自2020年年初起，達西環境DE公眾號將對《Groundwater》期刊每期論文開始傳送，《Groundwater》期刊為雙月刊。轉眼一年過去了，近期會陸續放出，下面是2020年第四期刊發論文，供閱覽。
前三期可見頁面最後的「往期推薦」。
Global Groundwater Sustainability
by Matthew Currell ,Tom Gleeson , Peter Dahlhaus
全球地下水可持續性
Alpine Hydrogeology: The Critical Role of Groundwaterin Sourcing the Headwaters of the World
by Masaki Hayashi
高山水文地質：地下水在尋找世界源頭方面的關鍵作用
1.Episodic and Continuous Recharge Estimation from High‐Resolution Well Records
byTimothy T. Eaton
高解析度井記錄間歇和連續補給估算
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.
地下水位波動（WTF）法是根據地下水位對降水輸入量的直接響應來確定地下水補給量的一種行之有效的方法。補給的複雜性主要表現在其新的補給出現時在短暫時間內還是保持連續的穩態過程，但是，大多數研究並未將重點放在這些短期和長期時標上，部分原因是缺乏數據解析度。在這裡，使用兩種具有通用數學基礎的對比WTF方法（適用於連續過程和連續過程），對紐約市郊區的油井進行了高解析度（亞小時）降水和水位數據分析。每小時的補給量結果，就像可比較井的單個水位記錄一樣，是敏感的含水層狀況細微差異的指標，例如非飽和區的厚度，流動系統中的位置和局部優先流動。間歇性瞬態方法通過設計排除了擴散補給，而連續穩態方法受短期降水事件的影響，因此在某種程度上整合了瞬態過程。但是，連續的穩態方法受其自身在含水層系統中位置的限制，如果對含水層的狀況不了解，可能會高估補給量。更廣泛地使用更高解析度的數據以及了解含水層條件，完善含水層參數將改善WTF補給估算。
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
模擬地下水與相互作用的簡單方法以預測開發效果
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.
保護沼澤、溼地取決於地下水排放量即需要表徵地下水源和應力。由於測量和數值建模較為複雜，因此需要一種易於應用的方法來模擬分布及其開發的脆弱性。在這裡，我們證明了當包含非飽和區流（UZF）程序包時，可以使用現有的穩態MODFLOW模型來模擬分水嶺區域。在地下水位靠近陸地表面的單元中，UZF程序包計算「滲漏」單元的水頭差和比例電導，以生成平均垂直滲入土地的速率。這種方法是用排水口覆蓋MODFLOW域的一種替代方法，由於不飽和流不活躍且結果主要由容易獲得的地形信息驅動，因此用戶輸入的信息很少。像排水法一樣，它的優點是，滲流面積的分布不是由建模人員預先確定的，而是由模擬水頭產生的。除排水方法外，它還考慮了細胞內陸地表面的變化，以明確地量化與滲透，拒絕補給，補給和地表滲漏相對應的多種表面流。該方法在威斯康星州東南部盆地的應用證明了如何將其用作決策支持工具，首先，明確分布，其次，預測響應淺水抽出的口水位下降和滲透率降低。
3. Numerical Studyof Tide‐Induced Airflowand Salt–Fresh WaterDynamics in Unconfined Aquifers
by Yong G, Zang Dong M, Sun Ping Feng
承壓含水層中潮汐引起的氣流和鹽淡水動力學的數值模擬研究
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.
這項研究採用了水-氣兩相流和鹽水耦合的輸運模型，分析了帶傾斜海灘的兩層無側壓含水層中非飽和區產生的氣流的行為以及鹽-淡水界面的鹽度波動，其表面遭受潮汐振蕩。仿真結果表明，由於通過多個潮汐周期達到了包括潮汐波動影響的新的動態穩態，下部鹹水楔中的分散區變寬了，因為其中的淡水/鹽水在潮汐周期中不斷地向陸或向海流動。上部的鹽-淡水界面更容易受到潮汐波動的影響，其中鹽度的變化是周期性的，與水壓頭無關，但受周圍水流的方向和速度的影響。隨著潮汐水平的波動，由於上部半透水層的約束，氣流主要集中在下部透水層，並且孔隙空氣壓力和潮汐水平之間的時間滯後隨距海岸線的距離而增加。氣流在不飽和區的影響可以向下傳播，由於氣流對水流的阻力，使得有氣流的情況下的鹽度和淡水上部界面中的鹽度值及其幅度都小於沒有氣流的情況。敏感性分析表明，非飽和區中氣流的分布受上/下層滲透率和下層van Genuchten參數的影響，而不是受上層van Genuchten參數的影響，而鹽分中的鹽度波動淡水界面僅受下層土壤參數的影響。
4.Numerical Simulations of Seasonally Oscillated Groundwater Dynamics in Coastal ConfinedAquifers
by Wenjing Qu, Hailong Li , Chaoyue Wang, Chunmiao Zheng , Xuejing Wang, Yan Zhang
沿海承壓含水層季節性振蕩的地下水動態數值模擬
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.
研究內陸補給對沿海地下水動力學影響的研究通常是在無限制含水層中進行的，而在受限含水層中很少進行。本研究通過數值模擬，研究了內陸地下水水位呈季節正弦波動且海平面恆定的承壓含水層中的地下水動力學。眾所周知，響應內陸地下水頭的季節性振蕩，鹹水楔形混合區（MZ）圍繞穩態MZ擺動。然而，我們的模擬結果表明，當在給定的參數值下，在一定的邊界條件下水力傳導率K ≤10−4 m / s時，即使是一年中最陸上的淡水-鹽水界面也從穩態位置向海。也就是說，當K≤10−4 m / s時，內陸地下水位的季節性波動可以減少海水在受限的承壓含水層中的侵入。敏感性分析表明，對於K≤10−4 m / s的含水層，內陸水頭波動幅度越大，海水的侵入越少。這可能是由於當K≤10-4 m / s時，海水入侵時間隨波動幅度的增加而減少的原因。數值模擬表明，季節性內陸地下水水頭振蕩促進了跨海邊界的年平均再循環海水排放量。
5. Evaluation of NegativeEconomic‐Environmental Externalities of Overextraction ofGroundwater
byMostafa Baniasadi, Mohammad Reza Zare'Mehrjordi, Hossein Mehrabi Boshrabadi , HamidReza Mirzaei Khalilabad, Abbas RezaeiEstakhrooye
地下水超採對經濟和環境的負面影響
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.近幾十年來，用於人類和農業的地下水開採量增加，導致世界上大部分地區的地下水位大幅下降。地下水位下降本身就是一個嚴重的問題，並且具有多種經濟，社會，文化，政治，安全相關和環境外部性。使用重置成本，生產函數，市場價格，影子價格以及投入的邊際產品價值等方法評估了伊朗克爾曼省平原地下水超採的負面經濟環境外部影響。在評估了外部性之後，使用正數學規劃方法來評估不同的水政策，以減少地下水的消耗。據計算，由於外部因素造成的總經濟損失相當於2.8億美元。據計算，環境外部性造成的損失等於436.1億美元。與積極計劃模型相關的結果表明，在不同方案中的最佳政策（例如赤字灌溉政策或聯合政策）涉及實施加壓灌溉系統。
6.MonteCarlo Simulations as a Decision Support to Interpret δ15N Values of Nitrate inGroundwater
byLisa M. Wild , Arno Rein , Florian Einsiedl
蒙特卡羅模擬是地下水硝酸鹽δ15N值的決策依據
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.
密集耕作通常與過度使用肥料或化肥以及隨後全球範圍內許多含水層的地下水質量下降有關。溶解的硝酸鹽的穩定同位素（δ15N和δ18O）被廣泛用於確定地下水中硝酸鹽汙染和反硝化過程的來源，但通常難以解釋。因此，對德國下巴伐利亞的一個地點進行了蒙特卡洛模擬，以解釋在具有兩個含水層，主要含水層（MA）和幾個較小的棲息含水層（PA）的多孔地下水系統中的δ15N觀測值。為了評估潛在風險，模擬了δ15N的頻率分布，其源於（I）與土地利用有關的不同硝酸鹽源的混合，作為地下水的輸入，結合（II）地下水中硝酸鹽的運輸和（III）微生物反硝化。模擬結果表明，由源驅動的同位素轉移到地下水中硝酸鹽的δ15N值較高，這可以用土地利用向集約化農業轉變為釋放大量肥料的方式來解釋。微生物反硝化作用可能在PA中起作用，模擬的δ15N分布接近觀測值。然而，MA不太可能進行反硝化過程，因為針對這種情況的合理模擬曲線主要是針對不切實際的硝酸鹽來源和相關土地利用而獲得的。應用的方法可用於定性和定量評估不同潛在貢獻的影響，由於重疊的δ15N範圍可能相互掩蓋，並且可以支持與土地利用有關的硝酸鹽輸入估算。
7.Mapping Groundwater Potential Through an Ensemble of Big Data Methods
byP. Martínez‐Santos , P. Renard
通過系列大數據方法繪製地下水潛力
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.
地下水資源對於撒哈拉以南非洲地區的安全飲用水供應至關重要，在氣候變化的背景下，越來越多依賴地下水資源。為了更好地了解地下水，需要採用創新的方法來充分利用現有信息。本文提出了一種基於機器學習分類器的地圖來繪製地下水潛力的方法。一個大型鑽孔資料庫（n = 1848）已集成到地理信息系統（GIS）環境中，並用於訓練，驗證和測試12種機器學習算法。每個分類器都基於公共家庭供應所需的最小流速來預測二進位目標（正井眼或負井眼）。分類基於許多解釋性變量，包括地貌，界線，土壤，植被，地質和坡度等。然後，將目標變量與解釋變量之間的相關性進行概括，以開發地下水潛力圖。多數算法在測試分數方面都獲得了80％到96％的成功率，這表明結果可以提供對現場條件的準確描述。觀察到統計學習者的表現比大多數其他算法要好，隨機森林和支持向量機除外。此外，得出的結論是，集成方法通過將不確定性度量結合到結果中來提供附加值。在有足夠的歷史數據但無法進行全面野外工作的地區，可以使用此技術快速繪製地下水潛力以用於農村供水或人道主義緊急情況。
8.Numerical Investigation of a Methane Leakage from a Geothermal Well into a ShallowAquifer
byAndrea D'Aniello , Massimiliano Fabbricino , Daniela Ducci, Domenico Pianese
地熱井向淺層含水層中洩漏甲烷的數值研究
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.
非常規天然氣生產對地下水資源的潛在環境影響仍存在爭議。因此，解決有關氣體洩漏對地下水資源的潛在不利影響至關重要。在本文中，提出了一個有趣的現實案例，以便進一步了解與深層地下的行為相比常常被忽略的淺層地下的甲烷多相和輸運行為。通過多相流和溶質運移模擬，評估了現有的淺層無限制含水層相對於由前深層地熱井的井身完整性故障導致的甲烷洩漏的脆弱性。分析表明，氣態甲烷通過受檢查含水層的遷移可能非常快（幾分鐘左右），主要發生在井附近垂直向上。相比之下，溶解的甲烷遷移在很大程度上受地下水流場的影響，並發生在較大的時間範圍內（數月/年的量級），覆蓋距離井口較遠。總體而言，如果發生氣體洩漏，此地點的真正問題在於井附近爆炸的危險。預測的最大氣體通量（0.89至22.60m3 / d）與洩漏井的報告值相當，並且最大的溶解甲烷濃度可能會在幾年內超過風險緩解閾值（7至10mg / L）。因此，強烈建議在停運前進行地面和地下監測，以確保現場安全。
9. An Approximation of Inner BoundaryConditions for Wells Intersecting Highly Conductive Structures
byMarkus Giese , Thomas Reimann, Rudolf Liedl, Benoit Dewandel, Jean‐ChristopheMaréchalMartin Sauter
與高導電結構相交的井的內部邊界條件的近似值
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.
內部邊界條件描述了抽水過程中地下水井與周圍含水層的相互作用與表皮損壞有關，其限制了水的生產和井筒儲水。在即時流量和早期流量期對井的抽水測試評估要求考慮內部邊界條件。最初，這些概念是為垂直井開發的，後來又轉移到與高傳導性結構相交的井筒中，例如裂縫和巖溶系統中的優先流動區。複雜基巖地質中抽水試驗分析的概念模型通常得到簡化。經典的分析解決方案通常會在泵送開始時沿井篩限制或忽略限制或提高井生產率的條件。通過考慮額外的物理過程並避免假設和簡化，數值解決方案可以比分析法更精確地表示複雜地質環境（例如巖溶系統）中的井位下降。用於巖溶流動模擬的合適數值模擬法是離散管道連續模型，這些模型考慮了各種物理作用，例如在抽水過程中與高導電結構相交的井筒的瞬態水力。
10. Variation in Saturated HydraulicConductivity at the Outcrop Scale, the Whanganui Basin, New Zealand
byCallum Rees, Alan Palmer, Julie Palmer , Ranvir Singh
紐西蘭旺格努伊盆地露頭尺度的飽和導水率變化
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.
地下水流量和汙染物運移受水文地質空間變化的影響。了解含水層的各向異性對於預測優先流動路徑至關重要，但通常因不完整水文地質數據，間隔較大的數據點和複雜的地層而受阻。在這裡，我們演示了一種相對較新的空氣滲透儀技術的應用，為表徵現場水文地層提供了一種經濟高效的快速替代方案。這項研究的目的一是表徵紐西蘭旺格努伊盆地淺海水文地層單元中飽和水力傳導率的變化，二是評估各個水文地層單元中飽和水力傳導率的變化並將這些變化聯繫起來到相和沉積環境。結果表明細粒弱透水層的各項異質受到生物擾動控制，由於其挖洞，攝入和排便導致粒度偏析和差分微晶膠結。粗粒含水層在平面到交叉層組的滲透率顯示出急劇變化，這與淺海沉積環境中的電流和波能波動有關。順層平面定向可形成高滲透率帶，從而促進下傾地下流體流動。建議沿古海岸線-陸架斷面將粗粒近岸相向下傾斜成細粒陸相，以促進盆地填充物中的橫向和垂直地下水流。空氣滲透儀技術在世界範圍內的地下水盆地中都有潛在的應用前景，它提供的數據集有助於人們更好地了解地下水系統，為有針對性的水質管理提供實踐和理論依據。
1.AcceleratingStreamline Tracking in Groundwater Flow Modeling on GPUs
byXiaohui Ji, Mulan Luo , Xusheng Wang
在GPU上加速簡化跟蹤地下水流模擬
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.
當分析大量流線時，地下水流模型中的流線模擬是一個耗時的過程。我們針對Pollock（1988）開發的半分析粒子跟蹤算法，在圖形處理單元（GPU）上開發了並行化方法。計算統一設備體系結構用於實現並行方法。流線的向前和向後跟蹤由單個線程處理。 GPU包括一塊塊的網格，其中一塊可處理32個線程。我們使用多GPU來加速具有數百萬個粒子的流模型中的流線跟蹤。檢查了該方法以模擬流線，以識別Tóthian盆地的三維（3D）流動系統。當使用8個NVIDIA GPU模擬500萬或更多流線時，加速超過1000。
1．A Search for Freshwater in the Saline Aquiferof Coastal Bangladesh
byChelsea N. Peters， George M. Hornberger
在孟加拉國沿海鹹水層中尋找淡水
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.
在孟加拉國沿海的田地區，淺層地下水主要是微鹹的，並且出現了不可預測的淡水袋。三角洲的形成，包括新鮮到鹹水的孔隙水和沉積物的共存，形成了淺層含水層。滲透性差的粘土相和缺乏地形梯度限制了地下水的流動及其與地表水的混合，因此對鹽度空間變異性的控制並不明顯。通過表徵地下水-地表水（GW-SW）的相互作用，本研究試圖確定社區的飲用水區域。我們使用了壓力計，巖心，電磁感應和水化學調查的樣板，探索了潛在的新鮮地下水的兩種來源：（1）潮汐通道-含水層交換，（2）大氣補給。由於巖層的非均質性，潮汐動力學不對稱，降雨極端季節性波動以及田間數據有限，因此難以找到新鮮地下水。地球物理觀測表明，淺層地下電導率剖面存在較大的橫向變化。測壓儀顯示遠離通道的潮汐壓力衰減程度不同。然而，由於堤岸和表層沉積物的低滲透性，淡水的主動交換似乎受到限制。結果表明，使用現成的水文地質方法無法識別出新鮮的地下水，因此應尋求替代的飲用水源。通過更好地了解系統的水文地質學，社區將能夠更好地將水資源管理資源轉移到更可行，更可持續的飲用水方案上。
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
流溫和光纖溫度傳感表徵地下水流量
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).
以恩貢塔哈河為例來評估光纖分布式溫度傳感（FODTS）的適用性，確定彈簧的位置並量化其排放量共確定了十三座溫泉，大部分位於115 m範圍內，右岸排出了五處，左岸排出了八處。為了量化地下水排放量，開發了一種新方法，其中將一維瞬態傳熱模型擬合到FODTS測量中，其中感興趣的主要校準參數是未知的春季排放量。地下水排放估算問題的空間分布受到兩個信息來源的約束：首先，根據流量測量確定的流量增益約為500 L / s。其次，左右堤壩的溫度分布提供了彈簧及其相對排放量的空間分布。 FODTS用於測量左岸和右岸附近的河流溫度，從而創建了兩個溫度數據集。然後計算兩個數據集的加權平均值，其中的權重反映了彈簧下遊左右堤岸之間的混合程度。本研究中的新方法與以前的研究不同，後者的一般方法是使用穩態熱混合模型（Selker等人2006a；Westhoff等人2007；Briggs等人2012）推斷地下水。流量，然後將其用作方程式一般形式的瞬態模型的輸入，以模擬河流溫度（Westhoff等，2007）。
3．Producer Attitudes Toward GroundwaterConservation in the U.S. Ogallala‐High Plains
StephenLauer, Matthew R. Sanderson
生產者對美國奧加拉拉-高平原地區地下水保護的態度
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.
我們對美國奧加拉拉-高平原含水層地區的1,226位農業生產者進行了調查，提出了對地下水保存和管理態度的描述性發現。我們發現，絕大多數生產者都認為應該保護地下水而不是將其完全消耗掉。大多數人認為地下水枯竭是一個嚴重的問題。與他們自己的農業經營活動相比，生產者認為完全耗盡地下水對他們的社區來說是一個更大的問題。人們已經達成共識，出於利他的原因，應該保護地下水，以造福社區後代。大多數生產者認為，他們在農場上進行額外地下水保護的個人能力有限，很少有人參與自願的團體保護計劃。我們認為關鍵因素是社會問題，未來的努力應集中發展高原地區地下水保護網站，能力和文化。
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