Water table fluctuation in response to transient recharge from a rectangular basin

A problem of water-table fluctuation in a finite two-dimensional aquifer system in response to transient recharge from an overlying rectangular area is studied. An analytical solution is obtained by using the method of finite Fourier transform to predict the transient position of the water-table. The solution for constant rate of recharge is shown as a special case of the present solution. Effects of variation in the rate of recharge on the growth of two-dimensional groundwater mound is illustrated with the help of a numerical example.Notation A half width of the aquifer [L] - B half length of the aquifer [L] - D half width of the recharge basin [L] - e specific yield - h varying water-table height [L] - h ₀ initial water-table height [L] - h weighted mean of the depth of saturation [L] - K hydraulic conductivity [LT^–1] - L half length of the recharge basin [L] - P(t) time varying rate of recharge [LT^–1] - P ₁ +P ₀ initial rate of time varying recharge [LT^–1] - P ₁ final rate of time varying recharge [LT^–1] - t time of observation [T] - x, y coordinate axes - decay constant [T^–1]     

An analytical solution for water-table fluctuation in a finite aquifer due to transient recharge from a strip basin

Two cases of water-table fluctuation in a finite aquifer in response to transient recharge from a strip basin are investigated. In the first case the aquifer is bounded by open water-bodies, whereas in second one the aquifer is bounded by impermeable boundaries on both sides. Analytical solutions are presented to predict the transient position of the water-table. The solutions are obtained by using finite Fourier sine and cosine transforms.Notations A width of the aquifer [L] - e specific yield - h variable water-table height [L] - h ₀ initial water-table height [L] - weighted mean of the depth of saturation [L] - K hydraulic conductivity [LT^–1] - m,n integers - P ₁ +P ₀ initial rate of transient recharge [LT^–1] - P ₁ final rate of transient recharge [LT^–1] - P constant rate of recharge [LT^–1] - x ₁ distance of left boundary of the strip basin [L] - x ₂ distance of right boundary of the strip basin [L] - t time of observation [T] - decay constant [T^–1]     

Water table fluctuation due to transient recharge in a 2-D aquifer system with inclined base

Recharging of aquifers due to irrigation, seepage from canal beds and other sources leads to the growth of water table near to the ground surface causing problems like water logging and increase of salinity in top soils in many regions of the world. This problem can be alleviated if proper knowledge of the spatio — temporal variation of the water table is available. In this paper an analytical solution for the water table fluctuation is presented for a 2-D aquifer system having inclined impervious base with a small slope in one — direction and receiving time varying vertical recharge. Application of the solution in estimation of water table fluctuation is demonstrated with the help of an example problem.Notations A length of the aquifer [L] - B width of the aquifer [L] - D mean depth of saturation [L] - e specific yields - h variable water table height [L] - K hydraulic conductivity [LT ^–1] - P(t) transient recharge rate [LT ^–1] - P ₁+P _o initial rate of transient recharge [LT ^–1] - P ₁ final rate of transient recharge [LT ^–1] - q slope of the aquifer base in percentage - r decay constant [T ^–1] - t time of observation [T] - x, y coordinate axes - x ₂–x ₁ length of the recharge basin [L] - y ₂–y ₁ width of the recharge basin [L]     

Two-Dimensional Modelling of Water Table Fluctuations due to Time-Varying Recharge from Rectangular Basin

A prior knowledge of the water table fluctuations, in response to the proposed recharge scheme, is essential to achieve the preset objectives of ground water resources management. In this paper an analytical solution of the linearised Boussinesq's equation is presented to predict the spatio-temporal variation of the water table in an aquifer system in response to time-varying recharge applied through a rectangular basin. The recharge function is approximated by introducing a number of line segments depending on its nature of variation. The solution is obtained by using finite Fourier sine transform and its application is demonstrated for a case of periodically applied recharge.     

Water-table variation in a sloping aquifer due to random recharge

Variation in the level of the water table is closely linked with recharge. Therefore, any uncertainty associated with the recharge rate is bound to affect the nature of the water-table fluctuation. In this note, a ditch-drainage problem of a sloping aquifer is considered to investigate the effect of uncertainty in the recharge rate on water-table fluctuation. The rate of recharge is taken as an exponentially decaying function with its decay constant as a Gaussian random variable. Expressions for the first two moments of the water-table height, i.e. mean and standard deviation, are presented. By using these expressions, the effect of uncertainty in the recharge rate on the water-table fluctuation has been analyzed with the help of a numerical example.     

Response of an Unconfined Aquifer Induced by Time Varying Recharge from a Rectangular Basin

An analytical solution is developed to predict spatio-temporal variation of the water table in a 2-D aquifer system which is receiving transient recharge from an overlying basin of rectangular shape. The transient recharge function is approximated by a number of line segments. Application of the solution is demonstrated with the help of an example problem.     

On the Prediction of Ground-Water Mound Formation in Response to Transient Recharge from a Circular Basin

An analytical solution of the linearized Boussinesq equation is developed to predict the formation of a ground-water mound in an aquifer system in response to localized time-varying recharge. The recharge is applied from a centrally located circular basin. The solution is obtained using an eigenvalue-eigenfunction method. The solution for a constant recharge rate is shown as a special case of the solution for a time-varying recharge rate. Application of the solution to predict ground-water mound formation is demonstrated by a numerical example. Effects of variation in the rate of reachrge, size of recharge basin and the saturated hydraulic conductivity on the growth of the water-table are also investigated.     

Evolution of the Water Table in a Finite Aquifer Due to Transient Recharge from Two Parallel Strip Basins

Understanding the dynamic response of phreatic aquifers due to recharge is most important for the proper management of ground-water systems. In this paper an analytical solution is developed to describe the water-table fluctuation in a finite aquifer system due to transient recharge from two parallel strip basins. Application of the solution in the prediction of spatiotemporal variation of the water table and in the sensitivity analysis of the effects of various controlling parameters on the water-table fluctuation is demonstrated with the help of an example problem.     

涠洲岛地下水人工回灌的可行性分析

通过对北海市涠洲岛水资源的供需现状和发展趋势分析,提出实施地下水人工回灌的必要性和可行性;在对地质构造、水文地质条件、水源条件、工程效益等进行分析后,认为在涠洲岛实施地下水人工回灌是可行的。     

Impact of sedimentation on groundwater recharge at Sahalanowt Dam,Salalah, Oman

Recharge dams in Oman detain floods to recharge groundwater. The impact of sedimentation on recharge at Wadi Sahalanowt Recharge Dam, in Salalah, Oman, was evaluated using field data and numerical modelling. Analysis of the thickness of sediments after flood events shows that maximum depositions were at the same locations after each event, coinciding with the lowest positions in the wadi. Numerical modelling suggests that the current practice of periodic removal of sediments will restore the storage capacity of the reservoir, but that ploughing or raking of the underlying native sedimentary rocks could be required to significantly improve infiltration rates.     

外源地下水补给二连浩特盆地

为了查明二连浩特地下水的补给来源,采用同位素地球化学分析方法,研究了二连浩特地区的大气降水、地表水、土壤水与地下水之间的转化关系。结果表明:土壤含水率在蒸发作用下长期处于亏缺状态,入渗降水不足以改变土壤含水亏损状态;土壤水的氘氧值相比大气降水贫化,将土壤水、地下水和当地降水的氘氧同位素比较发现,土壤水主要来自于地下水补给;西藏羌塘盆地的降水氘氧关系与二连浩特地下水的氘氧关系相似,表明二连浩特盆地的地下水接受外源水补给;二连浩特盆地玄武岩喷发地区广泛分布着铁白云岩、红土、钙华、硅华、膏盐等矿物,矿物中的Fe、Mg、Ca、Si等元素,可能来自深循环地下水;铁白云岩与红土的形成,表明深循环地下水曾经历过了高温过程;外源水可能来自青藏高原河流或湖泊的渗漏水,深循环地下水通过火山熔岩管道补给二连浩特等火山玄武岩地区的地下水。根据地下水深循环原理,在二连浩特火山口附近打出了4口自流井,单井自流水量达到30 m~3/h。     

滨海深部含水层地下水排泄量评估

为了进一步计算评估滨海深部含水层地下水排泄量,以一个海底深部承压含水层系统为例,包括承压含水层及上覆弱透水含水层(海底),在内陆补给上考虑了与时间无关的年平均补给(常数)和由季节性降雨引起的周期性补给两种情况,从而建立了一个描述承压含水层中海底地下水排泄的数学模型,并得到其解析解。继而利用解析解分析了位于美国南大西洋Onslow海湾的SGD。结果显示,SGD排泄宽度变化范围为0.5~3.0 km,在承压含水层中海岸线处高于平均海平面1.0 m的水头值,其所产生的SGD速率为1.1~10.0 m2/d。     

南水北调工程北京段地下水回灌对含水层水质影响

采集南水北调北京蓄调池附近地下砂样、地下水水样、丹江口水库水样,通过室内试验模拟含水层方法,分析不同比例的丹江口水库水、地下水与含水层介质混合后的水化学作用,探讨水化学成分随时间的变化规律。结果表明,模拟含水层在可溶盐溶解作用、矿物溶解-沉淀作用、微生物作用、阳离子交换吸附作用等影响下,各项水质指标都发生了变化,但均符合地下水质量Ⅰ类或Ⅱ类标准。     

苏北盆地地下水补给源问题讨论

分析对比地下水和地表水中的碳酸氢根含量,推测深部CO_2释放造成碳库中的"死碳"混入地下水中,因此14C定年不适用于苏北盆地。通过氚分析确定地下水的循环周期约为40 a,氚与氢氧同位素数据都不支持地下水来自长江渗漏水侧向补给的结论。结合水文地质证据,推断苏北承压水可能接受深循环地下水越流补给,隐伏火山口与断裂带可能是地下水的排泄通道。     

辽阳首山地下水人工回灌可行性研究

辽阳首山地区由于地下水长时期的过量开采,地下水位大幅下降,形成了地下水漏斗区,产生了一系列生态环境问题。通过对该地区地下水开发利用现状和供需矛盾分析,研究了实施地下水人工回灌的必要性和可行性;在对水文地质条件、回灌水源条件、水质等进行分析后,认为在首山地区实施地下水人工回灌是可行的,并提出了几点建议。     

基于GIS的山东省地下水回灌补源管理信息系统

山东省地下水回灌补源管理信息系统是在MapGIS平台基础上开发完成的,它以山东省地下水回灌补源现状和前景预测及评价为主要研究内容.软件包括系统介绍、专业计算、信息查询、专题地图制作及帮助等模块,由数据库、图形库、属性库及模型库组成.该系统将有关山东省地下水回灌补源的所有信息包括文字、图形、影像、数据、声音等按时间、空间进行分类并做成不同的工程项目,进行空间分析和属性的汇总、统计、计算和查询.应用表明,系统通用性好,实用性强.     

建筑屋面雨水有压回补地下水理念与潜力评估

城市雨水回补地下水对增加城市地下水资源、减轻内涝灾害具有重大意义。屋面雨水水质较好,且具有高水头特点,并无需外界提供电能、不占据多余空间,可实现雨水收集、快速净化,形成屋面雨水有压回补地下水模式,增加地下水回补率。该技术理念提出后,尚处于研究阶段,故本文以天津大学新校区为研究区,通过水泵加压回补地下水的现场数据推导出了半经验公式,选取与实地状况基本相符的渗透率等相关参数,对该模式进行相关计算与潜力评估。利用天津市暴雨公式计算了不同降雨重现年及历时的设计雨强,并计算出本模式应用于研究区的不同设计情况下的回补率。计算结果显示,回补率与降雨历时(建筑屋面汇水或滞留时间)呈正相关关系;假设建筑屋面雨水滞留时间为24 h时,25年一遇以内降雨回补率大于90%,50年一遇和100年一遇降雨回补率达85%以上。本文论证了该种模式具有很强的应用价值,对雨水回补地下水技术研究有一定的参考价值。     

地下水补给影响下的河流水质模糊模拟

基于河流水环境系统的模糊性、不精确性,采用三角模糊数描述和表征沿岸地下水水文地质参数,建立了计算地下水补给量和补给强度的模糊模型。并进一步在三角模糊数的基础上,构建了考虑地下水补给影响的一维稳态河流水质模糊模拟模型。将该模型应用于淮河流域某支流的水质模拟研究。计算中采用α-截集技术,得到了各控制断面模糊数形式的污染物浓度值,并将其与确定性模型计算结果进行对比分析。分析结果表明,以三角模糊数原理模拟和表征考虑地下水补给影响的河流水体污染物浓度变化规律在理论上可行,其计算结果可信。     

Managed aquifer recharge in community water supply: the Finnish experience and some international comparisons

This paper analyzes the use of managed aquifer recharge (MAR) in community water supply in Finland and presents some international experiences for comparison. The framework of MAR consists of the natural environment and physical infrastructure, as well as socio-economic aspects, all of which are interrelated. Local conditions form the basis of an MAR system and to a large degree determine infiltration options and the most suitable methods. Finnish hydrogeology, climate and local conditions are highly comparable to those in Sweden but differ from those of other parts of Europe, Australia, the USA and Asia. This article provides a holistic view of MAR not only as a technical means of resource enhancement for water supply but also as an element interacting with the natural environment and society.     

地下水补给影响下的河流水质模糊模拟

摘 要：基于河流水环境系统的模糊性、不精确性，采用三角模糊数描述和表征沿岸地下水水文地质参数，建立了计算地下水补给量和补给强度的模糊模型。在将水质模型参数定义为三角模糊数的基础上，构建了考虑地下水补给影响的一维稳态河流水质模糊模拟模型。作为案例，将上述模型应用于淮河流域某支流水质模拟研究。采用-截集技术，计算得到各控制断面模糊数形式的污染物浓度值，并与确定性模型计算结果进行比较。实例研究表明，以三角模糊数原理模拟和表征考虑地下水补给影响的河流水体污染物浓度变化规律，理论上可行，计算结果可信，较好地弥补了传统确定性模型的不足。