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Storage and release functions of western U.S. traditional river valley irrigation systems may counteract early and rapid spring river runoff associated with climate variation. Along the Rio Grande in northern New Mexico, we instrumented a 20-km-long irrigated valley to measure water balance components from 2005 to 2007. Hydrologic processes of the system were incorporated into a system dynamics model to test scenarios of changed water use. Of river water diverted into an earthen irrigation canal system, some was consumed by crop evapotranspiration (7.4%), the rest returned to the fiver as surface return flow (59.3%) and shallow groundwater return flow that originated as seepage from canals (12.1%) and fields (21.2%). The modeled simulations showed that the coupled surface water irrigation system and shallow aquifer act together to store water underground and then release it to the river, effectively retransmitting river flow until later in the year. Water use conversion to nonirrigation purposes and reduced seepage from canals and fields will likely result in higher spring runoff and lower fall and winter river flow. DOI: 10.1061/(ASCE)IR.1943-4774.0000265 CE Database subject headings: Aquifers; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande. Author keywords: River-aquifer interaction; Hydrology; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande.

In this research, a data-driven modeling approach, support vector machines (SVMs), is compared to artificial neural networks (ANNs) for predicting transient groundwater levels in a complex groundwater system under variable pumping and weather conditions. Various prediction horizons were used, including daily, weekly, biweekly, monthly, and bimonthly prediction horizons. It was found that even though modeling performance (in terms of prediction accuracy and generalization) for both approaches was generally comparable, SVM outperformed ANN particularly for longer prediction horizons when fewer data events were available for model development. In other words, SVM has the potential to be a useful and practical tool for cases where less measured data are available for future prediction. The study also showed high consistency between the training and testing phases of modeling when using SVM compared to ANN. While for the proposed SVM model the relative error of mean square error increased by an average of 42% from the training phase to testing the phase, the corresponding testing error of the ANN model raised by approximately seven times the training error. DOI: 10.1061/(ASCE)CP.1943-5487.0000043 CE Database subject headings: Neural networks; Aquifers: Water levels: Predictions; Climates; Comparative studies. Author keywords: Support vector machines (SVMs); Artificial neural networks (ANNs); Aquifer water level elevation prediction; Climate data.

Neglecting the effect of well radius may lead to a significant error in the predicted drawdown distribution near the pumping well area. New analytical solutions describing aquifer responses to a constant pumping or a constant head maintained at a finite-diameter well in a wedge-shaped aquifer are derived based on the image-well method and applicable to an arbitrarily located well in the system. The solutions are useful for quantifying groundwater exploitation from a wedge-shaped aquifer and for determining the hydrogeological parameters of a wedge-shaped aquifer in inverse problems. CE Database subject headings: Analytical techniques; Aquifers; Groundwater management; Wells; Parameters.

A kernel method is proposed for calculating transient rate and cumulative volume of well discharge under constant drawdown. The new method can also be used for obtaining the drawdown (in pressure head) in the aquifer at some distance away from the well. Employing the new method, an optimization method is used to estimate the aquifer parameters from transient well discharge or drawdown in the aquifer pressure head. The proposed method can also be used to model the recovery of drawdown (in aquifer pressure head) after the plug-in of the well. CE Database subject headings: Groundwater management; Wells; Aquifers; Parameters; Unsteady flow; Estimation.

A comprehensive analytical solution for the quantity of seepage into an array of fully penetrating ditches from a ponded surface has been obtained using hodograph and Schwarz-Christoffel transformation. The solution includes equations for the quantity of seepage from the seepage face part as well as the water depth part of the ditch. The solution also comprises expressions for the velocity potential at the stagnation point and the variation in seepage velocity. The variation in seepage quantity is like the shape of a curved channel whose boundary maps along a circle onto the hodograph plane. This shape is average of a semiellipse and a parabola. The seepage contribution from the nonseepage face is maximum for half full condition and it is half of the total seepage in an empty ditch (full seepage face). Irrespective of the spacing between ditches the quantities of seepage from the seepage face part and the nonseepage part are equal for one third full ditch. The solution also deals with special cases like single ditch, unequal spacing between ditches, and unequal depth of water in adjacent ditches. The expressions the quantity of seepage have been simplified in explicit algebraic equations through minimization of errors. The simplified expressions, which are near exact, result in answers in single step computations. Also, an example and graphs have been included to demonstrate the sensitivity of the parameters. DOI: 10.1061/(ASCE)0733-9437(2008)134:6(815) CE Database subject headings: Drains; Drainage; Leaching; Seepage; Mapping; Porous Media; Groundwater; Ditches.

A model to calculate the quantity and quality of river flows by simulating hydro-chemical processes in soil and the spatial/ temporal distribution of irrigation return flows is introduced. By simulating the hydro-chemical processes, the quantity and quality of the deep percolating water can be predicted. The spatial and temporal distribution of the deep percolating water is simulated by constructing a groundwater flow path and calculating the groundwater travel time using response functions. A probabilistic approach was developed to calculate the groundwater travel time taking into account the fact that some irrigated fields have subsurface drainage which shortens travel times. All related hydrological components are integrated into the computation of river flow quantity and quality including groundwater return flow, irrigation tail water, tributary inflow, river diversion, phreatophyte consumption, river channel losses, and river depletion due to pumping. An illustrative example is included to demonstrate the capabilities of the model. The results of this example show that river salinity is lower during the irrigation season and higher during the off season. Due to salts carried by return flows, downstream reaches have higher salinity levels than upstream reaches. DOI: 10.1061/(ASCE)0733-9437(2008)134:6(757) CE Database subject headings: Simulation models; Salinity; Water quality; Water chemistry; Groundwater quality; Water supply.

Computer simulations often are used to design and to optimize groundwater remediation systems. We present a new computationally efficient approach that calculates the reliability of remedial design at every location in a model domain with a single simulation. The estimated reliability and other model information are used to select a best remedial option for given site conditions, conceptual model, and available data. To evaluate design performance, we introduce the nodal failure index (NFI) to determine the number of nodal locations at which the probability of success is below the design requirement. The strength of the NFI approach is that selected areas of interest can be specified for analysis and the best remedial design determined for this target region. An example application of the NFI approach using a hypothetical model shows how the spatial distribution of reliability can be used for a decision support system in groundwater remediation design. CE Database subject headings: Remedial action; Groundwater pollution; Uncertainty principles; Computer aided simulation.

'Brownfields' are real estate properties with subsurface or surface contamination. The redevelopment of Brownfields is required to clean, improve, and protect the environment. Pile foundations are often used in Brownfields and other contaminated site situations to support structures. Regulators are concerned about the environmental safety of pile foundations in Brownfields sites, since piling in Brownfields may lead to transport of contaminants from the contaminated region to underground aquifers. This investigation is an extension of previous research programs on pile foundations in Brownfields or contaminated sites conducted at the University of New Orleans. The purpose of the overall investigation is to evaluate the potential for contaminant transport due to pile foundations in Brownfields. The current paper summarizes the research carried out to ascertain the potential for contaminant transport from concrete piles of different shape, depth of penetration, and method of installation. The results of bench scale model tests and numerical studies are presented. Under full penetration conditions, the square shaped and circular cast-in-place piles were found to have a higher potential for contaminant transport than circular driven piles. There is a low potential for contaminant transport in the case of piles penetrating less than 95% of an aquitard. Selected results from a previous program on wooden and steel piles are summarized for comparison. CE Database subject headings: Pile foundations; Soil pollution; Environmental issues; Groundwater pollution; Aquifers.

The highway deicing agent groundwater plume from an infiltration basin in the Plymouth-Carver Aquifer near State Route 25 in southeastern Massachusetts is modeled and measured in order to assess the impact of the basin on groundwater transport processes. The advective transport model superimposes the existing steady models of axisymmetric basin hydraulics of Zlotnik and Ledder in 1992 and the two-dimensional ambient flow of Gelhar and Wilson in 1974. The basin component incorporates a surface source of finite-radius into a Hankel transform model for unconfined aquifers, whereas the ambient component varies linearly in the horizontal and vertical directions. Contaminant streamlines describe the resulting groundwater plume, and highway deicing agent constituents provide useful tracers. A simple vertical dispersion model quantifies the spread of contaminants across the bottom of the plume. Deicing agent constituent data calibrate a 17 m basin radius, a 45 m plume width, a bottom streamline 6-10 m below the water table, and a vertical dispersivity of 34 cm. The latter value is comparable to the amplitude of vertical excursions caused by storm scale fluctuations of hydraulic head, as measured by Ostendorf et al. in 2007. Infiltration basins alter ambient advection by displacing streamlines downward and augment vertical mixing by imposing aperiodic vertical fluctuations on the ambient flow field. CE Database subject headings: Stormwater management; Deicing; Runoff; Infiltration; Massachusetts; Highways and roads.

A diagnostic curve of unimodal shape is developed for identifying the confined aquifer parameters from early drawdowns. A scaled well function is proposed for the diagnostic curve and computationally simple functions are developed for its accurate approximation. The diagnostic curve may be viewed as an alteration of the Theis' curve or as the generalization of a previous approach proposed by the writer. Plotting the pumping test data in a convenient form and matching it to the diagnostic curve with a parallel shift of axes identify the aquifer parameters. The unimodal shape of the diagnostic curve facilitates matching and reduces the personal errors. The proposed method is simple, easy to apply, and yields accurate estimates of aquifer parameters from only early drawdowns, which would save considerable time and money involved in conducting a long-duration pumping test. The estimates obtained using the new method are as good as those obtained from much more complex methods. The new method does not require either the initial guess for the parameter values or repetitive evaluation of the well function. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(515) CE Database subject headings: Aquifers; Parameters; Drawdown; Ground water; Optimization; Pumps; Water storage; Coefficients.

Knowledge of the consumption of permanganate by naturally occurring reduced species associated with aquifer materials is required for site screening and design purposes to support permanganate in situ chemical oxidation (ISCO) applications. It has been established that this consumption is not a singled-valued quantity, but rather is kinetically controlled. Current methods to determine this permanganate natural oxidant demand (NOD) involve the use of well-mixed batch tests, which are time consuming and subject to test variables (e.g., concentration, mass of oxidant to solid ratio, reaction duration, and mixing conditions) that significantly affect the results. In this paper, we propose a modified chemical oxygen demand (COD) test using permanganate, which can be used to determine the maximum permanganate NOD of an aquifer material. As an initial point of comparison, we tested aquifer materials collected from eight potential ISCO sites using this modified or permanganate COD method, the traditional dichromate COD method, and a method based on well-mixed batch reactors. The results from this comparison indicated that there was no statistically significant difference ([alpha]=5%) between the results of the permanganate COD test and the maximum NOD from the well-mixed batch reactors, while on average the dichromate COD test overestimated the maximum NOD by 100%. The permanganate COD test results were highly correlated to the batch-test maximum NOD data (r=0.996), and to the total organic carbon and amorphous Fe content of the aquifer materials (r=0.91). A limited sensitivity investigation of this proposed permanganate COD test revealed that the suspected formation of manganese oxides, a reaction byproduct, may lead to increased experimental variability. However, in spite of this concern we recommend that this proposed permanganate COD method is a quick and economical approach for estimating the maximum permanganate NOD for aquifer materials to support permanganate ISCO site screening and initial design purposes. DOI: 10.1061/(ASCE)0733-9372(2008)134:5(353) CE Database subject headings: Aquifers; Chemical oxygen demand; Remedial action; Ground-water pollution.

Groundwater is the most widely used water resource in the Afram Plains area, Ghana. The objective of this study was to determine the distribution of fluoride, sodium adsorption ratio (SAR), and salinity (EC) in groundwater from the different aquifers in the Afram Plains area. The distribution of these parameters would enable a determination of the quality of groundwater from the different aquifer units for use in households and irrigation purposes. The inverse distance weighting, interpolator with a power of 2 was applied to 143 data points of each parameter to generate prediction maps for fluoride, SAR, and EC in the area. The distribution maps from this study show that the shale aquifers that underlie the southwestern sections of the area have the highest levels of fluoride, SAR, and EC. A narrow strip of the shale aquifer in the southwestern region produces groundwater whose fluoride level (2.2 mg/L) is higher than the World Health Organization minimum allowable fluoride concentration of 1.5 mg/L in drinking water. The feldsparthic sandstone, arkose, siltstone, and mudstone aquifers in the northeastern sections of the area produce groundwater with fluoride concentration in the range of 0.0-0.3 mg/L, which fall outside the minimum range of 0.7-1.2 mg/L required in drinking water for normal bone and dental health. The highest SAR and EC are also associated with the shale aquifers to the southwestern section of the area. Using the World Food and Agriculture Organization's guidelines for irrigation water quality, it was determined that groundwater from the Afram Plains area will generally have a mild to moderate effect on the hydraulic properties of soils when used as irrigation water. DOI: 10.1061/(ASCE)0733-9437(2008)134:2(222) CE Database subject headings: Ghana; Fluoridation; Sodium; Adsorption; Electrical conductivity; Potable water; Developing countries.

The key objectives of this study were to evaluate the use of an alternating current (AC) for the degradation of naphthalene in spiked aqueous solutions and to investigate the effect of current density on the degradation rates of naphthalene. Direct current (DC) was also used to compare the rates of degradation. Sodium chloride (NaCl) and anhydrous sodium sulfate ([Na.sub.2]S[O.sub.4]) were used as the supporting electrolytes. Degradation rates and byproducts formed were investigated when DC and AC were separately passed through naphthalene solutions. A square wave AC, having a frequency equal to 0.1 Hz was used. Naphthalene solutions having an initial concentration of about 20 mg/L (~0.15 mM) were subjected to an AC peak current density and DC density of 6 mA/[cm.sup.2], using NaCl as the supporting electrolyte. An approximate 65% reduction in the concentration of naphthalene was observed after a period of 48 h when DC was applied. Degradation was almost 100% when the AC was applied during the 48-h period. The effect of current density on the electrochemical degradation rate of naphthalene in aqueous solution was also investigated at alternating and direct current densities of 1, 3, and 6 mA/[cm.sup.2] using [Na.sub.2]S[O.sub.4] as the supporting electrolyte. AC peak current densities of 1, 3, and 6 mA/[cm.sup.2] resulted in overall conversions of 77, 87, and 95%, respectively, of naphthalene in solution. The corresponding values for DC application were 95% for all current densities while the initial degradation rates were greater at higher DC densities. Based on the degradation products formed, hydroxylation is believed to be the key mechanism for the degradation of naphthalene. CE Database subject headings: Electrokinetics; Pollution; Ground-water pollution; Organic chemicals.

In situ chemical oxidation (ISCO) using permanganate has been increasingly applied to deplete mass from dense nonaqueous-phase liquid (DNAPL) source zones. However, uncertainty in the performance of ISCO on DNAPL contaminants is partially attributable to a limited understanding of interactions between the oxidant, subsurface hydrology, and DNAPL mass transfer, resulting in failure to optimize ISCO applications. To investigate these interactions, a factorial design experiment was conducted using one-dimensional flow through tube reactors to determine how groundwater velocity, permanganate concentration, and DNAPL type affected DNAPL mass depletion rates. DNAPL mass depletion rates were found to increase with increasing groundwater velocity, or increasing oxidant concentration. An interaction occurred between the two factors, where high oxidant concentrations had little impact on mass depletion rates at high velocities. High oxidant concentration systems experienced gas generation. Mass depletion rates were fastest at high velocities, but required additional oxidant mass and pore volume addition to achieve complete mass depletion. Lower-velocity systems were more efficient with respect to oxidant mass and pore volume requirements, but mass depletion rates were reduced. CE Database subject headings: Oxidation; Mass transfer; Velocity; Remedial action; Ground-water pollution; PCE; TCE.

The solute transport equation is commonly used to describe the migration and fate of solutes in a groundwater flow system. Depending on the problem nature, the source of the solute may be represented as a point source term in the equation or specified as the first-type or third-type boundary condition. The solutions derived under the condition that the solute introduced into the flow system is from the boundary is herein considered as the boundary-source solutions. The solution obtained when solving the transport equation with a point-source term is considered as the point-source solution. The Laplace transform technique is employed to derive the formulas for those solutions expressed in terms of the normalized mass release rate. The underlying nature of different source release modes and the differences among those boundary-source solutions and the constant point-source solution can be easily and clearly differentiated based on the derived formulas for one-dimensional transport. The methodology could, however, be easily extended to two- and three-dimensional problems. DOI: 10.1061/(ASCE)0733-9372(2007)133:11(1032) CE Database subject headings: Analytical solutions; Groundwater management; Mathematical models; Solutes.

Because of increased public concern regarding the impact of tunneling on surrounding environments, the control of ground-water has become an essential part of the planning, design, and construction of a tunneling project. This paper presents the results of an investigation on interaction mechanism between tunneling and groundwater using a three dimensional stress--pore pressure coupled finite-element model. It is shown that the ground and lining responses are significantly influenced by the relative permeability of the lining, and that the circumferential pregrouting is an effective means for minimizing the tunneling and groundwater interaction. Also highlighted is the importance of the stress-pore pressure coupled analysis, in the numerical prediction of tunnel behavior. Practical implications of the findings from this study are discussed in great detail. CE Database subject headings: Tunneling; Ground water; Finite element method; Pore water pressure; Grouting; Tunnel linings; Settlement.

A computationally simple approximation of the Hantush M function is proposed. Using this approximation, an optimization method is proposed for identifying the aquifer parameters from early drawdowns around partially penetrating wells. The aquifer parameters are hydraulic conductivity and specific storage. The application of the method is illustrated using a field example. The proposed method results in a 120-fold saving in time when compared to the prior method. It is hoped that the proposed approximation and method will be of help to the field engineers and practitioners. DOI: 10.1061/(ASCE)0733-9437(2008)134:6(861) CE Database subject headings: Aquifers; Parameters; Wells; Drawdown; Hydraulic conductivity; Water storage; Estimation; Groundwater management.