HYDRUS-1D Model Research Articles

Coupling water, solute, and sediment transport into a new computationally efficient hydrologic model

While surface–subsurface interactions strongly impact water quality and quantity in ecosystems, only relatively little attention has been given to solute mass transfers at this boundary. The KINEROS2 (K2) model solves the 1D kinematic wave equation for water flow and the advection–dispersion equation for non-absorbing solute (or sediment) transport at the surface, whereas the HYDRUS-1D (H1D) model solves the Richards equation for flow and the advection–dispersion equation for solute transport in the subsurface. We previously coupled water flow in the surface and subsurface environments using the K2 and H1D models (H1D-K2). Herein, an innovative framework was developed to additionally couple solute transport at the surface–subsurface boundary in the simple, accurate, and computationally efficient H1D-K2 model. To test the H1D-K2 model’s accuracy and robustness, simulation results are compared to analytical solutions, experimental data, and results from the two-dimensional HYDRUS-2D (H2D) code. The relative differences in water and solute balance components between the H2D and H1D-K2 models are less than 1% for homogeneous cases and 4% for heterogeneous cases. The simulated hydrograph and chemograph are almost identical for the two models. Furthermore, simulated Bromide (Br) concentration in runoff is in good agreement with observations. The proposed model also accurately reproduces soil erosion under different rainfall patterns and intensities.

Groundwater flow modeling and recharge estimation of heterogeneous aquifer: Applied to Matmata aquifer, southeastern, Tunisia

Groundwater is an important source of water supply for several socioeconomic sectors. In particular, heterogeneous carbonate aquifers are an important potential reservoir of groundwater resources. The Matmata carbonate aquifer, located in southern Tunisia, suffers from over abstraction and severe anthropogenic pressure. This study aims to estimate diffusive recharge rates using climate and soil datasets, and proposes a combination of CMB techniques and numerical simulation methods. Groundwater chloride mass balance and numerical simulations were best practices for achieving these goals. The Hydrus-1D model was applied, calibrated and validated with soil water content measured at different depths and using long-term, diurnal-scale field and climate data. The results highlight that Richard's retention parameters give a close correlation with the observed saturated moisture content with RMSE of 0.07. The calculated evaporation is around 22.5 mm for the entire study period, and the contribution of rainfall to infiltration, which was estimated at 9.8 mm as 8.4%. The CMB model shows a recent recharge rate 4.83 mm. yr−1, corresponding to a groundwater recharge rate of 5.84 % of precipitation. Groundwater recharge estimation is one of the most important concepts of water balance, and its assessment is crucial for groundwater management and protection.

Prevention of Dry Cracking of Excavated Earthen Sites at Han Yangling Museum Using Ultrasonic Wetting

ABSTRACT Dry cracking is the most perilous weathering process threatening the structural stability of earthen sites. Even in a high-humidity environment, dry cracking resulting from soil water evaporation cannot be entirely prevented. This study examined use of an ultrasonic atomization system to create an atmosphere of water-mist above excavated earthen sites. This system was selected to facilitate liquid water transport from air to the soil, to prevent dry cracking of earthen sites. A validation experiment was conducted to assess the effectiveness of the system for wetting earthen sites. The experimental results revealed that the system could maintain a high water content at an excavated earthen sites with a minimal gradient in soil water content and significantly reduced salt concentrations in the soil surface layer. The HYDRUS-2D model was calibrated using 15 d of experimental data, enabling numerical simulation of water and salt transport at an excavated earthen site under various wetting scenarios for a one-year period. The simulations demonstrated a steady increase in water content and a gradual decrease in the water content gradient at the excavated earthen site when short wetting intervals were used, thereby enhancing the structural stability of the site. These findings offer a vital reference for the application of ultrasonic atomization in the wetting of excavated earthen sites to prevent dry cracking.

Improvements in saline soil and the law of water-salt transport based on salt inhibition using MICP technology

Soil desertification and salinization are the main environmental disasters in arid and semi-arid areas. It is of great significance to study the water - salt migration law of saline soil and propose corresponding water- salt regulation and control measures. Microbial-induced calcite precipitation (MICP) technology was proposed to improve saline soil based on salt inhibition, and the water–salt–heat coupling migration law and salt-frost heave deformation law of saline soil before and after improvement were studied using soil column model tests. XR1#, XR2#（Saline-alkali-tolerant mineralization bacteria isolated from saline soil) and Sporosarcina pasteurii were used in the MICP improvement and the effect of XR1# was the best. Under high-temperature evaporation, the water migration change rate, water loss rate, accumulated evaporation amount, and accumulated salt content of the improved soil columns within a depth range of 0–40 cm were reduced by an average of 53.6 %, 47.3 %, 69.5 %, and 40 %, respectively, compared with the untreated soil column. During low-temperature cooling, the characteristics of water-salt migration changed significantly, and the deformation of salt-frost heave decreased significantly. The water-salt content at the freezing point (−4.5 °C) changed from a cliff-like steep drop (untreated saline soil) to a slow decrease at environmental temperature (MICP-treated saline soil), and the amount of water crystallization decreased from 81 % to 56.7 % at −5 °C. At the end of the cooling process, the amount of salt-frost heaving on the surface of the soil columns decreased by an average of 62.7 %. Based on the measured data, a numerical simulation was conducted using the HYDRUS-1D model, which had good reliability and accurately simulated and predicted the law of water-salt migration in saline soil under the conditions of microbial solidification and improvement. MICP technology significantly reduced the change rate of water-salt migration and water evaporation in saline soil, hindered salt accumulation, and reduced salt-frost heave deformation, which effectively improved saline soil. The research results provide an important innovation and theoretical basis for the improvement of saline soil.

Interaction of focused recharge and deep groundwater discharge near a wetland: A study in the Ordos Basin, China

Groundwater mounds and depressions induced by rainfall and evapotranspiration near wetlands/lakes have been widely observed, but their effects on groundwater flow field are poorly known. Here, a sandy hillslope near a wetland in the Ordos Plateau, China, which has a semi-arid climate, is selected for investigation. After identifying temporary groundwater mounds/depressions based on three water level observation wells, a HYDRUS-2D model is setup to obtain the highly transient daily flow field. The variable thickness of unsaturated zone near the wetland, which controls soil water content and unsaturated hydraulic conductivity, is found to be responsible for groundwater mounds resulting from focused recharge and groundwater depressions resulting from nonuniform evapotranspiration. On nonrainy days, evapotranspiration in the lowland is supported by flowpaths from regional groundwater discharge, and in the slope is supported by a flow cell from the upland to the upper part of the slope, which causes water table recession in the upland. On rainy days, focused recharge in the lowland leads to two temporary local flow cells, which break the regional groundwater discharge flowpaths into two temporary flow cells. The two temporary flow cells toward the upland contribute to water table rises in the uplandMoreover, we find focused recharge in rainy days does not change the overall direction of flowpaths controlled by regional groundwater discharge and strong evapotranspiration, but only increase the tortuosity of flowpaths. By coupling daily atmospheric conditions and regional groundwater discharge, this study has implications for groundwater recharge estimation and future groundwater modelling in arid regions.

Estimation of water budget components and its driving factors analysis in arid grassland

Clarifying the dependence of the grassland water budget change and its components on environmental factors is significant for the sustainable development of dryland ecosystems. Here, the Hydrus-1D model was used to simulate the water budget of natural grassland for 42 years (1980–2021). The standardized precipitation evapotranspiration index (SPEI) and soil moisture deficit index (SMDI) were used to analyze the soil drought evolution characteristics and the water use dynamic of the grassland in dry and wet years. Here, the calibrated Hydrus-1D model accurately identified the dynamic of grassland soil moisture in 2020 and 2021. The simulated data showed that evaporation (E) and transpiration (Tc) were the main pathways of soil water consumption, accounting for 96.5 % and 86.1 % of rainfall in dry and wet years, respectively. The soil water storage did not present a difference in precipitation proportion in dry (2.4 %) and wet (1.2 %) years, and the deep percolation accounted for a maximum of 12.8 % in wet years. Rainfall from 380 to 400 mm was the threshold, as it not only corresponds to the maximum water use efficiency (Tc/ET = 0.52, ET = E + Tc) but also serves as an important turning point for drought and deep percolation (below 150 cm) within the soil. The structural equation model further indicated that the dependence of E and Tc on meteorological factors was the main reason for the change of their proportions in dry and wet years. Tc was more sensitive to meteorological factors (R2 = 0.63), while E was not (R2 = 0.27). The SMDI had a greater impact on determining the threshold for water budget components than the SPEI. These results deepen the understanding of the hydrological process of grasslands in sandy areas, including the interaction between water budget components and environmental factors in wet and dry scenarios.

Development and functional evaluation of pedotransfer functions for estimating soil hydraulic properties in Portuguese soils: Implications for soil water dynamics

Accurate knowledge of soil hydraulic properties is essential for effectively simulating soil water dynamics in field plots. However, determining these properties directly can be challenging, especially when a large amount of data is required. Therefore, the primary objective of this study was to develop four hierarchical pedotransfer functions (PTFs) to estimate the soil hydraulic parameters of the Mualem-van Genuchten model. The PTFs that were developed ranged from utilizing a limited set of variables to those comprising a more comprehensive set of variables. These included particle size distribution, soil bulk density, soil depth, and soil water contents at matric potentials of −33 and − 1580 kPa. The functional performance of these PTFs was also assessed in simulations of the soil water balance in ten agricultural fields over two growing seasons using the HYDRUS-1D model. The simpler PTFs exhibited moderate accuracy in estimating soil water contents at different matric potentials, while the more complex PTFs with a greater number of variables yielded increasing accuracy. However, estimation errors were more noticeable in the drier range of the soil water retention curve. The inclusion of bulk density as a predictor only affected the wetter range of the same curve. Estimation of log Ks improved from the simpler to the more complex PTFs, but the statistical indicators were consistently modest. The functional performance of the PTFs showed increased errors in simulating soil water contents in the ten study sites compared to reference simulations. The more complex PTFs with the greatest number of variables provided the best predictions in most cases. The PTFs primarily affected flow conditions in the soil profile, resulting in increased soil water storage and impacting predictions of deep percolation the most. Water availability in the soil profile then influenced actual transpiration, alleviating stress in some cases but causing waterlogging in one situation. The study emphasizes the cautious use of the PTFs and the need for additional information on clay-rich soils and hydraulic conductivity data to enhance their performance.

Hydrus-1D Model for Simulating Phosphorus Transport in Paddy Crop Irrigated with Alternate Wetting and Drying Practice

ABSTRACT The alternate wetting and drying (AWD) irrigation practice involves soil moisture stress-based irrigation scheduling which possibly affects the rice field’s phosphorus (P) transport and balance components. The focus of this study was to understand P-transport under AWD irrigation and estimate the associated balance components in rice using a solute transport model, Hydrus-1D. In this study, rice was cultivated in 30 lysimeter plots with three irrigation treatments (no soil water stress/NS, mild soil water stress/400 cm/MS, and severe soil water stress/750 cm/SS) and each treatment was replicated 10 times. The field experimental data were used to simulate P transport with the help of the Hydrus-1D model. The Hydrus-1D model was calibrated and validated for P transport within the soil matrix under AWD irrigation practice. The P distribution was mostly concentrated within the top puddled soil layer (0–20 cm) and did not move to the deeper soil layers. The simulated results indicate that the recommended dose of P with 3–5 cm ponding water depth will increase the P availability for rice and reduce the P leaching loss in AWD irrigation practice. The Hydrus-1D model can be used as a management tool to determine the appropriate P application rate and ponding water depth irrigated with AWD for which the required P nutrients are sufficiently available to rice and the P loss to the environment can be controlled for sustainable rice production.

Moderate water deficit and nitrogen application rate are conducive to improving the nitrogen uptake and yield of greenhouse tomatoes

Nowadays, improper irrigation and fertilization result in a waste of resources and a decrease in tomato production. In this study, we set three irrigation intervals (W1, W2 and W3 indicated upper and lower limit of irrigation of 65–75% θFC, 75–85% θFC and 85–95% θFC) and three nitrogen application rates (N1, N2 and N3 indicated nitrogen application rates of 120, 180 and 240 kg hm−2). The HYDRUS–2D model was first calibrated and validated using data collected during a two–year field investigation and then applied to explore the rules of soil water and nitrogen movement and root uptake. The Entropy weight TOPSIS model was optimized water and nitrogen management. Reliable estimates of soil nitrate nitrogen concentrations (R2 = 97%–99%, MRE = 0.05–0.19 and RMSE = 0.023–0.110), crop N uptake (R2 = 88%–99%, MRE = 0.17–0.44 and RMSE = 0.25–10.72), and soil water content (R2 = 82%–96%, MRE = 0.009–0.024 and RMSE = 0.003–0.007) were provided by HYDRUS–2D model. Based on the simulated results, the soil ammonium nitrogen was not easily affected by soil water movement and mainly distributed in 0–30 cm. W3 made soil water move deeper and carried nitrate nitrogen to accumulate in the deep soil comparison to W2 and W1. The combination of irrigation interval of 75–85% θFC and nitrogen application rate of 180 kg hm−2 improved root uptake, water use efficiency, nitrogen use efficiency and tomato yield. The evaluation result showed that N2W2 was the optimal water and nitrogen supply mode for our study. This study could promote the sustainable production of greenhouse tomatoes.

Evaluating The Effect of Initial Soil Moisture Content on Infiltration Characteristics Using Empirical and Hydrus 1D Models

Evaluating The Effect of Initial Soil Moisture Content on Infiltration Characteristics Using Empirical and Hydrus 1D Models

CNN deep learning performance in estimating nitrate uptake by maize and root zone losses under surface drip irrigation

Optimal fertigation regimes will minimize the leaching of agrochemicals while providing crops with sufficient nutrition for growth. A comprehensive objective function of optimization involves minimizing (i) difference between weekly plant nitrogen uptake and requirement and (ii) nitrate losses (nitrate leaching and accumulated nitrate in the root zone). Coupling a simulation model to an optimization algorithm for obtaining the objective function variables (N plant uptake and nitrate losses) typically requires long runtimes as the simulation model is repeatedly applied over iterations of the optimization algorithm. One attractive way to reduce the programming and computational demands associated with optimization is to construct a simpler, faster, but sufficiently accurate emulator of the simulation model based on machine-learning model. This study assessed the performance of convolutional neural networks (CNN) in modelling nitrate uptake by maize and estimation of nitrate losses in surface drip irrigation in three texturally different soils. To do this, the CNN was trained on output of the simulation model HYDRUS-2D. Various combinations of parameters influencing daily nitrate uptake (daily potential crop evapotranspiration, irrigation water and injected fertilizer amount) were evaluated as model inputs. Results indicated that daily nitrate uptake at any time t was predicted best with inputs of daily potential evapotranspiration at time t, irrigation and fertilizer amounts of the previous 1–7 days and the previous day’s nitrate uptake amount. Estimated nitrate losses for constant weekly fertigation (CWF) were about 32% in sandy loam and 38.5% in sandy clay loam soil. Variable weekly fertigation (VWF) reduced the nitrate losses to 24.5% in sandy loam and 31.5% in sandy clay loam soil, while losses in loam soil were intermediate to these. The study demonstrates that CNN estimation of nitrate uptake and root zone losses can be widely used in optimization of fertigation management.

Assessing Soil Dynamics and Improving Long-Standing Irrigation Management with Treated Wastewater: A Case Study on Citrus Trees in Palestine

Irrigation with Treated Wastewater (TWW) is a well-known agricultural practice in Palestine. The long-term use of irrigation with TWW, a source of water and nutrients, can affect plant development, soil, and groundwater quality. Consequently, the frequency and the intervals of irrigation events should be adequately scheduled, especially when nutrients (TWW-N) cannot be separated from the water. Achieving good water quality implies its immediate reuse in irrigated agriculture. In contrast, long-term soil and groundwater quality conservation is marked by the complex mechanisms that correlate the soil, water, plant, and atmosphere. Therefore, monitoring and modeling (MMA) are combined to retrieve the soil water and nitrate fluxes and identify a proper irrigation management plan in a case study in Beit Dajan-Palestine, where a schedule adapted to conventional water was applied to a 6-year-old citrus orchard continuously irrigated with TWW. Soil nitrogen concentration and water content data were collected from March to August 2021 to calibrate the Hydrus-1D model under the (1) farmer demand (F) scenario, where irrigation volumes are delivered according to the farmer experience, and to define an optimal irrigation management strategy with TWW according to the (2) model demand (M) scenario, based on the irrigation frequency. The latter respects the allowable thresholds of soil solution electrical conductivity, σe, assuming an average soil salinity profile and estimated leaf nitrogen concentrations tolerance as reference; 2021 was taken as a calibration year to retrieve water and nitrate fluxes for 2019 and 2020. In 2021, the measured soil electrical conductivity, σe, showed no salinity risk with an average value of 1.07 dS m−1 (low salinity < 2 dS m−1) but with a leaf nitrogen deficit. Although an acceptable level of available soil nitrogen was observed (ranging between 10 and 35 mg kg−1, whereas the standard value is 10–40 mg kg−1), critical concentrations were observed in the leaves (below 1%) in scenario (F) compared to scenario (M) (ranging between 1.7 and 1.9%). The latter also showed a decrease in nitrate leaching by 33% compared to the former. Overall, the comparison between the simulated and measured soil variables shows that the 1D-Hydrus model could follow the temporal variation in the monitored data, with some overestimation of the measured data during the simulation period. The simulations demonstrate that by modulating the salt tolerance threshold, the M scenario achieved better results in terms of root water and N uptake despite the stress inevitably experienced by citrus with long-term TWW irrigation. Moreover, the optimum threshold values used to assess the soil quality and citrus response under conventional water irrigation were inadequate for TWW practices. Therefore, MMA could be an alternative strategy to schedule proper TWW irrigation.

Indented Interfaces between Soil Strata: Analytical and HYDRUS2D Modeling of 2-D Seepage Towards a Wedge

Indented Interfaces between Soil Strata: Analytical and HYDRUS2D Modeling of 2-D Seepage Towards a Wedge

Effect of Different Irrigation Managements on Infiltration Equations and Their Coefficients

The main aim of this paper was to analyze the sensitivity of the five infiltration equations (Kostiakov, Kostiakov–Lewis, Philip, Horton and SCS) and their coefficients to various ponding depths and initial soil moisture under different irrigation managements. The treatments included three qualities of water (electrical conductivity = 6, 3 and 0.6 dS/m), two managements of irrigation (intermittent irrigation and daily irrigation) and three irrigation periods (100, 45 and 8 days). The HYDRUS-1D model was calibrated to simulate infiltration in various initial soil moistures and ponding depths. Evaluating the performance of infiltration equations showed that the Horton and Kostiakov–Lewis had better accuracy and Kostiakov and SCS had less accuracy than the other equations. The empirical coefficients of SCS and Kostiakov had the most and least sensitivities, respectively. Furthermore, Horton was the most sensitive equation, while SCS was the least sensitive one. The output parameters under daily management were the most sensitive to variations in infiltration coefficients, especially when the salinity and sodium contents of water and soil were higher. The results also showed that the effect of the initial soil moisture on the infiltration coefficient in high permeable soil (arising from daily management) was greater; but in low permeable soil (arising from intermittent management), the ponding depth was more effective. It is concluded that the infiltration equations (specifically the SCS equation) and their coefficients (specifically coefficient c) should be calibrated relative to the initial soil moisture, ponding depth, soil solution and water irrigation quality. Particularly in areas with high permeable soil (in the daily management), the calibration of the infiltration equation should be conducted with the initial soil moisture. In these areas, the irrigation period should be controlled. In areas with low permeable soil (in intermittent management), calibration should be carried out relative to the ponding depth. In these areas, the inflow rate should be controlled.

Monitoring Waterlogging Damage of Winter Wheat Based on HYDRUS-1D and WOFOST Coupled Model and Assimilated Soil Moisture Data of Remote Sensing

Waterlogging harms winter wheat growth. To enable accurate monitoring of agricultural waterlogging, this paper conducts a winter wheat waterlogging monitoring study using multi-source data in Guzhen County, Anhui Province, China. The hydrological model HYDRUS-1D is coupled with the crop growth model WOFOST, and the Ensemble Kalman Filter is used to assimilate Sentinel-1 inversion soil moisture data. According to the precision and continuity of soil moisture, the damage of winter wheat waterlogging were obtained. The experimental results show that the accuracy of the soil moisture is improved after data assimilation compared with that before data assimilation, and the Nash–Sutcliffe efficiency (NSE) of the simulated soil moisture values at three monitoring sites increased from 0.528, 0.541 and 0.575 to 0.752, 0.692 and 0.731, respectively. A new waterlogging identification criterion has been proposed based on the growth periods and probability distribution of soil moisture. The proportion, calculated from this identification criterion, of the waterlogging wheat farmland in total farmland shows a high correlation with the yield reduction rate. The correlation coefficient of the waterlogging farmland proportion and the yield reduction rate in 11 towns of Guzhen County reaches 0.78. Through the synchronization of geography, agriculture and meteorology, the framework shows great potential in waterlogging monitoring.

Analytical and HYDRUS solutions for exfiltration through inclined seepage faces

Steady, phreatic flows in wedge-shaped aquifers subtended by a tilted bedrock and discharged through a hillslope seepage face are studied by 2-D and 1-D analytical models for fully saturated and a FEM numerical model for saturated-unsaturated flows. The curvilinear triangle in the hodograph domain is conformally mapped onto a reference half-plane where the Hilbert problem is solved for two holomorphic functions. Free boundaries and sizes of seepage face segments are found for given flow rates of the incident flows seeping downhills. The approximate (Dupuit-Forchheimer) water table is conjugated with a saturated triangle where the exact 1-D solution gives a constant Darcian velocity as a function of the angles of the soil wedge. HYDRUS-2D model gives the distributions of the pressure head, volumetric moisture content, isotachs, vector-fields of velocity and other characteristics of seepage described by the Richards-Richardson equation. Applications to stability of exfiltrating zones near tailwaters of earth dams are discussed.

Groundwater recharge influenced by ephemeral river flow and land use in the semiarid Limpopo Province of South Africa

Determining the sustainability of groundwater use in drylands with high climate variability is complex. Central to this determination is an understanding of groundwater recharge and associated processes and controls. Groundwater recharge in drylands can occur by diffuse and focused recharge (focused recharge being associated with intense episodic rainfall events and ephemeral river flow, predicted to increase and intensify with climate change). This study evaluated the relative significance and dominant controls on these two recharge processes. Ten groundwater hydrographs with multidecadal observations were collated from the Limpopo Province, South Africa, based on their proximity to river channels and rain gauges, representing diversity in local climate, landscape, vegetation, and hydrogeological conditions. The hydrographs showed that groundwater-level rises are sensitive to rainfall intensity during the rainy season, with generally larger increases after years with large episodic rainfall events, which disproportionately contribute to groundwater replenishment. Recharge processes and annual recharge volumes were quantified using the water-table fluctuation method and the numerical model HYDRUS-1D. This allowed for the inference of additional recharge contributions from focused recharge in proximity to ephemeral rivers, up to a factor of five relative to diffuse recharge. The analysis revealed synchronicity and linear correlation between annual river discharge and recharge close to the river, substantiating the importance of focused recharge close to the river network. The study showed that recharge in drylands is subject to large spatial and temporal variation and that consideration of focused and episodic recharge is critically important for managing groundwater resources at various scales in these regions.

Evaluating soil water dynamics under a no-tillage system with residual plastic film mulching in an arid region of western China using HYDRUS-2D

No-tillage (NT) with residual plastic film mulching from an earlier year (NTR) is considered an excellent agricultural strategy in arid regions, recommended to reduce not only soil disturbance but also plastic film residues. However, the soil water dynamic in the root zone under this management is more complex due to variations in soil properties and upper boundary conditions. Soil compaction and a disintegrated fraction (DF) of the residual plastic film increase in NTR years. Soil water movement under NTR is not fully understood. It is also necessary to determine a suitable number of NTR years and optimize irrigation to increase water use efficiency (WUE) and maintain sustainable agricultural development. Therefore, the HYDRUS-2D model was calibrated and validated using experimental data from 2019 to 2021 collected in the corn field with conventional tillage (CTN), NT with a new plastic film (NTN), and NTR. The soil water contents (SWC), cumulative water fluxes (CWF), and soil water balances under CTNH, NTNH, and NTRH with the high (subscript H) irrigation depth of 315 mm (the local recommendation) were evaluated using both measured and simulated data. The results for NTRH, NTRM (a medium irrigation depth of 252 mm, 80% of local recommendation), and NTRL (a low irrigation depth of 189 mm, 60% of local recommendation) scenarios were compared, and a suitable number of NTR years was determined. The results of numerical simulations agreed with observations, with the mean relative error range for the calibration and validation periods between 4.9% and 5.4%. The larger number of experimental NTR years, the larger the SWC differences for all irrigation depths, tillage practices, and mulching due to larger soil compaction under NT and a higher DF of the residual plastic film. The largest SWC differences occurred in the 0–30 cm soil layer in the third experimental year (2021), with an average SWC decrease of 2.3% for NTNH compared to CTNH and 10.2% for NTRH compared to NTNH. Simulated two-dimensional SWC distributions further confirmed these experimental results. There were lower CWF under NT and new film mulching. CWF at a depth of 30 cm was 8.5 mm lower for NTNH than for CTNH in 2021. There was a 4.2%, 30.1%, and 43.1% increase in CWF for NTRH compared to NTNH due to higher soil evaporation evaluated from the soil water balance in 2019, 2020, and 2021, respectively. The scenario simulation results showed that SWCs decreased linearly with an increase in DF and that DF of 30% can be regarded as the maximum value for obtaining high WUE under NTR. The highest WUE of 28.3 kg ha–1 mm–1 under NTR during two years was found when the local recommended irrigation depth was reduced by 20% (to 252 mm). Therefore, this management can be recommended in arid regions to avoid plastic pollution with higher WUE.

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.

The assessment of the effectiveness of the unimodal and bimodal models to evaluate the water flow through nature-based solutions substrates.

Nature-based solutions are popular techniques for managing stormwater. Most of them allow porous media as their main layer. The description of the Soil Water Retention Curve (SWRC) as the Unsaturated Hydraulic Conductivity Curve (UHCC) is often required to run the hydrological simulations with the physically based models. Using the unimodal and bimodal models to assess the SWRC and UHCC of soils is a widespread technique but their evaluation is often present in literature only in terms of curve fitting. Based on these assumptions, this work presents the performance assessment of the van Genuchten unimodal and bimodal models by functional evaluation of them based on the runoff from several substrates. Four substrates were investigated to define the structure, the SWRC, and the UHCC. Results showed that all substrates had a bimodal behaviour with lowest values of RMSE (RMSE_Θ = 0.0023 to 0.0037, RMSE_K = 0.0636 to 0.1284). Finally, a numerical simulation using the HYDRUS-1D model was performed for a three-month data set to check the effectiveness of the unimodal model instead of the bimodal one. The findings have shown that the unimodal model must be preferred instead of the bimodal because it has fewer parameters and assured low discrepancies in runoff volume (ε=0.00% to 6.25%).