HYDRUS-1D Software Research Articles

Impact of Irrigation Management Decisions on the Water Footprint of Processing Tomatoes in Southern Spain

The water footprint is an increasingly demanded environmental sustainability indicator for certifications and labels in agricultural production. Processing tomatoes are highly water-intensive, and existing studies on water footprint have uncertainties and do not consider the impact of different irrigation configurations (e.g., surface drip irrigation (SDI) and subsurface drip irrigation (SSDI)) and irrigation strategies. This study presents a two-year experimental investigation to determine the water footprint of processing tomatoes grown in southern Spain (Andalusia) and the impact of SSDI and deficit irrigation. Five irrigation treatments were established: SDI1 (surface drip irrigation without water limitation), SDI2 (surface drip irrigation without water limitation adjusted by soil moisture readings), SSDI1 (subsurface drip irrigation without water limitation and a dripline depth of 15 cm), SSDI2 (similar to SSDI1 but with mild/moderate water deficit during the fruit ripening stage), and SSDI3 (subsurface drip irrigation without water limitation and a dripline depth of 35 cm (first year) and 25 cm (second year)). Measurements included crop vegetative growth, leaf water potential, leaf gas exchange, nitrate concentration in soil solution, and crop yield and quality. The soil water balance components (actual evaporation, actual transpiration, deep drainage), necessary for determining the total crop water footprint, were simulated on a daily scale using Hydrus 2D software. Results indicated that SSDI makes more efficient use of irrigation water than SDI. The water footprint of SSDI1 was 20–35% lower than that of SDI1. SSDI2 showed similar water footprint values to SDI1 under highly demanding environmental conditions and significantly lower values (≈40%) in a year with lower evaporative demand. The dripline depth in SSDI was critical to the water footprint. With a 35 cm installation depth, SSDI3 had a significantly higher water footprint than the other treatments, while the values were similar to SSDI1 when the depth was reduced to 25 cm.

Estimation of soil infiltration coefficient in the furrow irrigation using the combination of the hydrodynamics model and Richard's equation

Present study optimizes the coefficients of the Kostiakov-Lewis infiltration Eq. and estimates water infiltration in the soil with the help of simulation of the advancing phase using the numerical solution of the Saint-Venant equations. In order to validate the numerical model, two series of field data measured in two regions of Iran were used and the results of the simulation were compared with actual field results. Also, using the Richards' Eq., the HYDRUS-1D software, the Hydrus-2D software, and a combination of the Hydrodynamics model with each of the mentioned methods the infiltration simulation and prediction of coefficients of the Kostiakov-Lewis infiltration Eq. were provided. The criteria for the accuracy of the methods were considered the comparison between the infiltration volumes of the water (calculated from each method) and the actual infiltration volume of the water in Furrow irrigation. The results illustrated that the combination of the Hydrodynamics model with each of the HYDRUS-1D, HYDRUS-2D software and the numerical solution of the Richards' Eq. increased the accuracy of the estimation process of the coefficients of the Kostiakov-Lewis's infiltration equation and the infiltration volume. So, the best and worst methods for simulating water infiltration through the soil has been introduced based on the less error between numerical and observed values of the infiltration volume as the combined method of the Hydrodynamics- HYDRUS 2D with NRMSE = 17.62% and numerical solution of the Richard's Eq. with NRMSE = 36.02%, respectively. The results illustrated that the error of the Hydrodynamics- HYDRUS-2D compared with the numerical solution of the Richard's Eq. (t(10) = −3.018) was significantly less value.

Evaluation of Soil Hydraulic Properties in Northern and Central Tunisian Soils for Improvement of Hydrological Modelling

The hydrological cycle is strongly affected by climate changes causing extreme weather events with long drought periods and heavy rainfall events. To predict the hydrological functioning of Tunisian catchments, modelling is an essential tool to estimate the consequences on water resources and to test the sustainability of the different land uses. Soil physical properties describing water flow are essential to feed the models and must therefore be determined all over the watershed. A simple but robust ring infiltration method combined with particle size distribution (PSD) analysis (BEST method) was used to evaluate and derive the retention properties and the hydraulic conductivities. Physically based and statistical pedotransfer functions based on PSD were compared to test their potential use for different types of Tunisian soils. The functional sensitivity of these parameters was assessed by employing the Hydrus-1D software (PC Progress, Prague, Czech Republic) for water balance computations. This evaluation process involved testing the responsiveness and accuracy of the parameters in simulating various water balance components within the model. The evaluation of soil hydraulic parameters across the three used models highlighted significant variations, demonstrating distinct characteristics in each model. While notable differences were evident overall, intriguing similarities emerged, particularly regarding saturated hydraulic conductivity between BEST and Rosetta, and the shape parameter (n) between Arya–Paris and Rosetta. These parallels indicate shared hydraulic properties among the models, underscoring areas of agreement amid their diverse results. Significant differences were shown for scale parameter α for the various methods employed. Marginal differences in evaporation and drainage were observed between the BEST and Arya–Paris methods, with Rosetta distinctly highlighting a disparity between physically based models and statistical models.

Hydraulic Characterization of Green Roof Substrates by Evaporation Experiments

Green roofs can be a valid solution for stormwater management in urban environments. The objective of this study was to develop a laboratory procedure for the hydraulic characterization of artificial substrates, used in the realization of green roofs, based on transient evaporation and steady-state unit hydraulic gradient (UHG) experiments. The retention, θ(h), and hydraulic conductivity, K(h), curves of two commercial substrates Terra Mediterranea® (TMT) and AgriTERRAM® (ATV) and a specifically developed substrate made by mixing peat, compost and sandy loam soil (MIX) were investigated. The unimodal van Genuchten–Mualem (VGM) hydraulic functions obtained by the direct evaporation method with different choices of the fitting parameters were compared with UHG measurements of K(h) conducted close to saturation. A numerical inversion of the transient evaporation experiments performed by Hydrus-1D software was also conducted, assuming that the hydraulic properties could be expressed either by unimodal or bimodal VGM models. The results indicated that an appropriate a priori choice of the residual water content parameter improved the estimation of the water retention curve. Moreover, the water retention data estimated from the direct evaporation method were not statistically different from those obtained with the inverse Hydrus-1D. The unsaturated hydraulic conductivity estimations obtained by the direct and inverse methods were highly correlated and the use of the bimodal VGM model improved the estimation of K(h) in the wet range. The numerical inversion of laboratory evaporation data with the hydraulic characteristics expressed by the bimodal VGM model proved to be a reliable and effective procedure for hydraulic characterization of artificial substrates, thus improving the reliability of simulated water fluxes in green roofs.

Effects of Coal Gasification Slag on the Migration of Cd2+ and Pb2+ in Soil

In recent years, coal gasification slag has been widely used as an adsorbent in many countries worldwide. To better understand remediation of soil heavy metal pollution by coal gasification slag, it is necessary to examine and analyze the influence mechanism of the adsorption characteristics of coal gasification slag on the migration of heavy metal ions in the soil. In this study, we used a soil water movement model and convection-dispersion equation and constructed a model of heavy metal migration after soil improvement by coal gasification slag; then, we evaluated and predicted the influence of heavy metal infiltration with liquid on groundwater after soil improvement. Combined with the soil column experiment, HYDRUS-1D software was used to predict the migration behavior of heavy metals in the soil. The results showed that the dispersion of the sample with coal gasification slag was smaller than that of the original soil sample, and the permeability coefficient of the soil was reduced by 59.34%; after adding coal gasification slag, the adsorption rates of Cd2+ and Pb2+ on the soil samples were higher than 95% and 99% respectively. The constructed heavy metal migration model was fitted well and predicted the migration behavior of heavy metals in the soil satisfactorily. The addition of coal gasification slag can effectively prevent the infiltration of Cd2+ and Pb2+ in the soil and can mitigate groundwater pollution. Therefore, using the adsorption characteristics of coal gasification slag to study the migration behavior of Cd2+ and Pb2+ in soil has important practical significance for soil adsorption and provides a new idea for the comprehensive utilization of coal gasification slag.

Modeling the Transport of Inorganic Arsenic Species through Field Soils: Irrigation and Soil Structure Effect

Dissolved arsenic (As) may appear at the tile line level through preferential flow (PF), leading to contamination of shallow water bodies. Limited work on the movement of As forms in field soils urged the need for more research. The PF of arsenate (As(V)) and arsenite (As(III)) compared to chloride (Cl) at constant flow under saturated (10 mm), slightly unsaturated (−10 mm), and unsaturated (−40 mm) pressure heads was evaluated in replicated large field columns varying in subsoil structure. A solute containing As(V), As(III), and Cl was pulsed until the Cl concentration ratio in the drainage samples reached maxima and flushed with solute-free irrigation. HYDRUS-1D software version 4.15 was utilized to fit the breakthroughs of As(V) and As(III) in the dual-porosity physical non-equilibrium model (DP-PNE). The Langmuir equation was used to fit the As(V) and As(III) sorption isotherms, and blue dye staining was used for the marking of flow paths. Dye leaching was observed up to 50 cm or deeper in the soils. Under saturated conditions (+10 mm), Kotli, Guliana, and Mansehra soils showed chemical non-equilibrium (CNE) for As(V) and As(III); however, the extent of CNE was less under unsaturated conditions (−40 mm). These results implied that these well-structured soils had enough large macropores, which cause PF, but at the same time, they were also small enough to retain water and leach solutes under unsaturated conditions (−40 mm). It is concluded that irrigation of contaminated water or dumping solid waste on well-aggregated soil may exhibit PF of dissolved As during and after rains, and additionally As(III), which is more toxic and mobile under reduced conditions, has equal or greater potential for movement.

A new methodology to characterize the kinetics of a seed during the imbibition process

AimsAssuming the saturated, θs, and residual θr volumetric water contents of a seed as known inputs, we present a methodology to determine the hydraulic properties of a seed: α, n parameters and hydraulic conductivity Ks.MethodsThe seed is considered as a porous material in which water flow is governed with the same hydraulic properties defined for soils. Using the HYDRUS-2D software, the hydraulic properties of a seed were estimated from the inverse analysis of several cumulative seed imbibition curves measured at different seed water potentials, h. The optimum number of h was evaluated on synthetic seeds. The theoretical analysis was validated in laboratory experiments on barley, wheat and vetch seeds, where imbibition curves were measured with germination tests at seven levels of h (from 0 to -2.50 MPa).ResultsThe theoretical analysis showed that accurate estimates of α, n and Ks can be obtained if the most negative h-values are included in the optimization. The sensitivity analysis showed that the method allows obtaining a unique solution of α, n and Ks. The optimization error on the theoretical α, n and Ks was less than 1%. A satisfactory validation was also obtained on the experimental seed imbibition curves, with robust fits between the measured and optimized data. A unique solution of α, n and Ks was also obtained in all cases.ConclusionsA new method to determine the hydraulic properties of a seed is presented. This methodology could be used in different areas involving seed imbibition and also to simulate seed imbibition in different scenarios.

Vertical Moisture Transfer Investigation on Lysimeters Taking into Account Substrates Granulometric Heterogeneity

The issues of soil-hydrophysical support of mathematical models of moisture movement, taking into account the heterogeneity of the soil, due to the spatial change in texture, are considered. The processes of vertical movement of moisture on large-sized lysimeters of the Federal Scientific Center of Agroecology of the Russian Academy of Sciences (Volgograd) were studied. The influence of statistical heterogeneity of hydrophysical parameters of lysimeter substrates was studied on models of moisture transfer dynamics and formation of gravity flow developed in the environment of the HYDRUS-1D software package. The change in texture along the vertical profile of the lysimeters and the related variability of the main hydrophysical characteristic (WRC) were taken into account. The granulometric heterogeneity of the substrates was estimated by the scaling method, according to the scale factors of the WRC parameters, assuming a normal probability distribution of the logarithms of the pore space capillary radii between soil particles. The effect of texture on water-holding capacity, boundary and initial conditions, intensity of gravity runoff and cumulative accumulation of moisture was studied.

Estimating the impact of vadose zone heterogeneity on agricultural managed aquifer recharge: A combined experimental and modeling study

Agricultural managed aquifer recharge (Ag-MAR) is a promising approach to replenish groundwater resources using flood water and cropland as spreading grounds. However, site selection, particularly the layering of sediment deposits in the subsurface, can greatly influence Ag-MAR efficacy as it controls water flow and solute transport in the vadose zone. In this study, we use the HYDRUS-1D software to simulate water flow and solute transport from the land surface to the groundwater table in three vadose zone profiles (LS, MS, HS) characterized by differing fractions of sand (44 %, 47 %, and 64 %). For each profile, the single- and dual-porosity models (i.e., considering or not nonequilibrium water flow and solute transport) were calibrated using observed surface ponding, soil water content, and KBr breakthrough data. Water flow and bromide transport in the profile with the lowest sand fraction (LS) were best captured using the model that considered both preferential flow and nonequilibrium bromide transport. Water flow and bromide transport in the profile with the highest sand fraction (HS) was best simulated with the model that considered preferential flow and equilibrium bromide transport. Uniform water flow and nonequilibrium bromide transport provided the best fit for the third profile (MS). The degree of preferential flow was highest in the profile with the largest sand fraction (HS), which also showed the largest flow velocities compared to the profiles with lower sand amounts (LS and MS). Preferential flow did not significantly impact the overall water balance (within 3 %), but caused a significant decrease in vadose zone travel times (bromide) by up to 38 %, relative to a single-porosity model fit. Recharge efficiency varied between 88 % and 90 %, while the average travel times from the soil surface to groundwater varied up to 119 % (from 3.6 to 7.9 days) between the three sites. This study demonstrates that similar recharge efficiency can be achieved at sites with differing soil texture profiles, but subsurface heterogeneity can substantially affect contaminant transport processes and their travel times.

Modeling the effect of slope aspect on temporal variation of soil water content and matric potential using different approaches by HYDRUS-1D

Slope aspect affects microclimate and soil moisture conditions, and thus has an important effect on the hydrological cycle. Given the lack of precise field data on this effect, two soil temperature, moisture and matric potential monitoring sites on north- and south-facing slopes have been established since 2017 in sandy loam soil under beech forest in a small valley near Ebergötzen, central Germany. HYDRUS-1D software was used with different approaches (including Rosetta, RETC, and RETC–measured θs approaches) for deriving soil hydraulic parameters of the van Genuchten model, to simulate temporal variability of soil water content and matric potential in the two slope aspects. Due to different microclimatic conditions, the south-facing slope was warmer and drier than the north-facing slope (two-years average temperatures 9.71 and 9.36 °C, and two-years average soil water contents 0.17 and 0.26 cm3 cm-3, respectively). The model was satisfactorily calibrated and validated on the two slopes. The calibration for the wet period was better on the south-facing slope (R2 = 0.772) than on the north-facing slope (R2 = 0.690). The simulation performance by HYDRUS-1D was better in the wet period than in the dry period. In the dry period, the model was better calibrated for the north-facing slope (R2 = 0.880) than for the south-facing slope (R2 = 0.691). The better calibration results for the wet period of south-facing slope can be explained by the location of the majority of measured soil water retention data which were in the near-saturation zone on the north-facing slope, and discontinuity of second-order derivative of the van Genuchten equation at saturation point when shape parameter (n) is smaller than 2. According to the model ability and different datasets used for the model validation, the north-facing plot was validated better than the south-facing plot for both wet and dry periods. Given that Rosetta was developed based on a soil hydraulic dataset from temperate climates, and the shortcomings of the hydraulic model, our results indicated that the Rosetta–derived approach was a reliable source for soil hydraulic parameters in both slope aspects for the wet period. However, the RETC–derived parameters were more accurate than Rosetta for the dry period on the north-facing slope.

Response of Liquid Water and Vapor Flow to Rainfall Events in Sandy Soil of Arid and Semi-Arid Regions

In arid and semi-arid regions, rainfall takes on a critical significance to both agricultural and engineering construction activities, and the transport process and driving mechanism of soil water under rainfall conditions are in need of further investigation. To clarify the variations in soil moisture, temperature, and liquid and vapor flux under various rainfall scenarios, the Mu Us Sandy Land was selected as the study region, and a water–vapor–heat transport model was established using the Hydrus-1D software with in situ observed soil and meteorological data. The simulated results were in good agreement with the measured data during both the calibration and validation periods, suggesting that the model was accurate and applicable to the study region. The variations in the selected dry and rainy periods proved the significant effect of rainfall events on soil matric potential, temperature, and driving forces. When rainfall occurred, the hydraulic conductivity for liquid water rose by three to five orders of magnitude, driving the liquid water flow downward. In contrast, the vapor flux played a vital role in soil water movement, accounting for about 15% of the total water flux in the shallow layer when the soil was dry, while it became non-significant during rainy periods due to the reduction in hydraulic conductivity for vapor and the temperature gradient. These results clarified the mechanisms of soil liquid water and vapor movement in arid areas, which could provide scientific support for future studies on vegetation restoration and ecosystem sustainability in ecologically fragile areas.

A study of the water quality parameter and its impact using HYDRUS-1D in Deepor Beel, Guwahati, Assam

This study focuses on knowing the status of 12 water quality parameters with their variation and soil-solute interaction due to dumping of wastes at six different locations of Deepor Beel (a Ramsar site), finding their necessary correlations and development of a solute transport model using HYDRUS-1D software. HYDRUS-1D model used in this study will show the movement of iron through the soil profile in the area selected near the Municipal dumping yard at Boragaon. The results indicated that certain parameters are higher than their standard permissible limits with its extreme values obtained at the dumping location at Boragaon. The water near the dumping site is acidic (pH= 5.92), with high iron concentrations (3.68 mg/l), increasing hardness and turbidity as well as lower D.O level (3.67 mg/l). HYDRUS-1D solute transport model gives a distinct and clear picture of the solute movement, water flow, water content, pressure head and concentration profile variation along the soil profile with respect to time and depth. The results of this model showed that continuous influx of harmful solutes on the surface of the Deepor Beel could lead to break through of this solute through the soil column into the groundwater storage. Hence the present study showed that water quality is deteriorating at various locations of the beel and necessary steps are immediately required for sustaining the ecological balance of the wetland.

Experimental and numerical study on Zn and Pb migration in the farmland soil under wastewater irrigation conditions.

Long-term wastewater irrigation may lead to the accumulation, transformation, and migration of heavy metals in the farmland soil, increasing the risk of groundwater pollution. However, it is currently uncertain whether using wastewater for irrigation would lead to the migration of heavy metals zinc (Zn) and lead (Pb) into deeper layers of soil, in the local undeveloped wastewater irrigation farmland. In this study, the migration characteristics of Zn and Pb from irrigation wastewater in local farmland soil were investigated through a series of experiments including adsorption experiments, tracer, and heavy metals breakthrough experiments, as well as numerical simulations using HYDRUS-2D software. The results revealed that the Langmuir adsorption model, CDE model, and TSM model were effective in fitting the required adsorption and solute transport parameters for the simulations. Furthermore, both the soil experiments and simulation results showed that in the test soil, Pb had a stronger affinity for adsorption sites than Zn, while Zn exhibited greater mobility than Pb. After 10years of wastewater irrigation, it was found that Zn had migrated to a maximum depth of 32.69cm underground and Pb had only migrated to 19.59cm. Despite their migration, the two heavy metals have not yet reached the groundwater zone. Instead, they had accumulated to higher concentrations in the local farmland soil. Moreover, the proportion of active forms of Zn and Pb decreased after flooded incubation. The present results can improve understanding of the environmental behavior of Zn and Pb in the farmland soil and can be used as a basis for risk assessment of Zn and Pb polluting groundwater.

Mechanistic insights into the migration behavior of cadmium (Cd) in the soil and groundwater systems at a construction site: Experimental and numerical analysis

The environmental fates of cadmium (Cd) in the soil and groundwater systems largely depend on its adsorption isotherms and kinetic with the soil matrix. Combined with HYDRUS–1D software, batch and column studies were conducted in this study to investigate the adsorption and movement process of Cd in soil and groundwater systems. The results from static adsorption experiment indicated that the second order model and Langmuir model could provide the better description for adsorption behavior of Cd. The results from SEM –EDS and XPS analysis revealed that the main adsorption mechanism of Cd were ion exchange, complexation and precipitation. The results from Tessier's sequential extraction suggested that more Cd would be diffused to the deeper soils, since the higher percentage of Cd were found in the exchangeable fractions. The results from soil column experiments and numerical analyses demonstrated that standard convection–dispersion equation (CDE) could better describe Cd breakthrough curve (BTCs) of column adsorption than the other three solute transport models within HYDRUS–1D software. Noteworthy, the horizontal and vertical migration distance of Cd (II) reached about 8 m after 50,000 days and 10 m after 15,000 days, respectively, indicating the easily mobile Cd (II) might be eventually released from contaminated soils to groundwater. Based on the above results, this study not only provided a new insight into the migration mechanism of Cd in the soil and groundwater environment, but was also beneficial to formulating remediation strategies of contaminated sites.

Moisture content distribution model for the soil wetting body under moistube irrigation

This study investigated the moisture distribution characteristics of a soil wetting body under different influencing factors to inform the design and management of a moistube irrigation system. A mathematical model of soil moisture movement under moistube irrigation was established based on Hydrus-2D software. The suitability of the Hydrus-2D simulation model was verified by laboratory experiments. Numerical simulations were carried out with Hydrus-2D to investigate the influence of soil texture, initial moisture content, moistube specific discharge and irrigation time on the moisture distribution of a soil wetting body. The soil moisture content is highest at the moistube, and its value is related to the moistube-specific discharge and soil texture. The soil moisture content at any point in the wetting body decreased linearly with increasing distance from the wetting front to the moistube in the five set directions (vertical downward, 45° downward, horizontal, 45° upward and vertical upward). This trend is applicable to fine-textured and coarse-textured soil. An estimation model of soil moisture content including soil saturated hydraulic conductivity, initial soil moisture, the specific flow rate of the moistube and the maximum value of the wetting front distance in all directions is proposed. The model estimation is good (root mean square error = 0.008–0.018 cm3·cm−3, close to 0; Nash-Sutcliffe efficiency coefficient = 0.987, close to 1), and it can provide a practical tool for moistube irrigation design and agricultural water management.

Organization of the soil profile controls the risks of runoff in the humid Ethiopian Highlands

Erosion of agricultural land endangers the livelihood of millions of people who depend on natural resources. Soil and water conservation practices (SWCP) are intended to reduce runoff production and erosion. Understanding surface runoff drivers are crucial for the effective design and implementation of SWCPs. We present field observations of complex vertical soil profiles and variations in lithology along hillslopes ridge-channel transects from the Debre Mawi watershed in the upper Abay (Blue Nile) basin of the Ethiopian Highlands. Our study generates the first depth- and hillslope-distributed soil water retention curves, textural profiles and measures of hydraulic conductivity for the region. We provide guidance into preferred pedotransfer functions (PTFs) and their sensitivity to clay fraction. Hydrological processes associated with the observed vertical profiles and variations on them were simulated with the Hydrus-2D software package, revealing that dominant runoff generation mechanisms were sensitive to the vertical organization of soil texture, particularly at depths of 30 cm or more below the soil surface for soil profiles that have well-drained surface soil textures. This suggests that current practices of evaluating soil properties based on surface texture only is insufficient for understanding hillslope hydrology and mitigating soil erosion in these regions. In regions where comprehensive soil hydraulic profile data is not available, our study quantifies the uncertainties in both PTFs and hydrological fluxes due to variation of soil profile texture present; these can aid decision makers in data collection and accounting of errors for the intended application of interest.

Modeling and simulation of trifluralin herbicide movement due to its application on soils by chemigation

The Trifluralin (TFN) is a pre-emergent herbicide which is widely used in agriculture. Usually, this pesticide is directly applied to the soil, where it can remain for long periods or can be transported. In this sense, knowing the dynamics of an herbicide soil transport is essential to avoid environmental contamination problems and risks to human health. Thus, this study aims to model and simulate TFN movement on soils with two different textures, a sandy loam and clay loam soil. It was considered that the herbicide was applied via chemigation trough a subsurface drip irrigation system, under a non-steady regime. Therefore, the transport parameters of TFN in these soils and physical-hydric characteristics of these were used, while the physical environment modeling were conducted using the Hydrus 2D software. The results showed that both in sandy and clayey soils, the TFN tends to be retained by the soil, close to where it was applied, not exceeding a layer greater than 2.5 mm outside the dripper radius, even in more favorable conditions such as the presence of irrigation. Finally, it could be concluded that this herbicide movement in the soil is of low potential, due to this product high solid-liquid partition coefficient (Kd), even in sandy soil, which has low cation exchange capacity (CEC).

Surface soil water content as an indicator of Hass avocado irrigation scheduling

This study aims to determine whether Hass avocado irrigation can be triggered based on the surface soil water content (SSWC). To address this question, the soil water dynamics from three Hass avocado orchard plots located in Valle del Cauca (Colombia) was simulated using a model provided by Hydrus-1D software, which was calibrated through the genetic algorithm NSGA-II and validated using the soil matric potential measured at several depths at nine monitoring stations installed in the three plots. The influence of each superficial (0–5, 5–10, and 10–15 cm) and deeper (15–30 and 30–60 cm) available water (AW) computed from the simulated moisture on the SWB at 0–60 cm was estimated from the artificial neural network (ANN) trained weights. The most influential depth range was used to predict the soil water balance at 0–60 cm using ANN. For validation, the RMSE slightly increased regarding calibration, varying from 1.73 to 8.20, while the R2 value varied from 0.61 to 0.89 (P < 0.001 for all cases). The AW at 5–10 cm depth had a significant influence on SWB with an average relevance index of 2.87 (Wilcoxon signed-rank test P ≤ 0.05) for Laurentina farm. The AW at 0–5 cm depth had not significant influence on SWB with an average relevance index of 1.34 (independent group) and 0.97 (P < 0.05) for Laurentina and Poncena, respectively. The ANN model predicted the SWB with a RMSE no bigger than 13.76 mm. In conclusion, the SSWC at a depth of 5–10 cm can be used as an indicator for scheduling Hass avocado irrigation.

Modeling Soil Profile Salinity with HYDRUS-1D

Salt accumulation within the root zone significantly effects plant growth and development in arid and semi-arid regions. Today, use of low-quality irrigation water in agricultural production is increasing rapidly, because of continuous depletion and pollution of water resources. This means more salt transferred to the soil profile. It is of great importance to predetermine the effects of irrigation practices for sustainable crop production. For this purpose, models and tools that can produce reliable and fast results should be used. In this study, soil profile salinity was modeled with the HYDRUS-1D software. In present study, Three different irrigation water salinity levels (S1=0.25 – control/municipal tap water, S2=1.5, S3=3.0 dS m-1) and 4 different irrigation volumes (leaching ratio) (LR1=10%, LR2= 20%, LR3=35%, LR4=50%) were modeled in a randomized plots factorial experimental design with 3 replications. Each treatment was carried out in individual PVC lysimeters with a length of 115 cm and a diameter of 40 cm in open-field to determine the efficiency of the model at different salinity levels and leaching rates. Alfalfa (Medicago sativa L.) was preferred as a plant due to its economic value, effective root depth and being a perennial plant. During the growing period, a total of 7 irrigations were practiced and five soil samples were taken from 20, 40, 60, 80 and 100 cm depths at the last day of each month. Present findings revealed that values modeled with the HYDRUS-1D software were sufficient to determine the soil profile salinity. Relative error values (RE) ranged from 0.048 to 0.307. Increase in salinity and irrigation applications reduced the accuracy of the model. However, it can be said that the values produced by the model were sufficient even under the mentioned conditions. Especially for academic studies, the HYDRUS-1D software can be used to obtain fast and reliable results.

Simulation of experimental synthetic DNA tracer transport through the vadose zone

Although multiple experimental studies have proven the use of free synthetic DNA as tracers in hydrological systems, their quantitative fate and transport, especially through the vadose zone, is still not well understood. Here we simulate the water flow and breakthrough of deuterium (D) and one free synthetic DNA tracer from a 10-day experiment conducted in a transient variably saturated 1m3 10° sloped lysimeter using the HYDRUS-2D software package. Recovery and breakthrough flux of D (97.78%) and the DNA tracer (1.05%) were captured well with the advection-dispersion equation (R2 = 0.949, NSE = 0.937) and the Schijven and Šimůnek two-site kinetic sorption model recommended for virus transport modeling (R2 = 0.824, NSE = 0.823), respectively. The degradation of the DNA tracer was very slow (estimated to be 10% in 10 days), because the “loamy sand” porous media in our lysimeter was freshly crushed basaltic tephra (i.e., crushed rocks) and the microbes and DNase that could potentially degrade DNA in regular soils were rare in our “loamy sand”. The timing of the concentration peaks and the HYDRUS-2D simulated temporal and spatial distribution of DNA in the lysimeter both revealed the role of the solid-water-air contact lines in mobilizing and carrying DNA tracer under the experimental variably saturated transient flow condition. The free DNA was nearly non-selectively transported through the porous media, and showed a slightly early breakthrough, possibly due to a slight effect of anion exclusion or size exclusion. Our results indicate that free DNA have the potential to trace vadose zone water flow and solute/contaminant transport, and to serve as surrogates to trace viral pathogen pollution in soil-water systems. To our knowledge, this study is the first to simulate transport mechanisms of free synthetic DNA tracers through real soil textured porous media under variably saturated transient flow condition.