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A fast, efficient constant-head injection test (CHIT) for in situ estimation of hydraulic conductivity (K) of sandy streambeds is presented. This test uses constant-head hydraulic injection through a manually driven piezometer. Results from CHIT compare favorably to estimates from slug testing and grain-size analysis. The CHIT combines simplicity of field performance, data interpretation, and accuracy of K estimation in flowing streams., Introduction Numerous studies have shown that streambed hydraulic properties play a considerable role in ground water/surface water interaction (McDonald and Harbaugh 1984; Sophocleous et al. 1995; Hunt 1999; Zlotnik and [...]

In this study, a new method--the asymmetric dipole-flow test--is proposed and tested for characterization of conductive properties and structure of fractured aquifers. Analytical solutions were developed and then used for interpretation of a modification of the dipole-flow test with a single packer at the Bissen Quarry test site (Wisconsin, USA). The asymmetric dipole-flow tests were conducted by packing a well at various elevations, and fluids were pumped from the upper section (chamber) of the well to the lower section (chamber). The head was then monitored at 11 observation points and in both sections of the well, and the conductivities of the well segments were determined. The tests at seven packer elevations in the well were rapid (less than one hour to reach steady state). The asymmetric dipole-flow test demonstrates the potential to quantify heterogeneities of a fractured aquifer and delineate the applicability of the continuum and discrete approaches for conceptualization of ground water flow., Introduction In nature, intrinsic permeability (or simply, permeability) has a range covering at least 17 orders of magnitude, with more than nine orders of magnitude variation in a single aquifer [...]

Commonly used analytical approaches for estimation of pumping-induced drawdown and stream depletion are based on a series of idealistic assumptions about the stream-aquifer system. A new solution has been developed for estimation of drawdown and stream depletion under conditions that are more representative of those in natural systems (finite width stream of shallow penetration adjoining an aquifer of limited lateral extent). This solution shows that the conventional assumption of a fully penetrating stream will lead to a significant overestimation of stream depletion (> 100%) in many practical applications. The degree of overestimation will depend on the value of the stream leakance parameter and the distance from the pumping well to the stream. Although leakance will increase with stream width, a very wide stream will not necessarily be well represented by a model of a fully penetrating stream. The impact of lateral boundaries depends upon the distance from the pumping well to the stream and the stream lea kance parameter. In most cases, aquifer width must be on the order of hundreds of stream widths before the assumption of a laterally infinite aquifer is appropriate for stream-depletion calculations. An important assumption underlying this solution is that stream-channel penetration is negligible relative to aquifer thickness. However, an approximate extension to the case of nonnegligible penetration provides reasonable results for the range of relative penetrations found in most natural systems (up to 85%). Since this solution allows consideration of a much wider range of conditions than existing analytical approaches, it could prove to be a valuable new tool for water management design and water rights adjudication purposes., James J. Butler Jr. (1,3), Vitaly A. Zlotnik (2), and Ming-Shu Tsou (1) Introduction Stream-aquifer interactions are an important component of the hydrologic budgets of many watersheds and have significant [...]

Over the last decade the dipole-flow (DFT) evolved from the general idea of using recirculatory flow to evaluate aquifer properties, to the development of prototype instrumentation and feasibility studies, to a reliable tool for characterization of aquifer heterogeneity. The DFT involves the interpretation of head in recirculatory flow between injection and extraction sections (chambers) in a single well isolated the statistics of horizontal hydraulic conductivity ([K.sub.r]) of the highly permeable, heterogeneous, and thin aquifer at the Horkheimer Insel site, Germany. In previous studies, [K.sub.r] estimates were based on the steady-state head difference between chambers. A new by-chamber interpretation is proposed that is based on drawdown within each individual chamber. This interpretation yields more detailed information on structure of heterogeneity of the aquifer without introducing complexity into the analysis. The DFT results indicate that [K.sub.r] ranges from 49 to 6000 m/day (mean ln [K.sub.r] [(m /s)] ~ -4, and variance of ln [K.sub.r] [(m/s)] ~ 1-2). Descriptive statistics from the DFT compare well with those from previous field and laboratory tests (pumping, borehole flowmeter, and permeameter tests and grain-size analysis) at this site. It is shown that the role of confinding boundaries in the DFT interpretation is negligible even in this case of a thin (, Introduction Estimation of local horizontal hydraulic conductivity ([K.sub.r]) in highly permeable formations presents many experimental challenges. Transient processes in such aquifers are extremely rapid, and most small-scale single-borehoole tests become [...]

Introduction Numerous studies of well hydraulics in unconfined aquifers address the hydraulic head distribution near a well for different degrees of aquifer penetration (Boulton 1954, 1963; Dagan 1967; Neuman 1972, [...]

Introduction Partially penetrating wells are becoming a common element in ground-water remediation technologies. Commonly, the two-dimensional capture zone analysis by Javandel and Tsang (1986) is used to design remediation systems [...]

Introduction Most techniques commonly used for slug test or packer test interpretation disregard anisotropy of the tested formation. Although the pioneering work by Hvorslev (1951) considered anisotropic hydraulic conductivity, anisotropy [...]

We propose a new method for groundwater recharge rate estimation in regions with stream‐aquifer interactions, at a linear scale on the order of 10 km and more. The method is based on visual identification and quantification of classically recognized water table contour patterns. Simple quantitative analysis of these patterns can be done manually from measurements on a map, or from more complex GIS data extraction and curve fitting. Recharge rate is then estimated from the groundwater table contour parameters, streambed gradients, and aquifer transmissivity using an analytical model for groundwater flow between parallel perennial streams. Recharge estimates were obtained in three regions (areas of 1500, 2200, and 3300 km2) using available water table maps produced by different methods at different times in the area of High Plains Aquifer in Nebraska. One region is located in the largely undeveloped Nebraska Sand Hills area, while the other two regions are located at a transition zone from Sand Hills to loess‐covered area and include areas where groundwater is used for irrigation. Obtained recharge rates are consistent with other independent estimates. The approach is useful and robust diagnostic tool for preliminary estimates of recharge rates, evaluation of the quality of groundwater table maps, identification of priority areas for further aquifer characterization and expansion of groundwater monitoring networks prior to using more detailed methods. Article impact statement: A new, simple approach for estimating groundwater recharge from groundwater table contours by recognizing and quantifying their patterns. [ABSTRACT FROM AUTHOR]

Vitaly A. Zlotnik [a] Huihua Huang [a] Abstract An analytical model of stream-aquifer interaction is proposed that considers the effects from a small degree of aquifer penetration and low-permeability sediments [...]

Introduction It is well known that heterogeneity of hydraulic conductivity (K) controls the spread of contaminants in the subsurface. In the quadrennial report on advances and opportunities in hydrologic research, [...]

Design of managed aquifer recharge ( MAR) for augmentation of groundwater resources often lacks detailed data, and simple diagnostic tools for evaluation of the water table in a broad range of parameters are needed. In many large-scale MAR projects, the effect of a regional aquifer base dip cannot be ignored due to the scale of recharge sources (e.g., wadis, streams, reservoirs). However, Hantush's (1967) solution for a horizontal aquifer base is commonly used. To address sloping aquifers, a new closed-form analytical solution for water table mound accounts for the geometry and orientation of recharge sources at the land surface with respect to the aquifer base dip. The solution, based on the Dupiuit-Forchheimer approximation, Green's function method, and coordinate transformations is convenient for computing. This solution reveals important MAR traits in variance with Hantush's solution: mounding is limited in time and space; elevation of the mound is strongly affected by the dip angle; and the peak of the mound moves over time. These findings have important practical implications for assessment of various MAR scenarios, including waterlogging potential and determining proper rates of recharge. Computations are illustrated for several characteristic MAR settings. [ABSTRACT FROM AUTHOR]

Analytical models of groundwater flow with a spatially varying elevation of a top boundary are widely used. However, a vast majority of previous analytical studies truncated the irregularly shaped top section with little to no analyses of the shortcomings of the approximate solutions for the resulting rectangles or parallelepipeds. We present an analytical approach based on a perturbation technique that treats complete domains. It is especially accurate near the top boundary, where fluid circulation is most pronounced and higher accuracy is typically needed, such as in regional or hyporheic systems flow. The approach is illustrated by analyzing flow for a Tóthian unit basin. [ABSTRACT FROM AUTHOR]

An analysis method for slug tests performed in a partially penetrating well within a vertical cutoff wall is presented. A steady-state shape factor for evaluating hydraulic conductivity of the material within the wall was derived by applying the method of images to the previously developed analytical solution of Zlotnik et al. (2010) for an infinite aquifer. Two distinct boundary conditions were considered: constant-head boundary for the case of direct contact between the wall and the aquifer, and no-flux boundary representing an impermeable filter cake on the sides of the wall. The constant-head and no-flux boundary conditions yield significantly higher and lower shape factors, respectively, than those for the infinite aquifer. Consequently the conventional line-fitting method for slug test analysis would yield an inaccurate estimate of the hydraulic conductivity of a vertical cutoff wall. [ABSTRACT FROM AUTHOR]

One-km resolution MODIS-based mean annual evapotranspiration (ET) estimates in combination with PRISM precipitation rates were correlated with depth to groundwater ( d) values in the wide alluvial valley of the Platte River in Nebraska for obtaining a net recharge ( Rn) vs. d relationship. MODIS cells with irrigation were excluded, yielding a mixture of predominantly range, pasture, grass, and riparian forest covers on sandy soils with a shallow groundwater table. The transition depth ( dt) between negative and positive values of the net groundwater recharge was found to be at about 2 (±1) m. Within 1 (±1) m of the surface and at a depth larger than about 7 to 8 (±1) m, the mean annual net recharge became independent of d at a level of about −4 (±12)% and 13 (±10)%, respectively, of the mean annual precipitation rate. The obtained Rn( d) relationship is based on a calibration-free ET estimation method and may help in obtaining the net recharge in shallow groundwater areas of negligible surface runoff where sufficient groundwater-depth data exist. [ABSTRACT FROM AUTHOR]

by Vedat Batu Reviewed by Vitaly A. Zlotnik, Professor, University of Nebraska-Lincoln, Department of Geosciences, 214 Bessey Hall, Lincoln, NE 68588. Hydraulic testing of aquifers is a subject of interest [...]

Various subsurface flow systems exhibit a combination of small-scale to large-scale anisotropy in hydraulic conductivity ( K). The large-scale anisotropy results from systematic trends (e.g., exponential decrease or increase) of K with depth. We present a general two-dimensional solution for calculation of topography-driven groundwater flow considering both small- and large-scale anisotropy in K. This solution can be applied to diverse systems with arbitrary head distribution and geometry of the water table boundary, such as basin or hyporheic flow. In a special case, this solution reduces to the well-known Tóth model of uniform isotropic basin. We introduce an integral measure of flushing intensity that quantifies flushing at different depths. Using this solution, we simulate heads and streamlines and provide analyses of flow structure in the flow domain, relevant to basin analyses or hyporheic flow. It is shown that interactions between small-scale anisotropy and large-scale anisotropy strongly control the flow structure. In the classic Tóth flow model, the flushing intensity curves exhibit quasi-exponential decrease with depth. The new measure is capable of capturing subtle changes in the flow structure. Our study shows that both small- and large-scale anisotropy characteristics have substantial effects that need to be integrated into analysis of topography-driven flow. [ABSTRACT FROM AUTHOR]

Potentiomanometers (PMs) are commonly used to determine flux directions across interfaces between surface waters and aquifers. We describe a complementary function: estimating small-scale hydraulic conductivity ( K) in a lakebed, using the constant-head injection test (CHIT) by Cardenas and Zlotnik (2003) with the PM designed by Winter et al. (1988). A piezometer with a small screen is inserted into the lakebed. Local head potential is obtained by measuring the head difference between the test point and the aquifer interface. The piezometer is then used for water injection. This technique is illustrated by measurements taken from Alkali Lake in the Sand Hills, Nebraska, United States. Lakebed K and seepage fluxes ranged from 0.037 to 0.090 m/d and Darcy velocities ranged from 0.004 to 0.027 m/d. Results were consistent with the supplementary data gathered using a modified CHIT and a cone penetrometer. The compact size of the device and the small volumes used for injection enable this method to estimate lakebed K values as low as 0.01 to 0.1 m/d, a range seldom explored in lake-aquifer interface systems. [ABSTRACT FROM AUTHOR]

We present the closed form of a general steady-state shape factor for a partially penetrating well in a uniform anisotropic aquifer. Our simple analytical expression for the shape factor has a uniform representation for full range of parameters and meets or exceeds the accuracy of previous results obtained through semiempirical methods (e.g., Bouwer and Rice [1976] equations). This general shape factor pertains to the flow of fluids (water or air) in subsurface formations when the upper formation boundary has constant potential and the lower boundary is impermeable. The results of our investigation are directly applicable to analyses of (1) slug tests with falling or rising head and (2) injection/extraction tests with constant head, essential techniques for the characterization of hydraulic conductivity of aquifers, streambeds, or lakebeds as well as the design of aquifer and soil remediation systems. [ABSTRACT FROM AUTHOR]

A biography of Pelageya Yakovlevna Polubarinova-Kochina, a Russian mathematician is presented. She was born on May 13, 1899 on Volga River, Russia and graduated from the Pokrovsky Women's Gymnasium in 1916. She pursued her continuing education in pure mathematics in the Main Geophysical Laboratory while working. Kochina has made significant contributions in the field of mathematics and applied mechanics. A list of biographies of various mathematicians written by Kochina is offered.

The impact of ground water pumping on nearby streams is often estimated using analytic models of the interconnected stream-aquifer system. A common assumption of these models is that the pumped aquifer is underlain by an impermeable formation. A new semianalytic solution for drawdown and stream depletion has been developed that does not require this assumption. This solution shows that pumping-induced flow (leakage) through an underlying aquitard can be an important recharge mechanism in many stream-aquifer systems. The relative importance of this source of recharge increases with the distance between the pumping well and the stream. The distance at which leakage becomes the primary component of the pumping-induced recharge depends on the specific properties of the aquifer, aquitard, and streambed. Even when the aquitard is orders of magnitude less transmissive than the aquifer, leakage can be an important recharge mechanism because of the large surface area over which it occurs. Failure to consider aquitard leakage can lead to large overestimations of both the drawdown produced by pumping and the contribution of stream depletion to the pumping-induced recharge. The ramifications for water resources management and water rights adjudication can be significant. A hypothetical example helps illustrate these points and demonstrates that more attention should be given to estimating the properties of aquitards underlying stream-aquifer systems. The solution presented here should serve as a relatively simple but versatile tool for practical assessments of pumping-induced stream-aquifer interactions. However, this solution should not be used for such assessments without site-specific data that indicate pumping has induced leakage through the aquitard. [ABSTRACT FROM AUTHOR]

A response by James J. Butler Jr., Xiaoyong Zhan, and Vitaly A. Zlotnik in response to a letter to the editor about their article on the delayed-yield behavior commonly observed in unconfined aquifers in the 2007 issue is presented.

The article comments on an article about stream depletion produced by pumping in the vicinity of a partially penetrating stream. It is maintained that there are advantages in using the partially penetrating stream. A partially penetrating stream model allows the pumping disturbance to propagate underneath the stream, thus capturing an important mechanism that is commonly observed in the field. The computational effort required for the numerical inversion from transform space is often less than that required for numerical evaluation of closed-form solutions.