岩溶地下水特点与研究热点

岩溶区覆盖了超过20%的地壳面积,岩溶水作为供水水源发挥的作用举足轻重。然而,岩溶介质的非均质性十分突出,是有不同水力性质的双重介质系统,使得岩溶地下水系统入渗过程亦具有二元性。岩溶区降水、地表水和地下水间的关系十分密切、转化规律呈复杂的非线性关系。这使得岩溶地下水系统的水文过程、流速和排泄范围易受外界影响而多变。岩溶泉流量变化具有明显的尺度效应和多重分形特征,流量构成复杂多变。同时,受多变的岩溶水文过程和生物地球化学作用的影响,岩溶地下水系统的水化学变化对环境十分敏感。因此,传统方法不能直接应用于岩溶地区的水文研究,水文研究常见的困难在岩溶区被成倍放大。目前,岩溶水文研究相对滞后。我国岩溶类型多样,在国际上有范例性。在岩溶水文过程和岩溶地下水CO_2-H_2O-CaCO_3系统的研究中取得进展。岩溶地下水系统水文过程对全球变化的响应和反馈,岩溶地下水资源和水环境,以及岩溶水文系统模拟等方面将是未来的研究热点。     

鸡东县含水层及地下水类型

鸡东县地下水的形成与分布除受气象水文条件影响下,还受地层岩性及地质构造条件的控制。根据含水介质岩性和含水空隙类型,鸡东县内地下水类型可划分为松散岩层孔隙潜水、碎屑岩类型孔隙裂隙承压水、玄武岩孔洞裂隙水和一般基岩裂隙水。     

裂隙-管道介质泉流量衰减过程试验研究及数值模拟

岩溶多重介质含水系统泉流量特征的研究对岩溶水资源的开发利用具有重要的指导意义。利用自主研发的裂隙-管道介质物理模型,模拟岩溶裂隙-管道介质的泉流量衰减过程,设计多组试验探讨不同因素对泉流量衰减过程的影响。试验结果表明,衰减过程随释水介质的变化分为3个亚动态;衰减系数的大小主要受泉口大小、补给状态、含水介质初始蓄水状态的影响。基于物理试验结果,通过Visual MODFLOW软件结合等效渗透系数法建立符合物理模型机制的水流数值模型,对数值模型进行参数灵敏度分析,研究模型内部结构对泉流量过程的影响。结果表明,排水沟的综合水力传导系数对泉流量过程影响最大,垂直层面裂隙等效渗透系数的影响次之,管道等效渗透系数的灵敏度再次之,泉流量过程对层面裂隙等效渗透系数最不敏感。     

岩溶地下水系统演化的数值模拟

为了研究岩溶地区泉域系统演化过程及对泉流量进行预测,耦合了渗流模型和岩溶动力模型,对均质和非均质2种条件下泉域系统进行了溶蚀演化模拟。从模拟结果上可以看出,均质含水系统初期水位变化较小,中后期下降明显,而非均质含水系统初期下降明显,中后期水位稳定;在张开度方面,非均质模型在相同时段内张开度的最在值却比均质系统要大4~5 cm。2个泉域系统的泉流量都经过了初期较小,中后期迅速增大的过程,只是增大的时间和每个时间点的泉流量不同,非均质系统增大时间更早,流量更大,分别用指数函数和多项式函数来拟合了均质和非均质系统泉流量过程曲线。研究结果为岩溶地下水系统演化模拟提供了一个新方法,同时也为岩溶地区地下水资源评价研究提供了科学依据。     

沙颍河干流与地下水水量交换研究

以沙颍河干流界首至阜阳段为研究区,建立河流与地下水水量交换的数值模型,研究其主要河流与地下水之间的水量交换关系。在研究中发现：排泄河流是地下水的主要排泄方式之一,地下水与地表水的水量交换主要表现为地下水补给地表水。河流与地下水的交换水量与河流水力传导系数C直接相关,基本呈指数关系。当C值为100 m²/d,沙颍河干流高洪水位期间,河流对地下水的补给强度为4.77×10^-6m³/（s·km）,在距离河流小于1000 m范围内的潜水水位受补给影响明显;在枯水季节,地下水对河流平均补给强度为7.26×10^-3m³/（s·km）。枯水季节地下水对河流的补给强度较大,过度开采可能引起地下水对沙颍河的补给量减少,对枯水季节沙颍河河道流量产生重大负面影响。     

落水洞对裂隙-管道介质排水过程的影响

利用自行研制的裂隙-管道介质物理模型进行多组试验,探究落水洞对介质排水过程的影响。对裂隙-管道介质按照介质空隙结构特点进行分区,引入反映介质排水过程中水体排泄快慢的单位时间排水量,进而得到对应不同介质分区和介质整体的四个单位时间排水量。利用单位时间排水量分析九种落水洞横截面积对裂隙-管道介质排水过程的影响。结果表明:落水洞横截面积的增大对裂隙-管道介质结构的影响为增大其储水空间和导水空间;落水洞横截面积的增大会加快裂隙-管道介质的排水过程,排水过程对落水洞横截面积增大的响应在横截面积的增大量达到某一阈值后才会发生,该阈值和介质空隙结构有关;排水过程的三个不同阶段的阈值不同,末期的阈值小于初期、中期的阈值。     

地下水流速及介质非均质性对重非水相流体运移的影响

重非水相流体(DNAPL)在地下介质中的运移分布受多种因素影响,包括DNAPL的物化性质、泄漏速率、地下水流速和介质非均质性等。本文采用地质统计方法生成渗透率随机场刻画非均质性,运用T2VOC模拟不同流速情形下DNAPL在均质/非均质介质中的运移分布,以评估地下水流速和非均质性对DNAPL运移的影响。研究结果表明,地下水流速的增大显著促进了DNAPL的水平和垂向运移。相同流速情形下,非均质性的增强使得DNAPL污染羽分布形态及运移路径的空间变异性增强,出现明显的蓄积和绕流。当DNAPL运移的优势通道方向与流速方向相反时,水流对DNAPL水平运移的促进作用将减弱,反之,其促进作用增强。随着流速与非均质性的同时增强,水平方向上污染羽的扩散范围增大,另外水平和垂直方向上质心位置(一阶矩)及展布范围(二阶矩),污染池起始位置及其长度的空间变异离散程度增大。     

基于Monte Carlo方法的地表水地下水耦合模拟模型不确定分析

为分析参数的不确定性对地表水地下水耦合模拟模型输出结果的影响,本文运用Monte Carlo方法对地表水地下水耦合模拟模型进行不确定性分析,并根据不确定性分析结果进行生态恶化风险评估。以石头口门水库上游饮马河汇水流域为例,建立地表水地下水耦合模拟模型,并运用HydroGeosphere(HGS)软件求解。利用局部灵敏度分析方法甄选出耦合模拟模型中灵敏度较高的参数,作为随机变量。最后,运用Monte Carlo方法对耦合模拟模型进行不确定性分析。为了减少不确定性分析过程中的计算负荷,应用Kriging方法,建立耦合模拟模型的替代模型。结果表明:地表水地下水耦合模拟模型中灵敏度较高的参数为渗透系数、孔隙度和曼宁粗糙系数,其中渗透系数的变化不仅对耦合模型中地下水水位产生影响,也对地表水流量产生影响;Kriging替代模型可以在保证一定精度的条件下大幅度减少计算负荷;风险评估结果表明,在当前的水资源开发利用条件状态下,研究区地下水生态环境恶化风险的概率为6%,地表水生态环境恶化风险概率为15%。     

地下水位匀速下降条件下层状非均质多孔介质给水度的初步研究

本文通过室内实验验证了水位匀速下降条件下垂向一维土壤水分运动的数学模型和计算程序,并用数值模拟方法探讨了层状非均质介质给水度的变化规律,包括层状非均质条件(夹层性质、位置和厚度)、水位降速以及初始水位埋深对给水度变化规律的影响。     

岩溶管道网络数值模拟方法研究进展

采用数值模拟的方式获得管道网络空间信息是开展岩溶含水层非均质性研究的有效手段。介绍了近几年国内外有关岩溶管道网络数值模拟方法的研究进展,系统地总结了管道网络系统演化过程及溶管道网络结构模拟方法的应用及取得的相应成果。管道网络系统演化过程模拟,有利于清晰的理解岩溶演化过程,并能够提供较为精确的关于空隙、管道的演化信息。但该种方法很难反映出真实管道网络系统的空间特征。溶管道网络结构模拟方法,致力于对管道网络的空间特征刻画,目前主要存在的模型有全局式模型、分布模型及非均质模型。这些成果丰富和发展了岩溶管道网络数值模拟方法,对于岩溶含水层水资源开发利用和保护具有重要理论意义和实用价值。     

Global analysis of sensitivity of bioretention cell design elements to hydrologic performance

Analysis of sensitivity of bioretention cell design elements to their hydrologic performances is meaningful in offering theoretical guidelines for proper design. Hydrologic performance of bioretention cells was facilitated with consideration of four metrics: the overflow ratio, groundwater recharge ratio, ponding time, and runoff coefficients. The storm water management model (SWMM) and the bioretention infiltration model RECARGA were applied to generating runoff and outflow time series for calculation of hydrologic performance metrics. Using a parking lot to build a bioretention cell, as an example, the Morris method was used to conduct global sensitivity analysis for two groups of bioretention samples, one without underdrain and the other with underdrain. Results show that the surface area is the most sensitive element to most of the hydrologic metrics, while the gravel depth is the least sensitive element whether bioretention cells are installed with underdrain or not. The saturated infiltration rate of planting soil and the saturated infiltration rate of native soil are the other two most sensitive elements for bioretention cells without underdrain, while the saturated infiltration rate of native soil and underdrain size are the two most sensitive design elements for bioretention cells with underdrain.     

Spatial planning for adapting to climate change.

During the past decades human interference in regional hydrologic systems has intensified. These systems act as an integrating medium. They link climate, human activities and ecologic processes through groundwater and surface water interactions. For simulating these linkages an integrated regional hydrologic model has been coupled to an ecologic evaluation model. The simulated ecologic effects of climate change on mesotrophic riverine grasslands are clearly positive. Simulation results also indicate a high sensitivity of the peak discharges to the precipitation. For modelling the long-term development of land use and water management an integrated 'bio-economic' model has been constructed. It includes a model for the development of agriculture. Results for the autonomous development in reaction to climate change indicate a strong increase of field drainage by agriculture. This development would substantially reduce the predicted positive effects of climate change on riverine grasslands. The challenge is to guide regional developments in such a manner that opportunities for improving nature are not lost, but that at the same time the peak discharges are kept under control. Flow retardation in the 'fine arteries' of the upstream areas appear to be a viable option for the latter. The bio-economic model can provide help in anticipating on climate change through spatial planning.     

Simulating Unsaturated Zone of Soil for Estimating the Recharge Rate and Flow Exchange Between a River and an Aquifer

Coupling surface water and groundwater models dynamically based on a simultaneous simulation of saturated and unsaturated zones of soil is a useful method for determining the recharge rate and flow exchange between a river and an aquifer as well as simultaneous operation of water resources systems. Thus, the main objectives of this study are to investigate the effects of surface water and groundwater interactions through their systematic simulation and to create a dynamic coupling between surface water and groundwater resources of the area by relevant mathematical models. Accordingly, hydrologic soil moisture method and MODFLOW model were employed to simulate the unsaturated and saturated zones, respectively. The results revealed that simultaneous simulation of the saturated and unsaturated zones of the soil can illustrate the interaction between surface water and groundwater at any spatial and temporal intervals well through using complete hydroclimatological balance components in the form of a coupled model. The application of this method in the Loor-Andimeshk Plain, located in the southwest of Iran, showed that aquifer recharge through the plain area from November to March is due to precipitation. On the other hand, in the warm months (June to September), the plain is merely fed through irrigation water penetration. As the level of river water in both Dez and Balarood rivers is higher than the Loor-Andimeshk aquifer level, hence the exchange occurs as a leakage from the river to the aquifer. The highest and lowest values of average exchangeable water in Balarood River occur in March and April and in Dez River are from June to September.

     

Simulation of rainfall-underground outflow responses of a karstic watershed in Southwest China with an artificial neural network

Karstic aquifers in Southwest China are largely located in mountainous areas and groundwater level observation data are usually absent. Therefore, numerical groundwater models are inappropriate for simulation of groundwater flow and rainfall-underground outflow responses. In this study, an artificial neural network （ANN） model was developed to simulate underground stream discharge. The ANN model was applied to the Houzhai subterranean drainage in Guizhou Province of Southwest China, which is representative of karstic geomorphology in the humid areas of China. Correlation analysis between daily rainfall and the outflow series was used to determine the model inputs and time lags. The ANN model was trained using an error backpropagation algorithm and validated at three hydrological stations with different karstic features. Study results show that the ANN model performs well in the modeling of highly non-linear karstic aquifers.     

Artificial Neural Network (ANN) Based Modeling for Karstic Groundwater Level Simulation

A relatively new method of addressing different hydrological problems is the use of artificial neural networks (ANN). In groundwater management ANNs are usually used to predict the hydraulic head at a well location. ANNs can prove to be very useful because, unlike numerical groundwater models, they are very easy to implement in karstic regions without the need of explicit knowledge of the exact flow conduit geometry and they avoid the creation of extremely complex models in the rare cases when all the necessary information is available. With hydrological parameters like rainfall and temperature, as well as with hydrogeological parameters like pumping rates from nearby wells as input, the ANN applies a black box approach and yields the simulated hydraulic head. During the calibration process the network is trained using a set of available field data and its performance is evaluated with a different set. Available measured data from Edward??s aquifer in Texas, USA are used in this work to train and evaluate the proposed ANN. The Edwards Aquifer is a unique groundwater system and one of the most prolific artesian aquifers in the world. The present work focuses on simulation of hydraulic head change at an observation well in the area. The adopted ANN is a classic fully connected multilayer perceptron, with two hidden layers. All input parameters are directly or indirectly connected to the aquatic equilibrium and the ANN is treated as a sophisticated analogue to empirical models of the past. A correlation analysis of the measured data is used to determine the time lag between the current day and the day used for input of the measured rainfall levels. After the calibration process the testing data were used in order to check the ability of the ANN to interpolate or extrapolate in other regions, not used in the training procedure. The results show that there is a need for exact knowledge of pumping from each well in karstic aquifers as it is difficult to simulate the sudden drops and rises, which in this case can be more than 6 ft (approx. 2 m). That aside, the ANN is still a useful way to simulate karstic aquifers that are difficult to be simulated by numerical groundwater models.     

Rainfall-Driven Spring Hydrograph Modeling in a Karstic Water System,Southwestern China

Karstic water systems are usually characterized by high heterogeneity and lack boreholes and points of observation. Thus, a study of the karstic water system using lumped parameters may help distinguish the degree of the flow structure, the influence of any wide conduits, the controlling effect of stored reserves, and other hydrologic factors. A modified Darcian model derived from Criss and Winston (Geophys Res Lett 30(6):1314–1317, 2003) was developed in this study and used to model spring discharges in a highly karstified water system in Houzhai, Guizhou Province, China. The modified model successfully reproduced the discharge responses of the Houzhai karstic water system by using two lumped parameters. After analyzing 28 storm events, the authors obtained the parameter values which reflect the lag time to the rainfall input signal and verified the parameter values by spectral analysis results. The sensitivity analysis of the two lumped parameters indicated that the immediate rainfall event is the dominating factor influencing the discharge response.     

江汉平原西缘地下水水文地球化学过程研究

鄂西丘陵山区地下水向江汉平原运移是较复杂的水文地球化学过程,通过数理统计、水化学分析、Gibbs图以及水文地球化学模拟等方法对江汉平原西缘不同类型地下水运动及其化学组分变化规律进行了研究。结果表明:裂隙岩溶水主要化学类型为HCO_3-Ca和HCO_3-Ca+Mg型,碎屑岩类裂隙水为HCO_3-Ca和HCO_3-Ca+Na型,孔隙水以HCO_3-Ca型为主。方解石和白云石的溶解是丘陵山区主要的水文地球化学过程,孔隙水和裂隙水以岩盐和石膏的溶解为主,裂隙水中还存在阳离子交换吸附作用,少量孔隙水受蒸发-沉淀作用的影响。地下水由丘陵山区向平原区径流过程中发生了石膏以及少量岩盐和钾长石的溶解,同时伴随着阳离子交换吸附和硝化反应,方解石和少量的钠长石因为过饱和而发生沉淀。     

落水洞对裂隙-管道介质泉流量衰减过程影响的试验研究

岩溶裂隙-管道是我国西南地区的主要地下储水空间和导水通道,落水洞是岩溶地区临时性吸收地表水流的重要过水通道,在西南地区分布密集。开展落水洞大小对裂隙-管道介质中泉流量过程影响的研究,对指导岩溶水可持续开发利用和推动岩溶水研究具有深刻意义。文章研究了落水洞对泉流量衰减过程的影响,利用自制的裂隙-管道物理模型,模拟落水洞不同断面尺寸、填充程度下的泉流量衰减过程,由衰减曲线探求衰减系数受不同因子的敏感程度。试验表明:泉流量衰减过程可分为三个亚动态,大致符合指数型衰减。其中,第一亚动态的衰减系数受落水洞断面尺寸影响较大,落水洞断面尺寸越小,衰减系数越大;落水洞的填充程度越高,衰减系数越大。     

灌区地表水—地下水耦合模型的构建

为了定量描述灌区水平衡要素及其转化关系,构建了灌区地表水-地下水分布式模拟耦合模型。通过改进SWAT模型的稻田及旱作物水分循环、蒸发蒸腾量和渠系渗漏计算等模块,建立了灌区地表水分布式模拟模型;以SWAT模型中的水文响应单元(HRU)和MODFLOW模型中的有限差分网格(cells)作为基本交换单元,将改进SWAT模型的地下水补给量计算值加载到MODFLOW模型的地下水补给模块,实现了灌区地表水-地下水分布式模拟模型的耦合。耦合模型在柳园口灌区的应用结果表明,该模型能够准确模拟和预测灌区地表水和地下水的动态变化,为灌区水管理提供了科学依据。     

杨梅河流域“海绵型”综合管廊水文效应模拟EI北大核心CSCD

以广州市国家综合管廊试点区域——杨梅河流域为研究对象,利用SWMM和SUSTAIN模型对传统开发情景、传统综合管廊情景、低影响开发情景、低影响开发和综合管廊联合作用的“海绵型”综合管廊情景下的水文效应进行对比评估,结果表明:实测降雨条件下,SWMM模型的模拟结果与流域内涝实际情况相符,证明该模型适用于杨梅河流域水文效应研究;结合SWMM和SUSTAIN模型的优势,将SUSTAIN模型中的低影响开发优化布局方案输入至SWMM模型进行水文模拟,使得低影响开发布局更科学合理;“海绵型”综合管廊情景下,溢流量削减效果最佳,50 a重现期设计降雨条件下溢流总量削减率超过60%,与“快排”模式下的传统综合管廊情景相比,“海绵型”综合管廊使杨梅河出水口峰值流量明显降低,峰现时间也相应延迟。