IMPACTS OF FUTURE SEA LEVEL RISE ON SALT WATER INTRUSION IN THE CHANGJIANG RIVER ESTUARY

Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water.The implications of sea level rise for increasing salinity have been examined in the Changjiang(Yangtze)River estuary.By correlative analysis of chlorinity,discharge and tidal level and calculation of two-dimensional chlorinity,distribution of the Changjiang River estuary,the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50-100 cm.The intensity of salt water intrusion in the future will be far more serious than current trend.

Environmental evolution in the salt-water intrusion area south of Laizhou Bay since late Pleistocene

The south coastal plain of Laizhou Bay is one of the typical salt-water intrusion areas in China, the occurrence and development of which was closely related with the palaeoenvironment evolution. Systematic analyses of pollen, foraminifera and grain size composition based on ^14C and luminescence dating from two sediment cores were performed for the purpose of understanding the salt-water intrusion in the coastal plain of Laizhou Bay from the perspective of environmental evolution since late Pleistocene. It could be classified into seven evolution stages since 120 kaBP： 120-85 kaBP was a transition period from cold to warm; 85-76 kaBP was a period with warm and wet climate having swamp lakes developed in the lower reaches of the Weihe River, south coastal plain of Laizhou Bay; 76-50 kaBP was characterized by grassland vegetation and coarse sediments in terrestrial environment, which was the early stage of Dali Ice-Age; 50-24 kaBP was a period with alternate sea deposition in the south coastal plain of Laizhou Bay; 24-10 kaBP was the late stage of Dali Ice-Age with coldest period of Quaternary, the south coastal plain of Laizhou Bay was dry grassland and loess deposition environment; 10-4 kaBP was another warm and wet climate period, sea level was high and regressed at 4 kaBP; and has been the modern sedimentary environment since 4 kaBP. Among the three warm stages, including 85-76 kaBP, 50-24 kaBP and 10-4 kaBP, corresponded to late Yangkou, Guangrao and Kenli seawater transgression respectively. The duration of the latter one in south coastal plain of Laizhou Bay was longer than that in west coast of Bohai Sea and east coast of Laizhou Bay. The three periods of seawater transgression formed the foundation of salt-water intrusion in this area.

Characteristics analysis and model prediction of sea-salt water intrusion in lower reaches of the Weihe River,Shandong Province,China

Marine sedimentary strata are widely distributed in the coastal zone of the study area, and are rich in brine resources. The exploitation of underground water resources often first caused the intrusion of salt water in the marine strata. Based on the analysis of sea-salt water intrusion feature, the sea-salt water intrusion is divided into four stages: The occurrence and development stage(1976–1985), the rapid development stage(1986–1990), the slow development stage(1990–2000) and the stable development stage(2000–2015). Based on the comparative analysis of the relationship between seawater intrusion and influencing factors, this paper presents that the groundwater exploitation and the brine resources mining are the main control factors of sea-salt water intrusion. On this basis, we have established a numerical model of the sea-salt water intrusion. Using this model, we predicted the development trend of the sea-salt water intrusion. The results show that if the current development of groundwater and brine is maintained, the sea-salt water intrusion will gradually withdraw; once development of brine stops, sea-salt water will invade again. This provides the scientific basis for the rational exploitation of groundwater and the prevention of sea-salt water intrusion.

Visualizing the spatial water quality of Bentota, Sri Lanka in the presence of seawater intrusion

Seawater flows towards the inlands along with the rivers and canals, through the process of infiltration and leaks in the ground water characterized by high concentrations of soluble salts. High salinity concentrations can make groundwater unsuitable for public consumption and surface water unsuitable for irrigation and agricultural activities. This study envisages the fluctuations of ground and surface water quality of Bentota area in the presence of seawater intrusion. The temporal and spatial variations of eleven water parameters were monitored by collecting the water samples during one year period. Spatial distributions were assessed by applying the Inverse distance weighted (IDW) interpolation method in Arc GIS 10.5 software. Water quality is assessed on the integration of all parameters in terms of an index based on the World Health Organization (WHO) standards. The significant linear relationship between the considered parameters of surface water (SW) and groundwater (GW) were identified applying correlation analysis using SPSS software. All parameters of surface water were above the permissible limits of WHO standards. Surface water quality index values with respect to 60% of canals show very poor quality (>1 250) of surface water indicating their unsuitability for irrigation activities. Those surface water bodies indicated very highly saline conditions during dry months. The spatial distribution of ground water quality index with respect to the highest parameter values of each sampling location indicates that 52.2% of total land extent of Bentota Divisional Secretariat Division (DSD) has good quality of ground water which is suitable for drinking. Its 47.2% of total land extent has poor quality of ground water for drinking purpose and less than 0.5% of the area consists of excellent or very poor quality of ground water in each. This study helps to manage coastal aquifers by understanding the extreme water quality conditions and coastal salinity.

TWO DIMENSIONAL NUMERICAL CALCULATION FOR SALT WATER INTRUSION AT ESTUARIES

Based on 2-dimensional vertically governing equations of salt water intrusion at estuaries, a method is obtained, which can predict quantitatively current velocity and salinity distribution along depth when the intrusion occurs. The volume-controlling method proposed by Patanker and Spalding is used to form the computational pattern and the Power- Law Scheme is used as the diversion pattern of the diffusion term. The comparison between the computational results and the measured ones gives a satisfactory agreement.

FORECAST OF IMPACTS OF SEA-LEVEL RISE ON THELOW COLONIZED ISLANDS AND THEIR SURROUNDING WATERS IN THE CHANGJIANG RIVER MOUTH

As a worldwide authoritative, IPCC forecasted in 1990 that the world- s sea level would most probably rise by 0. 66 m by the end of the 21 st century. Combined with the local depression caused by the sink of the earth’s crust and the human activity, the relative sea level in the Chanaiiang River mouth will rise by about 1. 0 m during the same peried. Based on this figure, the article forecasted the impacts of sea-level rise on the safety coefficient of coastal structures and civil facilities, loss of wetlands, flood hazard as well as water intrusion. The results show that: 1 ) 40% as large as the present engil1eering mass should be added to the coastal structures in order to maintain the safety coefficient; 2 ) a dynamic loss of 60 km2 of wetlands, as much as 15% of the present total area, would be caused; 3) to hinder the increase inflood hazard dy11amic capacity to drain water must increase by at least 34 times as large as the present; 4) to maintain the present navigation conditions, about 100 million yuan (RMB) is needed to reconstruct over 30(X) bridges and 30 sluices;and 5 ) the disastrous salt water intrusion caused by the sea-level rise could be encountered by the increase in water discharge from the Three Gorge Reservoir in the dry season.

A method for estimating the fresh water-salt water interface with hydraulic heads in a coastal aquifer and its application

Examining the descriptions of piezometric heads at two points in both the salt water and fresh water zones reveals that when the groundwater flow system is in steady state and satisfies the Dupuit assumption, the location of the fresh water-salt water interface in a homogeneous, isotropic, and unconfined coastal aquifer can be estimated based on a piezometric head of fresh water at a point in the fresh water zone （from the water table to the interface） vertically lined up with a piezometric head of salt water at a point in the salt water zone （from the interface down）. Research shows that the new method is a general relation and that both the Hubbert relation describing the location of the interface and the Ghy- ben--Herzberg relation are special cases of this method. The method requires two piezometric wells to be close to each other and each tapping into a different zone. Measurements of piezometric heads at a well cluster consisting of piezometric wells tapping separately into fresh water and salt water zones near Beihai, China at 5-day intervals for 15 months are used to illustrate the estimation of interface location. The depth of the interface for well H5 ranges from 32 to 72 m below the sea level.

吉兰泰沙漠盆地高氟地下水分布规律与形成机理

【目的】分析吉兰泰沙漠盆地高氟地下水分布规律,探究绿洲径流区地下水超采对氟解离、迁移和富集的影响机理。【方法】基于SPSS24.0和ArcGIS软件对水化学特征进行数据统计和空间分析;采用Piper三线图、离子比值、Gibbs图解与饱和度指数等方法,结合1980—2020年查哈尔滩绿洲地下水位监测数据和开采数据,探究其高氟地下水水化学特征及成因。【结果】(1)从山地补给区→绿洲径流区→沙漠盐湖排泄区,地下水化学具有分带规律,矿化度、钾离子、钠离子、F-质量浓度逐渐增大,F-质量浓度为0.2~3.4 mg/L;(2)盐湖区地下水F-呈环形岛状分布;沙漠盆地地下水化学的形成主要受含氟岩石的风化作用和蒸发浓缩等自然因素影响;(3)绿洲径流区地下水超采驱动吉兰泰盐湖劣质地下水入侵沙漠绿洲,灌溉回归水的淋滤作用改变了土壤氟解离和迁移模式,导致地下水咸化、高氟化。【结论】综上可知,盐湖排泄区和绿洲径流区地下水氟富集反映了沙漠盆地水文生态环境退化,应采取管灌、滴灌等节水灌溉方式和压缩耕作面积等措施,使查哈尔滩绿洲年地下水开采量减少至700×10^(4)m^(3),以抑制吉兰泰沙漠盆地绿洲灌区的地下水高氟化趋势。

超大城市供水系统韧性评估与应用实践——以上海受咸潮入侵影响为例

供水系统韧性作为韧性城市建设的关键一环,近年来正面临着前所未有的挑战。文中探讨了供水系统韧性的评估方法,分析了当前供水系统韧性研究实践的现状及其存在的问题。通过事前、事中和事后不同阶段的定性和定量相结合的方式,识别解析了超大城市供水系统的韧性影响因素,创新构建了上海供水系统韧性评估体系。此外,以2022年上海受咸潮入侵影响为例,进行了详尽的供水系统韧性综合评价。结果表明,上海供水系统在咸潮期间的整体韧性介于“可控”与“健康”。文章对于供水系统的韧性评估与应用实践可为其他城市提供更完备的借鉴和策略参考。

基于杭州亚运会重大赛事期间的城市水质提升与保障对策

围绕亚运会水质保障提升,文中研究钱塘江原水在高藻、高pH、咸潮等水质突发情况下的水质情况,分析电导率和氯化物的相关性。同时,采取实验室小试联合生产性试验,线上线下联动监测,从源头到龙头加强水质监测,提出高效可行的水质应急处置方案。结果表明:原水pH值≥7.8时,采用CO_(2)调节pH技术,可有效降低出水pH和铝含量;高锰酸钾联合深度水工艺除藻效果较好,藻类去除率达99.6%以上;电导率和氯化物有一定的正相关性,当原水电导率大于500μS/cm,可作为钱塘江咸潮的预警阈值。此外,采取内外联动、亚运保障点水质专项摸排、对标新国标、提标增项等措施,为第19届杭州亚运会的优质供水提供强有力的支持,也为其他地区重大赛事的水质保障提供实践参考。

入海船闸防盐措施规模数值模拟分析评价研究

本研究基于长江口海域及大治河河口地形、潮汐、径流、风场等水文地质气象条件,以及船闸运行规则、潮汐动力学参数等,搭建了河口二维潮汐盐度计算模型,对大治河大芦线东延伸航道整治工程新建船闸运行过程中可能带来的盐水入侵风险进行了评估,根据风险评估结果,计算模拟分析了不同情景方案条件下的防咸措施效果。研究结果表明:大芦线东延伸段船闸运行时,盐水团会在潮汐动力以及船闸运行时随水流汇入内河,在船闸内河侧累积并进行上溯,也会出现海域涨潮时段的高盐水倒灌、累积性的咸水(高盐水)急剧上溯的情况,针对本项目防咸各类设计方案情景,进行模型计算分析,为工程设计方案实施提供相应的理论依据和技术支撑。

节水改造工程对灌区土壤盐渍化的影响

为了探明节水改造措施对盐渍化灌区土壤盐分含量的影响效果,通过设置点位取样测量的方式,对比不同土层深度、不同区域以及不同时间下土壤中的盐分含量。结果表明,在未进行节水改造时,表层土壤在秋浇之前盐分含量较高,为3.44g/kg,而秋浇之后各深度土壤含量依次减小29%、28.7%、20.9%,表明对土壤盐分的淋洗起到很好的效果;0~10cm、10~30cm以及30~50cm土层深度的变异性,依次为强变异性、中等变异性和中等变异性;缓冲区内土壤盐分含量与渠道距离呈线性负相关的关系,即随着距离的增长,土壤含盐量逐渐降低;距离增长时,与0~30cm深度土层相比,30~50cm深度土层内盐分含量减小程度更快。在采取节水改造措施后,短期缓冲区土壤盐分含量平均值减小速度低于长期改造区;在经历秋浇之后,缓冲区对土壤含盐量的解释能力得到提高,表明秋浇可以在一定程度上缓解盐分在土壤中的表聚作用。

Types of saltwater intrusion of the Changjiang Estuary

The Changjiang Estuary is characterized by multi-order bifurcations, unsteady submerged sandbars, mid-channel sandbars, creeks and riffles. The following four types of saltwater intrusion are found: (1) direct intrusion from the sea; (2) intrusion during tidal flooding; (3) intrusion from tidal flats overflow; and (4) salt water coming upstream through other waterways. These result in a complicated temporal and spatial salinity distribution. A high chlorinity concentration zone exists from the Liuhekou to the Sidongkou along the South Branch. The salinity during neap tide or ordinary tide is higher than during spring tide.

A Study of Impacts of Global Sea Level Rise on Salt Water Intrusion Into the Changjiang Estuary

Using the methods of empirical correlation and numerical analogue computation of the longitudinal distribution of two-dimensional chlorinity and combined with the actual situation of water supply in the Changjiang Estuary, a calculation and analysis have been made in this paper of the impacts of sea level rise of 0.5—1.0 m in the Changjiang Estuary in the next century on the probabilities of hourly chlorinity of more than 100×10^(-6), 200×10^(-6) and 250×10^(-6) during the dry season st Wusong station and on the intrusion distance of the isohalines of 1×10^(-3) and 5×10^(-3) during the ebb tide stand of the dry season in the South Branch as well as on the longitudinal distribution of the chlorinity of the South Branch in the most unfavorable situation with the minimum monthly mean discharge during the special dry year.

The Effect of Sodium Chloride on Hybrid Taxodium Selections

Saltwater intrusion is a major cause of coastal erosion. New hybrid bald cypress species have been shown to exhibit salinity tolerance compared to native bald cypress species. Planting these hybrids, or Nanjing Bot Garden genotype (NBG), trees where their roots can stabilize soil and preserve land may reduce coastal erosion in areas subjected to saltwater intrusion. The purpose of this experiment was to determine whether or not selected bald cypress NBG genotype tree species survive better than native bald cypress trees in areas inundated with saline water. Leaves were harvested, dried and analyzed for their elemental concentration. NBG genotype trees excluded more sodium than native bald cypress trees. NBG genotype tree roots were also less effected by brackish water. Finally, the growth of the NBG genotype trees and the control were measured. All NBG genotype trees tested showed growth while the control trees maintained little or no growth, and a decrease in tree height in sodic soil. If these NBG genotype trees are subjected to a surge of brackish water, NBG genotype bald cypress trees may be used to stabilize soil that may be otherwise subject to coastal erosion.

Measuring Salinity within Shallow Piezometers:Comparison of Two Field Methods

The objective of this study is to understand the validity of salinity vertical profiles collected from shallow piezometers that are not previously flushed. This study shows that salinity data collected from boreholes are only an average value along the entire screened section of the piezometer. In order to collect data that is rep-resentative for the salinity of the adjacent aquifer, a new monitoring strategy has been developed. This strat-egy includes measurement of the salinity at the top of the watertable in an auger hole which is a shallow boreholes made with an handheld drill. This should be combined with measurements in piezometers that are first flushed to take out stagnant water. From the piezometers on can measure the average salinity of the screened part and the salinity at the bottom of the aquifer. By using this monitoring strategy it is also possi-ble to define where the piezometers screens are located if this is not known beforehand.

强潮河口盐水入侵特征数值模拟研究

以强潮河口——椒江河口为研究对象,通过数学模型研究不同径流、潮差条件下的盐水入侵特征,明晰强潮河口的盐水入侵特性,为相关科学研究以及工程建设提供技术支撑和依据。结果表明:椒江为枯季低流量(10m^(3)/s)时,0.1‰盐水可以上溯至始丰溪与永安溪的交汇处三江村附近,5‰盐水可以上溯至八仙岩附近,椒江达洪峰流量(3000m^(3)/s)时,海门以上河段的盐水浓度均小于0.1‰;在径流变化潮差不变条件下,盐水上溯距离变化梯度涨憩大于落憩,小潮大于大潮,随着径流量的增大,盐水上溯距离变化梯度逐渐增大;在潮差变化径流不变条件下,盐水上溯距离变化区间呈线性增长趋势,随着径流量的增大,同等潮差下的盐水上溯距离变化区间逐渐减小;拟合出了椒江河口盐水最大上溯距离与径流、潮差的函数关系式,预测值偏差在2%~6%,可为椒江其他相关盐水研究提供借鉴。

Sea water intrusion and salt water intrusion in the coastal area of Laizhou Bay

The characteristics, pattern, hydrodynamic and hydrochemical features, and the movement pattern of the salt water-fresh water interface of the sea water intrusion and the salt water intrusion, which occur in the coastal area of Laizhou Bay in Shandong Province, are analysed. The characteristics of the two kinds of intrusion are compared as well. A three-dimensional sea water intrusion model to describe the sea water intrusion with a transitional zone 1.56.0 km wide in the phreatic aquifer and a solute transport model describing the behavior of cations exchange in the process of sea water intrusion are established.