盆地多级次地下水流系统盐分运移实验模拟

地下水年龄和滞留时间包含了地下水循环和演化的重要信息,被广泛用于盆地地下水循环模式的研究.使用多级次地下水流系统演示仪,实验模拟了三级水流系统模式中地下水年龄及滞留时间分布.研究发现,盆地底部、区域流线的下游、盆地滞留区最晚响应;浅部的局部水流系统稳定后的浓度值相对较低;中间水流系统相对深部的区域水流系统也较低,滞留区...     

利用CFC研究地下水混合作用——以关中盆地浅层地下水为例

从介绍了CFC在识别地下水混合中的应用入手,将此方法实际应用于关中盆地浅层下水研究。理论分析表明CFC浓度比值不受地下水混合作用的影响,利用CFC浓度年龄和CFC比值年龄可分析地下水混合作用,并可估算新水所占的比例。关中盆地下水CFC浓度从山前向渭河谷地有下降趋势,反映地下水以侧向流动为主,山前补给的新水与含水层中的老水有混合作用。地下水中新水所占的比例可达50%以上,表明该区地下水较易接受现代水补给。     

迭代法在现代地下水年龄估算中的应用——以银川平原为例

为克服应用氚同位素方法确定现代地下水年龄过程中存在的,需确定地下水系统输入项的历史背景浓度问题,本文根据地下水同位素数学物理方程,以全混模型为例,利用不同时期地下水同位素的测试结果,通过数学迭代运算,推导出计算现代地下水年龄的计算公式。该方法不仅可以很好地解决地下水系统输入项氚背景浓度恢复时间序列较长的问题,而且对于提高地下水的定年精度具有十分重要的意义。该方法应用到银川平原取得良好的效果,研究表明银川平原浅层地下水的周转时间为30 a。      

CFCs法在鄂尔多斯白垩系地下水盆地浅层地下水年龄研究中的应用

鄂尔多斯白垩系地下水盆地是中国重要的能源基地,利用CFCS方法对鄂尔多斯白垩系地下水盆地年轻地下水年龄进行测定,取得了比较准确的结果。结果表明,盆地地下水系统可以分为局部地下水系统、中间地下水系统和区域地下水系统。地下水盆地内局部地下水系统地下水循环更替快,年龄为20 a左右,地下水年龄随深度增加而增加;中间地下水系统和区域地下水系统地下水循环更替相对较慢,年龄大于70 a,可以寻求14C等其他同位素方法确定准确年龄。     

反向地球化学模拟技术在地下水14C年龄校正中应用的进展与思考

地下水¹⁴C年龄校正一直是地下水年代学研究中的一个热点问题,将反向地球化学路径模型与同位素质量传输模型耦合起来,在综合考虑不同碳源、不同水文地球化学反应对¹⁴C质量传输影响的基础上,提出了一种新的综合性的校正方法,从而使地下水¹⁴C定年技术得到了进一步发展。识别深层地下水演化过程中影响¹⁴C浓度变化的主要因素并定量确定其对地下水¹⁴C浓度的影响程度是地下水¹⁴C校正的精度和可信度的重要考虑因素;在应用水文地球化学路径模拟技术进行地下水¹⁴C年龄校正时,必须要充分考虑地下水补给环境特点以及反向地球化学模拟模型中的非可行解的排除。     

ASMWIN在地下水资源评价中的应用

以山东省费县朱田地下水盆地为例,阐述了含水层模拟模型软件包(ASMWIN)的应用方法与步骤,包括模型建立、模型区水文地质条件概化、模型识别与校正及在地下水补给量计算与水位预测方面的应用等。     

应用氚和14C方法确定柴达木盆地诺木洪地区地下水年龄

以柴达木盆地的诺木洪为研究区,利用氚与¹⁴C方法计算了当地各水体的年龄,分析地下水年龄分布特征及其可更新能力。结果表明：山区至冲洪积扇中部地下水年龄为15~18 a,为1952年之后补给的现代水,更新能力较强;冲洪积扇前缘地下水年龄不超过2 ka,具有现代水与古水混合的特征,更新能力较差;溢出带到盆地中心地下水年龄急剧变老,变化范围为5~28 ka,据此推测研究区溢出带位置的隐伏断层具阻水性质,该位置的地下水基本无更新能力。     

鄂尔多斯盆地白垩系沉积建造对地下水的控制

有关鄂尔多斯盆地地下水系统,前人已做过大量的研究,总结出不少的成果和规律.但从沉积建造方面研究地下水系统的不多.本文详细研究了白垩系沉积建造的特征和规律,探讨其对于研究区白垩系地下水系统的形成、富集和赋存的影响和控制,对于研究区白垩系地下水的开发和利用提供了重要的依据.     

碳酸盐岩地区地下水年龄的同位素研究

在太原地区测试了240个地下水、地表水和大气降水的~3H、~14C和~13C值。结果表明研究区有三维地下水流动系统,岩溶地下水补给、径流、排泄区应选用不同的地下水混合模型。通过年轻水混入校正、死碳稀释校正和~14C初始浓度变化校正,求得了研究区内13个点上的地下水年龄,并据此计算了地下水流速和径流量。      

非均质含水层中地下水年龄数值模拟

地下水年龄数值模拟是近年来国际地下水领域的一个全新研究方向。在简单介绍地下水年龄数值模拟相关理论和方法基础上,通过一个简单算例模拟对比了稳定流条件下不同非均质含水层中的水流运动和年龄分布,探讨了夹层透水性的强弱对地下水年龄分布的影响。结果表明,在地下水系统保持补径排通量不变的前提下,弱透水夹层的存在对于特定区域地下水的深部循环和更新具有积极作用。同时,在模拟区域深部含水层的年龄分布时,不能忽略其弥散作用。地下水年龄模拟为研究区域尺度上的地下水循环和地下水资源可持续利用提供了一种新的途径。     

Flow and transport model of a polder area in the Belgian coastal plain: example of data integration

Tracer data can serve to derive parameters related to groundwater systems or can be used in the calibration of transport and flow models. Temperature, ³H/³He (age dating) and hydrochemical data, together with head measurements, borehole logs and an aquifer test, were used to obtain insight into the flow and transport of a Quaternary aquifer system located in the Belgian polder area. Flow and transport model code SEAWAT acted as the integration medium for the different data. Each type of data has its own interpretation technique and adds components to the model. Additionally, different types of data aid in verification of the results. For instance, fluxes from temperature logs (used with the SEAWAT model), and water quality and age dating all provide information on flow to and velocities in the vicinity of drainage ditches. Different data also provide information on different scales. Temperature logs and aquifer tests act on a small scale, groundwater age is influenced by larger-scale flow, and water quality is determined by the general flow of the area. Integration of different kinds of geological, hydrological, geophysical and geochemical data is shown to be an important way forward in the efforts to model real-world cases.     

Simulation of spatial and temporal trends in nitrate concentrations at the regional scale in the Upper Dyle basin,Belgium

Models are the only tools capable of predicting the evolution of groundwater systems at a regional scale, by taking into account a large amount of information. This study presents the association of a water balance model (WetSpass) with a groundwater flow and solute transport model (SUFT3D, saturated and unsaturated flow and transport in 3D) in order to simulate the present and future groundwater quality in terms of nitrate in the Upper Dyle basin (439 km²) Belgium. The HFEMC (hybrid finite element mixing cell) method implemented in the SUFT3D code is used to model groundwater flow and nitrate transport. Spatially distributed recharge, modelled with WetSpass, is considered for prescribing the recharge to the groundwater flow model. The feasibility of linking the WetSpass model with the finite-elements SUFT3D code is demonstrated. Time evolution and distribution of nitrate concentration are then simulated using the calibrated model. Nitrate inputs are spatially distributed according to land use. The spatial simulations and temporal trends are compared with previously published data on this aquifer and show good results.     

氢氧同位素在地下水流系统的重分布：从高程效应到深度效应

大气降水的氢氧同位素含量具有高程效应,降水入渗后参与地下水循环,其高程效应如何受地下水流系统的影响转化为地下水氢氧同位素的深度效应？现有研究对于这个问题缺少定量认识。文章构建单向倾斜盆地和双峰波状盆地的稳态地下水循环理论模型,采用MODFLOW模拟剖面二维地下水流场、采用MT3DMS模拟重同位素分子的对流-弥散过程,得到地下水D和¹⁸O含量的空间分布,探讨了氢氧同位素高程效应在地下水流系统转化为深度效应的机理。结果表明：在单斜盆地,补给区大气降水D和¹⁸O含量的高程效应转化为排泄区地下水δD和δ¹⁸O值随埋深增大而指数型衰减的深度效应;在双峰波状盆地,当含水层渗透性相对入渗强度较大时(K₀/w=1 000),仅发育一个区域地下水流系统,在区域地下水的排泄区δD和δ¹⁸O随埋深增大呈现S形曲线分布;当含水层渗透性相对入渗强度较小时(K0/w=250),双峰波状盆地发育多个局部地下水流系统,区域地下水的排泄区δD和δ¹⁸O随埋深增大呈现S形曲线,而局部地下水排...     

用环境同位素论区域地下水资源属性

从可持续角度提出了区域地下水资源属性的概念; 分析了含水层系统中地下水质点的时间效应; 利用大量同位素资料分析了不同区域含水层系统中的地下水资源属性和人类活动对地下水资源属性的影响.指出利用环境同位素是研究区域地下水资源属性最直接、有效的方法; 正确认识评价区域地下水资源属性对实现地下水资源可持续性具有重要意义.      

Sensitivity Analysis of a Combined Groundwater Flow and Solute Transport Model Using Local-Grid Refinement: A Case Study

Combining groundwater flow models with solute transport models represents a common challenge in groundwater resources assessments and contaminant transport modeling. Groundwater flow models are usually constructed at somewhat larger scales (involving a coarser discretization) to include natural boundary conditions. They are commonly calibrated using observed groundwater levels and flows (if available). The groundwater solute transport models may be constructed at a smaller scale with finer discretization than the flow models in order to accurately delineate the solute source and the modeled target, to capture any heterogeneity that may affect contaminant migration, and to minimize numerical dispersion while still maintaining a reasonable computing time. The solution that is explored here is based on defining a finer grid subdomain within a larger coarser domain. The local-grid refinement (LGR) implemented in the Modular 3D finite-difference ground-water flow model (MODFLOW) code has such a provision to simulate groundwater flow in two nested grids: a higher-resolution sub-grid within a coarse grid. Under the premise that the interface between both models was well defined, a comprehensive sensitivity and uncertainty analysis was performed whereby the effect of a parameter perturbation in a coarser-grid model on transport predictions using a higher-resolution grid was quantified. This approach was tested for a groundwater flow and solute transport analysis in support of a safety evaluation of the future Belgian near-surface radioactive waste disposal facility. Our reference coarse-grid groundwater flow model was coupled with a smaller fine sub-grid model in two different ways. While the reference flow model was calibrated using observed groundwater levels at a scale commensurate with that of the coarse-grid model, the fine sub-grid model was used to run a solute transport simulation quantifying concentrations in a hypothetical well nearby the disposal facility. When LGR coupling was compared to a one-way coupling, LGR was found to provide a smoother flow solution resulting in a more CPU-efficient transport solution. Parameter sensitivities performed with the groundwater flow model resulted in sensitivities at the head observation locations. These sensitivities identified the recharge as the most sensitive parameter, with the hydraulic conductivity of the upper aquifer as the second most sensitive parameter in regard to calculated groundwater heads. Based on one-percent sensitivity maps, the spatial distribution of the observations with the highest sensitivities is slightly different for the upper aquifer hydraulic conductivity than for recharge. Sensitivity analyses were further performed to assess the prediction scaled sensitivities for hypothetical contaminant concentrations using the combined groundwater flow and solute transport models. Including all pertinent parameters into the sensitivity analysis identified the hydraulic conductivity of the upper aquifer as the most sensitive parameter with regard to the prediction of contaminant concentrations.     

Estimation of nitrate load from septic systems to surface water bodies using an ArcGIS-based software

Nitrate, as a commonly identified groundwater and surface water pollutant, poses serious threats to human health and the environment. One important source of nitrate in the environment is due to wastewater treatment using Onsite Sewage Treatment and Disposal Systems (OSTDS) (a.k.a., septic systems). To facilitate water resources and environmental management, an ArcGIS-Based Nitrate Load Estimation Toolkit (ArcNLET) is developed to simulate nitrate transport and estimate nitrate load from septic systems and collocated fertilizer applications in groundwater to surface water bodies. It is a screening tool based on a simplified conceptual model of groundwater flow and nitrate transport. It is used in this study to estimate nitrate load from thousands of septic systems to surface water bodies in two neighborhoods located in Jacksonville, FL, USA, where nitrate due to septic systems is believed to be one of the reasons of nutrient enrichment and an isotope study indicates that denitrification is significant. A global sensitivity analysis is performed to identify critical parameters for model calibration, and the most critical parameter is the first-order decay coefficient used to simulate the denitrification process. Hydraulic conductivities at different soil zones have different levels of influence on simulated nitrate concentrations at different locations. By manually adjusting model parameters, simulated shapes of water table and nitrate concentration agree reasonably with average field observations, suggesting that ArcNLET is able to simulate spatial variability of field observations. Estimated nitrate loads exhibit spatial variability, which is useful to facilitate decisions on the conversion of OSTDS into sewers in certain areas for reducing nitrate load from septic systems to surface water bodies.     

分布式水文模型在岩溶地区的改进与应用研究

在我国西南岩溶峰林地区,碳酸盐岩岩溶的强烈发育使含水层空间结构具有高度非均质性,加之表层岩溶带对降雨入渗的影响,导致传统的含水层高度概化的水文模型难以定量刻画地表水对地下水的补给过程。文章在开源的SWAT（土壤和水评估工具）模型基础上,通过改进土壤水及地下水模块,刻画水分经表层岩溶带以慢速流和快速流的方式进入含水层的过程,分别以活塞式推进方式及以捷径式入流方式进入浅层含水层,构建了适应于岩溶地区的分布式水文模型。以桂林市漓江流域为例,在碳酸盐岩和碎屑岩交叉分布的流域建立水文模型,并对构建的模型进行率定与验证,结果表明:与原模型径流模拟相比,本文构建的模型较好体现了表层岩溶带的调蓄作用,改善了各水文站枯水期模拟较差的情况（其中潮田站纳什系数由0.78提高到0.92,决定系数由0.85提高到0.92,比改进前有明显提高）;改进后的模型能适用于碎屑岩与碳酸盐岩分布不均的岩溶流域水分循环模拟。     

纵向弥散作用与渗透介质非均质性定量关系的模拟研究

在地下水污染模拟预报中,弥散参数是很难确定的一个模型参数。因实验室小尺度弥散规律一般不能用于大尺度弥散过程,而野外示踪试验却耗资大、周期长,限制了其实用性。文中利用随机数值模拟手段、基于随机理论的蒙特卡罗方法及序贯高斯模拟技术来生成渗透系数随机场,并研究渗透系数对数场的方差、相关长度以及变异函数类型在不同尺度上对纵向弥散度的影响,进而建立纵向弥散度与随机分布渗透系数场的方差和相关长度的统计定量关系,并与Gelhar理论计算结果进行比较。数值模拟结果表明,经过一定迁移距离后纵向弥散度与随机分布渗透系数对数场的方差和相关长度具有良好的线性统计关系,与Gelhar理论公式表达的关系类型类似。但对于较大的方差,纵向弥散度模拟结果明显大于Gelhar理论计算值,而对于较大相关长度在迁移距离不很大时,纵向弥散度模拟结果明显小于Gelhar理论计算值。本研究可为野外大尺度地下水污染预报模型中水动力弥散参数的确定提供方法借鉴。     

银川平原承压水氢氧同位素组成与~(14)C年龄分布特征

利用地下水氢氧同位素(2H、3H和18O)和碳同位素(14C)方法,分析银川平原承压水的补给更新能力。在平原区采集承压水氢、氧、碳同位素样品45组,测试其氢氧同位素含量和14C年龄。据测试结果分析,地下水氢、氧、碳环境同位素分布特征存在较好的一致性,揭示了该区承压水的补给、流动的区域规律和局部变化特征。地下水14C测年结果显示,承压水年龄大多介于3000~22290 a之间,同时采用Tamers和Gonfiantinie模型对14C年龄校正进行了对比分析。沿同位素水文地质剖面计算得出:银川以北贺兰山前向平原中部地下水的流动速率为2.22~0.63 m/a,呈现由南向北递减的特征;从青铜峡冲洪积区向平原中部地下水由每年流动十余米减少至2 m。综合分析认为,银川平原承压水流动缓慢,水交替循环时间长,局部与潜水水力联系较密切,在承压水开采区,潜水越流补给量可达45%,适量开采存在一定程度的可更新性。