【研究】Groundwater | Volume 58, Issue 4
自2020年年初起，达西环境DE公众号将对《Groundwater》期刊每期论文开始传送，《Groundwater》期刊为双月刊。转眼一年过去了，近期会陆续放出，下面是2020年第四期刊发论文，供阅览。
前三期可见页面最后的“往期推荐”。
Guest Editorial
Global Groundwater Sustainability
by Matthew Currell ,Tom Gleeson , Peter Dahlhaus
全球地下水可持续性
Issue Paper
Alpine Hydrogeology: The Critical Role of Groundwaterin Sourcing the Headwaters of the World
by Masaki Hayashi
高山水文地质：地下水在寻找世界源头方面的关键作用
Research Papers
1.Episodic and Continuous Recharge Estimation from High‐Resolution Well Records
byTimothy T. Eaton
高分辨率井记录间歇和连续补给估算
Watertable fluctuation (WTF) methods are a primary and well‐establishedway to determine groundwater recharge based on the direct response of the watertable to precipitation input. An emerging complexity of recharge is whether itoccurs as an episodic and transient process, or a continuous steady‐stateprocess, however, most studies have not focused on these short‐termvs. long‐term timescales, in part because ofa lack of data resolution. Here, high‐resolution (subhourly)precipitation and water‐level data are analyzedfor wells in the suburbs of New York City using two contrasting WTF approaches,with a common mathematical basis, that are suited to episodic and continuousprocesses. The resulting hourly recharge results, like the individual water‐levelrecords from comparable wells, are sensitive indicators of subtle differencesin aquifer conditions such as thickness of the unsaturated zone, position inthe flow system and localized preferential flow. While the episodic, transientapproach excludes diffuse recharge by design, the continuous, steady‐stateapproach is influenced by short‐term precipitationevents, and therefore integrates transient processes to some extent. However,the continuous, steady‐state approach issubject to its own limitations relating to position in the aquifer system, andmay overestimate recharge if aquifer conditions are not well understood. Morewidespread use of higher resolution data as well as understanding aquiferconditions and refining aquifer parameters would improve WTF rechargeestimation.
地下水位波动（WTF）法是根据地下水位对降水输入量的直接响应来确定地下水补给量的一种行之有效的方法。补给的复杂性主要表现在其新的补给出现时在短暂时间内还是保持连续的稳态过程，但是，大多数研究并未将重点放在这些短期和长期时标上，部分原因是缺乏数据分辨率。在这里，使用两种具有通用数学基础的对比WTF方法（适用于连续过程和连续过程），对纽约市郊区的油井进行了高分辨率（亚小时）降水和水位数据分析。每小时的补给量结果，就像可比较井的单个水位记录一样，是敏感的含水层状况细微差异的指标，例如非饱和区的厚度，流动系统中的位置和局部优先流动。间歇性瞬态方法通过设计排除了扩散补给，而连续稳态方法受短期降水事件的影响，因此在某种程度上整合了瞬态过程。但是，连续的稳态方法受其自身在含水层系统中位置的限制，如果对含水层的状况不了解，可能会高估补给量。更广泛地使用更高分辨率的数据以及了解含水层条件，完善含水层参数将改善WTF补给估算。
2. A Simple Methodfor Simulating Groundwater Interactions with Fens to Forecast Development Effects
by Daniel T. Feinstein David J. Hart Sarah Gatzke RandallJ. Hunt Richard G. Niswonger Michael N. Fienen
模拟地下水与相互作用的简单方法以预测开发效果
Protection of fens–wetlands dependent on groundwater discharge–requires characterization of groundwater sources andstresses. Because instrumentation and numerical modeling of fens is labor intensive,easy‐to‐apply methods that model fen distribution and theirvulnerability to development are desirable. Here we demonstrate that fen areascan be simulated using existing steady‐state MODFLOW models when the unsaturated zone flow (UZF)package is included. In cells where the water table is near land surface, theUZF package calculates a head difference and scaled conductance at these“seepage drain” cells to generate average rates of vertical seepage to theland. This formulation, which represents an alternative to blanketing theMODFLOW domain with drains, requires very little input from the user becauseunsaturated flow‐routing is inactiveand results are primarily driven by easily obtained topographic information.Like the drain approach, it has the advantage that the distribution of seepageareas is not predetermined by the modeler, but rather emerges from simulatedheads. Beyond the drain approach, it takes account of intracell land surfacevariation to explicitly quantify multiple surficial flows corresponding toinfiltration, rejected recharge, recharge and land‐surface seepage. Application of the method to a basin insoutheastern Wisconsin demonstrates how it can be used as a decision‐support tool to first, reproduce fen distribution and,second, forecast drawdown and reduced seepage at fens in response to shallowpumping.
保护沼泽、湿地取决于地下水排放量即需要表征地下水源和应力。由于测量和数值建模较为复杂，因此需要一种易于应用的方法来模拟分布及其开发的脆弱性。在这里，我们证明了当包含非饱和区流（UZF）程序包时，可以使用现有的稳态MODFLOW模型来模拟分水岭区域。在地下水位靠近陆地表面的单元中，UZF程序包计算“渗漏”单元的水头差和比例电导，以生成平均垂直渗入土地的速率。这种方法是用排水口覆盖MODFLOW域的一种替代方法，由于不饱和流不活跃且结果主要由容易获得的地形信息驱动，因此用户输入的信息很少。像排水法一样，它的优点是，渗流面积的分布不是由建模人员预先确定的，而是由模拟水头产生的。除排水方法外，它还考虑了细胞内陆地表面的变化，以明确地量化与渗透，拒绝补给，补给和地表渗漏相对应的多种表面流。该方法在威斯康星州东南部盆地的应用证明了如何将其用作决策支持工具，首先，明确分布，其次，预测响应浅水抽出的口水位下降和渗透率降低。
3. Numerical Studyof Tide‐Induced Airflowand Salt–Fresh WaterDynamics in Unconfined Aquifers
by Yong G, Zang Dong M, Sun Ping Feng
承压含水层中潮汐引起的气流和盐淡水动力学的数值模拟研究
This study employed acoupled water‐air two‐phase flow and salt water transport model to analyze thebehaviors of generated airflow in unsaturated zones and the fluctuations ofsalinity at the salt–fresh water interfacein a two‐layered unconfinedaquifer with a sloping beach surface subjected to tidal oscillations. Thesimulation results show that as the new dynamic steady state including effectsof tidal fluctuations is reached through multiple tidal cycles, the dispersionzone in the lower salt water wedge is broadened because fresh water/salt watertherein flows continuously landward or seaward during tidal cycles. The uppersalt–fresh water interface exhibits more vulnerable to the tidal fluctuations,and the variation of salinity therein is periodic, which is irrelevant to thehydraulic head but is influenced by the direction and velocity of surrounding water‐flow. With the tidal level fluctuating, airflow is mainlyconcentrated in the lower permeable layer due to the restraint of the uppersemi‐permeable layer, and the time‐lag between the pore‐air pressure and the tidal level increases with distancefrom the coastline. The effect of airflow in unsaturated zones can betransmitted downward, causing both the magnitude of salinity and its amplitudein the upper salt–fresh water interfaceto be smaller for the case with airflow than without airflow due to theresistance of airflow to water‐flow. Sensitivity analysis reveal that distributions ofairflow in unsaturated zones are affected by the permeability of theupper/lower layer and the van Genuchten parameter of the lower layer, not bythe van Genuchten parameter of the upper layer, whereas the salinityfluctuations in the salt–fresh water interface are affected only by soilparameters of the lower layer.
这项研究采用了水-气两相流和盐水耦合的输运模型，分析了带倾斜海滩的两层无侧压含水层中非饱和区产生的气流的行为以及盐-淡水界面的盐度波动，其表面遭受潮汐振荡。仿真结果表明，由于通过多个潮汐周期达到了包括潮汐波动影响的新的动态稳态，下部咸水楔中的分散区变宽了，因为其中的淡水/盐水在潮汐周期中不断地向陆或向海流动。上部的盐-淡水界面更容易受到潮汐波动的影响，其中盐度的变化是周期性的，与水压头无关，但受周围水流的方向和速度的影响。随着潮汐水平的波动，由于上部半透水层的约束，气流主要集中在下部透水层，并且孔隙空气压力和潮汐水平之间的时间滞后随距海岸线的距离而增加。气流在不饱和区的影响可以向下传播，由于气流对水流的阻力，使得有气流的情况下的盐度和淡水上部界面中的盐度值及其幅度都小于没有气流的情况。敏感性分析表明，非饱和区中气流的分布受上/下层渗透率和下层van Genuchten参数的影响，而不是受上层van Genuchten参数的影响，而盐分中的盐度波动淡水界面仅受下层土壤参数的影响。
4.Numerical Simulations of Seasonally Oscillated Groundwater Dynamics in Coastal ConfinedAquifers
by Wenjing Qu, Hailong Li , Chaoyue Wang, Chunmiao Zheng , Xuejing Wang, Yan Zhang
沿海承压含水层季节性振荡的地下水动态数值模拟
Studies investigatingthe effects of inland recharge on coastal groundwater dynamics were carried outtypically in unconfined aquifers, with few in confined aquifers. This studyfocused on the groundwater dynamics in confined aquifers with seasonally sinusoidallyfluctuated inland groundwater head and constant sea level by numericalsimulations. It is known that the mixing zone (MZ) of saltwater wedge inresponse to the seasonal oscillations of inland groundwater head swings aroundthe steady‐state MZ. However,our simulation results indicate that even the most landward freshwater‐saltwater interface over a year is seaward from thesteady‐state location when the hydraulicconductivity K is ≤10−4 m/s undercertain boundary conditions with given parameter values. That is, seasonaloscillations of inland groundwater head may reduce seawater intrusion inconfined coastal aquifers when K ≤ 10−4 m/s. Sensitivity analysis indicates that foraquifers of K ≤ 10−4 m/s, the largerthe inland head fluctuation amplitude is, the less the seawater intrudes. Thisis probably due to the reason that the seawater intrusion time decreases withthe increase of fluctuation amplitude when K ≤ 10−4 m/s. Numerical simulations demonstrate thatseasonal inland groundwater head oscillations promote the annual averagedrecirculated seawater discharge across the seaward boundary.
研究内陆补给对沿海地下水动力学影响的研究通常是在无限制含水层中进行的，而在受限含水层中很少进行。本研究通过数值模拟，研究了内陆地下水水位呈季节正弦波动且海平面恒定的承压含水层中的地下水动力学。众所周知，响应内陆地下水头的季节性振荡，咸水楔形混合区（MZ）围绕稳态MZ摆动。然而，我们的模拟结果表明，当在给定的参数值下，在一定的边界条件下水力传导率K ≤10−4 m / s时，即使是一年中最陆上的淡水-盐水界面也从稳态位置向海。也就是说，当K≤10−4 m / s时，内陆地下水位的季节性波动可以减少海水在受限的承压含水层中的侵入。敏感性分析表明，对于K≤10−4 m / s的含水层，内陆水头波动幅度越大，海水的侵入越少。这可能是由于当K≤10-4 m / s时，海水入侵时间随波动幅度的增加而减少的原因。数值模拟表明，季节性内陆地下水水头振荡促进了跨海边界的年平均再循环海水排放量。
5. Evaluation of NegativeEconomic‐Environmental Externalities of Overextraction ofGroundwater
byMostafa Baniasadi, Mohammad Reza Zare'Mehrjordi, Hossein Mehrabi Boshrabadi , HamidReza Mirzaei Khalilabad, Abbas RezaeiEstakhrooye
地下水超采对经济和环境的负面影响
Inrecent decades, increased extraction of groundwater for human and agricultureconsumption has led to a substantial drop in groundwater level in large areasof across the world. Declining groundwater levels is a serious problem initself and has multiple economic, social, cultural, political, security‐related,and environmental externalities. The negative economic‐environmentalexternalities of overextraction of groundwater in the Orzouiyeh plain in theKerman Province, Iran, were evaluated using methods such as replacement cost,production function, market prices, shadow price, and the value of the inputmarginal product. After evaluating externalities, the Positive MathematicalProgramming method was used to evaluate different water policies to reduce theconsumption of groundwater. The total economic losses due to the externalitieswere calculated to equal 2.8 U.S. million dollars. The damages caused byenvironmental externalities were calculated to equal 436.1 U.S. milliondollars. The results related to the positive planning model show that the bestpolicy among different options, such as deficit irrigation policy or combinedpolicies, involves implementation of pressurized irrigation systems.近几十年来，用于人类和农业的地下水开采量增加，导致世界上大部分地区的地下水位大幅下降。地下水位下降本身就是一个严重的问题，并且具有多种经济，社会，文化，政治，安全相关和环境外部性。使用重置成本，生产函数，市场价格，影子价格以及投入的边际产品价值等方法评估了伊朗克尔曼省平原地下水超采的负面经济环境外部影响。在评估了外部性之后，使用正数学规划方法来评估不同的水政策，以减少地下水的消耗。据计算，由于外部因素造成的总经济损失相当于2.8亿美元。据计算，环境外部性造成的损失等于436.1亿美元。与积极计划模型相关的结果表明，在不同方案中的最佳政策（例如赤字灌溉政策或联合政策）涉及实施加压灌溉系统。
6.MonteCarlo Simulations as a Decision Support to Interpret δ15N Values of Nitrate inGroundwater
byLisa M. Wild , Arno Rein , Florian Einsiedl
蒙特卡罗模拟是地下水硝酸盐δ15N值的决策依据
Intensefarming is often associated with the excessive use of manure or fertilizers andthe subsequent deterioration of the groundwater quality in many aquifersworldwide. Stable isotopes of dissolved nitrate (δ15N and δ18O) are widely usedto determine sources of nitrate contamination and denitrification processes ingroundwater but are often difficult to interpret. Thus, Monte Carlo simulationswere carried out for a site in lower Bavaria, Germany, in order to explain δ15Nobservations in a porous groundwater system with two aquifers, the main aquifer(MA) and several smaller perched aquifers (PA). For evaluating potentialcontributions, frequency distributions of δ15N were simulated deriving from (I)the mixing of different nitrate sources, related to land use, as input togroundwater, combined with (II) transport of nitrate in groundwater and (III)microbial denitrification. Simulation results indicate a source‐drivenisotopic shift to heavier δ15N values of nitrate ingroundwater, which may be explained by land use changes toward a moreintensified agriculture releasing high amounts of manure. Microbialdenitrification may play a role in the PA, with simulated δ15N distributionsclose to the observations. Denitrification processes are however unlikely forthe MA, as reasonable simulation curve fits for such a scenario were obtainedpredominantly for unrealistic portions of nitrate sources and related land use.The applied approach can be used to qualitatively and quantitatively evaluatethe influence of different potential contributions, which might mask each otherdue to overlapping δ15N ranges, and it can support the estimation of nitrateinput related to land use.
密集耕作通常与过度使用肥料或化肥以及随后全球范围内许多含水层的地下水质量下降有关。溶解的硝酸盐的稳定同位素（δ15N和δ18O）被广泛用于确定地下水中硝酸盐污染和反硝化过程的来源，但通常难以解释。因此，对德国下巴伐利亚的一个地点进行了蒙特卡洛模拟，以解释在具有两个含水层，主要含水层（MA）和几个较小的栖息含水层（PA）的多孔地下水系统中的δ15N观测值。为了评估潜在风险，模拟了δ15N的频率分布，其源于（I）与土地利用有关的不同硝酸盐源的混合，作为地下水的输入，结合（II）地下水中硝酸盐的运输和（III）微生物反硝化。模拟结果表明，由源驱动的同位素转移到地下水中硝酸盐的δ15N值较高，这可以用土地利用向集约化农业转变为释放大量肥料的方式来解释。微生物反硝化作用可能在PA中起作用，模拟的δ15N分布接近观测值。然而，MA不太可能进行反硝化过程，因为针对这种情况的合理模拟曲线主要是针对不切实际的硝酸盐来源和相关土地利用而获得的。应用的方法可用于定性和定量评估不同潜在贡献的影响，由于重叠的δ15N范围可能相互掩盖，并且可以支持与土地利用有关的硝酸盐输入估算。
7.Mapping Groundwater Potential Through an Ensemble of Big Data Methods
byP. Martínez‐Santos , P. Renard
通过系列大数据方法绘制地下水潜力
Groundwaterresources are crucial to safe drinking supplies in sub‐SaharanAfrica, and will be increasingly relied upon in a context of climate change.The need to better understand groundwater calls for innovative approaches tomake the best out of the existing information. A methodology to map groundwaterpotential based on an ensemble of machine learning classifiers is presented. Alarge borehole database (n = 1848) was integrated into a Geographic InformationSystems (GIS) environment and used to train, validate and test 12 machinelearning algorithms. Each classifier predicts a binary target (positive ornegative borehole) based on the minimum flow rate required for communaldomestic supplies. Classification is based on a number of explanatory variables,including landforms, lineaments, soil, vegetation, geology and slope, amongothers. Correlations between the target and explanatory variables were thengeneralized to develop groundwater potential maps. Most algorithms attainedsuccess rates between 80% and 96% in terms of test score, which suggests thatthe outcomes provide an accurate picture of field conditions. Statisticallearners were observed to perform better than most other algorithms, exceptingrandom forests and support vector machines. Furthermore, it is concluded thatthe ensemble approach provides added value by incorporating a measure ofuncertainty to the results. This technique may be used to rapidly map groundwaterpotential for rural supply or humanitarian emergencies in areas where there issufficient historical data but where comprehensive field work is unfeasible.
地下水资源对于撒哈拉以南非洲地区的安全饮用水供应至关重要，在气候变化的背景下，越来越多依赖地下水资源。为了更好地了解地下水，需要采用创新的方法来充分利用现有信息。本文提出了一种基于机器学习分类器的地图来绘制地下水潜力的方法。一个大型钻孔数据库（n = 1848）已集成到地理信息系统（GIS）环境中，并用于训练，验证和测试12种机器学习算法。每个分类器都基于公共家庭供应所需的最小流速来预测二进制目标（正井眼或负井眼）。分类基于许多解释性变量，包括地貌，界线，土壤，植被，地质和坡度等。然后，将目标变量与解释变量之间的相关性进行概括，以开发地下水潜力图。多数算法在测试分数方面都获得了80％到96％的成功率，这表明结果可以提供对现场条件的准确描述。观察到统计学习者的表现比大多数其他算法要好，随机森林和支持向量机除外。此外，得出的结论是，集成方法通过将不确定性度量结合到结果中来提供附加值。在有足够的历史数据但无法进行全面野外工作的地区，可以使用此技术快速绘制地下水潜力以用于农村供水或人道主义紧急情况。
8.Numerical Investigation of a Methane Leakage from a Geothermal Well into a ShallowAquifer
byAndrea D'Aniello , Massimiliano Fabbricino , Daniela Ducci, Domenico Pianese
地热井向浅层含水层中泄漏甲烷的数值研究
Thepotential environmental impacts on subsurface water resources induced byunconventional gas production are still under debate. Solving the controversyregarding the potential adverse effects of gas leakages on groundwaterresources is therefore crucial. In this work, an interesting real‐worldcase is presented in order to give further insight into methane multiphase andtransport behavior in the shallow subsurface, often disregarded compared to thebehavior in the deep subsurface. Multiphase flow and solute transportsimulations were performed to assess the vulnerability of an existing shallowunconfined aquifer with respect to a hypothetical methane leakage resultingfrom a well integrity failure of a former deep geothermal well. The analysisshowed that migration of gaseous methane through the aquifer under examinationcan be extremely fast (of the order of a few minutes), occurring predominantlyvertically upwards, close to the well. By contrast, dissolved methane migrationis largely affected by the groundwater flow field and occurs over larger timescales (of the order of months/years), covering a greater distance from thewell. Overall, the real concern for this site in case of gas leakages is therisk of explosion in the close vicinity of the well. Predicted maximum gaseousfluxes (0.89 to 22.60 m3/d) are comparable to those reported for leaking wells,and maximum dissolved methane concentrations may overcome risk mitigation thresholds(7 to 10 mg/L) in a few years. Therefore, surface and subsurface monitoringbefore decommissioning is strongly advised to ensure the safety of the site.
非常规天然气生产对地下水资源的潜在环境影响仍存在争议。因此，解决有关气体泄漏对地下水资源的潜在不利影响至关重要。在本文中，提出了一个有趣的现实案例，以便进一步了解与深层地下的行为相比常常被忽略的浅层地下的甲烷多相和输运行为。通过多相流和溶质运移模拟，评估了现有的浅层无限制含水层相对于由前深层地热井的井身完整性故障导致的甲烷泄漏的脆弱性。分析表明，气态甲烷通过受检查含水层的迁移可能非常快（几分钟左右），主要发生在井附近垂直向上。相比之下，溶解的甲烷迁移在很大程度上受地下水流场的影响，并发生在较大的时间范围内（数月/年的量级），覆盖距离井口较远。总体而言，如果发生气体泄漏，此地点的真正问题在于井附近爆炸的危险。预测的最大气体通量（0.89至22.60m3 / d）与泄漏井的报告值相当，并且最大的溶解甲烷浓度可能会在几年内超过风险缓解阈值（7至10mg / L）。因此，强烈建议在停运前进行地面和地下监测，以确保现场安全。
9. An Approximation of Inner BoundaryConditions for Wells Intersecting Highly Conductive Structures
byMarkus Giese , Thomas Reimann, Rudolf Liedl, Benoit Dewandel, Jean‐ChristopheMaréchalMartin Sauter
与高导电结构相交的井的内部边界条件的近似值
Innerboundary conditions describe the interaction of groundwater wells with thesurrounding aquifer during pumping and are associated with well‐skindamage that limits water production and water derived from wellbore storage.Pumping test evaluations of wells during immediate and early time flow requireassignment of inner boundary conditions. Originally, these concepts weredeveloped for vertical well screens, and later transferred to wellboresintersecting highly conductive structures, such as preferential flow zones infractured and karstic systems. Conceptual models for pumping test analysis incomplex bedrock geology are often simplified. Classic analytical solutionsgenerally lump or ignore conditions that limit or enhance well productivityalong the well screen at the onset of pumping. Numerical solutions canrepresent well drawdowns in complex geological settings, such as karst systems,more precisely than many analytical solutions by accounting for additionalphysical processes and avoiding assumptions and simplifications. Suitablenumerical tools for flow simulations in karst are discrete pipe‐continuummodels that account for various physical processes such as the transienthydraulics of wellbores intersecting highly conductive structures during pumping.
内部边界条件描述了抽水过程中地下水井与周围含水层的相互作用与表皮损坏有关，其限制了水的生产和井筒储水。在即时流量和早期流量期对井的抽水测试评估要求考虑内部边界条件。最初，这些概念是为垂直井开发的，后来又转移到与高传导性结构相交的井筒中，例如裂缝和岩溶系统中的优先流动区。复杂基岩地质中抽水试验分析的概念模型通常得到简化。经典的分析解决方案通常会在泵送开始时沿井筛限制或忽略限制或提高井生产率的条件。通过考虑额外的物理过程并避免假设和简化，数值解决方案可以比分析法更精确地表示复杂地质环境（例如岩溶系统）中的井位下降。用于岩溶流动模拟的合适数值模拟法是离散管道连续模型，这些模型考虑了各种物理作用，例如在抽水过程中与高导电结构相交的井筒的瞬态水力。
10. Variation in Saturated HydraulicConductivity at the Outcrop Scale, the Whanganui Basin, New Zealand
byCallum Rees, Alan Palmer, Julie Palmer , Ranvir Singh
新西兰旺格努伊盆地露头尺度的饱和导水率变化
Groundwaterflow and contaminant transport are strongly influenced by hydrogeologicalspatial variation. Understanding the textural heterogeneity of aquifer andaquitard units is critical for predicting preferential flow pathways, but isoften hindered by sparse hydrogeological data, widely spaced data points, andcomplex stratigraphy. Here, we demonstrate the application of a relatively newair permeameter technology, providing a cost‐effective, rapidalternative for characterizing hydrostratigraphic units in the field. The aimof this research is to (1) characterize the variation of saturated hydraulicconductivity across shallow‐marine hydrostratigraphicunits of the Whanganui Basin, New Zealand, and (2) assess the variation ofsaturated hydraulic conductivity within individual hydrostratigraphic units andrelate these changes to facies and depositional environments. Results suggestheterogeneity within fine‐grained aquitard unitsis controlled by bioturbation, whereby burrowing, ingestion and defecationresults in grain size segregation and differential micrite cementation. Coarse‐grainedheterolithic aquifer facies display sharp changes in permeability across planarto cross‐bedded sets, related to current andwave energy fluctuations within shallow‐marine depositionalsettings. Bedding plane orientation creates high permeability zones thatpromotes down dip subsurface flow. Down dip gradation of coarse‐grainednearshore facies into fine‐grained shelf faciesalong the paleo shoreline‐shelf transect is suggestedto promote lateral and vertical groundwater flow within the basin fill. Airpermeameter techniques have potential for application within groundwater basinsaround the world, providing datasets that facilitate greater understanding ofgroundwater systems, informing practices and policies for targeted water qualitymanagement.
地下水流量和污染物运移受水文地质空间变化的影响。了解含水层的各向异性对于预测优先流动路径至关重要，但通常因不完整水文地质数据，间隔较大的数据点和复杂的地层而受阻。在这里，我们演示了一种相对较新的空气渗透仪技术的应用，为表征现场水文地层提供了一种经济高效的快速替代方案。这项研究的目的一是表征新西兰旺格努伊盆地浅海水文地层单元中饱和水力传导率的变化，二是评估各个水文地层单元中饱和水力传导率的变化并将这些变化联系起来到相和沉积环境。结果表明细粒弱透水层的各项异质受到生物扰动控制，由于其挖洞，摄入和排便导致粒度偏析和差分微晶胶结。粗粒含水层在平面到交叉层组的渗透率显示出急剧变化，这与浅海沉积环境中的电流和波能波动有关。顺层平面定向可形成高渗透率带，从而促进下倾地下流体流动。建议沿古海岸线-陆架断面将粗粒近岸相向下倾斜成细粒陆相，以促进盆地填充物中的横向和垂直地下水流。空气渗透仪技术在世界范围内的地下水盆地中都有潜在的应用前景，它提供的数据集有助于人们更好地了解地下水系统，为有针对性的水质管理提供实践和理论依据。
Methods Note
1.AcceleratingStreamline Tracking in Groundwater Flow Modeling on GPUs
byXiaohui Ji, Mulan Luo , Xusheng Wang
在GPU上加速简化跟踪地下水流模拟
Streamlinesimulation in groundwater flow modeling is a time‐consuming process when alarge number of streamlines are analyzed. We develop a parallelization methodon graphics processing units (GPUs) for the semi‐analytical particle trackingalgorithm developed by Pollock (1988). Compute Unified Device Architecture wasused to implement the parallel method. Forward and backward tracking of astreamline is handled by an individual thread. A GPU includes a grid of blockswhere a block handles 32 threads. We use multi‐GPUs to acceleratestreamline tracking in a flow model with millions of particles. The method wasexamined to simulate streamlines for identifying three‐dimensional(3D) flow systems in a Tóthian basin. The speedupexceeds 1000 when 8 NVIDIA GPUs are used to simulate 5 million or morestreamlines.
当分析大量流线时，地下水流模型中的流线模拟是一个耗时的过程。我们针对Pollock（1988）开发的半分析粒子跟踪算法，在图形处理单元（GPU）上开发了并行化方法。计算统一设备体系结构用于实现并行方法。流线的向前和向后跟踪由单个线程处理。 GPU包括一块块的网格，其中一块可处理32个线程。我们使用多GPU来加速具有数百万个粒子的流模型中的流线跟踪。检查了该方法以模拟流线，以识别Tóthian盆地的三维（3D）流动系统。当使用8个NVIDIA GPU模拟500万或更多流线时，加速超过1000。
Case Study
1．A Search for Freshwater in the Saline Aquiferof Coastal Bangladesh
byChelsea N. Peters， George M. Hornberger
在孟加拉国沿海咸水层中寻找淡水
Inthe polder region of coastal Bangladesh, shallow groundwater is primarilybrackish with unpredictable occurrence of freshwater pockets. Delta buildingprocesses, including the codeposition of fresh‐to‐salineporewater and sediments, have formed the shallow aquifer. Impermeable clayfacies and the lack of a topographical gradient limit the flow of groundwaterand its mixing with surface water so controls on spatial variability ofsalinity are not obvious. By characterizing groundwater‐surfacewater (GW‐SW) interactions, this studyattempted to identify areas of potable groundwater for the polder communities.We used transects of piezometers, cores, electromagnetic induction, and waterchemistry surveys to explore two sources of potential fresh groundwater: (1)tidal channel‐aquifer exchange and (2) meteoricrecharge. Fresh groundwater proved difficult to find due to heterogeneoussubsurface lithology, asymmetrical tidal dynamics, extreme seasonalfluctuations in rainfall, and limited field data. Geophysical observationssuggest substantial lateral variability in shallow subsurface conductivityprofiles. Piezometers show varying degrees of tidal pressure attenuation awayfrom the channels. Nevertheless, the active exchange of freshwater appears tobe limited due to low permeability of banks and surface sediments. Results indicatethat pockets of fresh groundwater cannot be identified using readily availablehydrogeological methods, so alternative drinking water sources should bepursued. By better understanding the hydrogeology of the system, however,communities will be better equipped to redirect water management resources tomore feasible and sustainable drinking water options.
在孟加拉国沿海的田地区，浅层地下水主要是微咸的，并且出现了不可预测的淡水袋。三角洲的形成，包括新鲜到咸水的孔隙水和沉积物的共存，形成了浅层含水层。渗透性差的粘土相和缺乏地形梯度限制了地下水的流动及其与地表水的混合，因此对盐度空间变异性的控制并不明显。通过表征地下水-地表水（GW-SW）的相互作用，本研究试图确定社区的饮用水区域。我们使用了压力计，岩心，电磁感应和水化学调查的样板，探索了潜在的新鲜地下水的两种来源：（1）潮汐通道-含水层交换，（2）大气补给。由于岩层的非均质性，潮汐动力学不对称，降雨极端季节性波动以及田间数据有限，因此难以找到新鲜地下水。地球物理观测表明，浅层地下电导率剖面存在较大的横向变化。测压仪显示远离通道的潮汐压力衰减程度不同。然而，由于堤岸和表层沉积物的低渗透性，淡水的主动交换似乎受到限制。结果表明，使用现成的水文地质方法无法识别出新鲜的地下水，因此应寻求替代的饮用水源。通过更好地了解系统的水文地质学，社区将能够更好地将水资源管理资源转移到更可行，更可持续的饮用水方案上。
2．Stream Temperature Modeling and Fiber OpticTemperature Sensing to Characterize Groundwater Discharge
byMaryam Moridnejad， Stewart Cameron， Asaad Y. Shamseldin， Floris Verhagen， Catherine Moore，Bruce W.Melville， Nick Dudley Ward
流温和光纤温度传感表征地下水流量
TheNgongotaha Stream was used as a case study to assess the applicability of fiberoptic distributed temperature sensing (FODTS) to identify the location ofsprings and quantify their discharge. Thirteen springs were identified, mostlylocated within a 115 m reach, five discharged from the right bank and eightfrom the left bank. To quantify groundwater discharge, a new approach wasdeveloped in which the one‐dimensional transientheat transport model was fitted to the FODTS measurements, where the maincalibration parameters of interest were the unknown spring discharges. The spatialdisposition of the groundwater discharge estimation problem was constrained bytwo sources of information; first, the stream gains ∼500 L/s as determined bystreamflow gauging. Second, the temperature profiles of the left and rightbanks provide the spatial disposition of springs and their relative discharges.FODTS was used to measure stream temperature near the left and right banks,which created two temperature datasets. A weighted average of the two datasetswas then calculated, where the weights reflected the degree of mixing betweenthe right and left banks downstream of a spring. The new approach in this studymarks a departure from previous studies, in which the general approach was touse the steady‐state thermal mixing model (Selkeret al. 2006a; Westhoff et al. 2007; Briggs et al. 2012) to infer groundwaterdischarge, which is then used as an input into a transient model of the generalform of equation to simulate stream temperature (Westhoff et al. 2007).
以恩贡塔哈河为例来评估光纤分布式温度传感（FODTS）的适用性，确定弹簧的位置并量化其排放量共确定了十三座温泉，大部分位于115 m范围内，右岸排出了五处，左岸排出了八处。为了量化地下水排放量，开发了一种新方法，其中将一维瞬态传热模型拟合到FODTS测量中，其中感兴趣的主要校准参数是未知的春季排放量。地下水排放估算问题的空间分布受到两个信息来源的约束：首先，根据流量测量确定的流量增益约为500 L / s。其次，左右堤坝的温度分布提供了弹簧及其相对排放量的空间分布。 FODTS用于测量左岸和右岸附近的河流温度，从而创建了两个温度数据集。然后计算两个数据集的加权平均值，其中的权重反映了弹簧下游左右堤岸之间的混合程度。本研究中的新方法与以前的研究不同，后者的一般方法是使用稳态热混合模型（Selker等人2006a；Westhoff等人2007；Briggs等人2012）推断地下水。流量，然后将其用作方程式一般形式的瞬态模型的输入，以模拟河流温度（Westhoff等，2007）。
3．Producer Attitudes Toward GroundwaterConservation in the U.S. Ogallala‐High Plains
StephenLauer, Matthew R. Sanderson
生产者对美国奥加拉拉-高平原地区地下水保护的态度
Wepresent descriptive findings on attitudes towards groundwater conservation andmanagement from a survey of 1,226 producers farming in the High Plains/Ogallalaaquifer region of the United States. We find that a super‐majorityof producers agree that groundwater should be conserved rather than entirelydepleted. The majority perceives groundwater depletion to be a serious problem.Producers perceive depletion to be a greater problem for their communities thanfor their own farming operations. There is overwhelming agreement thatgroundwater should be conserved for altruistic reasons to benefit futuregenerations in the community. Most producers believe they have limited personalcapacity for additional groundwater conservation on their farms, and few areinvolved in voluntary group conservation initiatives. We suggest that a keyelement of the conservation challenge is social and that future efforts shouldfocus on developing networks, capacities, and cultures of groundwater conservationon the High Plains.
我们对美国奥加拉拉-高平原含水层地区的1,226位农业生产者进行了调查，提出了对地下水保存和管理态度的描述性发现。我们发现，绝大多数生产者都认为应该保护地下水而不是将其完全消耗掉。大多数人认为地下水枯竭是一个严重的问题。与他们自己的农业经营活动相比，生产者认为完全耗尽地下水对他们的社区来说是一个更大的问题。人们已经达成共识，出于利他的原因，应该保护地下水，以造福社区后代。大多数生产者认为，他们在农场上进行额外地下水保护的个人能力有限，很少有人参与自愿的团体保护计划。我们认为关键因素是社会问题，未来的努力应集中发展高原地区地下水保护网站，能力和文化。
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