Alex Furman

Neuro-Drip: estimation of subsurface wetting patterns for drip irrigation using neural networks

Design of efficient drip irrigation systems requires information about the subsurface water distribution of added water during and after infiltration. Further, this information should be readily accessible to design engineers and practitioners. Neuro-Drip combines an artificial neural network (ANN) with a statistical description of the spatio-temporal distribution of the added water from a single drip emitter to provide easily accessible, rapid illustrations of the spatial and temporal subsurface wetting patterns. In this approach, the ANN is an approximator of a flow system. The ANN is trained using close to 1,000 numerical simulations of infiltration. Moment analysis is used to encapsulate the spatial distribution of water content. In practice, the user provides soil hydraulic properties and discharge rate; the ANN is then used to estimate the depth to the center of mass of the added water, and the vertical and radial spreading around the center of mass; finally, this statistical description of the added water is used to visualize the fate of the added water during and after the infiltration event.

Modeling biofilm dynamics and hydraulic properties in variably saturated soils using a channel network model

Biofilm effects on water flow in unsaturated environments have largely been ignored in the past. However, intensive engineered systems that involve elevated organic loads such as wastewater irrigation, effluent recharge, and bioremediation processes make understanding how biofilms affect flow highly important. In the current work, we present a channel-network model that incorporates water flow, substrate transport, and biofilm dynamics to simulate the alteration of soil hydraulic properties, namely water retention and conductivity. The change in hydraulic properties due to biofilm growth is not trivial and depends highly on the spatial distribution of the biofilm development. Our results indicate that the substrate mass transfer coefficient across the water-biofilm interface dominates the spatiotemporal distribution of biofilm. High mass transfer coefficients lead to uncontrolled biofilm growth close to the substrate source, resulting in preferential clogging of the soil. Low mass transfer coefficients, on the other hand, lead to a more uniform biofilm distribution. The first scenario leads to a dramatic reduction of the hydraulic conductivity with almost no change in water retention, whereas the second scenario has a smaller effect on conductivity but a larger influence on retention. The current modeling approach identifies key factors that still need to be studied and opens the way for simulation and optimization of processes involving significant biological activity in unsaturated soils.

Biofilm effect on soil hydraulic properties: Experimental investigation using soil‐grown real biofilm

Understanding the influence of attached microbial biomass on water flow in variably saturated soils is crucial for many engineered flow systems. So far, the investigation of the effects of microbial biomass has been mainly limited to water-saturated systems. We have assessed the influence of biofilms on the soil hydraulic properties under variably-saturated conditions. A sandy soil was incubated with Pseudomonas Putida and the hydraulic properties of the incubated soil were determined by a combination of methods. Our results show a stronger soil water retention in the inoculated soil as compared to the control. The increase in volumetric water content reaches approximately 0.015 cm3 cm−3 but is only moderately correlated with the carbon deficit, a proxy for biofilm quantity, and less with the cell viable counts. The presence of biofilm reduced the saturated hydraulic conductivity of the soil by up to one order of magnitude. Under unsaturated conditions, the hydraulic conductivity was only reduced by a factor of four. This means that relative water conductance in biofilm-affected soils is higher compared to the clean soil at low water contents, and that the unsaturated hydraulic conductivity curve of biofilm-affected soil cannot be predicted by simply scaling the saturated hydraulic conductivity. A flexible parameterization of the soil hydraulic functions accounting for capillary and non-capillary flow was needed to adequately describe the observed properties over the entire wetness range. More research is needed to address the exact flow mechanisms in biofilm-affected, unsaturated soil and how they are related to effective system properties. This article is protected by copyright. All rights reserved.

Hydro‑geophysical monitoring of orchard root zone dynamics in semi‑arid region

AbstractMonitoring the moisture patterns at the root zone is necessary for agricultural, hydrological, and environmental applications. Conventional monitoring methods are usually invasive, destructive, and only sample at a small spatial scale. Electrical resistivity tomography (ERT) can set an alternative or be complementary to common traditional methods in evaluating the moisture content and its spatiotemporal patterns. In this study, we used the ERT method to monitor the hydro-geophysical dynamics under a drip-irrigated citrus orchard in a semi-arid region. Geophysical surveys were performed monthly for over a year. The obtained data from the electrical measurements were inverted to produce 2D tomograms of the bulk electrical conductivity. Calibrations of the petrophysical relations were conducted using both laboratory and field procedures. The obtained electrical results, and especially their temporal dynamics, cannot always be explained using the common assumption of uniform spatiotemporal distribution of the pore water electrical conductivity. To separate the two main components of the petrophysical relations, namely water content and pore water conductivity, we used a modeling approach. A coupled flow and transport model was calibrated using the electrical conductivity measurements, allowing separation of the contribution of the water content and pore water electrical conductivity to the bulk electrical conductivity. This allowed explaining the temporal dynamics of the measured electrical signal and a better understanding of the water and solute dynamics in the root zone.

Sampling at high spatial and temporal resolutions with an experimental chamber: High resolution sampling using experimental chamber

Laboratory-scale studies of the dynamics of soil biogeochemical processes often require destructive sampling for chemical, biological and genetic analyses. The consequences are either ‘end-of-experiment’ sampling or a set-up with multiple experiments in parallel, of which some are sacrificed over time. We propose an alternative experimental set-up to enable matrix sampling and monitoring at high spatiotemporal resolution of chemical, biological and physical properties. A customized experimental chamber was constructed, including an array of sensors on one side and hundreds of sampling ports on the other. A vertical unidirectional flow regime was maintained in the chamber, and soil samples were collected through ports that were not adjacent laterally to ones used in an earlier sampling campaign. We give an example of an experiment with such a chamber in which the environmental conditions (matric head and redox) were kept almost uniform in the horizontal dimension. Under these conditions nitrogen cycling was also almost the same in the lateral dimension. This system offers a unique combination of high spatial and temporal resolution sensors in the same system that is destructively sampled.

Groundwater Management in Israel

In recent years, groundwater (GW) is becoming increasingly important due to population growth, preparation for climate change, flood control, and above all water quality awareness. While in far and recent history most of the water for agricultural and domestic use was of surface origin, in the recent few decades, the portion of groundwater used in many countries is significantly higher than the portion of surface water used. This makes the study of groundwater and related fields such as vadose zone hydrology, subsurface contaminant fate and transport of high importance.