Investigation of the elevation of saltwater wedge due to subsurface dams     

Qinpeng Chang  Tianyuan Zheng  Youyuan Chen  Xilai Zheng  Marc Walther 《水文研究》2020,34(22):4251-4261

Subsurface dams are rather effective and used for the prevention of saltwater intrusion in coastal regions around the world. We carried out the laboratory experiments to investigate the elevation of saltwater wedge after the construction of subsurface dams. The elevation of saltwater wedge refers to the upward movement of the downstream saltwater wedge because the subsurface dams obstruct the regional groundwater flow and reduce the freshwater discharge. Consequently, the saltwater wedge cannot further extend in the longitudinal direction but rises in the vertical profile resulting in significant downstream aquifer salinization. In order to quantitatively address this issue, field-scale numerical simulations were conducted to explore the influence of various dam heights, distances, and hydraulic gradients on the elevation of saltwater wedge. Our investigation shows that the upward movement of the saltwater wedge and its areal extension in the vertical domain of the downstream aquifer become more severe with a higher dam and performed a great dependence on the freshwater discharge. Furthermore, the increase of the hydraulic gradient and the dam distance from the sea boundary leads to a more pronounced wedge elevation. This phenomenon comes from the variation of the freshwater discharge due to the modification of dam height, location, and hydraulic gradient. Large freshwater discharge can generate greater repulsive force to restrain the elevation of saltwater wedge. These conclusions provide theoretical references for the behaviour of the freshwater–seawater interface after the construction of subsurface dams and help optimize the design strategy to better utilize the coastal groundwater resources.  相似文献   

多点液压式波浪能海水淡化系统建模与仿真   总被引：1，自引：1，他引：0  

胡缘  杨绍辉  何宏舟  陈沪  郑松根  张迪 《海洋工程》2019,37(1):134-141

为缓解淡水资源短缺及化石能源过度使用问题,提出多点液压式波浪能海水淡化系统,该系统主要由采能装置、液压传递系统与反渗透膜海水淡化设备组成。系统的采能装置采用振荡浮子式,可将波浪能转换为浮子振荡从而被液压系统吸收达到采集波浪能的目的。为了提高液压式波浪能海水淡化系统的采能效率及淡水率,利用AMEsim软件对液压传递系统进行建模与仿真,分析了蓄能器、浮子个数及波高对液压传递系统输出响应的影响。结果表明:蓄能器能够使液压马达的输出响应更加稳定;当浮子的数量增加时,液压系统达到稳定的运行状态所需的时间更短,从而有利于提高系统的效率;波高在2 m左右时,本系统的产水量达到最大。  相似文献   

南海盐致环流对台风降水的响应特征分析     

刘娜  王桂华  巩远发  刘磊 《热带海洋学报》2019,38(3):13-21

本文采用多源卫星遥感数据通过统计分析的方法研究了17年间(2000—2016年)南海夏季(6—9月)台风对该海域降水、淡水通量的贡献及其可能导致的环流异常。主要结论如下: 1) 台风是南海中北部降水的重要影响因子, 可导致日平均降水量增加12mm, 约占南海夏季日平均降水(25mm·d ^-1)的一半, 且西北太平洋台风和南海“土台风”产生的降水分布存在显著的区域和强度差异; 2) 夏季, 南海由淡水通量引起的盐致环流表现为以海南岛东南部海域为中心的弱气旋式, 其流量量级约为-0.15Sv, 约占同期风生环流流量(约为-1.5Sv)的10%; 3) 夏季, 台风带来的降水使得南海中北部的气旋式盐致环流增强, 且西北太平洋台风降水导致的淡水通量变化引起的盐致环流强度要强于南海“土台风”。  相似文献   

Environmental determinants of species turnover of aquatic Heteroptera in freshwater ecosystems of the Western Ghats,India     

《Limnologica》2020

Partitioning beta diversity into its two components of spatial turnover and nestedness is a more robust method for checking spatial variability in biological communities than calculating the total beta diversity alone. The relative contribution of spatial turnover and nestedness has been used to test the effects of climatic, environmental, spatial and temporal variables on community composition. In this study, we tested the effects of environmental factors and microhabitat features on total beta diversity and its spatial turnover and nestedness components using a comprehensive dataset of aquatic Heteroptera collected from four types of permanent freshwater habitats (i.e. streams, ponds, rock tanks and reservoirs) in the Western Ghats of India. We observed that communities in all four types of habitats were predominantly shaped by dissimilarity caused due to spatial turnover (>85 %). Each type of habitat showed the presence of one or more species uniquely associated with it, which might contribute to the turnover between communities. The abiotic environment (climatic factors, topological factors, soil characteristics and microhabitat features) as well as assemblage structure differed significantly between habitat types. Communities in each type of habitat were affected by different environmental factors, such as precipitation and temperature patterns for streams, altitude and rocky substrate for rock tanks, and soil characteristics and the presence of aquatic macrophytes for ponds and reservoirs. Assemblages observed in the four types of permanent habitats are thus compositionally distinct due to species replacements between local communities, which in turn are strongly influenced by environmental variables. Similar to previous studies, our results show that spatial turnover largely measures the same phenomenon as total beta diversity on a regional scale.  相似文献   

舟山北部海域海底第四系淡水资源赋存潜力   总被引：1，自引：1，他引：0  

张志忠  邹亮  周良勇 《海洋学报》2018,40(3):50-61

为了解东海舟山北部海域海底第四系淡水资源赋存情况，本文在系统分析舟山北部海域地质钻孔和单道地震资料基础上，分析了研究海域海底第四纪地层结构与沉积环境，阐述了研究海域海底松散沉积物分布规律，探讨了上海陆地地区早更新世中、晚期和早期古河道在研究海域的延伸和分布状况，分析了研究海域海底第四系含水层赋存状况。研究海域第四系可供开发利用的主要含水层为早更新世中、晚期的第四承压含水层（Ⅳ）和早更新世早期的第五承压含水层（Ⅴ）；第四承压含水层古河道分布区富水性最佳，含水层顶部发育厚层黏性土隔水层区域赋存淡水资源的可能性很大，含水层开发利用潜力可分为开发前景良好A区、开发前景较好B区和开发前景一般C区3类；第五承压含水层在古河道分布区富水性强，具有很好的淡水赋存潜力和良好的开发利用前景。  相似文献   

Geologic and hydrologic settings for development of freshwater lenses in arid lands   总被引：2，自引：0，他引：2       下载免费PDF全文

Adam Milewski  Mohamed Sultan  Ahmad Al‐Dousari  Eugene Yan 《水文研究》2014,28(7):3185-3194

Satellite observations were used to test the validity of previously identified favourable conditions for the formation of freshwater lenses, identify additional potential occurrences, and model modern potential recharge in the Raudhatain Watershed (3696) in northern Kuwait. Favourable conditions include infrequent yet intensive precipitation events, drainage depressions to collect the limited runoff, and presence of conditions (e.g. high infiltration capacity) that promote groundwater recharge and preservation (e.g. underlying saline aquifer) of infiltrating groundwater as freshwater lenses floating over saline aquifer water due to differences in density. Specifically, the following field and satellite‐based observations were noted for the Raudhatain Watershed: (1) Over ~30 precipitation events were identified from the Tropical Rainfall Measuring Mission precipitation data (1998–2009); (2) slope is gentle (2 m/km), and the surface is largely (80%) covered by alluvial deposits with high infiltration capacities (up to 9 m/day); (3) no flows and long‐term ponding were reported at the watershed outlet or detected from Landsat thematic mapper images; (4) infiltration is high based on increases in soil moisture content (from an advanced microwave scanning radiometer) and vegetation index following large precipitation events; and (5) freshwater lenses that overlie highly saline [total dissolved solids (TDS): >35 000] unconfined aquifers underlying the watershed are absent in the southern regions, where infiltrating fresh water mixes with the less saline groundwater (TDS: <10 000). Twenty potential locations (size: 1 to 75 km²) for freshwater lens development were identified in northern Kuwait, and continuous rainfall–runoff models (Soil Water and Assessment Tool) were applied to provide a first‐order estimation of the average annual recharge in the watershed (127 × 10⁶ m³) and freshwater lenses (8.17 × 10⁶ m³). Results demonstrate the settings for enhanced opportunities for groundwater recharge, outline the amounts of and preservation conditions for the groundwater feeding the freshwater lenses, and highlight potential applications and locations of freshwater lenses in similar settings elsewhere in the Arabian Peninsula and beyond. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Spatial analysis of water quality and its suitability in farming giant freshwater prawn (Macrobrachium rosenbergii) in Negeri Sembilan region,Peninsular Malaysia     

Benjamin Ezekiel Bwadi  Firuza Begham Mustafa  Mohammad Lokman Ali  Subha Bhassu 《Singapore journal of tropical geography》2019,40(1):71-91

Finding potential sites for resilient prawn production in the tropical environment that also prevents wastage of natural resources is not an easy task. The purpose of this study is to evaluate water quality suitability for prawn farming in Negeri Sembilan of Peninsular Malaysia based on Geographic Information System (GIS). To achieve this goal, numerous criteria including sources of water, water temperature, water pH, sources of pollution, salinity, soil texture and availability of phytoplankton criteria were considered for the modelling process. Analytic Hierarchy Process (AHP) technique was performed to standardize the criteria and the weighting process. The weighted overlay of indicators and results were accomplished by applying the Multi‐Criteria Decision Analysis (MCDA) method in GIS. It was indicated that the Negeri Sembilan area has potential for prawn farming. The results showed that about 25 per cent (163 056.93 ha) of the area was most suitable for prawn farming, about 58 per cent (384 656.88 ha) was considered moderately suitable, while 18 per cent (117 633.49 ha) was regarded as least suitable. The study concluded that the multi‐criteria decision analysis of water quality for prawn farming is vital for regional economic planning in the Negeri Sembilan area and also significant when establishing a model for aquaculture development.  相似文献   

青海湖地区生物中正构烷烃及其氢同位素组成与影响因素     

段毅  吴应忠  吴保祥  孙涛 《地质学报》2018,92(7):1541-1550

青海湖是我国最大的内陆咸水湖泊。本文应用GC-MS和GC-TC-IRMS同位素分析技术,对青海湖水生生物和周围地区陆生生物中正构烷烃及其氢同位素进行了分析,研究了生物中正构烷烃及其同位素组成。结果显示了不同生物中正构烷烃碳数分布范围在C1 5~C33之间,呈单峰型分布;主峰碳数是水生生物(除海韭菜外)相对较低,主要为C23和C25,陆生木本植物次之,为C27;陆生草本植物较高,为C27和C29;CPI值分布在4.0~29.7之间;ACL值为26.0~29.6,分布与植物类型有关。青海湖水生生物中正构烷烃氢同位素组成分布在-209.8‰~-85.6‰之间,平均值为-169.2‰~-121.2‰;陆生植物的正构烷烃δD值为-196.7‰~-84.3‰之间,平均值为-173.0‰~-108.6‰。青海湖不同水生生物和不同陆生生物之间的正构烷烃氢同位素组成差别显著。研究发现,湖泊的含盐量对水生植物的正构烷烃氢同位素具有显著影响,环境湿度和降水量明显影响了陆生植物的正构烷烃氢同位素组成;植物的正构烷烃平均氢同位素组成随着其ACL值增加,具有变轻的趋势;不同种类植物的正构烷烃合成期间具有不同的氢同位素分馏效应,与陆生植物相比较,水生植物的正构烷烃相对于环境水更富集轻氢同位素,并且随着ACL值增加,环境水和正构烷烃之间的氢同位素分馏增大。  相似文献   

基于投入产出理论的水资源研究进展及水资源管理展望     

杨洋  效存德  王晓明  刘世伟 《冰川冻土》2021,43(1):214-224

近年来,气候变化背景下的水资源问题得到日益增加的关注,其研究从水资源短缺、供需平衡等内容转向适应可持续发展的综合研究。基于投入产出理论的水资源研究,从系统循环的角度分析资源的流动性和持续性,能够揭示水资源-经济社会复合系统中各要素的内在数量关系,提出面向可持续发展的水资源价值观和方法论。首先,从模型拓展和实际应用两条主线梳理了国内外基于投入产出理论的水资源相关研究。在模型方面,概括了投入占用产出模型、水资源投入产出模型和区域间投入产出模型的发展和适用性,对比分析了不同区域间投入产出模型的优缺点。在应用方面,分别从不同时空尺度、驱动力因素等方面对虚拟水、水足迹和水资源优化配置三个热点内容进行了整理,并指出：基于投入产出理论的水资源研究基本建立在价值型模型的基础上;区域间投入产出模型已成为分析区域间经济结构、资源流动等环境问题的重要工具。其次,讨论了投入产出模型在冰冻圈水资源管理中的应用,提出基于服务角度的水资源管理模式。最后,展望了投入产出理论在水资源研究中的应用,以期能够为决策者提供额外的信息以便更好的管理水资源。  相似文献   

寒武纪生物大爆发之后的底栖生态系统工程建造者:以河南地区为例          下载免费PDF全文

刘炳辰  齐永安  代明月  白万备  樊钰超  庆国帅 《地球科学》2021,46(1):148-161

扰动生物作为生态系统工程建造者,通过对沉积底质的改造直接影响沉积物和水体之间的相互作用（营养物质的循环、迁移和存储）,对底栖生态系统工程有重要的影响.遗迹化石作为底栖生物活动的载体,为研究寒武纪大爆发之后底栖生态系统工程建造者的演化规律,并评价底栖生态系统工程建造者对生态系统工程产生的影响提供了依据.对河南地区8个寒武系剖面的遗迹化石数据进行统计,应用现代生物学中生态系统工程影响值的概念,从功能群、阶层、生物灌溉3个方面对底栖生态系统工程建造者进行研究.研究结果表明,寒武系第三阶至鼓山阶底栖生态系统工程建造者功能群类型由生物扩散型扰动者往向上/下运输者转变,阶层逐渐加深,生物灌溉越来越普及,生态系统工程影响值不断增大.鼓山阶至第十阶,遗迹化石类型及结构变化不大,生态系统工程影响值趋于稳定.这表明从寒武纪生物大爆发至鼓山阶,底栖生态系统工程建造者的行为策略发生着明显的进化与创新,生态系统工程建造者不仅开拓了重要的生态空间,而且为其他底栖生物和微生物创造了新的生境,在寒武纪海洋生态系统中扮演着重要的角色.   相似文献