Vadose Zone Water Pressure Variation during Infiltration Events

Abstract

Measurements of vadose zone water pressure using custom‐made tensiometers provided insight into the dynamics of rainfall‐induced infiltration events in a 22‐m‐thick sandy formation. The tensiometers, based on vadose zone sampling ports, were assembled in a vadose zone monitoring system that allowed in situ, real‐time measurements of the temporal variation in vadose zone water content and pore water pressure. Results revealed the critical relationship between temporal variations in vadose zone water content and water pressure, as well as the dynamic connectivity of the vadose zone gas phase to the atmosphere. As expected, variation in the sediment water contents, induced by infiltration events across the vadose zone, resulted in corresponding variations in pore water pressure; however, the measured responses of sediment water pressure to wetting events were delayed compared with the measured variations in water content. The delay in the pressure response to a wetting process varied with location as well as between wetting events. Most of the time, the vadose zone gas phase was well connected to the atmosphere; however, this connectivity was limited during rain events and, therefore, compensation of the measured water pressure variation for the measured atmospheric pressure fluctuation is not straightforward. Connectivity of the vadose zone gas phase to the atmosphere was reestablished simultaneously across the entire vadose zone following redistribution of the percolating water in the upper part of the cross‐section.

Ammonia transformations and abundance of ammonia oxidizers in a clay soil underlying a manure pond

“…It is highly possible that desiccation cracks from the margins create a network of horizontal connectivity under the pond, as has been observed in large‐scale lysimeter experiments and modeled by numerical models (Chertkov, ; Greve et al ., ). It is suggested that the formation of desiccation cracks around and under the manure pond can accelerate the aeration of the unsaturated vadose zone, via a variety of mechanisms: (1) thermal‐induced air convection in the cracks (Nachshon et al ., ), (2) barometric pressure fluctuations in the vadose zone caused by daily atmospheric pressure fluctuations (Rimon et al ., ), and (3) wind gusts (Auer et al ., ; Neeper, ).…”

Nitrate leaching from intensive organic farms to groundwater

“…The ability to characterize flow and transport processes in the vadose zone was recently improved following the development of a vadose zone monitoring system (VMS) that provides realtime, in situ information on the hydraulic and chemical state of the percolating water across the entire vadose zone. Up to now, the VMS has been implemented in a variety of hydrological setups, including (1) flood water percolation (Dahan et al, , 2008Amiaz et al, 2011), (2) rain water percolation through thick unsaturated sand and clay formations (Rimon et al, 2007(Rimon et al, , 2011bBaram et al, 2012a), and (3) solute transport in the vadose zone (Dahan et al, 2009;Rimon et al, 2011a;Baram et al, 2012b).…”

Investigation of Groundwater Recharge under Agricultural Fields Using Transient Deep Vadose Zone Data

“…However, natural percolation events driven by natural wetting and drying cycles might occur on a scale of hours to days. Moreover, recent studies have demonstrated that the bulk chemical and isotopic characteristics of sediment samples often do not represent the properties of the mobile water due to macro‐scale preferential flow (McMahon et al, 2006; Gurdak et al, 2008; Kurtzman and Scanlon, 2011; Baram et al, 2012) and pore‐scale preferential flow (Rimon et al, 2011).…”