Diffusive mass exchange of non‐reactive substances in dual‐porosity porous systems – column experiments under saturated conditions          下载免费PDF全文

Bastian Knorr  Piotr Maloszewski  Florian Krämer  Christine Stumpp 《水文研究》2016,30(6):914-926

Diffusive mass exchange into immobile water regions within heterogeneous porous aquifers influences the fate of solutes. The percentage of immobile water is often unidentified in natural aquifers though. Hence, the mathematical prediction of solute transport in such heterogeneous aquifers remains challenging. The objective of this study was to find a simple analytical model approach that allows quantifying properties of mobile and immobile water regions and the portion of immobile water in a porous system. Therefore, the Single Fissure Dispersion Model (SFDM), which takes into account diffusive mass exchange between mobile and immobile water zones, was applied to model transport in well‐defined saturated dual‐porosity column experiments. Direct and indirect model validation was performed by running experiments at different flow velocities and using conservative tracer with different molecular diffusion coefficients. In another column setup, immobile water regions were randomly distributed to test the model applicability and to determine the portion of immobile water. In all setups, the tracer concentration curves showed differences in normalized maximum peak concentration, tailing and mass recovery according to their diffusion coefficients. These findings were more pronounced at lower flow rates (larger flow times) indicating the dependency of diffusive mass exchange into immobile water regions on tracers' molecular diffusion coefficients. The SFDM simulated all data with high model efficiency. Successful model validation supported the physical meaning of fitted model parameters. This study showed that the SFDM, developed for fissured aquifers, is applicable in porous media and can be used to determine porosity and volume of regions with immobile water. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Quantification of river water infiltration in shallow aquifers using acesulfame and anthropogenic gadolinium          下载免费PDF全文

Andrea Bichler  Christian Muellegger  Robert Brünjes  Thilo Hofmann 《水文研究》2016,30(11):1742-1756

This study has investigated the use of the artificial sweetener acesulfame and the magnetic resonance imaging contrast agent gadolinium as quantitative tracers for river water infiltration into shallow groundwater. The influence of a river on alluvial groundwater in a subalpine catchment in western Europe has been assessed using the ‘classical’ hydrochemical tracer chloride and the trace contaminants acesulfame and anthropogenic gadolinium. Mixing ratios for riverine bank filtrate with ambient groundwater and the uncertainties associated with the temporal and spatial tracer variability were calculated using acesulfame and gadolinium and compared with those obtained using chloride. The temporal variability of tracer concentrations in river water of gadolinium (standard deviation SD: 63%) and acesulfame (SD: 71%) both exceeded that of chloride (SD: 27%), and this was identified as the main source of uncertainty in the mixing analysis. Similar spatial distributions were detected in the groundwater for chloride and gadolinium, but not for acesulfame. Mixing analyses using acesulfame resulted in calculated mixing ratios that differed from those obtained using gadolinium and chloride by up to 83% and 92%, respectively. At the investigated site, which had oxic conditions and moderate temperatures, acesulfame was found to be a less reliable tracer than either gadolinium or chloride, probably because of natural attenuation and input from other sources. There was no statistically significant difference between the mixing ratios obtained using chloride or gadolinium, the mixing ratios obtained using gadolinium were 40–50% lower than those obtained using chloride. This is mainly due to a bias of the mean gadolinium concentration in river water towards higher values. In view of the uncertainties of the two tracers, neither could be preferred over the other for the quantification of bank filtrate in groundwater. At this specific site gadolinium was able to reliably identify river water infiltration and was a more precise tracer than chloride at low mixing ratios (<20%), because of the exclusive occurrence of gadolinium in river water and its high dynamic range. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Improved spatial delineation of streambed properties and water fluxes using distributed temperature sensing          下载免费PDF全文

Landon J. S. Halloran  Hamid Roshan  Gabriel C. Rau  Martin S. Andersen  R. Ian Acworth 《水文研究》2016,30(15):2686-2702

A new method was developed for analysing and delineating streambed water fluxes, flow conditions and hydraulic properties using coiled fibre‐optic distributed temperature sensing or closely spaced discrete temperature sensors. This method allows for a thorough treatment of the spatial information embedded in temperature data by creating a matrix visualization of all possible sensor pairs. Application of the method to a 5‐day field dataset reveals the complexity of shallow streambed thermal regimes. To understand how velocity estimates are affected by violations of assumptions of one‐dimensional, saturated, homogeneous flow and to aid in the interpretation of field observations, the method was also applied to temperature data generated by numerical models of common field conditions: horizontal layering, presence of lateral flow and variable streambed saturation. The results show that each condition creates a distinct signature visible in the triangular matrices. The matrices are used to perform a comparison of the behaviour of one‐dimensional analytical heat‐tracing models. The results show that the amplitude ratio‐based method of velocity calculation leads to the most reliable estimates. The minimum sensor spacing required to obtain reliable velocity estimates with discrete sensors is also investigated using field data. The developed method will aid future heat‐tracing studies by providing a technique for visualizing and comparing results from fibre‐optic distributed temperature sensing installations and testing the robustness of analytical heat‐tracing models. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

An alternative Boussinesq equation considering the effect of hysteresis on coastal groundwater waves          下载免费PDF全文

Jun Kong  Zhaoyang Luo  Chengji Shen  Guofen Hua  Hongjun Zhao 《水文研究》2016,30(15):2657-2670

This paper presents an alternative Boussinesq equation considering hysteresis effect via a third‐order derivative term. By introducing an improved moisture–pressure retention function, this equation describes, with reasonable precision, groundwater propagation in coastal aquifers subject to Dirichlet boundary condition of different oscillation frequencies. Test results confirmed that it is necessary to consider horizontal and vertical flows in unsaturated zone, because of their variable influences on hysteresis. Hysteresis in unsaturated zone can affect the water table wave number of groundwater wave motion, such as wave damping rate and phase lag. Oscillations with different periods exert different hysteresis effect on wave propagation. Truncation/shrinkage of unsaturated zones also affects the strength of hysteresis. These impacts can be reflected in the alternative Boussinesq equation by adjusting the parameter representing the variation rate of moisture associated with pressure change, as opposed to traditional computationally expensive hysteresis algorithms. The present Boussinesq equation is simple to use and can provide feasible basis for future coupling of groundwater and surface water models. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Use of a watershed hydrologic model to estimate interbasin groundwater flow in a Costa Rican rainforest          下载免费PDF全文

Carlo Zanon  David P. Genereux  Steven F. Oberbauer 《水文研究》2014,28(10):3670-3680

The watershed hydrologic model TOPMODEL was used to estimate interbasin groundwater flow (IGF) into a small lowland rainforest watershed in Costa Rica. IGF is a common hydrological process but often difficult to quantify. Four‐year simulations (2006–2009) using three different model approaches gave estimates of IGF that were very similar to each other (10.1, 10.2, and 9.8 m/year) and to an earlier estimate (10.0 m/year) based on 1998–2002 data from a budget study that did not use a hydrologic simulation model, providing confidence in the new estimates and suggesting each of the three model approaches is viable. Results show no significant temporal variation in IGF during 2006–2009 (or between this period and the earlier study from 1998–2002). Simulations of the 16 consecutive 3‐month periods in 2006–2009 gave 16 values of IGF rate with a mean (10.1 m/year, standard deviation = 0.6 m/year) very similar to the estimates above from the 4‐year simulations. This suggests the modified version of TOPMODEL can be used to model stream discharge and estimate IGF for sub‐annual time periods during which change in water storage is not necessarily equal to zero. Thus, simple watershed models may be used to estimate IGF based on even relatively short calibration periods, making such models useful tools in the study of this widespread hydrological process that affects water and chemical fluxes and budgets but is often difficult and costly to quantify. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Sea‐level rise impact on fresh groundwater lenses in two‐layer small islands          下载免费PDF全文

Hamed Ketabchi  Davood Mahmoodzadeh  Behzad Ataie‐Ashtiani  Adrian D. Werner  Craig T. Simmons 《水文研究》2014,28(24):5938-5953

The fresh groundwater lenses (FGLs) of small islands can be highly vulnerable to climate change impacts, including sea‐level rise (SLR). Many real cases of atoll or sandy islands involve two‐layer hydrogeological conceptualizations. In this paper, the influential factors that affect FGLs in two‐layer small islands subject to SLR are investigated. An analytical solution describing FGLs in circular islands, composed of two geological layers, is developed for the simplified case of steady‐state and sharp‐interface conditions. An application of the developed model is demonstrated to estimate the FGL thickness of some real‐world islands by comparison with existing FGL thickness data. Furthermore, numerical modelling is applied to extend the analysis to consider dispersion effects and to confirm comparable results for both cases. Sensitivity analyses are used to assess the importance of land‐surface inundation caused by SLR, relative to other parameters (i.e. thickness of aquifer layers, hydraulic conductivity, recharge rate and land‐surface slope) that influence the FGL. Dimensionless parameters are used to generalize the findings. The results demonstrate that land‐surface inundation has a considerable impact on a FGL influenced by SLR, as expected, although the FGL volume is more sensitive to recharge, aquifer thickness and hydraulic conductivity than SLR impacts, considering typical parameter ranges. The methodology presented in this study provides water resource managers with a rapid‐assessment tool for evaluating the likely impacts of SLR and accompanying LSI on FGLs.  相似文献   

The effects of floods on the temperature of riparian groundwater          下载免费PDF全文

Jeffery A. Watson  M. Bayani Cardenas  Stephen B. Ferencz  Peter S.K. Knappett  Bethany T. Neilson 《水文研究》2018,32(9):1267-1281

The transition area between rivers and their adjacent riparian aquifers, which may comprise the hyporheic zone, hosts important biochemical reactions, which control water quality. The rates of these reactions and metabolic processes are temperature dependent. Yet the thermal dynamics of riparian aquifers, especially during flooding and dynamic groundwater flow conditions, has seldom been studied. Thus, we investigated heat transport in riparian aquifers during 3 flood events of different magnitudes at 2 sites along the same river. River and riparian aquifer temperature and water‐level data along the Lower Colorado River in Central Texas, USA, were monitored across 2‐dimensional vertical sections perpendicular to the bank. At the downstream site, preflood temperature penetration distance into the bank suggested that advective heat transport from lateral hyporheic exchange of river water into the riparian aquifer was occurring during relatively steady low‐flow river conditions. Although a small (20‐cm stage increase) dam‐controlled flood pulse had no observable influence on groundwater temperature, larger floods (40‐cm and >3‐m stage increases) caused lateral movement of distinct heat plumes away from the river during flood stage, which then retreated back towards the river after flood recession. These plumes result from advective heat transport caused by flood waters being forced into the riparian aquifer. These flood‐induced temperature responses were controlled by the size of the flood, river water temperature during the flood, and local factors at the study sites, such as topography and local ambient water table configuration. For the intermediate and large floods, the thermal disturbance in the riparian aquifer lasted days after flood waters receded. Large floods therefore have impacts on the temperature regime of riparian aquifers lasting long beyond the flood's timescale. These persistent thermal disturbances may have a significant impact on biochemical reaction rates, nutrient cycling, and ecological niches in the river corridor.  相似文献   

A multi‐storage groundwater concept for the SWAT model to emphasize nonlinear groundwater dynamics in lowland catchments          下载免费PDF全文

Matthias Pfannerstill  Björn Guse  Nicola Fohrer 《水文研究》2014,28(22):5599-5612

Hydrological models are useful tools to analyze present and future conditions of water quantity and quality. The integrated modelling of water and nutrients needs an adequate representation of the different discharge components. In common with many lowlands, groundwater contribution to the discharge in the North German lowlands is a key factor for a reasonable representation of the water balance, especially in low flow periods. Several studies revealed that the widely used Soil and Water Assessment Tool (SWAT) model performs poorly for low flow periods. This paper deals with the extension of the groundwater module of the SWAT model to enhance low flow representation. The current two‐storage concept of SWAT was further developed to a three‐storage concept. This was realized due to modification of the groundwater module by splitting the active groundwater storage into a fast and a slow contributing aquifer. The results of this study show that the groundwater module with three storages leads to a good prediction of the overall discharge especially for the recession limbs and the low flow periods. The improved performance is reflected in the signature measures for the mid‐segment (percent bias ?2.4% vs ?15.9%) and the low segment (percent bias 14.8% vs 46.8%) of the flow duration curve. The three‐storage groundwater module is more process oriented than the original version due to the introduction of a fast and a slow groundwater flow component. The three‐storage version includes a modular approach, because groundwater storages can be activated or deactivated independently for subbasin and hydrological response unit level. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

淮南顾北矿F₁₀₄断层两侧岩溶水化学形成机制及导隔水性评价     

郑竹艳  许光泉  杨婷婷  余世滔  张海涛 《煤田地质与勘探》2020,48(1):129-137

利用断层两盘岩溶水化学特征判断其导隔水性对于我国华北型煤田水害防治具有十分重要的实践意义。以顾北矿F₁₀₄断层两侧太原组岩溶地下水为研究对象，在分析断层两盘水文地质条件基础上，采用Piper三线图、离子组合比和主成分法，分析了主要组分来源及水-岩作用差异性，并采用PHREEQC软件对岩溶地下水进行反向水化学模拟。结果表明:南北区岩溶水均存在方解石和白云石的溶解和沉淀现象，南区阳离子交换吸附和脱硫酸作用程度强于北区，而北区黄铁矿氧化和岩盐溶解作用较南区明显，南北两区水化学环境及水-岩作用存在显著差异，进而推断F₁₀₄断层具有较好的阻水性，且影响了其两侧的氧化-还原环境及温度差异，控制着地下水径流方向和水-岩作用程度。   相似文献   

Scales and magnitude of hyporheic,river–aquifer and bank storage exchange fluxes          下载免费PDF全文

Roger H. Cranswick  Peter G. Cook 《水文研究》2015,29(14):3084-3097

Many studies have investigated the exchange processes that occur between rivers and groundwater systems and have successfully quantified the water fluxes involved. Specifically, these exchange processes include hyporheic exchange, river–aquifer exchange (groundwater discharge and river loss) and bank storage exchange. Remarkably, there are relatively few examples of field studies where more than one exchange process is quantified, and as a consequence, the relationships between them are not well understood. To compare the relative magnitudes of these common exchange processes, we have collected data from 54 studies that have quantified one or more of these exchange flux types. Each flux value is plotted against river discharge at the time of measurement to allow the different exchange flux types to be compared. We show that there are positive relationships between the magnitude of each exchange flux type and increasing river discharge across the different studies. For every one order of magnitude increase in river discharge, the hyporheic, river–aquifer and bank storage exchange fluxes increase by factors of 2.7, 2.9 and 2.5, respectively. On average, hyporheic exchange fluxes are almost an order of magnitude greater than river–aquifer exchange fluxes, which are, in turn, approximately four times greater than bank storage exchange fluxes for the same river discharge. Unless measurement approaches that can distinguish between different types of exchange flux are used, there is potential for hyporheic exchange fluxes to be misinterpreted as river–aquifer exchange fluxes, with possible implications for water resource management decisions. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献