3)^(2)小层为限制性曲流河模式;L_(3)^(0)小层为串珠状曲流河模式;L_(2)油组主力储层为低弯度入湖曲流河模式。【结论】明下段时期,研究区古地质背景也不断发生演化,受沉积基准面旋回、古气候、古地貌、沉积区水体环境等古地质因素耦合作用影响,形成了不同时期多种类型的曲流河模式。

基于改进波形聚类方法的复合河道砂体沉积微相预测--以渤海A油田为例

渤海新近系河湖过渡带复合河道砂体叠置关系复杂、相带变化剧烈,利用传统地震属性划分沉积微相多解性较强。提出了改进振幅谱距离-K中心聚类方法并将其应用于复合河道砂体沉积微相预测。方法包括两个方面:①以测井标定沉积微相对应的典型波形作为初始聚类中心以及聚类中心更新过程中的约束条件;②利用振幅谱距离评价波形之间的差异,进一步提升波形聚类精度。根据渤海新近系A油田地质条件设计复合河道砂体三维模型,模型试验结果证实改进后的方法微相预测准确率达95%,相比传统K均值聚类算法精度提升15%,较好地区分了泥岩、单期河道边部、单期河道主体、河道边部叠置、河道边部与主体叠置、河道主体叠置(或多期叠置)共6种河道不同部位或叠置样式。利用改进后的方法指导A油田10个砂体沉积微相划分,将大型砂体S沉积微相划分为分流河道、河口坝、席状砂、决口河道、分流间湾、天然堤6类,指导开发方案中优先动用分流河道、河口坝等优势微相的地质储量,证明了方法的实用价值。

Changes in lake area and water level in response to hydroclimate variations in the source area of the Yellow River:a case study from Lake Ngoring

In the north-eastern Qinghai-Tibet Plateau(QTP),the source area of the Yellow River(SAYR)has been experiencing significant changes in climatic and environmental conditions in recent decades.To date,few studies have combined modern hydrological conditions with paleoclimate records to explore the mechanism(s)of these changes.This study seeks to improve understanding of hydrological variability on decadal and centennial timescales in the SAYR and to identify its general cause.We first determined annual fluctuations in the surface area of Lake Ngoring from 1985 to 2020 using multi-temporal Landsat images.The results show that lake surface area changes were generally consistent with variations in precipitation,streamflow and the regional dry-wet index in the SAYR,suggesting that the water balance of the Lake Ngoring area is closely associated with regional hydroclimate changes.These records are also comparable to the stalagmite δ^(18)O monsoon record,as well fluctuations in the Southern Oscillation Index(SOI).Moreover,an association of high TSI(total solar insolation)anomalies and sunspot numbers with the expansion of Lake Ngoring surface area is observed,implying that solar activity is the key driving factor for hydrologic variability in the SAYR on a decadal timescale.Following this line of reasoning,we compared the δ^(13)C org-based lake level fluctuations of Lake Ngoring for the last millennium,as previously reported,with the hydroclimatic history and the reconstructed TSI record.We conclude that the hydrological regime of Lake Ngoring has been mainly controlled by centennial fluctuations in precipitation for the last millennium,which is also dominated by solar activity.In general,it appears that solar activity has exerted a dominant influence on the hydrological regime of the SAYR on both decadal and centennial timescales,which is clearly manifested in the variations of lake area and water level of Lake Ngoring.

鄱阳湖水位对五河来水的时空响应研究

鄱阳湖水位受到长江干流和湖泊流域五河来水(五河分别为赣江、抚河、信江、饶河、修水)的共同影响,其中五河径流为鄱阳湖的主要来流。为探究五河来水变化对鄱阳湖水位的时空影响,结合数据驱动模拟与敏感性分析方法,定量研究了鄱阳湖水位与五河来水的响应关系。首先,结合PSO-GA算法和支持向量回归(SVR)技术建立了湖泊水位预测模型,模拟分析鄱阳湖水位与五河来水的时间响应关系;然后,基于此模型采用连续预测方法研究了鄱阳湖水位对五河来水响应的空间分布特征。结果表明,鄱阳湖水位对五河来水变化响应较强的时期在5~7月,尤以5月响应程度为甚;空间分布上,鄱阳湖湖区中部对五河来水变化的响应程度最高,以2010年5月为例,当五河来流增加40%时,都昌站水位一周内平均可抬高1.16 m,北部星子站、湖口站分别平均抬高1.15、1.03 m,南部棠荫站、康山站平均抬高0.97 m。结果明确了鄱阳湖水位对五河来水的时空响应特征,可为鄱阳湖水资源管理及流域优化调控提供科学依据。

对基层推进幸福河湖建设的思考——以江苏省张家港市谷渎港为例

河湖是生态环境的重要载体,建设幸福河湖是保护生态环境、提升人民群众获得感、实现人水和谐的重要途径。新征程上,幸福河湖建设面临新问题、新挑战。探究了幸福河湖基本内涵,总结提炼了江苏省张家港市建设幸福河湖过程中综合打造健康宜居水环境、全力构建传统与现代相融合人文景观、注重水利遗产保护和传承等有益探索,并从建设思路、资金渠道、管护模式、宣传引导等方面提出相关意见和建议。

营养状态指数在长江下游小型浅水湖泊富营养化水平评价中的局限及改进建议

基于多个环境变量、以等权或者加权平均法获得的综合营养状态指数(Carlson指数:TSIc;修正后的Carlson指数:TSImc;综合营养状态指数:TLIc;湖库营养状态指数:EIc)得分是当前评价湖泊营养水平的主要依据,其值计算时先要获得基于单个环境变量的营养状态指数分值。若基于总氮(TN)、总磷(TP)和透明度(SD)等的单个理化指标与基于叶绿素a(Chl.a)的营养状态指数得分间存在显著差异,表明依据理化指标的评估结果低估或者高估湖泊的实际营养水平。长江下游分布大量的小型浅水富营养化湖泊,但基于理化指标的评估结果是否会误判湖泊的实际富营养化水平的研究很少。本研究以长江下游的14个浅水富营养化湖泊为对象,于20192020年按照季度采集水样并测定水环境因子,分析基于理化指标和基于Chl.a的各营养状态指数(TSI、TSIm、TLI和EI)得分间的差异。结果表明,基于SD的TSI、TSIm、TLI和EI的年均得分均显著高于基于Chl.a的相应营养状态指数的年均值;除TSI(TP)vs.TSI(Chl.a)外,基于TP与基于Chl.a的其他营养指数的年均得分间均有显著性差异;仅TLI(TN)与TLI(Chl.a)的年均得分间无显著性差异。这表明,除TSI(TP)和TLI(TN)外,基于理化指标与基于Chl.a的其他营养状态指数的评估结果间均不能相互匹配。针对基于理化指标的营养状态指数在长江下游小型湖泊富营养化水平评估中的问题,提出如下改进建议:1)依据lnSD-lnChl.a-lnTP间的回归关系重构了营养状态指数(TSIr、TSImr和TLIr)方程,结合基于单个理化指标与基于Chl.a的各指数得分间的匹配性、基于多个环境变量的综合营养状态指数TSIrc、TSImrc和TLIrc得分间的差异性及其与水体实测Chl.a浓度对应的营养状态指数赋分区间的一致性,建议在长江下游小型浅水湖泊的富营养化水平评估中使用TSImr和TLIr指数;2)以加权平均法计算综合营养状态指数TLIrc得分时,发现基于理化指标实测值的归一化相关权重(W j1)与基于直接引用文献数据的相关权重(W j2)的TLIrc得分间无显著差异。从简便性角度出发,建议直接以W j2计算TLIrc指数得分。

干群关系、收入水平与农户村域河湖环境治理意愿

为探究干群关系、收入水平对农户村域河湖环境治理意愿的影响,基于902份农户调研数据,利用双栏模型(Double Hurdle Model)进行实证分析。结果表明:(1)农户村域河湖环境治理参与意愿较高;(2)干群关系、收入水平对农户村域河湖环境治理参与意愿、支付意愿有显著正向影响;(3)收入水平在干群关系对农户村域河湖环境治理意愿的影响中发挥正向调节作用。因此建议在政策层面,应通过重视干群关系培养、提升农户收入水平和完善政策瞄准精度促进农户参与村域河湖环境治理。

从塔里木河河岸地下水与植被覆盖看尾闾湖维持面积

实施塔里木河下游生态输水工程(简称生态输水工程)是塔里木河下游“绿色走廊”保护的重要举措。以塔里木河下游(含湖区)为研究对象,采用密集时序遥感技术对自2000年生态输水工程实施以来的生态输水过程中河岸带与湖区植被面积和植被覆盖度的变化特征进行定量分析,结果表明:生态输水对河道两岸地下水水位的影响范围局限在1~2 km内,越往尾闾方向影响范围越窄;植被面积与植被覆盖度增长趋势显著的区域中,湖区占比较大,主要体现在尾闾湖区。为提高生态水利用效率,建议优化目前的生态输水方式。

三峡工程运用后荆江与洞庭湖关系变化研究进展

荆江与洞庭湖之间存在复杂的江湖水沙交换关系,水沙变化引起江湖冲淤变化,进而影响长江中游地区的防洪安全与水资源利用等。三峡工程运用后坝下游水沙条件发生较大改变,江湖关系进一步调整。从江湖水沙关系变化、荆江特别是分流口门附近河道冲淤演变、三口分流洪道冲淤演变、洞庭湖区冲淤变化及城陵矶水位变化等方面,系统梳理了三峡工程运用后荆江与洞庭湖关系变化研究进展,得到以下结论:荆江三口分流量略有减少,分沙量大幅下降,藕池口河势调整较剧烈,进流条件有所恶化,洞庭湖由淤积转为微冲,湖区水位下降,城陵矶—汉口河段冲刷,城陵矶水位下降等,江湖水沙驱动机制仍存在一定不足,在荆江洪水位变化及洞庭湖未来演变趋势方面仍存在争议;指出了目前研究中存在的不足,如缺乏定量分析和系统性与完整性研究,并提出了下一步研究需重点关注的问题。

基于湖北省河湖管理范围划定关键问题的对策研究

河湖管理范围划界是生态文明建设需求、河湖长制工作的重要任务之一。无堤防河湖划界相关水位确定、毗邻对象边界不清晰、管理范围与“三区三线”其他空间融合交叉等是划界工作顺利开展及划界成果是否科学合理的决定性因素。以典型地区、典型湖泊为例,利用资料收集、数据分析、图像比对、走访调研等手段,分析无堤防河湖占比、河湖特点、水文监测点布设情况,摸查无水文监测资料河湖的历史高水位及设计水位的推求方法,比对管理范围与三区三线交叉及重叠情况。结果显示:对于无堤防河湖,可采用已有相关规划或设计成果,无现有成果的采取经验公式及经验参数计算设计洪水从而推算设计洪水位,无水文监测资料的历史最高洪水位通过资料查阅、洪痕调查、群众走访等方法获取;毗邻对象边界按照当地已约定俗成的管理习惯或共用相对高级别河湖的管理范围线的原则划定;某地河流、湖泊管理范围涉及基本农田面积,在划界实施中基本农田部分面积未避让,典型湖泊的生态保护区与管理范围不吻合,河湖管理范围按照相对较大的生态保护区范围适当调整。划界水位的科学及可靠性是管理范围是否合理的控制性因素,采用现有成果、调查法、经验公式法等手段获取划界水位时,对现有成果进行充分分析论证、保证调查方法的规范科学、选取经验公式及经验值的合理可信是重要基础;毗邻对象边界确定属于管理范畴问题,遵循管理现状及规则是较好的解决途径;河湖管理范围与“三区三线”、城市规划控制线等区域空间有重叠或交叉时,可在不改变重叠部分范围用地类型及权属的情况下,通过制定用途管制规则进行范围管控,达到水资源安全、行洪安全、水生态安全的保护目标。这些关键问题的研究是科学划定河湖管理范围的根本前提,为社会发展提供资源保护、生态安全、可持续利用的基本保障。

岷江流域保护与发展对策建议——基于强化河湖长制工作的思考

岷江作为长江上游重要生态屏障和水源涵养地,对四川省水源涵养和水生态环境保护有着极其重要的战略地位。回顾总结了岷江流域河湖长制工作主要内容、成效和存在的问题,从强化各级河湖长履职尽责,坚持“三水统筹、系统治理”,统筹协调保护与发展等方面入手,提出了以岷江流域生态环境高水平保护助推经济社会高质量发展的对策建议。

赣江尾闾河段近30年汛期水位变化

赣江尾闾河段汛期受上游来水与鄱阳湖顶托的双重影响,研究其汛期水位变化对河道防洪和航运有重要的指导意义。为此,根据赣江尾闾控制性水文站1990~2019年的实测水文资料,采用Mann-Kendall趋势检验和Pettitt检验方法对赣江尾闾河段汛期(河洪及湖洪)特征水位的趋势性及突变性进行分析。结果表明,赣江尾闾河段河洪期和湖洪期特征水位均呈显著下降趋势,河洪期水位年际变化较为均匀,湖洪期水位年际变化呈现出波动状,两者的突变年份均为2002年左右。河洪期特征水位下降的主要原因是河床下切,其下切趋势于2013年后明显减缓,故河洪期水位在2016年之后趋于稳定。湖洪期特征水位主要受河床下切影响,下游水位变化也会产生一定的影响。