Search results for "Vadose zone"

Field testing parameter sensitivity of the two-term infiltration equation using differentiated linearization

2003

Knowledge of soil hydraulic conductivity in the vadose zone is important in many agronomic, engineering and environmental areas. Transient tension infiltrometer experiments can be used to estimate the hydraulic conductivity, K0, corresponding to a given pressure head by the single-test (TST) method that uses the coefficients C1 and C2 of the two-term infiltration equation. The “Differentiated Linearization” (DL) method has been proposed to estimate these coefficients when a layer of contact material is used for the experiment. A field test of the DL and TST methods was conducted on a sandy loam and a clay soil. Eliminating the early-time influence of the contact layer was easy when the sorp…

Effects of initialization on response of a fully-distributed hydrologic model

2008

Summary Knowledge of initial conditions is very important to correctly model the basin response at the storm event scale. Of particular interest is the influence of topography and soil type on the principal hydrologic variables and runoff generation mechanisms as a function of antecedent wetness conditions. This study addresses the influence of initial states on the short-term hydrologic response and characterizes the effects of topography and soils on the dissipation of the influence of the initialization conditions. Two case studies are considered: a synthetic two-dimensional planar hillslope with various assumed slope magnitudes and soil types; and a real basin (∼800 km2) with actual lan…

Shear-thinning fluids for gravity and anisotropy mitigation during soil remediation in the vadose zone

2018

Abstract Surfactant foam has been proposed as an effective treatment fluid for in situ environmental remediation of soils. In the vadose zone, it could improve treatment homogeneity, but its use remains challenging. To better understand and predict foam formation and propagation in vadose zone, we studied them in 24 soils with wide range of properties (including permeability: 2 10−12 to 3.3 10−9 m2). Foam rheology showed to be complex and mostly influenced by soil permeability and grading. Below 2 10−11 m2, foam propagation velocity was not influenced by permeability. Conversely, slight shear thinning to Newtonian behavior was observed for higher permeabilities. Benefits for remediation in …

Carbon Budget and Molecular Structure of Natural Organic Matter in Bank Infiltrated Groundwater

2021

Groundwater : : journal of the Association of Ground-Water Scientists and Engineers, a division of the National Ground Water Association (2021). doi:10.1111/gwat.13087

Shallow urban aquifers under hyper-recharge equatorial conditions and strong anthropogenic constrains. Implications in terms of groundwater resources…

2021

Abstract Humid equatorial regions are recognized as the least documented in term of hydrogeological functioning of aquifers despite the fact that they house a lot of developing countries and that groundwater is often the main water resource. Regarding this aspect, a study was conducted in sub-Saharan Africa, focusing on the Mio-Pliocene aquifer in Douala megacity (Cameroon) which is the rainiest city in West-Africa (about 4000 mm/year) with one of the greatest demographic growth rate of the African continent. Firstly, groundwater recharge rate has been calculated through water balance and Water Table Fluctuation methods. Results show that the aquifer is characterized by a high recharge of 6…

Characterization and modeling of water movement and salts transfer in a semi-arid region of Tunisia (Bou Hajla, Kairouan) – Salinization risk of soil…

2012

Abstract The semi-arid region of Bou Hajla (Kairouan – Central Tunisia) is exposed to the risk of soils and aquifers salinization. A characterization of water movement through the use of TDR probes installed at up to 4 m in depth, and of salts transfer by soil sampling was conducted to highlight this risk. At the same time, climatic parameters were monitored. The results were gathered over the period of approximately 1 year (June 12, 2006 to May 08, 2007). Water infiltration and evaporation, occurred at within distinct materials: two zero flux planes at 1 and 3 m, and a clay-silt layer at 2 m where the soil water content and electrical conductivity is highly varied. Saline profiles show sal…

Discussion of "Hydraulic Model of Transition of Transient to Steady Flows in the Vadose Zone" by Yaguo Zhang, Tonglu Li, Wei Shen, and Yu Wang

2020

The authors wrote an interesting article dealing with a simple hydraulic model to illustrate the transition mechanism of transient to steady flows in the vadose zone. The soil behavior is described by a set of nine vertically aligned cylinders, each opened at the top and with a small outlet at the bottom. The water level dynamic of each cylinder, associated with an intermittent constant rainfall applied to the top cylinder, C0, was analyzed and numerical simulations were performed. The only objective of this discussion is to show that results similar to those proposed by the authors could be obtained by using the recently introduced Richards equation analytical solution, under gravity-drive…

Upper pleistocene interstratal piping-cave speleogenesis: The seso cave system (central pyrenees, northern spain)

2015

The Seso Cave System (SCS, South Central Pyrenees, Northeastern Spain) develops in poorly soluble marly interstratum between limestone beds of Eocene age. We propose an innovative and singular pseudokarstic speleogenetic model under vadose conditions based on cave morphological evidence, physicochemical and mineralogical characteristics of the Eocene marly host rock, U-Th dating of cave deposits, and local geological and geomorphological information. Eocene marls are shown to be sensitive to dispersion processes supported by their high clay content and the high concentration of sodium and low electrical conductivity in the seepage water. Runoff inside the cave results from water that infilt…

2017

Abstract. The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection–diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection–diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, wh…

Comparative assessment of a foam-based oxidative treatment of hydrocarbon-contaminated unsaturated and anisotropic soils.

2019

Abstract In situ delivery of liquid reagents in vadose zone is limited by soil anisotropy and gravity. The enhanced delivery of persulfate (PS) as oxidant, using a new foam-based method (F-PS) was compared at bench-scale to traditional water-based (W-PS) and surfactant solution-based (S-PS) deliveries. The goal was to distribute PS uniformly in coal tar-contaminated unsaturated and anisotropic soils, both in terms of permeability and contamination. Water was the less efficiently delivered fluid because of the hydrophobicity of the contaminated soils. Surfactant enhanced PS-distribution into contaminated zones by reducing interfacial tension and inverting soil wettability. Regardless of coal…