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Ground Water

Ashley M Bandy, Kimberly Cook, Alan E Fryar, Junfeng Zhu
Lack of filtration and rapid transport of groundwater and particulate matter make karst aquifers susceptible to bacterial contamination. This study utilized qPCR (quantitative polymerase chain reaction) to examine the transport and attenuation of two non-virulent isolates of Escherichia coli (E. coli) in relation to traditional groundwater tracers (rhodamine WT dye and 1-μm diameter latex microspheres) in a karst-conduit aquifer in central Kentucky. Bacterial isolates were labeled with stable isotopes (15 N and 13 C)...
April 15, 2019: Ground Water
Yao Du, Yamin Deng, Teng Ma, Shuai Shen, Zongjie Lu, Yiqun Gan
It becomes increasingly important and challenging for nitrogen pollution prevention to identify key controls for spatial variability of nitrogen in groundwater that could be affected by multiple factors, including anthropogenic input, groundwater flow and local geochemistry. This study characterized spatial variability of both nitrate and ammonium in the Pleistocene aquifer of central Yangtze River Basin and assessed the effect of various factors in controlling nitrate and ammonium levels based on multiple statistical approaches (correlation, geostatistics, multiple liner regression)...
April 12, 2019: Ground Water
Henk Haitjema
No abstract text is available yet for this article.
April 8, 2019: Ground Water
Peter R Jørgensen, Klaus Mosthaf, Massimo Rolle
Intact soil columns can bridge the gap between field studies and idealized laboratory investigations of flow and transport in macropores and fractured media. However, the value of intact column studies is often hampered by shortcomings such as lack of column intactness, small column size, and column rim flow, which can cause serious artifacts and hamper system understanding. The flexible-wall pressurized Large Undisturbed Column (LUC) method minimizes these limitations and is a valuable approach to analyze fluid flow and solute transport in macroporous and fractured geological formations...
April 2, 2019: Ground Water
Liang Xiao, Ming Ye, Yongxin Xu, Fuwan Gan
This paper derives an equivalent of Darcian Theis solution for non-Darcian flow induced by constant rate pumping of a well in a confined aquifer. The derivation, which is valid at later times only, is original. It utilizes Izbash's equation. This introduces an additional parameter to Darcian condition, namely empirical exponent. The solution is a non-Drcian equivalent of Jacob straight line method for analyzing pumping tests at late times. It can be used to determine aquifer parameters: storativity, analogous hydraulic conductivity and empirical exponent...
April 1, 2019: Ground Water
Reynold Chow, Jeremy Bennett, Jürnjakob Dugge, Thomas Wöhling, Wolfgang Nowak
Hyporheic exchange is the interaction of river water and groundwater, and is difficult to predict. One of the largest contributions to predictive uncertainty for hyporheic exchange has been attributed to the representation of heterogeneous subsurface properties. Our study evaluates the trade-offs between intrinsic (irreducible) and epistemic (reducible) model errors when choosing between homogeneous and highly complex subsurface parameter structures. We modelled the Steinlach River Test Site in Southwest Germany using a fully coupled surface water-groundwater model to simulate hyporheic exchange and to assess the predictive errors and uncertainties of transit time distributions...
March 25, 2019: Ground Water
M Adil Sbai, N Amraoui
Widely used numerical models of solute transport processes in subsurface aquifers are limited to non-locally refined rectangular, or logically rectangular, structured grids. This presents an unsuitable option to efficient numerical simulations maintaining an acceptable level of accuracy. Optimal selection of locally refined cells for efficient solute transport models is challenging to the current generation of numerical models. We present a novel and relatively simple to implement algorithm addressing these shortcomings...
March 20, 2019: Ground Water
Willem J de Lange
The absence of recent research on dispersion in engineering applications indicates the need for a description that is more focused on field and modeling practice. Engineers may benefit from simple calculation tools allowing them to understand the processes encountered in the field. Based on a conceptual model for advective transport through an elongated conductivity zone e.g. in fluvial sediments, explicit expressions are presented for macro-scale phenomena: 1) The different travel distances of water particles traveling in laminar flow through and adjacent to a single zone with conductivity higher or lower than that of the aquifer...
March 20, 2019: Ground Water
L J M Peeters, C Turnadge
Explicitly accounting for uncertainty in boundary conditions during calibration and uncertainty analysis invariably means increasing the complexity of a model. This increases computational requirements, as more parameters imply more model runs and more complex models often have a longer runtime.
March 19, 2019: Ground Water
Jet-Chau Wen, Jyun-Lin Chen, Tian-Chyi Jim Yeh, Yu-Li Wang, Shao-Yang Huang, Zhong Tian, Chia-Yii Yu
Drawdown data from independent pumping tests have widely been used to validate the estimated hydraulic parameters from inverse modeling or hydraulic tomography (HT). Yet, the independent pumping test has not been clearly defined. Therefore, this goal of this paper is to define this independent pumping test concept, based on the redundant or non-redundant information about aquifer heterogeneity embedded in the observed heads during cross-hole pumping tests. The definition of complete, moderate redundancy and high non-redundancy of information are stipulated using cross-correlation analysis of the relationship between the head and heterogeneity...
March 11, 2019: Ground Water
Matthias Loschko, Thomas Wöhling, David L Rudolph, Olaf A Cirpka
Numerical models for reactive transport can be used to estimate the breakthrough of a contaminant in a pumping well or at other receptors. However, as natural aquifers are highly heterogeneous with unknown spatial details, reactive transport predictions on the aquifer scale require a stochastic framework for uncertainty analysis. The high computational demand of spatially explicit reactive-transport models hampers such analysis, thus motivating the search for simplified estimation tools. We suggest performing an electron balance between the reactants in the infiltrating solution and in the aquifer matrix to obtain the hypothetical time of dissolved-reactant breakthrough at a receptor if the reaction with the matrix was instantaneous...
March 8, 2019: Ground Water
Michael Cardiff, Ben Heinle
Heterogeneity in aquifer properties, and the influence of transport processes other than advection and dispersion, often produce transport "surprises" in that measurements become difficult to reconcile with predictions from the traditional advection-dispersion equation (ADE) that students are introduced to early in their hydrogeology training. Students should be aware of and prepared for the reasons why the ADE (as commonly applied) may not always "work" in the sense of generating valid predictions...
March 6, 2019: Ground Water
William D Robertson, Dorothy L Garda
We have established a monitoring record of phosphate (PO4 3- ) migration in the Long Point, ON campground septic system plume that now spans 26 years. Previously, at year 16 (2006), a P plume 16 m in length was documented and provided a good fit with an analytical advection dispersion model when a P migration velocity of 0.8 m/yr was used (retardation factor of 37) and when P behaved in an otherwise conservative manner (sorption only). However, between years 16 and 26 (2016), the P plume length expanded by only 2 m (0...
March 6, 2019: Ground Water
Haley A Schneider, W Andrew Jackson, Ken Rainwater, Danny Reible, Stephen Morse, Paul B Hatzinger, Uriel Garza-Rubalcava
The fate and transport of groundwater contaminants depends partially on groundwater velocity, which can vary appreciably in highly stratified aquifers. A high resolution passive profiler (HRPP) was developed to evaluate groundwater velocity, contaminant concentrations, and microbial community structure at ~ 20 cm vertical depth resolution in shallow heterogeneous aquifers. The objective of this study was to use mass transfer of bromide (Br- ), a conservative tracer released from cells in the HRPP, to estimate interstitial velocity...
February 27, 2019: Ground Water
Zachary K Curtis, Hua-Sheng Liao, Shu-Guang Li, Prasanna Venkatesh Sampath, David P Lusch
Managing non-point-source (NPS) pollution of groundwater systems is a significant challenge because of the heterogeneous nature of the subsurface, high costs of data collection, and the multitude of scales involved. In this study, we assessed a particularly complex NPS groundwater pollution problem in Michigan, namely, the salinization of shallow aquifer systems due to natural upwelling of deep brines. We applied a system-based approach to characterize, across multiple scales, the integrated groundwater quantity-quality dynamics associated with the brine upwelling process, assimilating a variety of modeling tools and data - including statewide water well datasets scarcely used for larger scientific analysis...
February 25, 2019: Ground Water
Xueyan Ye, Ruijuan Cui, Xinqiang Du, Sijia Ma, Jingtong Zhao, Ying Lu, Yuyu Wan
Managed aquifer recharge is an effective strategy for urban stormwater management. Chemical ions are normally retained in stormwater and groundwater and may accelerate clogging during the recharge process. However, the effect of water chemistry on physical clogging has not previously been investigated. In this study, we investigated the hydrogeochemical mechanism of saturated porous media clogging in a series of column experiments. The column was packed with river sand and added suspensions of kaolinite particles...
February 25, 2019: Ground Water
Bander A M Algaydi, Ali M Subyani, Mohamed Hafedh M M Hamza
In arid and hyper-arid zones, groundwater exploration is one of the most significant ways to locate potential new water supplies. Geophysical prospecting is currently the most successfully used method for locating new supplies, but it is rather costly. Satellite remote sensing (RS) detection, however, with its integration of Geographic Information Systems (GIS) provides the best chance for identifying and initially evaluating water-bearing formations. In the western part of Saudi Arabia, Wadi Na'man has for centuries been one of the major water sources for the city of Makkah Al-Mukarramah...
February 17, 2019: Ground Water
Kurt O Thomsen
The needs of sub-regional and local entities for water resource management are immediate, and required information is not forthcoming in a timely and relatively inexpensive manner. The following method allows one to use all available well record data to produce baseline hydrogeologic unit maps using geographic information system (GIS) querying and mapping techniques. Subjective borehole and geophysical strata descriptions are converted to objective equivalent numerical values by establishing the average hydraulic conductivity of the combined soils making up the stratum of interest...
February 14, 2019: Ground Water
Pawan Jeet, D K Singh, A Sarangi
Rainfall is the major source for groundwater recharge in basins areas of central region of India. Now a day, the river basins are experiencing acute shortage of water which has resulted in lowering of groundwater level and drying up of water bodies. In order to maintain water sustainability; a composite hydrologic index was developed in the Betwa basin of Madhya Pradesh and Uttar Pradesh states, India. The index was developed using principal component analysis (PCA) through hydrologic, topographic as well as geographic parameters derived from the Soil and Water Assessment Tool (SWAT) and MODFLOW model...
February 10, 2019: Ground Water
Shaymaa Mustafa, Mohamad Darwish, Arifah Bahar, Zainal Abdul Aziz
Analytical studies for well design adjacent to river banks are the most significant practical task in cases involving the efficiency of riverbank filtration systems. In times when high pollution of river water is joined with increasing water demand, it is necessary to design pumping wells near the river that provide acceptable amounts of river water with minimum contaminant concentrations. This will guarantee the quality and safety of drinking water supplies. This article develops an analytical solution based on the Green's function approach to solve an inverse problem: based on the required level of contaminant concentration and planned pumping time period, the shortest distance to the riverbank that has the maximum percentage of river water is determined...
February 10, 2019: Ground Water
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