There is no need to elaborate on the paramount role that peer reviewing plays in maintaining the high quality of Transport in Porous Media. Without the reviews, which help the editor to make the right decisions and help authors to improve their submitted papers through their comments and questions, we would not be able to maintain the high quality of the journal. Their contribution ensures that only innovative high quality articles are published. With this in mind, we are certain that you will all join us in thanking all those scientists and experts in the various fields represented in Transport in Porous Media, for devoting time and effort to review the papers that we have been sending them. In particular, we thank, also on behalf of authors, all those who reviewed a large number of papers. The editor and publisher acknowledge the colleagues1 listed below for their excellent reviews of papers for which final decisions have been made during the period January 2012 to December 2012. Special thanks go to those who reviewed six or more scripts during this period: Lateef Akanji, Moh’d A. Al Nimr, Rosalind Archer, Christoph Arns, J.L. Auriault, Hans Bruining, Mofid Gorji Bandpy, Alex Hansen, Kamel Hooman, Theodoros Karalis, A.V. Kuznetsov, Tongjing Liu, Eugen Magyari, Valeri Mourzenko, Donald Nield, Victor Nikolaevskiy, Ioan Pop, Iuliu Sorin Pop, D. Andrew S. Rees, J.F. Thovert, P. Vadasz, Francisco Valdes Parada, Y.C. Yortsos, Ge Zhou, Robert Zimmerman.

The paper introduces a preliminary physical measure of vulnerability of groundwater to pollution called “mean relative travel time of a pollutant”, which is defined as the time of passage through the unsaturated zone of a front of water containing a conservative pollutant and applied to the ground surface at a unit intensity of supply. A methodology for mapping the mean relative travel time is presented and applied to the recharge area of the Western Mountain, (Yarkon-Taninim) aquifer. The aquifer, which extends from the mountain range west of the Jordan River to the Mediterranean coast line, is subdivided into a set of 5×5 km 2 cells, and a mean relative travel time is computed for each cell within the recharge area of the aquifer. The estimated mean travel times are directly proportional to the depth to groundwater and inversely proportional to the ratio between the coefficient of replenishment and the water content of the unsaturated zone. Estimates of the latter are obtained from regression of the rise in well water levels during the winter season on the corresponding seasonal rainfall depth. They show relative travel times in the range of one decade in the outcrops of the lower subaquifer and along the foothills, and relative travel times in the range of two to three decades along the mountain range outcrops of the upper subaquifer.

A methodology for eliminating nondominant effects in models that describe transport phenomena in porous media is presented. The methodology is based on the introduction of dimensionless numbers and on a proper evaluation of the order of magnitude of terms. These dimensionless numbers are redefined as characteristics of transport and transformation phenomena in porous media. It is shown that different time scales and different length scales may have to be employed for different variables. A method for evaluating the order of magnitude of the error of prediction when terms are deleted, is presented.

The coefficients of groundwater replenishment from surficial sources are the most critical parameters in assessing the exploitable yield of an aquifer. So far, the methods used for estimating these coefficients failed to yield plausible results, either because of crude models of the system or because of a simultaneous estimation of many parameters requiring long and diverse data records. This paper proposes a method for obtaining the in situ chronological sequence of the coefficients of replenishment at a given site, independently from the estimates of other parameters. It is based on the profiles of water content and concentrations of tritium and chloride in a single borehole penetrating the unsaturated zone. A combination of these data with the historical record of their inputs at the surface of the ground enables dating of the moisture content in each depth interval. This yields a series of seasonal replenishment coefficients from both natural and anthropogenic sources. The application of the method is illustrated at two sites in the central and southern parts of Israel.

The mathematical model and its numerical solution presented here were constructed for a hydraulic system composed of two deep aquifers that are partially separated by an aquiclude in the Negev Desert, Israel. Groundwater in these aquifers is confined, except for small areas, and it is not homogeneous because of large variations in salinity and temperature. The model is designed to predict aquifer response to pumpage in terms of water pressure and density. Increasing the rate of pumpage is likely to enlarge the unconfined area. The conceptual model has been transformed to a three-dimensional mathematical model. Two factors made it possible to reduce the mathematical model to two dimensions in each aquifer by averaging equations along the vertical: little variation in state variables along the vertical plane and the presence of a hydrostatic distribution of pressure. We used differential mass and volume balance equations for which the averages of water density and pressure along the vertical at any given point were the dependent variables. The piezometric head at any geographical point, however, could be used as a means for distinguishing between confined and water-table conditions in the hydraulic system at the initial state and at various pumpage states. The transformation of these equations into finite differences results in a large system of nonlinear equations. The sparse structure of this system suggests the use of a succession over relaxation (S.O.R.) scheme. However, the presence of highly nonlinear terms in the difference equations introduces considerable difficulty in applying this method. We therefore designed a special linearization technique to overcome this difficulty. Other features that complicate the solution process are the dynamic confined-unconfined nature of the aquifers and the irregular shape of the aquiclude. We tested and verified the validity of the model by a series of simple test cases and then used the model to study aquifer response to various pumpage alternatives.

The system is well-defined and the objectives set forth are definite and feasible.

A profile of tritium concentrations measured in the unsaturated zone in loessial sediments in a semiarid area is interpreted in terms of mobile and immobile water domains, according to a nonequilibrium transport model. The mobile domain is represented by percolating freshwater from both rain and irrigation, and the immobile one is represented by isolated fossil saline water pockets. The two domains are connected by partially saturated narrow passages within dispersed clay minerals. The transport of the mobile water is described by convective‐dispersive flow and by mass exchange between the two water domains. The relevant equations with the given initial and boundary conditions are solved numerically, and the simulated profile is adjusted to fit the measured one. In this study we concentrate on examination of the mass exchange law between the two domains. It was assumed that matrix characteristics vary in time due to the dispersion of clays at the interface between fresh and saline waters. Accordingly, a time‐dependent mass exchange was adopted, which made it possible to obtain an adequate reconstruction of the measured tritium profile. By using a least squares optimization procedure it was found that the best fit between the simulated and measured profiles is attained when the fraction of mobile water is 30%, and the rate of mass exchange decreases from 0.60 to 0.01 year−1 in 26 years. The proposed model implies is that it is the immobile water domain which contains the memory of the “high tritium period” (thermonuclear tests period) of the 1960s.

The governing equation describing solute transport in porous media is reformulated using standard volume averaging techniques. The alternative formulation is based on a modified definition of the deviation, which allows for variation of macroscopic velocity across the REV. The new equation contains additional scale-dependent terms which are functions of the size of the averaging volume (REV). This result indicates that the scale-dependent nature of the dispersion phenomenon is inherent even at the scale of the REV.

The deep aquifers (Jurassic-Paleozoic, 1–5 km deep) underlying the Negev Desert, Israel, contain brackish to saline water (800–120,000 ppm Cl−) and have been penetrated by only 47 wildcat oil drillings. The objective of this study was to evaluate the water potential of these aquifers for irrigation and for industrial consumption as well as their potential for serving as host rocks for hazardous wastes. We developed a special methodology for constructing a conceptual model for the thick sequence of layers in which these aquifers are found. It seems that, although these aquifers have different lithologies, they may be hydraulically connected. Statistics of the distribution of the aquifer system's parameters of state and analysis of their variance are used to aggregate individual formations into a few large hydrologic units. We employed regression analysis to supplement missing data and to evaluate estimation errors. Based on this methodology, a model consisting of three aquifers was defined. The consistency of the conclusions of the model is confirmed by our studies of pressure, permeability, salinity, temperature, and isotopic distribution. Wherever data were scarce, we estimated hydraulic parameters by linear regression. According to our study, the lower aquifer in the northern Negev contains only brines and is hydrologically separated from the two aquifers above it. The lower aquifer could, therefore, be considered as a possible site for toxic waste disposal or, at suitable locations, for hydrocarbon exploration. Hydrological continuity probably exists between the upper and middle aquifers in the eastern and central Negev, where brackish water is found in both aquifers. The methodology used here is suitable for constructing a conceptual model of any complex geohydrologic system in an area with scarce data.