Haim Gvirtzman

Pore scale spatial analysis of two immiscible fluids in porous media

A conceptual model is introduced describing the spatial distribution of two immiscible fluids in the pore space of sphere packings. The model is based on the ideal soil concept of homogeneous arrangement of identical spheres but is generalized to include random packing. It quantitatively analyzes the interfacial area between wetting and nonwetting fluids and between the fluids and the solid spheres, as a function of the saturation degree. These relationships depend on the packing arrangement of the spheres, the sphere radius, and the fluid-solid contact angle. The model focuses on the region of low saturation of the wetting phase, where the wetting phase is comprised of pendular rings. When the nonwetting phase appears as ganglia, the model assumes single-chamber ganglia. Three-dimensional graphical illustrations are provided. Three potential applications are pointed out: (1) to quantify the water-air interface in the unsaturated zone; (2) to analyze connate water interfacial area in petroleum reservoirs and to assess the effect of surfactants during enhanced oil recovery; and (3) to estimate the interface between groundwater and floating nonaqueous phase liquids above the water table.

MICROSCALE CHEMICAL HETEROGENEITY IN GROUNDWATER

Ronen, D., Magaritz, M., Gvirtzman, H. and Garner, W., 1987. Microscale chemical hetereogeneity in groundwater. J. Hydrol., 92: 173-178. Large variations in the concentration of Cl-, NO a and SO42 in the upper water layers of a polluted aquifer were found between samples that were vertically separated by as little as 3 cm. This was disclosed when a multilayer dialysis cell device was used to obtain undisturbed, real-time samples from test wells. This first time presentation of chemical fine structure provides new insights into mechanisms of contamination of an aquifer by surface inputs and raises the question of the validity of groundwater quality data based on single samples, however obtained.

Anion exclusion during transport through the unsaturated zone

A 20-year chronological record of the flow of water and anions, along 27 m, in the unsaturated zone of a phreatic aquifer was reconstructed. Water was traced according to its tritium content, using the difference between the environmental tritium content of rain and irrigation water. Anions were traced using data about their sequential input to the overlying cultivated field and their concentration in the profile. Evidences of anion exlcusion were found along a 10-m thick clay loam layer. The vertical velocities of water molecules and anions (SO2−4 and Cl−) were calculated to be 0.7 ± 0.05 and 1.35 ± 0.05m yr−, respectively. The average thickness of the water films and the equivalent distance of exclusion, at a 15% gravimetric water content, were 25 and 12A, respectively. These field data fit and support the theoretical relationship between the water film thickness and the relative exclusion concentration proposed by Bresler (1973).

The tectonic framework of a complex pull-apart basin: Seismic reflection observations in the Sea of Galilee, Dead Sea transform

Abstract A multi-channel seismic reflection survey consisting of 20 lines with a total length of 180 km was conducted in the Sea of Galilee. The data provide new insights into the Pliocene–Quaternary evolution of the Kinarot–Beit–Shean pull-apart basin (KBSB) along the Dead Sea transform. Two distinct zones are defined beneath the lake: (1) a graben that underlies most of the lake, bounded by steep north–south longitudinal strike-slip faults and (2) shallow pre-rift units underlying the northwestern wider part of the lake. We suggest that before approximately 4 Ma, the KBSB grew due to northward movement of the Korazim Plateau and by crustal stretching along the rift axis. Since the Pliocene (∼4 Ma), lateral slip has been transferred from the southern segment of the basins western marginal fault to normal faults in the Galilee, and to the eastern margin of the Korazim Plateau by the newly formed, Almagor fault, which makes a restraining bend along the transform. N–S lithospheric stretching below the KBSB has diminished and the Korazim Plateau has changed from being a detached block to a compressional saddle. A phase of rapid subsidence, and formation of a half-graben structure in the northern part of the basin approximately 1 Ma ago was coeval with major deformation in areas adjacent to the KBSB, indicating major reorganization of the plate boundary in the region. Currently, most transform motions are probably taken up along a single fault on the eastern side of the KBSB, implying that the main trough under the Sea of Galilee is in a late stage of growth as a pull-apart.

Hydrogeological modeling of the saline hot springs at the Sea of Galilee, Israel

Meteoric fresh groundwater from shallow aquifers and hot brines from deep aquifers mix while emerging from several springs along the western coast of the Sea of Galilee, a freshwater lake located within the Dead Sea Rift Valley, Israel. After the rainy season, when elevations of the groundwater table rise in the regional aquifers and discharge rates of springs increase, solute concentrations decrease at Tabha springs but, surprisingly, increase at Fulya springs, apparently suggesting two different salinization mechanisms. Two detailed geologic cross sections were constructed, one across the rift valley at Tabha and a second at Fulya, each about 6 km deep and 70 km long. The hydrodynamics in these cross sections were analyzed using a two-dimensionalfinite element code that solves the coupled variable-density groundwaterflow and heat transfer equations. Numerical simulations indicate that a topography-drivenflow model explains both spring systems, and the opposite salinity behavior results from the different hydrogeological configurations of the two subsurface drainage basins. At Fulya, both aquifers, the shallow one and the deeper one, are partially phreatic, whereas at Tabha, the deeper aquifer is totally confined. The response of springs to changes in elevation of groundwater table were simulated, reproducingfield observations. This analysis has implications for the management scheme for the lake and its surrounding aquifers.

BASIN-SCALE MIGRATION OF CONTINENTAL-RIFT BRINES : PALEOHYDROLOGIC MODELING OF THE DEAD SEA BASIN

It was suggested that brine of the Dead Sea rift has originated from a residual product of intensively evaporated seawater that invaded the rift, precipitated halite, and later interacted through dolomitization with the host rock during subsurface migration. Detection of this brine in many deep wells located at distances as far as 100 km away from the rift was attributed to long-distance migration of the brine. The physical feasibility of such migration, which probably spanned the past 3‐6 m.y., is quantitatively tested and verified in this study by using paleohydrologic modeling. The structural formation of the rift is described by a chronological sequence of geologic cross sections serving as the basis for hydrodynamic calculations, which assess the effects of the structure on fluid migration, salinity redistribution, and heat transport across the sedimentary basin. Results indicate that two basin-scale ground-water systems, one atop the other but with opposite flow directions, coexisted in the Dead Sea rift valley. The first is a topography-driven flow of meteoric water from the surrounding highlands toward the rift through relatively shallow aquifers (≤1 km). The second is a density-driven migration of the Dead Sea brine through deep aquifers (4‐5 km) in the opposite direction. The configuration of these flow systems has changed during the structural evolution of the Dead Sea rift, illustrating the interrelationships among basin formation, paleohydrology, and paleogeochemistry.

Thermal anomalies associated with forced and free ground-water convection in the Dead Sea rift valley

The Dead Sea rift valley is a left-lateral transform, along which several rhombshaped grabens were formed. At the Sea of Galilee, which is one of these rhomb-shaped grabens, ambiguous heat fluxes were measured: 70‐80 mW/m 2 at the central part of the lake, 36 mW/m 2 at the lake’s southern coast (10 km apart), and most surprising, about 135 mW/m 2 at the southern Golan Heights, 6‐8 km east of the graben margin. A detailed geologic cross section, traversing the entire sedimentary basin, was constructed. The hydrodynamics in this cross section were analyzed quantitatively using a two-dimensional finite element code that solves the coupled variable-density ground-water flow and conductive-convective heat transfer equations. On the basis of numerical simulations, different mechanisms of basin-scale groundwater convection are suggested for the two sides of the rift that could influence the transport of heat: (1) forced convection (gravitydriven flow) of hot brines from deeper aquifers to the land surface at the western side; and (2) large-scale free convection (buoyancy-driven flow) of deep ground water at the eastern side. The different heat fluxes within the rift valley are attributed to the different lithologies and to the locations of specific conduits through which the hot ground waters ascend from deeper horizons. These simulations also explain the different salinities of the hot springs on the two sides of the rift.

The Concept of In-Situ Vapor Stripping for Removing VOCs from Groundwater

An in-situ remediation procedure is proposed to remove Volatile Organic Compounds (VOCs) dissolved in groundwater. This is accomplished by injecton of air into a well, using a combined technique of air-lift pumping with a form of vapor stripping. When air is injected into a well, it causes water to be lifted and forces groundwater flow towards the well, creating a recirculating cleanup zone. During this process, VOCs are transferred from the contaminated water to the rising air bubbles inside the well. The air bubbles are separated from the liquid near the top of the well, and the VOC vapor is collected and treated. In this system, water is not permitted to be lifted to the ground surface. Rather, the water is diverted into the unsaturated zone through a series of drains that are installed beneath the root-zone. The water then, free of a portion of VOCs, infiltrates back to the water table. As water continues to circulate, the VOC concentrations are gradually reduced.The feasibility of the proposed method was analyzed using concepts of mass transfer of VOCs from water to air-bubbles. Calculations indicate that the method has promise because equilibrium partitioning between the contaminated liquid and the gas bubbles is rapidly established.

Spatial and Temporal Characteristics of Saline Springs: Sea of Galilee, Israel

Spatial and temporal characteristics of the saline springs that emerge along the western shore of the Sea of Galilee (Lake Kinneret) are analyzed. Three groups of onshore springs (Tiberias, Fuliya, and Tabgha) and two groups of offshore springs (Barbutim and Maagan), contribute saline water to the lake with concentrations in the range of 300 to 18,000 mg Cl/L, depending on location and season. It is well accepted that water emerging from these springs is a mixture of two endmembers: deep-seated saline ground water and shallow, fresh circulating ground water. Temporal trends of discharge rates and of chloride (representing the deep saline aquifer) and nitrate (representing the shallow fresh water aquifer) concentrations within each group of springs are presented. Results show the proportions of the two water bodies while mixing are time dependent. Discharge and concentration peaks in Tabgha springs precede those in Fuliya and Tiberias springs by approximately two months. An analytical solution shows that in Tabgha, variations of these parameters are mainly controlled by recharge variations in the Galilee, and follow an exponential function. In Fuliya and Tiberias, variations of these parameters are mainly dependent on lake level, and follow a sine-cosine function. The different patterns are attributed to different hydraulic properties of the discharge area.

Hydrometeorological daily recharge assessment model (DREAM) for the Western Mountain Aquifer, Israel: Model application and effects of temporal patterns

[1] Recharge is a critical issue for water management. Recharge assessment and the factors affecting recharge are of scientific and practical importance. The purpose of this study was to develop a daily recharge assessment model (DREAM) on the basis of a water balance principle with input from conventional and generally available precipitation and evaporation data and demonstrate the application of this model to recharge estimation in the Western Mountain Aquifer (WMA) in Israel. The WMA (area 13,000 km 2 )i s a karst aquifer that supplies 360–400 Mm 3 yr −1 of freshwater, which constitutes 20% of Israel’s freshwater and is highly vulnerable to climate variability and change. DREAM was linked to a groundwater flow model (FEFLOW) to simulate monthly hydraulic heads and spring flows. The models were calibrated for 1987–2002 and validated for 2003– 2007, yielding high agreement between calculated and measured values (R 2 = 0.95; relative root‐mean‐square error = 4.8%; relative bias = 1.04). DREAM allows insights into the effect of intra‐annual precipitation distribution factors on recharge. Although annual precipitation amount explains ∼70% of the variability in simulated recharge, analyses with DREAM indicate that the rainy season length is an important factor controlling recharge. Years with similar annual precipitation produce different recharge values as a result of temporal distribution throughout the rainy season. An experiment with a synthetic data set exhibits similar results, explaining ∼90% of the recharge variability. DREAM represents significant improvement over previous recharge estimation techniques in this region by providing near‐real‐time recharge estimates that can be used to predict the impact of climate variability on groundwater resources at high temporal and spatial resolution. Citation: Sheffer, N. A., E. Dafny, H. Gvirtzman, S. Navon, A. Frumkin, and E. Morin (2010), Hydrometeorological daily recharge assessment model (DREAM) for the Western Mountain Aquifer, Israel: Model application and effects of temporal patterns, Water Resour. Res., 46, W05510, doi:10.1029/2008WR007607.