Simulation of Lake-Groundwater Interaction under Steady-State Flow

MODFLOW is one of the most popular groundwater simulation tools available; however, the development of lake modules that can be coupled with MODFLOW is lacking apart from the LAK3 package. This study proposes a new approach for simulating lake - groundwater interaction under steady-state flow, referred to as the sloping lakebed method (SLM). In this new approach, discretization of the lakebed in the vertical direction is independent of the spatial discretization of the aquifer system, which can potentially solve the problem that the lake and groundwater are usually simulated at different scales. The lakebed is generalized by a slant at the bottom of each lake grid cell, which can be classified as fully submerged, dry, and partly submerged. The SLM method accounts for all lake sources and sinks, establishing a governing equation that can be solved using Newton's method. A benchmarking case study was conducted using a modified model setup in the LAK3 user manual. It was found that when there is a sufficient number of layers at the top of the groundwater model, SLM simulates an almost identical groundwater head as the LAK3-based model; when the number of layers decreases, SLM is unaffected while LAK3 may be at a risk of giving unrealistic results. Additionally, the SLM can reflect the relationship between the simulated lake surface area and lake water depth more accurately. Therefore, the SLM method is a promising alternative to the LAK3 package when simulating lake - groundwater interaction.     

Vertical concentration profile of nonuniform sediment

A new formula for the concentration profile of nonuniform sediment is derived using the diffusion differential equation with equilibrium bed concentration.The interaction coefficient for nonuniform sediment particles as a function of both relative diameter and geometric standard deviation of nonuniform sediment is taken into account in the settling velocity.The diffusion coefficient is obtained from the logarithmic velocity profile.This new formula possesses several advantages as follows:(1)avoids theoretical defect of the Rouse formula,which states that the sediment concentration is infinite at the bottom and zero at the water surface.(2)suitable for an arbitrary fraction of nonuniform sediment,and(3)easy to apply with a simple form.The formula yields less difference among concentration profiles for various particles than that for uniform sediment and reveals the lawfor fractional concentration distribution of nonuniform sediment.The calculated concentration agrees well with the measured data from the Yangtze River.     

Impacts of coastal reclamation on tidal and sediment dynamics in the Rui’an coast of China

Ocean Dynamics - Coastal reclamation projects have been extensively constructed along the coastline of the East China Sea over the past decades. To investigate the impact of reclamations on the...     

西安市地裂缝地震效应的理论分析

本文采用有限元方法对西安市地裂缝的地震效应进行了分析,其目的在于探索强震时地裂缝对地面运动的影响。所用方法的理论基础是在双向地震动的作用下求解多质点体系的强迫振动方程组。[M]{(?)}+[C](?)}+[K]{X}=[M]({A_x}(?)。(t)+{A_y}(?)。(t))。式中[M]、[C]、[K]分别为体系的质量、阻尼、刚度矩阵,{x}、{x}、{x}分别为体系自由度的加速度、速度、位移向量,{A_x}、{A_y}为水平和垂直方向的自由度向量,(?)。(t)、(?)。(t)为水平及垂直方向上的基岩强震加速度时程向量。分析时根据西安市地裂缝的具体情况,做了如下简化: 1.裂缝不作为发震构造,即强震时裂缝不是弹性波的发源地。强震是通过铰结支座输入进来的。2.裂缝带在模型上是一向下尖灭的楔体,楔体顶面宽10米,楔体深20米,中间有一宽1米、深2米的裂口。整个模型的土质是层状的,各层土的主要参数在现场测定。裂缝带楔体的参数不易取得,按经验强度取周围原土的一半左右。3.模型厚度为50米,输入地震为El Centro和文县强震记录,输入时将最大加速度值调整为150gal。计算结果表明,西安裂缝带在强震时对地面运动没有显著的影响,如地裂缝带内外的各种反映强震运动特征的指标几乎都没有什么差异。因为地裂缝带从区域上看毕竟是个很小的地质单元体,这样小的规模尚不足以对强震地面运动产生显著的影响。但是,地裂缝带在强震时的永久地形变却是值得注意的。从这一点上看,裂缝带内外地基失效程度必定有很大的差别,从而使裂缝上的震害加重。可见,在强震时,除地裂缝带本身因地基失效使震害加重而外,裂缝基本不对强震地面运动规律产生影响。所以在进行防震规划时,不必在常规的设防带之外再加宽防震地带。     

Analyzing interactions between risk factors for ice disaster in Ning-Meng reach of Yellow River based on grey rough DEMATEL method

Natural Hazards - The ice disaster risk in Ning-Meng reach of Yellow River in China is affected by many factors, and the various risk factors are not independent with each other but present...     

Energy transition,CO2 mitigation,and air pollutant emission reduction: scenario analysis from IPAC model

The salinization of freshwater-dependent coastal ecosystems precedes inundation by sea level rise. This type of saltwater intrusion places communities, ecosystems, and infrastructure at substantial risk. Risk perceptions of local residents are an indicator to gauge public support for climate change adaptation planning. Here, we document residential perspectives on the present and future threats posed by saltwater intrusion in a rural, low-lying region in coastal North Carolina, and we compare the spatial distribution of survey responses to physical landscape variables such as distance to coastline, artificial drainage density, elevation, saltwater intrusion vulnerability, and actual salinity measured during a synoptic field survey. We evaluate and discuss the degree of alignment or misalignment between risk perceptions and metrics of exposure to saltwater intrusion. Risk perceptions align well with the physical landscape characteristics, as residents with greater exposure to saltwater intrusion, including those living on low-lying land with high concentrations of artificial drainages, perceive greater risk than people living in low-exposure areas. Uncertainty about threats of saltwater intrusion is greatest among those living at higher elevations, whose properties and communities are less likely to be exposed to high salinity. As rising sea levels, drought, and coastal storms increase the likelihood of saltwater intrusion in coastal regions, integrated assessments of risk perceptions and physical exposure are critical for developing outreach activities and planning adaptation measures.

     

济阳坳陷义和庄凸起东部燕山期构造负反转及层序地层样式响应

通过钻井、测井与地震数据,依据不整合面分析、断层活动速率分析与地层的"负向结构"分析,在义和庄凸起东部燕山期内识别出一期发生于中晚侏罗世之交的构造负反转,并据此将义和庄凸起燕山期划分为早期与晚期两个阶段.通过单井与连井层序地层分析,分别建立了燕山早期与晚期的层序地层样式,两者在层序结构及内部沉积充填等方面表现出巨大差异.早期层序地层不具有显著的沉积厚度分异,且格架内部充填河流相沉积;晚期因构造负反转而形成小型拉张断陷盆地,沉积厚度分异明显,内部以扇三角洲沉积充填为主,呈现出对构造负反转的显著响应.燕山期构造-层序地层学的研究可为中国东部其他具有相似构造背景盆地前新生代的油气勘探提供借鉴.     

Jurassic granitoid dike in Luodian,Guizhou Province: discovery and geological significance

Acta Geochimica - In this paper, the Jurassic granitoid dike that intrudes into Permian diabase was reported in Luokun, Luodian County, south Guizhou. Zircon LA-ICP-MS U–Pb dating of the...