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   

Quantifying groundwater sensitivity and resilience over peninsular India     

Nikhil Kumar  Jhilam Sinha  Chandra A. Madramootoo  Manish Kumar Goyal 《水文研究》2020,34(26):5327-5339

Groundwater in India plays an important role to support livelihoods and maintain ecosystems and the present rate of depletion of groundwater resources poses a serious threat to water security. Yet, the sensitivity of the hydrological processes governing groundwater recharge to climate variability remains unclear in the region. Here we assess the groundwater sensitivity (precipitation–recharge relationship) and its potential resilience towards climatic variability over peninsular India using a conceptual water balance model and a convex model, respectively in 54 catchments over peninsular India. Based on the model performance using a comprehensive approach (Nash Sutcliffe Efficiency [NSE], bias and variability), 24 out of 54 catchments are selected for assessment of groundwater sensitivity and its resilience. Further, a systematic approach is used to understand the changes in resilience on a temporal scale based upon the convex model and principle of critical slowing down theory. The results of the study indicate that the catchments with higher mean groundwater sensitivity (GWS) encompass high variability in GWS over the period (1988–2011), thus indicating the associated vulnerability towards hydroclimatic disturbances. Moreover, it was found that the catchments pertaining to a lower magnitude of mean resilience index incorporates a high variability in resilience index over the period (1993–2007), clearly illustrating the inherent vulnerability of these catchments. The resilience of groundwater towards climatic variability and hydroclimatic disturbances that is revealed by groundwater sensitivity is essential to understand the future impacts of changing climate on groundwater and can further facilitate effective adaptation strategies.  相似文献   

基岩倾角对盆地地震响应的影响分析          下载免费PDF全文

卓发成 《地震工程学报》2020,42(4):1035-1042

为了研究盆地基岩倾角对盆地地表动力反应的影响,选取了一个跨度2 km,深度500 m的二维成层盆地为研究对象进行有限元动力反应分析。以持时0.25 s的狄拉克脉冲作为输入地震动,探讨了P波和SV波垂直入射时,盆地基岩倾角从10°\,20°\,30°\,40°依次增加的情况下盆地地震反应。结果表明:入射波在倾斜基岩处发生波型转化,同时产生面波,在盆地中心区域发生汇聚;随着基岩倾角的增加地表中心处的卓越频率有减小的趋势。  相似文献   

基于点云数据的不规则文物三维重建——以经幢为例     

喜文飞  李灵索  杨勇  李国柱  李春梅  李金平 《测绘通报》2020,(12):87-89

海量点云数据可以较好地构建文物的三维建模，针对文物复杂的表面结构，传统的算法很难达到精细建模，为了解决复杂模型表面的空间三角网构网问题，本文结合空间三角形的法向量构建三角网，以空间三角网表面的曲率为约束条件，构建物体表面的空间三角网，然后对构建的空间三角网进行精细建模。以昆明市文物——经幢为例进行三维重建试验，结果表明，新方法适合室内文物的三维建模，可以达到较好的效果。  相似文献   

融合多源数据的三维建模方法及精度分析     

祖立辉 《北京测绘》2020,(3):347-351

以地面相机影像、低空无人机影像和地面三维激光点云数据为融合对象,研究空地影像融合、低空影像融合地面三维激光点云和低空影像融合三维白模进行三维建模的方法,并对其三维建模精度和建模效果进行综合分析。这3种融合方法进行三维建模丰富了三维模型的色彩纹理信息,提高了三维模型的几何结构精度,能满足较大场景的三维实景模型的建模要求,为数字化古建筑(古文物)保护提供具有较高价值的参考数据。  相似文献   

青海湖沙柳河流域浅层地下水不同时期补给特征          下载免费PDF全文

杨羽帆  曹生奎  曹广超  雷义珍  刘英  兰垚 《干旱区地理》2020,43(3):633-643

地下水稳定同位素组成的时空变化特征可以反映不同时期、不同区域地下水补给来源的差异。通过青海湖沙柳河流域浅层地下水氢氧稳定同位素组成的时空变化特征以及地下水、河水与降雨之间的补给关系的分析，结果显示：季风时期，地下水主要受降雨入渗和河流侧向补给为主，在补给过程中蒸发作用是影响地下水稳定同位素值的主要因素；非季风期，冰雪融水对低值区的地下水影响显著，同时降水的快速入渗则是该时期高值区地下水的主要补给方式之一。地下水同位素高值区，地下水与河水间补给作用较弱，补给时间超过5个月；地下水同位素低值区，地下水与河水补给关系较为密切，补给时间在1~4个月间。本文所得结论可初步反映干旱半干旱内陆流域地下水稳定同位素特征以及补给方式的基本规律，在一定程度上可为流域地下水及其他水体间的转换研究提供科学依据，并为地下水资源管理和水环境治理提供一定理论指导。  相似文献   

气候变化下基于物种与植物耦联机制的小白额雁(Anser erythropus)潜在生境及适宜性研究--以长江流域中下游为例     

向伶  高翔  彭玉辉  梁婕 《资源与生态学报(英文版)》2020,11(2):140-149

气候变化和人类活动通过改变物种生境而影响物种多样性。小白额雁是长江流域中下游的一种具有较高生态价值的食草型濒危候鸟,受气候变化和人类活动威胁。本文以小白额雁为代表性物种,定量分析了气候变化对长江流域中下游候鸟潜在生境及适宜性空间分布格局的影响。采用Maxent模型模拟了当前情景和全球环流模型(GCMs)气候场景下小白额雁潜在生境及其适宜性分布。研究结果表明,小白额雁分布特征与其栖息地周边植物分布呈显著相关关系;运用Maxent模型模拟小白额雁六种主要食源植物的分布特征,并将其结果作为环境变量,将显著改善小白额雁潜在生境及其适宜性模型的模拟性能;在两种典型浓度情景(RCP 2.6和RCP8.5)下,2070年小白额雁潜在生境适宜性面积将下降。为应对气候变化对小白额雁的影响,应采取更加合理的管理措施和保护政策,包括调整保护区的大小、形状和用途。  相似文献   

Integration schemes with substepping algorithms for creep analysis in geomaterials     

Roberto Quevedo  Pedro Firme  Deane Roehl 《国际地质力学数值与分析法杂志》2019,43(7):1467-1487

This paper describes a robust and efficient methodology for predicting displacements, deformations, and stresses in geomaterials that are susceptible to creep. The methodology is based on two integration schemes, which consider substepping algorithms. The first scheme is used for integrating space-time relations in a global sense, whereas the second scheme is used for integrating stress-stain relations in a local sense. Different from previous studies, both integration schemes are easy to implement and general in the sense that they can be applied to any type of creep law. Through an in-house finite element simulator, several numerical tests are performed. They include triaxial and wellbore closure analyses considering soft soils and salt rocks. The results show that the combination of both schemes leads to stable and accurate solutions with reduced computational time.  相似文献   

成矿预测:从二维到三维   总被引：1，自引：0，他引：1  

袁峰  张明明  李晓晖  葛粲  陆三明  李建设  周宇章  兰学毅 《岩石学报》2019,35(12):3863-3874

随着矿产资源勘探方法以及计算机科学技术的不断发展,成矿预测的理论和方法已从定性发展至定量,从二维拓展到三维。近十年来,随着深部矿产资源勘探工作的推进,三维成矿预测研究得到了迅猛发展,相关理论与方法也已逐步走向成熟。本文总结了国内外二维成矿预测研究的现状,同时对近十年来国内外学者在三维地质建模技术、三维成矿预测方法等方面的主要成果和进展做了系统总结和分析。目前,国内外多个地区已相继开展了三维成矿预测工作,并成功圈定多个深部找矿靶区,相关成果为深部找矿勘探工作提供了新的方法和方向。在此基础上,本文对未来三维成矿预测的发展趋势进行展望,相较于传统的二维成矿预测,三维成矿预测往往受限于三维预测信息的缺乏。如何更好的挖掘二维数据在深度方向的指示能力,将二维数据推演至三维环境,利用数值模拟、机器学习等方法开展数据挖掘、充分发挥已有数据的内蕴信息将在未来推动三维成矿预测理论的深入发展,提高三维成矿预测的理论方法及应用实践水平。  相似文献   

Upper ocean high resolution regional modeling of the Arabian Sea and Bay of Bengal     

Suneet Dwivedi  Alok Kumar Mishr  Atul Srivastava 《海洋学报(英文版)》2019,38(5):32-50

In this paper, effort is made to demonstrate the quality of high-resolution regional ocean circulation model in realistically simulating the circulation and variability properties of the northern Indian Ocean(10°S–25°N,45°–100°E) covering the Arabian Sea(AS) and Bay of Bengal(BoB). The model run using the open boundary conditions is carried out at 10 km horizontal resolution and highest vertical resolution of 2 m in the upper ocean.The surface and sub-surface structure of hydrographic variables(temperature and salinity) and currents is compared against the observations during 1998–2014(17 years). In particular, the seasonal variability of the sea surface temperature, sea surface salinity, and surface currents over the model domain is studied. The highresolution model's ability in correct estimation of the spatio-temporal mixed layer depth(MLD) variability of the AS and BoB is also shown. The lowest MLD values are observed during spring(March-April-May) and highest during winter(December-January-February) seasons. The maximum MLD in the AS(BoB) during December to February reaches 150 m (67 m). On the other hand, the minimum MLD in these regions during March-April-May becomes as low as 11–12 m. The influence of wind stress, net heat flux and freshwater flux on the seasonal variability of the MLD is discussed. The physical processes controlling the seasonal cycle of sea surface temperature are investigated by carrying out mixed layer heat budget analysis. It is found that air-sea fluxes play a dominant role in the seasonal evolution of sea surface temperature of the northern Indian Ocean and the contribution of horizontal advection, vertical entrainment and diffusion processes is small. The upper ocean zonal and meridional volume transport across different sections in the AS and BoB is also computed. The seasonal variability of the transports is studied in the context of monsoonal currents.  相似文献