אסיף מאגר המחקר החקלאי

Stochastic analysis of transport in a combined heterogeneous vadose zone-groundwater flow system

Year:

2009

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Volume :

45

Co-Authors:

Russo, D., Department of Environmental Physics and Irrigation, Institute of Soils, Water and Environmental Sciences, Volcani Center, Bet Dagan, Israel, Department of Environmental Physics and Irrigation, Institute of Soils, Water and Environmental Sciences, Agricultural Research Organization, Bet Dagan 50250, Israel
Fiori, A., Dipartimento di Scienza dell'Ingegneria Civile, Università di Roma Tre, Rome, Italy, Dipartimento di Scienza dell'Ingegneria Civile, Università di Roma Tre, via Volterra 62, 1-00146 Roma, Italy

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Abstract:

First-order analysis was used to investigate the effect of a few characteristics of the vadose zone and the solute source at the soil surface on the expected breakthrough curves (BTCs) of tracer solutes in a combined unsaturated-saturated spatially heterogeneous formation with a three-dimensional, statistically anisotropic structure. The analysis is based on a stochastic continuum representation of the stationary and nonstationary Eulerian velocity vectors in the unsaturated and saturated domains, respectively, and a general Lagrangian description of the solute mass flux in steady state flow. Results of the present analysis suggest that the length scales and the flow characteristics of the spatially heterogeneous, unsaturated zone that affect the travel time probability density function between the soil surface and the water table also affect the expected solute BTC at a control plane located downstream in the groundwater. The flow in the unsaturated zone might enhance the early arrival time and the spreading of the expected solute BTC in the groundwater, especially when the vertical extent of the unsaturated zone is relatively large; when the unsaturated zone consists of relatively dry, coarse-textured, stratified soil material; and when the horizontal extent of the solute source in the direction of the mean groundwater flow is relatively large. The effect of the characteristics of the vadose zone and the solute source at the soil surface on the expected solute BTC in the groundwater decreases as the distance to the control plane increases and as the process of the solute breakthrough is more advanced. The relatively good agreement between the results of the present first-order, stochastic analysis with the results of detailed, numerical analyses of flow and transport in a three-dimensional heterogeneous, combined vadose zone-groundwater flow domain suggests that the first-order stochastic analyses may be sufficiently reliable to show appropriate trends which might occur in realistic combined vadose zone-groundwater flow systems. © 2009 by American Geophysical Union.

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