Jiri, Jirka Simunek

Jiri, Jirka Simunek
University of California, Riverside | UCR · Department of Environmental Sciences

PhD

About

603
Publications
229,312
Reads
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34,836
Citations
Citations since 2017
152 Research Items
16137 Citations
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201720182019202020212022202305001,0001,5002,0002,5003,000
201720182019202020212022202305001,0001,5002,0002,5003,000
Introduction
Jirka currently works at the University of California, Riverside. He is the main co-developer of the widely popular HYDRUS models. He is a fellow of AAAS, AGU, ASA, and SSSA, and a recipient of SSSA Don and Betty Kirkham Soil Physics Award, 2019 SSSA Soil Science Research Award, and 2021 AGU Hydrological Science Award. He received a degree "Doctor Honoris Causa" (dr.h.c.) from the Czech University of Life Sciences, Prague, Czech Republic. He is an Editor-in-Chief of Journal of Hydrology.
Additional affiliations
September 2003 - present
University of California, Riverside
Position
  • Professor and Hydrologist

Publications

Publications (603)
Article
As a critical element in preserving the health of urban populations, water distribution systems (WDSs) must be ready to implement emergency plans when catastrophic events such as contamination events occur. A risk-based simulation-optimization framework (EPANET–NSGA-III) combined with a decision support model (GMCR) is proposed in this study to det...
Article
The application of inverse modeling to determine the hydraulic properties of layered soils with rock fragments (RF > 2 mm) is associated with complex challenges such as selecting suitable hydraulic functions and defining a strategy to optimize many parameters. These two issues were addressed in this study by performing field drainage experiments in...
Article
Soil salinization caused by shallow, saline groundwater represents a serious threat to field productivity, especially in arid regions with intense soil evaporation. Plastic film mulching (PM) has been increasingly applied to reduce soil evaporation and alleviate soil salinity stress. However, PM introduces into the soil a significant amount of pla...
Article
Considering surface and subsurface interactions is imperative to predict water movement, water quantity and quality in the environment. However, substantial execution time and over-parameterization presently limit the applicability of integrated hydrologic models at larger scales. Herein, a new efficient coupling routine for one-dimensional (1D) su...
Article
Biosolids are an important resource for agricultural practice but have recently received increased focus as a potential source of per- and polyfluoroalkyl substances (PFAS) in the environment. Few studies have investigated the transport of PFAS through the unsaturated zone under conditions relevant to biosolids application sites. Herein, the unsatu...
Article
CONTEXT Intercropping systems have been widely used worldwide due to their high economic benefits and land-use efficiency. While it is well known that inter-species nutrition competition in intercropping systems leads to high production efficiency, the effects of different spatial arrangements of intercropping species on these mechanisms remain unc...
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Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is typically used to quantify surface interactions between engineered nanoparticles (ENPs), soil nanoparticles (SNPs), and/or porous media, which are used to assess environmental risk and fate of ENPs. This study investigates the co-transport behavior of functionalized multiwalled carbon nanotubes (MWC...
Article
Choosing a suitable process-oriented eco-hydrological model is essential for obtaining reliable simulations of hydrological processes. Determining soil hydraulic and solute transport parameters is another fundamental prerequisite. Research discussing the impact of considering evaporation fractionation on parameter estimation and practical applicati...
Article
Drip irrigation with alternate use of fresh and brackish waters is an excellent irrigation strategy to overcome salt stress problems induced by brackish water. Understanding salt stresses in the soil profile and their relationship with crop growth is critical when optimizing irrigation strategies with alternate use of fresh and brackish waters. The...
Article
When performing calculations or numerical simulations for the fate and transport of PFAS and other surface-active solutes in the vadose zone, accurately representing the relationship between the area of the air-water interfaces (Aaw) as a function of water saturation (Sw), and changes in that relationship resulting from changes in soil texture, are...
Article
The creation of artificial dunes for coastal protection may have important consequences for freshwater lenses in coastal aquifers. The objective of this study was to compare the recharge processes below such a young dune with scant vegetation to an older dune covered by grass and herbaceous vegetation. To this aim, soil and water samples were colle...
Article
Darcian, 2-D flows to subterranean holes are studied analytically (by the methods of complex analysis) and numerically (by HYDRUS). For flow towards two circular or quasi-circular tunnels, reconstructed as isobars generated by two sinks under a ponded homogeneous soil surface, the flow nets, the velocity vector fields, and Riesenkampf's seepage for...
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Optimization problems in hydrological modeling are frequently solved using local or global search strategies, which either maximize exploitation or exploration. Thus, the elevated performance of one strategy for one class of problems is often offset by poor performance for another class. To overcome this issue, we propose a hybrid strategy, G-CLPSO...
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Many different equations have been proposed to describe quantitatively one‐dimensional soil water infiltration. The unknown coefficients of these equations characterize soil hydraulic properties and may be estimated from a n record, {t∼i,I∼i}i=1n$\{ {\tilde t_i},{\tilde I_i}\} _{i = 1}^n$, of cumulative infiltration measurements using curve fitting...
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Given the hazardous effects of sudden dam reservoir contamination — as might occur upon the intrusion of the fuel additive methyl tert-butyl ether (MTBE) — the contaminant’s effect on the quality of allocated waters requires careful study. Employed to determine optimal reservoir operational rules in the case of sudden MTBE pollution, a risk-based s...
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Quantification of groundwater recharge is one of the most important issues in hydrogeology, especially in view of the ongoing changes in climate and land use. In this study, we use numerical models of 1D vertical flow in the vadose zone and the water table fluctuation (WTF) analysis to investigate local-scale recharge of a shallow sandy aquifer in...
Article
The EU Nitrates Directive calls for urgent integration of process-oriented indicators of nitrate fate with map overlay approaches for assessing nitrate vulnerable zones (NVZs). In the region of Campania (southern Italy), groundwater contamination represents a serious concern because of the presence of intensive agricultural practices and livestock...
Article
The use of Green Roofs (GRs) for domestic wastewater treatment and nitrogen (N) removal is an appealing opportunity to conjugate hydrological, energetic, and water quality benefits. However, the research in this direction has been limited to few experimental studies, while the role of numerical modeling for analysis and design has been overlooked....
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California is increasingly experiencing drought conditions that restrict irrigation deliveries to perennial nut crops such as almonds and pistachios. During drought, poorer quality groundwater is often used to maintain these crops, but this use often results in secondary salinization that requires skilled management. Process-based models can help i...
Article
Analytical solutions are obtained for water extinction from an axisymmetric crater, filled at t < 0 and depleted by evaporation and transient infiltration into a Gardner or capillarity-free homogeneous soil during the time interval 0 ≤ t ≤ Te. The extinction time Te is found for crater beds, the shapes of which are shallow cones, spherical, spheroi...
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Soil salinity increases when growers are forced to use higher salinity irrigation waters due to water shortages. It is necessary to estimate the impact of irrigation water on soil properties and conditions for crop growth to manage the effects of salinity on perennial crops. Therefore, in this study, we monitored root zone salinity in five almond a...
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Long-term use of recycled water (RW) for irrigation in arid and semiarid regions usually changes the soil solution composition and soil exchange characteristics, enhancing the risk for sa-linity and sodicity hazards in soils. This modelling study focuses on developing alternative management options that can reduce the potentially harmful impacts of...
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Artificial capillary barriers (CBs) are used to improve root zone conditions as they can keep water and nutrients in the root zone by limiting downward percolation. Numerical analysis is one of the promising tools for evaluating CB systems’ performance during the cultivation of leafy vegetables. This study aims to investigate the effects of the CB...
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Soil contains the largest terrestrial pool of organic matter, and the cycling of organic carbon in soils plays a crucial role in controlling atmospheric carbon dioxide (CO2) and global climate change. Although considerable progress has been made in previous modeling studies on the fate of soil organic matter (SOM), only a few models used a process-...
Article
Optimization of nitrogen (N) fertigation is a formidable challenge involving complex interactions between water and N uptake and their effects on crop production. Numerical models can be useful in studying the interaction of multiple variables like those found in mechanistic simulations of N fertigation strategies. The physical aspects can often be...
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Soil pollution from emerging contaminants poses a significant threat to water resources management and food production. The development of numerical models to describe the reactive transport of chemicals in both soil and plant is of paramount importance to elaborate mitigation strategies. To this aim, in the present study, a multiscale biophysical...
Article
Ecohydrological processes are often evaluated by studying the fate of stable water isotopes. However, isotopic fractionation during evaporation is often ignored or simplified in current models, resulting in simulation errors that may be propagated into practical applications of stable isotope tracing. In this study, we adapted and tested the HYDRUS...
Article
The use of plastic film mulching (PM) has steadily increased in the past few decades due to many advantages compared to no film mulching (NM). However, PM also has many drawbacks, such as producing plastic film residues and causing high temperatures at later crop growth stages. Thus, biodegradable film mulching (BM) has recently been used as an exc...
Article
Enhanced water use efficiency (WUE) is the key to sustainable agriculture in arid regions. The installation of capillary barriers (CB) has been suggested as one of the potential solutions. CB effects are observed between two soil layers with distinctly different soil hydraulic properties. A CB helps retain water in the upper, relatively fine-textur...
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Numerical simulation of three-dimensional water flow and solute transport in containerized variably saturated soilless substrates with complex hydraulic properties and boundary conditions necessitates high-resolution discretization of the spatial and temporal domains, which commonly leads to several million nodes requiring numerical evaluation. Eve...
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The authors appreciate Dr. Kabala's interest in our work and his commitment to protecting research work integrity and scientific records accuracy. They are of the utmost importance to us as well. After receiving the Comment, we made it our highest priority to respond, address the concerns raised, and carefully re‐examine our manuscript. This reply...
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This study presents a conceptual Dual-Permeability Non-Equilibrium (DPNE) model that accounts for both physical and chemical non-equilibria to describe the reactive solute transport through a porous medium. A semi-analytical solution of the DPNE model is derived in the Laplace domain, which is then numerically inverted to obtain concentrations in d...
Article
The classical Barenblatt solution of an initial-boundary value problem (IBVP) to the parabolic Boussinesq equation, which gives a rectangular triangle of full saturation, propagating from a reservoir into an adjacent porous bank with a vertical slope, is shown to coincide with a solution of IBVP to the elliptic Laplace equation with a phreatic surf...
Article
The hydraulic properties of the soil top layer may change during the growth period due to various factors such as wetting and drying cycles, tillage practices, and crop root growth. In this study, the potential of the assimilation method to estimate time-varying soil hydraulic parameters is explored. Four assimilation schemes, including the simulta...
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Pakistan is facing severe water shortages, so using the available water efficiently is essential for maximizing crop production. This can be achieved through efficient irrigation practices. Field studies were carried out to determine the dynamics of soil water and the efficiency of water utilization for maize grown under five irrigation techniques...
Article
Many arid and semi-arid regions of the world face challenges in maintaining the water quantity and quality needs of growing populations. A drywell is an engineered vadose zone infiltration device widely used for stormwater capture and managed aquifer recharge. To our knowledge, no prior studies have quantitatively examined virus transport from a dr...
Article
In cold regions, freeze-thaw cycles play a critical role in many engineering and agricultural applications and cause soil water flow and heat transport studies to be much more complicated due to phase changes involved. A fully coupled numerical module for simulating the simultaneous movement of water, vapor, and heat during freezing-thawing periods...
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Food contamination is a major worldwide risk for human health. Dynamic plant uptake of pollutants from contaminated environments is the preferred pathway into the human and animal food chain. Mechanistic models represent a fundamental tool for risk assessment and the development of mitigation strategies. However, difficulty in obtaining comprehensi...
Article
Seepage through an aquifer, the hydraulic conductivity of which varies vertically, is studied by using the Dupuit-Forchheimer approximation (Girinskii’s potential) and numerically by FDM-MODFLOW and FEM-HYDRUS-2D. In urban water hydrology, the effect of compaction of the top stratum of an aquifer on the flow rate and the position of the water table...
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The impact of global warming on water and nitrate losses from a rainfed-canola cropping system under various artificial drainage systems was assessed using an integrated field-modeling approach. Four subsurface drainage systems with different drain depths (Dx) and spacings (Ly), including D0.90L30, D0.65L30, D0.65L15, and Bilevel (with a drain spac...
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Aims Plant roots often encounter heterogeneity in soil water content and respond by compensating water uptake from wet zones to cope with the transpiration demand. Simultaneously, plants may also exhibit root-mediated hydraulic redistribution from wet to dry zones. Experiments were conducted to simultaneously monitor compensated root water uptake a...
Article
The appearance and distribution of soil pores have a significant influence on water flow and solute transport in the soil vadose zone. The pore system is highly variable in arable soils where crop rotation, tillage, trafficking, soil amendments, and various management practices are commonly implemented. The aim of this study was to assess the porou...
Article
The concentration of nonionic surfactants like Triton X-100 (TX100) can influence the transport and fate of emerging contaminants (e.g., carbon nanotubes) in porous media, but limited research has previously addressed this issue. This study investigates the co-transport of functionalized multi-walled carbon nanotubes (MWCNTs) and various concentrat...
Article
Irrigation with brackish water is a possible solution to alleviate freshwater shortages in arid and semi-arid regions. However, necessary measures need to be taken to leach accumulated salts out of the root zone. This can be accomplished by leaching with freshwater applied by surface irrigation (LFSI), which needs to be optimized to improve the lea...
Article
In arid areas, vapor flow has been recognized to contribute significantly to the mass and energy transfers and to play a critical role in maintaining surface vegetation and ecosystems. To better understand the continuous spatial and temporal variations in liquid water and water vapor contents under different climatic conditions, soil water contents...
Article
Drywells (DWs) and infiltration basins (IBs) are widely used as managed aquifer recharge (MAR) devices to capture stormwater runoff and recharge groundwater. However, no published research has compared the performance of these two engineered systems under shared conditions. Numerical experiments were conducted on an idealized 2D‐axisymmetric domain...
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Full-text available
The HYDRUS unsaturated flow and transport model was modified to simulate the effects of non-linear air-water interfacial (AWI) adsorption, solution surface tension-induced flow, and variable solution viscosity on the unsaturated transport of per- and polyfluoroalkyl substances (PFAS) within the vadose zone. These modifications were made and complet...
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Many different equations ranging from simple empirical to semi-analytical solutions of the Richards equation have been proposed for quantitative description of water infiltration into variably saturated soils. The sorptivity, S, and the saturated hydraulic conductivity, K s , in these equations are typically unknown and have to be estimated from me...
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The use of treated wastewater (WW) for irrigation is steadily increasing worldwide. However, irrigation with WW requires special attention as it may alter soil hydraulic properties, and eventually, affect crop yields. The main goal of this study was to investigate two approaches that could mitigate this adverse impact: (i) mixing WW with local fres...
Article
An analytical model is proposed in this study to describe transient drawdown induced by non-Darcian flow in a confined aquifer with a single well circulation groundwater heat pump system. The Izbash equation and a linearization method are employed to describe non-Darcian flow in the horizontal direction of a confined aquifer and to approximate the...
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Organic amendments are often reported to improve soil properties, promote plant growth, and improve crop yield. This study aimed to investigate the effects of the biochar and compost produced from sewage sludge and olive pomace on soil hydraulic properties, water flow, and P transport (i.e., sorption) using numerical modeling (HYDRUS-1D) applied to...
Article
An isobar generated by a line or point sink draining a confined semi-infinite aquifer is an analytic curve, to which a steady 2-D plane or axisymmetric Darcian flow converges. This sink may represent an excavation, ditch, or wadi on Earth, or a channel on Mars. The strength of the sink controls the form of the ditch depression: for 2-D flow, the sh...
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In this study, a general analytical model for the single well circulation system is developed to analyze transient drawdown in a confined aquifer. The analytical solution of transient drawdown in the Laplace domain, which is numerically inverted into the time domain using the Stehfest method, is derived by employing a combination of the Laplace and...
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In Tunisia, water used for irrigation is often saline, increasing the risk of salinization for soils and crops. In this study, an experiment was conducted on a tomato crop cultivated on a silty-clay soil irrigated with three different water qualities: 0, 3.5, and 7 dS.m−1. Experimental data were then used to calibrate and validate the Hydrus-1D mod...
Article
Water flow in the unsaturated zone is an important component of the water cycle. Accurate estimation of soil hydraulic parameters ensures precise simulations of water flow in the unsaturated zone. In this study, a Gaussian Process-based Iterative Ensemble Kalman Filter method (GPIEnKF) is proposed and applied for estimating soil hydraulic parameter...
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New water-conserving irrigation technologies are vital in arid countries. We investigated the effects of (i) soil substrates made of Smart Capillary Barrier Wick (SCB-W), consisting of silt loam blocks surrounded by sand-sheathes and irrigated with a sand wick cylinder (WC) as compared to a control (homogenous soil irrigated by the same wick system...
Article
Quantitative analyses of empirical data requirements for hydrological simulations are rare. This study aims to analyze how a multi-objective optimization framework and information content computations aid in quantifying field-scale data worth in drainage studies. The results showed how a 1D numerical model and a differential evolution algorithm per...
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Freeze-thaw cycles play a critical role in affecting ecosystem services in arid regions. Monitoring studies of soil temperature and moisture during a freeze-thaw process can generate data for research on the coupled movement of water, vapor, and heat during the freezing-thawing period which can, in turn, provide theoretical guidance for rational ir...
Article
Altering the soil surface features can potentially regulate water and solute movement processes in the soils, and reduce the accumulation of salts in the plant root zone. In this study, HYDRUS-2D was used consecutively for three years (2011- 2014) to evaluate the potential impact of different rainfall redirection and water harvesting techniques suc...
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Simulation models that describe the flow and transport processes of pesticides in soil and groundwater are important tools to analyze how surface pesticide applications influence groundwater quality. The aim of this study is to investigate whether the slow decline and the stable spatial pattern of atrazine concentrations after its ban, which were o...
Article
Drywells are widely used as managed aquifer recharge devices to capture stormwater runoff and recharge groundwater, but little research has examined the role of subsurface heterogeneity in hydraulic properties on drywell recharge efficiency. Numerical experiments were therefore conducted on a 2D‐axisymmetric domain using the HYDRUS (2D/3D) software...
Article
Macroscopic modeling approaches based on the solution of the Richards equation with root water uptake (RWU) as a sink term can help in understanding soil-water-plant interactions within the rhizosphere. However, these models currently cannot capture the differences in RWU attributed to variations in plant health. Errors in simulating RWU from unhea...
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The variably-saturated flow and multi-component transport module UNSATCHEM of HYDRUS-1D was used to evaluate the impact of the long-term (2018-2050) application of recycled water (RCW) for irrigating perennial horticulture (almonds, pistachios), viticulture (grapevines), annual horticulture (carrot, onion, and potato), and pasture crops in represen...
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New mathematical models are developed and corresponding boundary value problems are analytically and numerically solved for Darcian flows in earth (rock)–filled dams, which have a vertical impermeable barrier on the downstream slope. For saturated flow, a 2-D potential model considers a free boundary problem to Laplace’s equation with a traveling-w...
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The HYDRUS model can be used to evaluate the effects of different soil surface treatments at the bottom of the furrow, different initial nitrogen fertilizer locations, and different furrow irrigation rates on deep drainage and solute leaching in furrow irrigated systems. This paper extends our 2012 study, in which we considered only one irrigation...
Article
Highly parameterized numerical models are frequently used in environmental sciences to interpret physicochemical processes. Despite their popularity, unjustified model complexity often undermines model generalizability, resulting in poor model predictive capabilities. A trade-off between model performance and complexity can be achieved using model...