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Ground Water

Seiyed Mossa Hosseini, Behzad Ataie-Ashtiani
In this study, two conceptual models, the classic reservoir (CR) model and exchange reservoirs model embedded by dual porosity approach (DPR) are developed for simulation of karst aquifer functioning drained by multiple outlets. The performances of two developed models are demonstrated at a less developed karstic aquifer with three spring outlets located in Zagros Mountain in the south-west of Iran using 22-years of daily data. During the surface recharge, a production function based on water mass balance is implemented for computing the time series of surface recharge to the karst formations...
February 16, 2017: Ground Water
Fred D Tillman, Subhrendu Gangopadhyay, Tom Pruitt
The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin (UCRB), particularly during low-flow periods. Understanding impacts on groundwater in the basin from projected climate change will assist water managers in the region in planning for potential changes in the river and groundwater system...
February 16, 2017: Ground Water
Julien Farlin, Michael Bayerle, Denis Pittois, Tom Gallé
Although pesticides are primarily degraded in the topsoil, significant attenuation can be expected in groundwater systems where the transit time of pesticides usually are orders of magnitude longer than in the soil. Because degradation and transport processes in the subsurface take place at time scales of months to years or even decades, direct measurements of natural attenuation are hampered by practical and logistical limitations (for instance the limited duration of sampling or a correct estimation of the pesticide flux into groundwater)...
February 2, 2017: Ground Water
Robert Harrington, Keith Rainville, T Neil Blandford
No abstract text is available yet for this article.
January 31, 2017: Ground Water
Fred J Molz
No abstract text is available yet for this article.
January 30, 2017: Ground Water
Yohann Cousquer, Alexandre Pryet, Nicolas Flipo, Célestine Delbart, Alain Dupuy
Most groundwater models simulate stream-aquifer interactions with a head-dependent flux boundary condition based on a river conductance (CRIV). CRIV is usually calibrated with other parameters by history matching. However, the inverse problem of groundwater models is often ill-posed and individual model parameters are likely to be poorly constrained. Ill-posedness can be addressed by Tikhonov regularization with prior knowledge on parameter values. The difficulty with a lumped parameter like CRIV, which cannot be measured in the field, is to find suitable initial and regularization values...
January 25, 2017: Ground Water
Jean-Philippe Nicot, Toti Larson, Roxana Darvari, Patrick Mickler, Michael Slotten, Jordan Aldridge, Kristine Uhlman, Ruth Costley
Understanding the source of dissolved methane in drinking-water aquifers is critical for assessing potential contributions from hydraulic fracturing in shale plays. Shallow groundwater in the Texas portion of the Haynesville Shale area (13,000 km(2) ) was sampled (70 samples) for methane and other dissolved light alkanes. Most samples were derived from the fresh water bearing Wilcox formations and show little methane except in a localized cluster of 12 water wells (17% of total) in a approximately 30 × 30 km(2) area in Southern Panola County with dissolved methane concentrations less than 10 mg/L...
January 19, 2017: Ground Water
Kamini Singha
No abstract text is available yet for this article.
January 11, 2017: Ground Water
Chao Zhuang, Zhifang Zhou, Walter A Illman
The vertical hydraulic conductivity (Kv ), elastic (Sske ), and inelastic (Sskv ) skeletal specific storage of aquitards are three of the most critical parameters in land subsidence investigations. Two new analytic methods are proposed to estimate the three parameters. The first analytic method is based on a new concept of delay time ratio for estimating Kv and Sske of an aquitard subject to long-term stable, cyclic hydraulic head changes at boundaries. The second analytic method estimates the Sskv of the aquitard subject to linearly declining hydraulic heads at boundaries...
January 10, 2017: Ground Water
Vasileios E Katzourakis, Constantinos V Chrysikopoulos
No abstract text is available yet for this article.
January 6, 2017: Ground Water
Ziv Moreno, Amir Paster
Contaminant plumes whose characteristic length is smaller than the horizontal integral scale of the hydraulic conductivity, K, are abundant in shallow, phreatic aquifers. In such cases, the aquifer can be regarded as layered, with K being only a function of the vertical coordinate. The heterogeneity of K has a critical role upon the efficiency of remediation of such sites, for example, by Pump and Treat schemes. The expected efficiency is a random variable, with uncertainty. Quantifying this uncertainty can be of great importance to decision making...
January 3, 2017: Ground Water
Hubert J Morel-Seytoux, Calvin D Miller, Cinzia Miracapillo, Steffen Mehl
Flow exchange between surface and groundwater is of great importance be it for beneficial allocation and use of water resources or for the proper exercise of water rights. In large-scale regional studies, most numerical models use coarse grid sizes, which make it difficult to provide an accurate depiction of the phenomenon. In particular, a somewhat arbitrary leakance coefficient in a third type (i.e., Cauchy, General Head) boundary condition is used to calculate the seepage discharge as a function of the difference of head in the river and in the aquifer, whose value is often found by calibration...
December 20, 2016: Ground Water
Yong Ge Zang, Dong Mei Sun, Ping Feng, Stephan Semprich
An investigation of groundwater table fluctuations induced by rainfall should consider interactions between the liquid and gas phases in soils. In this study, a water-air two-phase flow model was initially verified by simulating an infiltration experiment. It was then employed to model the interactions between liquid and gas phases regarding actions of airflow on the groundwater table and the fluctuations of the phreatic level and water level in the well induced by rainfall. The effects of airflo7w caused by rainfall on phreatic level fluctuations were also studied quantitatively by comparing the results obtained using the proposed model with those obtained from a water single-phase flow model...
December 20, 2016: Ground Water
Tariq Laattoe, Vincent E A Post, Adrian D Werner
The assumption of spatial repetition is commonly made when producing bedform scale models of the hyporheic zone. Two popular solute transport codes, MT3DMS and PHT3D, do not currently provide the necessary boundary condition required to simulate spatial periodicity in hyporheic zone transport problems. In this study, we develop a spatially periodic boundary (SPB) for solutes that is compatible with a SPB that was previously developed for MODFLOW to simulate the flow component of spatially periodic problems...
December 14, 2016: Ground Water
P G Cook, A Miller, M Shanafield, C T Simmons
The rapid expansion in unconventional gas development over the past two decades has led to concerns over the potential impacts on groundwater resources. Although numerical models are invaluable for assessing likelihood of impacts at particular sites, simpler analytical models are also useful because they help develop hydrological understanding. Analytical approaches are also valuable for preliminary assessments and to determine where more complex models are warranted. In this article, we present simple analytical solutions that can be used to predict: (1) the spatial extent of drawdown from horizontal wells drilled into the gas-bearing formation, and rate of recovery after gas production ceases; (2) the potential for upward transport of contaminants from the gas-bearing formation to shallow aquifers during hydraulic fracturing operations when pressures in the gas-bearing formation are greatly increased; and (3) the potential downward leakage of water from shallow aquifers during depressurization of gas-bearing formations...
December 12, 2016: Ground Water
(no author information available yet)
No abstract text is available yet for this article.
January 2017: Ground Water
Fred J Molz
No abstract text is available yet for this article.
January 2017: Ground Water
Lee J Florea, Dave Hart, James Tinjum, Chris Choi
No abstract text is available yet for this article.
January 2017: Ground Water
Stewart W Taylor, Hillol Guha
An analytical solution for calculating the contaminant discharge rate in an aquifer following an instantaneous release of reactive contaminant mass to groundwater is used to derive relationships for the time and magnitude of peak concentration in a river receiving the transported material. Relationships are developed for the time of peak concentration relative to the time of travel for the contaminant, and the magnitude of peak concentration relative to the concentration calculated at the time of travel. Both quantities are found to be a function of two dimensionless parameters characterizing advective-dispersive-reactive transport-the Peclet number and the Damkohler number...
January 2017: Ground Water
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