HYDRUS simulation of vertical and horizontal water distribution for continuous and intermittent water flow under subsurface line source

This study investigates the critical challenges of water management in arid regions, focusing on the optimization of irrigation practices to mitigate water scarcity, improve soil water retention, and reduce deep percolation losses in loamy sand soils. Emphasizing the significance of emitter placement depth. Utilizing the HYDRUS model with validation under empirical experiment, this work presents a robust scientific approach to developing intermittent irrigation strategies that enhance water use efficiency (WUE). The study employs the HYDRUS model to simulate water movement under both continuous and intermittent subsurface flow conditions. It assesses the impacts of various ON:OFF time ratios, specifically 1ON:1OFF, 1ON:3OFF, and 1ON:5OFF, across different irrigation cycles ranging from one to five. Furthermore, it evaluates the effectiveness of two emitter burial depths (25 cm and 35 cm) on water retention efficiency. The findings aim to optimize irrigation schedules and inform sustainable agricultural practices. A comprehensive simulation framework reveals that the optimal irrigation configuration consists of a two-cycle intermittent flow (1ON:5OFF) with a 25 cm emitter depth. This configuration provides novel insights into how ON:OFF time ratios influence soil moisture retention, particularly at the critical root-zone depths of 20–40 cm. In conducting this research, a series of five irrigation scenarios were tested: continuous flow (WF1C) and four intermittent flows (WF2C through WF5C), under different ON:OFF, applied for 30 min at a discharge rate of 3.41 L/h. The study assessed both vertical and horizontal water movement and soil retention over a 360 min observation period. Results indicated that intermittent irrigation markedly improved water retention compared to continuous flow, particularly at critical depths of 20–40 cm that are vital for root activity. The two-cycle intermittent flow (WF2C) achieved the highest soil water retention—up to 87% at 30 cm and 57% at 20 cm—while the 1ON:3OFF ratios displayed retention rates ranging from 70 to 78%. In contrast, minimal impact was observed at a 10 cm depth, with no significant variations noted at 50 cm, suggesting limited irrigation influence at greater depths. Overall, this research demonstrates the enhanced WUE of intermittent irrigation, reinforcing its application in promoting sustainable agricultural productivity in arid regions.

Effective water utilization is critical for sustainable agriculture, particularly in light of escalating demands from non-agricultural sectors, the impacts of climate change, and variability in precipitation patterns (Mukhopadhyay et al., 2021). As the significance of water resources intensifies, the need for efficient utilization becomes paramount (Tian et al., 2021). A variety of strategies aimed at optimizing water usage in agricultural practices underscore the importance of effective management techniques (Jha et al., 2019; Olgarenko et al., 2018). Enhancing water use efficiency (WUE) presents substantial opportunities for cost savings, primarily through mechanisms such as reducing evaporation, developing innovative crop varieties, improving irrigation practices, and reallocating water resources to higher-value crops (Bwambale et al., 2022). Traditional flood irrigation systems exert pressure on water resources and contribute to wastefulness (Darfaoui and Assiri, 2010). In contrast, contemporary irrigation methods, such as drip irrigation, facilitate precise application of both water and nutrients, thereby enhancing efficiency and adaptability across diverse agricultural conditions (Jin et al., 2022). Micro-irrigation techniques, characterized by localized application of water, operate at low application rates, with prolonged durations and frequent intervals, effectively delivering water close to the root zone. Specifically, drip irrigation is a prominent method within the micro-irrigation category (Geng et al., 2022). Its advantages encompass improved WUE, increased crop yields, diminished evaporation rates, and optimized fertilizer application (Martínez and Reca, 2014). Subsurface drip irrigation (SDI) is particularly noteworthy for its capability to deliver water and nutrients effectively (Douh and Boujelben, 2010). A comprehensive understanding of soil water behavior is essential for the optimization of water use (Gültekin and Ertek, 2023). Emitters in SDI systems, situated within the drip line, contribute to reduced evaporation while supporting sustainable agricultural practices (Devasirvatham, 2009a). Nevertheless, deeper placement of these emitters may adversely affect seed germination and nutrient uptake (Lamm and Camp, 2007). Conversely, shallow emitter placement is critical for the cultivation of shallow-rooted crops, particularly in sandy soil conditions (Devasirvatham, 2009a). Notably, SDI can achieve a wetted area up to 50% larger than that of traditional surface irrigation methods, leading to water savings of 31 and 23% respectively, compared to conventional practices (Singh et al., 2023). Furthermore, optimal scheduling and appropriate emission rates are influential factors affecting root development and crop yields (Vadar et al., 2019). Selecting the correct depth for the installation of subsurface irrigation pipes is crucial and must consider variables such as root zone depth, soil texture and properties, as well as considerations regarding intermittent flow (Devasirvatham, 2009b).

Intermittent irrigation enhances the wetting zone through cycles of water supply and moisture redistribution, where reduced frequency improves both horizontal and vertical moisture spread (Mohammed and Abed, 2020). The distribution of soil moisture around a water emitter is influenced by several factors, including the applied water volume, emitter flow rate, emitter configuration, soil properties, initial boundary conditions, plant root activity, and overall irrigation management practices (Al-Ogaidi et al., 2016). Wetting patterns in drip irrigation can be modified by manipulating dripper discharge rates, emitter spacing, irrigation frequency, and the design of subsurface drip irrigation (SDI) tape (Kilic, 2018). The configuration of the wetting pattern is crucial for optimizing emitter spacing and selecting appropriate irrigation systems (Dabral et al., 2012). Wetting characteristics are contingent upon the specific soil properties (such as texture and hydraulic conductivity) and the application scheme, which encompasses method, position, rate, and frequency of irrigation (Moncef and Khemaies, 2019). Effective scheduling of water application is vital for the efficient operation of drip irrigation systems, as both excessive and insufficient irrigation can adversely affect crop yield and exacerbate water stress (Rank and Vishnu, 2021). Pulse irrigation is a contemporary technique that involves applying small, frequent doses of irrigation water to saturate the soil, thereby satisfying plant water requirements while minimizing leaching and runoff (Lal Mehriya et al., 2020). Continuous water application is generally associated with increased root zone percolation; conversely, intermittent irrigation strategies employing pulsed discharge can significantly enhance water management practices and irrigation efficiency (Ruskin, 2000). Pulsating irrigation, which delivers small volumes of water through microtubes, effectively reduces the average irrigation rate to align with the soil’s hydraulic conductivity, consequently limiting percolation beyond the root zone (Lal Mehriya et al., 2020). This method is gaining traction globally due to its multitude of benefits, including improved crop yield and quality, water conservation, a reduction in dripper clogging, and decreased energy consumption. Furthermore, it fosters enhanced horizontal soil moisture distribution, particularly in sandy soil types (Zafari and Mohammadi, 2019). In drip irrigation systems, this technique maintains a smaller volume of wet soil while achieving higher water content within a restricted range, thereby promoting soil health (Rank et al., 2019). Research indicates that splitting irrigation depth into six pulses with 50 min intervals can enhance lettuce yield by 5.78% and conserve 25% of water in sandy soils (d' Almeida et al., 2015). Intermittent SDI facilitates the redistribution of water between applications, thereby accelerating lateral moisture movement within the soil (Gültekin and Ertek, 2024). Various application regimes have been employed, including defined ON and OFF durations, fixed ON intervals, and specific applied water depths (New and Roberts, 2012). Furthermore, researchers have adjusted the shape of the wetted zone to more closely align with patterns of root extraction (Appels and Karimi, 2021). Increasing irrigation frequency has the potential to optimize the wetting pattern around buried emitters, thereby enhancing the movement of surface water (Lozano et al., 2020; Mohammed and Abed, 2020).

Unlike other micro-irrigation facilities like drip, trickle, and sprinklers that emit water at regularly spaced intervals with predefined discharges, porous rubber pipes have openings of variable sizes that become unevenly spaced with uneven distribution. The latter makes a discharge variant along its lateral (Salisu et al., 2021). Experimental and simulation studies consistently highlight 20–30 cm as the ideal burial depth for PRP to balance water distribution efficiency and crop root zone needs while avoiding evaporation losses (Rasheed, 2021). Wetted front geometry varies significantly with soil type; sandy soils produce deeper, narrower wetting zones, while clay soils disperse water more laterally. Depth optimization should adapt to specific soil capillarity and crop requirements (Qiaosheng et al., 2007). PRP systems provide significant water use efficiency, saving 20–35% water compared to drip irrigation systems while improving crop yield (e.g., 9% higher lettuce biomass under PRP irrigation) (Kunze et al., 2021; Siyal and Skaggs, 2009). Theoretical models suggest pulse irrigation can enhance water distribution uniformity and minimize clogging in PRP, but experimental validation is scarce (Mohammad, 1998). Pulsing encourages lateral water spread and oxygen availability between cycles, aiding plant growth and reducing deep percolation losses. However, specific pulse schedules optimized for PRP are not well-documented (Lazarovitch et al., 2006). The Challenges and durability that face the use of PRP, including clogging risks: biological, physical, and chemical clogging, are major concerns (Siyal and Skaggs, 2009). Also, the Material Innovations: Recycled rubber-based pipes perform well in lab setups but face challenges in long-term usage due to variability in pore size and durability under buried conditions. Some studies propose fiber-reinforced materials for better longevity (Junpunya et al., 2022). Lastly, the Limitations and Research Gaps Pulse Compatibility: Minimal empirical studies test how PRP integrates with pulse schedules. This is a critical research gap despite the potential benefits (Rasheed, 2023).

Progress in computer technology has heightened interest in numerical models for subsurface irrigation systems (Dirwai et al., 2025). HYDRUS, a prevalent software package for simulating water and solute transport in variably saturated soils, is especially favored for modeling drip irrigation (Phogat et al., 2025). HYDRUS-2D/3D is a Windows-based model that simulates water flow, thermal transfer, and solute conveyance in two and three dimensions (Song et al., 2025). Numerous studies have evaluated the software’s potential for predicting water and nutrient movement in various drip irrigation methods (Morianou et al., 2023). One advantage of HYDRUS is its input parameters, which closely relate to soil physical properties measurable in situ or in the lab (Morianou et al., 2023). The applicability of HYDRUS-2D/3D to diverse plant/soil scenarios has been empirically validated, encompassing surface and subsurface drip irrigation systems (Jafari et al., 2022). Applications in agriculture frequently entail assessing various irrigation plans, researching groundwater recharge, root water uptake, and pollutant transport (Šimůnek et al., 2016).

For instance, Tehrani et al. (2023) identified 1ON:5OFF as the most effective timing for maximizing water retention at 30 cm depth in loamy sand, improving irrigation efficiency. Nogueira et al. (2021) showed that 25 cm emitter depth balances evaporation control and moisture delivery, with intermittent flow outperforming continuous irrigation. Abdelraouf et al. (2019) found that pulse irrigation boosts water use efficiency by 30% and enhances crop yield, especially when paired with porous pipe systems (Elhagarey, 2020). Validated that porous rubber pipes combined with intermittent flow improve water retention and reduce clogging risks. Darzi-Naftchali et al. (2018) showed that intermittent irrigation enhances redistribution and reduces water loss, especially under loamy sand conditions. Singh et al. (2025) demonstrated that pulse irrigation enhances lateral moisture spread and crop productivity, with 1ON:3OFF and 1ON:5OFF outperforming other configurations (Morianou et al., 2023). This study modeled dual-line SDI systems and found that parallel emitters enhance water distribution uniformity and reduce salt accumulation, especially in sandy soils with high infiltration rates (Khashaei et al., 2024). Using HYDRUS-2D, the authors simulated moisture and salinity profiles under SDI and confirmed that emitter depth and pulse timing significantly influence retention and salt leaching (Song et al., 2025). Validated HYDRUS-3D predictions against field sensor data, showing high accuracy in simulating vertical and horizontal moisture movement under intermittent irrigation in loamy sand (Morianou et al., 2023). A comprehensive review of HYDRUS applications in surface and subsurface irrigation, highlighting its reliability in simulating water flow, solute transport, and root uptake across soil types (Geng et al., 2022). Integrated root growth dynamics with HYDRUS to simulate water uptake under SDI, demonstrating enhanced retention when emitter depth and cycle timing are optimized (Faraj and Abid, 2021). Modeled root water uptake under SDI for tomatoes, recommending 25 cm emitter depth for optimal retention and minimal percolation losses. Gültekin and Ertek (2024) demonstrated that intermittent SDI improves moisture retention at 20–40 cm depths, especially under longer OFF cycles, enhancing root-zone wetting and reducing deep percolation.

In this study, a comprehensive simulation framework employing HYDRUS (2D/3D) was introduced to analyze soil water movement under various subsurface irrigation scenarios, specifically focusing on continuous and intermittent applications. The research provided valuable insights into the influence of differing ON:OFF time ratios and water application cycles on soil water retention and the behavior of wetting fronts in loamy sand soils. Notably, the optimal irrigation parameters were identified as the two-cycle intermittent flow (1ON:5OFF) with an emitter depth of 25 cm, which emerged as the most effective configuration for enhancing water retention while minimizing losses. Furthermore, the findings demonstrated how intermittent irrigation significantly improves soil moisture distribution, particularly within the critical root-zone depths (20–40 cm), compared to continuous flow. The applicability of the HYDRUS model was validated as a reliable tool for simulating subsurface irrigation under arid and semi-arid conditions. This work also highlighted the performance potential of porous rubber pipes (PRP) in conjunction with pulse irrigation, illustrating improvements in water use efficiency and reductions in percolation losses. Ultimately, the study contributes to sustainable water management by developing site-specific irrigation strategies that balance conservation with crop needs, setting the scientific groundwork for future research in this area.

Subsurface drip water application (SDI) modeling

The software numerically solves Richards’ equation for saturated-unsaturated water flow, analyzing water and solute movement in unsaturated, partially saturated, or fully saturated porous media (Zhou et al., 2007). It handles prescribed head and flux boundaries (constant or time-varying), boundaries influenced by atmospheric conditions, as well as free drainage boundary conditions (Simunek et al., 2008; Provenzano, 2007). The governing flow and transport equations are solved numerically using Galerkin-type linear finite element schemes, with time integration achieved through an implicit (backward) finite difference scheme for both saturated and unsaturated conditions (Simunek et al., 2008). HYDRUS software requires hydraulic parameters for soil layers, including θs, θr, ks, and α, along with boundary conditions, initial conditions, and flow field geometry. The accuracy of the numerical model in simulating the wetting pattern is linked to the precision of these parameters. Hydraulic parameters were estimated using the Rosetta software (Schaap et al., 2001), available in HYDRUS-2D through the Neural Network Predictions option, where soil characteristics like volumetric distribution of sand, clay, and silt for each layer, along with bulk density and water content at pressures of 33 and 1,500 kPa. The initial conditions of the software were represented by the initial water content of 10% in the initial condition case.

In this study, the van Genuchten–Mualem soil hydraulic parameters and saturated hydraulic conductivity for the loamy sand were estimated using the Rosetta pedotransfer function, which is widely employed to derive unsaturated hydraulic properties from basic soil texture and bulk density data (Schaap et al., 2001; Weihermüller et al., 2021). The resulting parameter values are consistent with those reported for similar loamy sand soils in previous irrigation and modeling studies, supporting their plausibility under our experimental conditions (Ungurașu et al., 2012). While pedotransfer-based parameters inevitably involve some uncertainty (Vrugt et al., 2001), the subsequent calibration and validation of HYDRUS against field-measured soil water contents in this work provide strong evidence that the adopted parameter set adequately represents the hydraulic behavior of the studied soil.

Numerical modeling

The Richards equation governing water flow from a point source through variably saturated, porous media can be written in axisymmetric coordinates as follows, Equation 1 (Elnesr et al., 2014):

Where θ is the volumetric water content [L3L-3], t is the time [T], h is the soil water pressure head [L], r is the radial (horizontal) coordinate [L], z is the vertical coordinate that is positive upward [L], K(h) is the unsaturated hydraulic conductivity [LT −1 ], and S(h) is the sink term representing root water uptake expressed as a volume of water removed from a unit volume of soil per unit time [L 3 L −3 T −1 ].

The soil water retention was modeled using the Van Genuchten (1980) Equation 2:

Where Se is the effective degree of saturation or the reduced water content, 𝜃r and 𝜃s are the residual and saturated water contents [L 3 L −3 ], respectively, 𝛼 is an empirical parameter [L -l ] inversely related to the air entry value, and n and m are empirical constants affecting the shape of the retention curve. The value of m is restricted by m = 1−1/n.

The hydraulic conductivity as a function of Se was assumed to be described using the closed-form equation of Van Genuchten (1980), which combines the analytical expression with the pore size distribution model of Mualem (1976) Equation 3:

Where ɤ is the pore connectivity parameter estimated by Mualem (1976) to be about 0.5 as an average for many soils, and Ks is the saturated hydraulic conductivity [LT −1 ].

The sink term S(h) as Equation 4 was computed using the Feddes et al. (1978) model adapted for a radially symmetric problem:

Where S and Sp are the actual and potential (during no-stress periods) root water uptake rates [L 3 L −3 T −1 ], respectively, (h) is a dimensionless water stress response function for water uptake by plant roots (Feddes et al., 1978), β (r, z) is a function describing the spatial root distribution (Vrugt et al., 2001) [L −3 ], Tp is the potential transpiration rate, and A T is the surface area associated with transpiration [L 2 ].

Modeled scenarios

To address the main objectives of this study, the following scenarios were conducted: Different emitting depths (25, 35 cm).

Three ratios of ON:OFF times (1ON:1OFF, 1ON:3OFF, and 1ON:5OFF).

Intermittent water flow (one cycle, two cycles, three cycles, four cycles, five cycles).

The present work used the HYDRUS (2D/3D) software package (version 2.05) for numerical simulations (Lu et al., 2016). The simulations will focus on water flow, root water uptake, and solute transport, utilizing a vertical plane XZ as the transport domain, consistent with prior research (Kandelous et al., 2011). Figure 1 displays the initial window for selecting geometry and domain options in the HYDRUS software.

Figure 2 illustrates the transport domain where the emitters are placed, measuring 200 cm in width and 75 cm in depth. The soil profile was initially homogeneous and uniformly dry with a pressure head of −1,000 cm. An unstructured triangular mesh with 15,241 nodes and 30,174 2D elements was employed for discretization, focusing on a drip line 25and 35 cm beneath the soil surface, with mesh refinement near the soil surface and around the emitter due to rapid flux changes.

Boundary conditions

This study presents the boundary conditions (BCs) utilized for the simulations conducted, as shown in Figure 3. In order to simulate the field experiment, the scenarios were designed with the following boundary conditions. The upper boundary was simulated as atmospheric conditions with no rain. This assumption is consistent with the arid climatic conditions at the Riyadh experimental site, where no rainfall was recorded during the irrigation and monitoring period, so excluding rainfall does not bias the assessment of subsurface drip irrigation with porous pipes (Badni et al., 2018). At the lower boundary, a free drainage condition was applied to allow water flow freely from the bottom of the domain, without accumulation or resistance. The free drainage condition was assumed due to the high saturated hydraulic conductivity of the Loamy sand soil (K s = 350.2 cm·day −1), representing nearly ideal drainage behavior at the lower limit (Elnesr et al., 2014). The trial area was reconstructed with a 1-m layer of pure loamy sand, and field observations did not indicate significant textural heterogeneity within the 0–75 cm domain used in HYDRUS, justifying the representation of the soil profile as a single homogeneous layer. Moreover, no saturation cases were recorded during the experiment. In addition, the model was initialized under a dry condition (θ = 10%). The mesh comprised 15,241 nodes and 30,174 triangular elements with refinement near the emitter and surface, ensuring an accurate numerical representation of the imposed gradient. For both vertical sides, “no-flux” was applied. The emitters were modeled as circular geometries with a radius of 1 cm, positioned at the specified soil depths, employing a “Variable Flux” BC to represent their influence. In this study, the constant potential transpiration rate of 4.0 mm·day −1 was chosen to represent an average mid-season water demand of potato, when irrigation scheduling decisions are most critical; using a fixed transpiration rate allows us to isolate the impact of pulsed irrigation and emitter depth on soil water redistribution under identical root uptake forcing.

The simulation period spanned 15 days, with analysis of results occurring after 1 week. The effective root zone of potato plants, which are planted at a depth of 15 cm, extends within the upper 60 cm of soil. Consequently, simulations were conducted at depths of 25 cm (10 cm below tubers) and 35 cm to evaluate water conservation efficiency. Potatoes were chosen as a representative crop for these simulations, although the study acknowledges the applicability of the findings to other plant species as well. This approach serves to illustrate the impact of evapotranspiration, effectively simulating field conditions. In this experimental framework, it was assumed that no precipitation occurred and that the free drainage condition was suitable, given the characteristics of the loamy sand soil utilized, which facilitates such drainage (Simunek et al., 2008; Provenzano, 2007). A 15-day simulation duration was selected to allow for comprehensive readings and observations to be made 1 week after the water addition process. This timeframe enables a detailed examination of the events occurring in real agricultural settings. Initial measurements taken at the start of planting would not accurately reflect the soil and hydraulic conditions throughout the growing season; thus, readings and observations were systematically collected over the course of a single day at multiple time intervals: 30 min before and after the water addition, as well as at 60, 120, 180, and 360 min thereafter. This comprehensive timing strategy ensures a thorough representation of the water addition process and its immediate impacts, thereby extending the observational period from 0 to 360 min post-application. Time-variable boundary conditions were used to simulate drip water application, with a dripper discharge (Q) set at 3.41 L/h, equating to a flux of approximately 5 cm/min (q = Q/4πr 2). Here, q represents boundary flux [cm/min], Q is emitter discharge [cm 3 /min], and r is the wetted radius of the emitter [cm]. Root water uptake was simulated using the Feddes et al. (1978) model in HYDRUS (2D/3D). The pressure head parameters defining the reduction function α (h) were derived from the HYDRUS database for Solanum tuberosum (potato) and slightly adjusted to account for Loamy sand soil conditions. The parameters were h₁ = −10 cm, h₂ = −25 cm, h₃ (upper–lower) = −300 to −500 cm, and h₄ = −800 cm (Elnesr et al., 2014). A constant potential transpiration rate of 4.0 mm·day −1 was imposed throughout the simulation to maintain uniformity across treatments.

Treatments

The varying parameters established the treatments for the simulation process, including 30 distinct treatments. These treatments resulted from two different pipe depths (25, and 35 cm) of discharging water sources, represented by the abbreviated SDI, combined with five water flow regimes (WF1C, WF2C, WF3C, WF4C, and WF5C, with WF1C as the continuous water flow) under 3 different ratios of ON:OFF times (1ON:1OFF, 1ON:3OFF, and 1ON:5OFF). The five flow regimes can be categorized into one continuous flow and four intermittent flows. The intermittent flows are defined by the number of “ON:OFF” cycles; for instance, one cycle indicates a continuous water flow, while a two-cycle consists of one “OFF” period and two “ON” periods. Similarly, a three-cycle entails two “OFF” periods followed by three “ON” periods, and this pattern continues for the four-cycle and five-cycle. The simulations were conducted using loamy sand soil, with hydraulic parameters sourced from the soil catalog provided by the HYDRUS software (Carsel and Parrish, 1988) and are given in Table 1. Additionally, parameters representing the model crop, potatoes (Solanum tuberosum), were incorporated into the simulations.

In the one-cycle water flow (WF1C) (continuous water flow), the duration of water application was set to 30 min, representing uninterrupted water flow with an equal OFF time of 30 min. In the two-cycle water flow (WF2C), the water application lasted for 15 min, followed by one cycle of OFF, which also took 15 min, resulting in a total applied water time of 45 min. For the three-cycle water flow (WF3C), the water application was 10 min long, with two OFF cycles of 10 min each, leading to a total water application time of 50 min. In the four-cycle water flow (WF4C), the water application duration was 7.5 min, coupled with one OFF cycle lasting 7.5 min, resulting in a total application time of 52.5 min. Lastly, in the five-cycle water flow (WF5C), the water application lasted 6 min, with four OFF cycles of 6 min each, summing up to a total applied water time of 54 min, as shown in Table 2. This is a simplified explanation in case of use ratios of ON:OFF times (1 ON: 1 OFF).

However, in the case of applying different stopping times, i.e., 3 or 5 times the operating time, the total time to add water is clear from the following Equation 5 and as shown in Table 3.

Where, WAT denotes the total water application time (i.e., the cumulative duration of all ON phases in one irrigation event), while NOC represents the number of ON cycles per event; Equation 5 is therefore used to calculate the total ON+OFF duration (TOT) for each irrigation scenario under different ON:OFF ratios, and the resulting TOT values are summarized in Table 3.

TOT stands for Total ON:OFF Time (min), meaning the total time that includes the off and on periods. Therefore, for example, when following a three-cycle irrigation cycle that includes two off cycles and an on time of 30 min, we find that when using equal on and off rates, the cycle is 10 min on, followed by 10 min off, then 10 min on, then 10 min off, then 10 min off, and then 10 min on, meaning a total time of 50 min. When using an on and off ratio of 1:3, meaning the off time is three times the on time, the cycle is 10 min on, followed by 30 min off, then 10 min off, then 30 min off, and then 10 min on, meaning a total time of 90 min. When using an on and off ratio of 1:5, meaning the off time is five times the on time, the cycle is 10 min on, followed by 50 min off, then 10 min off, and then 50 min off. Then run for 10 min, so the total time is 130 min.

In this study, Equation 5 is employed to determine the total ON+OFF duration (TOT) for each irrigation scenario, where WAT represents the cumulative ON time (minutes) and NOC denotes the number of ON cycles per event; the resulting TOT values under the different ON:OFF ratios are summarized in Table 3, thereby clarifying both the physical meaning and the practical use of this formulation in describing the pulsing structure of the treatments.

In all irrigation scenarios (WF1C–WF5C and the different ON:OFF ratios), the total applied water volume per event was kept constant by fixing the cumulative ON duration at 30 min and the emitter discharge rate. This design ensures that each treatment receives the same irrigation depth, while only the temporal structure of application (number of cycles and ON:OFF ratio) and the resulting total event duration (TOT) differ. Consequently, the comparisons of soil water retention within the 0–360 min observation window reflect differences in pulsing and redistribution dynamics under equal water input, rather than differences in the amount of water supplied.

Evaluate the reliability and validity of the Hydrus program readings

The study investigates the dynamics of soil water movement in proximity to an emitter within a soil profile ranging from 10 to 50 cm depth, employing various subsurface flow systems designated as WF1C through WF5C over durations of 0 to 360 min. To evaluate the reliability and validity of the Hydrus program readings, a field experiment was conducted at King Saud University’s educational farm in Riyadh, Saudi Arabia. This site serves as a hub for environmental sciences, agriculture, and renewable energy education. The water application system consisted of a pumping unit with various components (pumps, filters, pressure gauges, fertilizers, flow meters, and valves), a controlling unit (controllers, computer, and network for automated water application based on plant needs), and a field unit for measuring soil water content and analyzing samples. Consistent parameters included a loamy sand soil, municipal water, and potato (Solanum tuberosum) crops spaced 75 cm apart, with water application adjusted according to plant growth. Variable parameters comprised five flow treatments and pipeline depths of 25 and 35 cm. Soil water content was measured volumetrically and with a stationary EnviroScan instrument across five depths (10–50 cm) utilizing ten devices with 50 sensors. Some of the processes including Preparing the experiment and taking the measurements. Can be shown in Figure 4.

The difference in water content values before and after the water application process is explained as a percentage through the following Equation 6:

Where θ initiall is the initial water content value that represents the value before water application and adding water to the soil, θ after is the water content value after water application and at a specific time.

Statistical criteria used to ensure the accuracy of models

There were some statistical criteria used to ensure the accuracy and quality of models and results, such as the correlation coefficient (R), the root mean square error (RMSE), the mean absolute error (MAE), and model efficiency (ME). It can be expressed Table 4:

This section provides a comprehensive analysis of the observed soil water content at varying depths (10–50 cm) under distinct ON:OFF ratios and irrigation cycles (WF1C–WF5C), specifically examining both SDI 25cm and SDI3 5cm configurations. The reliability and validity of the Hydrus program readings are evaluated through Model Performance Indicators, including R, R 2, RMSE, ME, and MAPE. Furthermore, the effects of intermittent flow on soil moisture dynamics are investigated for both SDI PRP 25cm and SDI PRP 35cm configurations.

Model performance indicators (R, R 2, RMSE, ME, MAPE)

HYDRUS 2D/3D simulations were calibrated and validated against field-observed soil moisture data obtained from EnviroScan sensors at various depths. To correlate water content readings from EnviroScan devices with HYDRUS program outputs, statistical analyses were performed on two groups based on depth and measurement methods. The results, depicted in Figure 5, showed a significant correlation between field measurements and HYDRUS modeling data, confirming the reliability of the fieldwork. The comparison revealed a high degree of consistency between simulated and measured water contents across all treatments and depths. As shown in Table 5 for the PRP 35 cm configuration, the correlation coefficient (R) reached 0.94 with a coefficient of determination (R 2 = 0.89), model efficiency (ME = 0.91), root mean square error (RMSE = 2.69), and mean absolute percentage error (MAPE = 0.16). Similarly, for the PRP25 cm configuration, R = 0.92, R 2 = 0.85, ME = 0.95, RMSE = 1.73, and MAPE = 0.09, indicating excellent model performance and a strong predictive capacity. These results confirm the model’s robustness and accuracy in representing soil water movement under both continuous and intermittent flow conditions.

As shown in Figure 6, the overall analysis revealed a strong relationship, with a combined correlation coefficient, a regression coefficient, and a model efficiency, underscoring Hydrus’s significant role in reliably assessing soil water content and optimizing agricultural practices. The graphical representations in Figures 6A,B substantiate the numerical findings, highlighting the effectiveness of the different treatments in promoting enhanced water retention in the soil. The observations indicate that varying subsurface flow systems significantly influence water movement, thereby offering valuable implications for optimizing water application efficiency and soil management practices.

Impact of intermittent flow on soil moisture dynamics SDI PRP 25cm

This study evaluates the effects of varied water application cycles and ON:OFF time ratios on soil water content across different depths. The findings, displayed in Figure 7, reveal critical insights into water retention dynamics under distinct irrigation strategies. Under the continuous water application method (WF1C), a 30 min irrigation interval produced the highest soil water content immediately post-application, although it lacked variability due to the absence of OFF cycles. In contrast, the intermittent water application approach (WF2C) was examined through two cycles. Notably, the equal ON:OFF ratio of 1ON:1OFF over 45 min achieved a peak water content of 25% at 60 min, specifically within the 15 cm to 35 cm depth range. The ratio of 1ON:3OFF (75 min) generated a maximum water content of 23% at 30 min within the same depth range. Furthermore, the 1ON:5OFF ratio (105 min) exhibited a peak water content of 25% at 120 min, again within 15–35 cm. Subsequent analysis incorporating a three-cycle intermittent method (WF3C) demonstrated that the 1ON:1OFF ratio (50 min) reached its peak water content of 25% at 30 min, while the 1ON:3OFF (90 min) ratio peaked at 60 min, extending to a depth of 15–40 cm. Conversely, the 1ON:5OFF (130 min) sustained notable soil moisture levels for up to 30 min. This trend was further observed in the four-cycle method (WF4C), where the 1ON:1OFF ratio (52.5 min) also achieved peak soil water content at 60 min (15–35 cm), and the 1ON:3OFF (97 min) showed maximum retention at 120 min (15–40 cm). The 1ON:5OFF (142.5 min) reached its maximum at 60 min, consistent with findings across other ratios. In the five-cycle configuration (WF5C), Scenario 1 (1ON:1OFF ratio, 54 min) peaked at 30 min (15–35 cm). Scenario 2 (1ON:3OFF, 102 min) exhibited maximum content at the same interval, while Scenario 3 (1ON:5OFF, 150 min) demonstrated superior water retention, sustaining elevated moisture levels for up to 120 min within 15–35 cm. Figure 7 illustrates the distribution of soil water content throughout the profile at various time intervals, providing visual corroboration of the numerical data discussed. This representation underscores the effectiveness of diverse irrigation strategies in augmenting soil water retention.

Impact of intermittent flow on soil moisture dynamics SDI PRP 35cm

Figure 8 presents a detailed analysis of how different water application methodologies affect soil water content. The study began with the continuous water application method (WF1C), which delivered a steady flow of water for 30 min. This approach produced the highest immediate increase in soil water content, highlighting the effectiveness of continuous irrigation in improving moisture levels in the soil. In contrast, the intermittent water application method (WF2C) involved two cycles with a balanced ON:OFF ratio of 1ON:1OFF over a total duration of 45 min, achieving a maximum moisture content of 25% at the 60 min mark, particularly within the 25–45 cm depth range. Exploration of varying ON:OFF ratios revealed significant differences in soil water retention. The 1ON:3OFF ratio, with a total cycle time of 75 min, recorded a peak soil moisture of 22.5% at 30 min, while a 1ON:5OFF ratio, totaling 105 min, reached 25% moisture at the 120 min interval, also within the same depth range. Further results were obtained from the three-cycle intermittent method (WF3C), where different ON:OFF ratios influenced the outcomes. The 1:1OFF ratio, with a 50 min cycle, yielded maximum soil moisture at the 30 min interval within the 25–45 cm depth. Conversely, the 1ON:3OFF (90 min) peaked at 60 min, maintaining substantial moisture levels at the same depth. The 1ON:5OFF ratio (130 min) displayed durable soil water retention, sustaining significant levels for up to 30 min. In the four-cycle intermittent method (WF4C), comparative observations revealed insights into efficiency. The 1ON:1OFF ratio (52.5 min) peaked at 60 min within the 25–45 cm interval, while the 1ON:3OFF configuration (97.5 min) achieved maximum soil moisture of 25% at the 120 min mark for the 25–50 cm depth. The 1ON:5OFF ratio (142.5 min) also peaked at 60 min for this depth range. The five-cycle intermittent method (WF5C) provided further clarity through three scenarios. Scenario 1, using a 1ON:1OFF ratio for 54 min, led to maximum moisture content at the 30 min interval within 25–45 cm. Scenario 2 (1ON:3OFF for 102 min) also peaked at 30 min, with positive trends continuing at 60 and 120 min. Remarkably, Scenario 3 (1ON:5OFF for 150 min) demonstrated superior retention, maintaining elevated moisture levels for up to 120 min in the 25–45 cm range. Collectively, these findings underscore the critical role of water application methods and timing in optimizing soil water retention, thereby enhancing agricultural productivity and sustainability.

This study examines the impact of various water application cycles and ON:OFF ratios on soil water content at different soil depths. The focus is on the relative percentage change in soil water movement around the emitter compared to the initial soil water content throughout the entire soil profile. Key aspects of the investigation include the effects of the ON:OFF ratio and water use efficiency at two depths: 25 cm (PRP 25cm) and 35 cm (PRP 35cm). Additionally, the analysis compares soil water retention characteristics between different systems, specifically the Subsurface Drip Irrigation (SDI) at 25 cm (SDI 25 cm) and 35 cm (SDI 35 cm), for two distinct water flow scenarios (WF1C and WF5C) under an ON:OFF time ratio of 1ON:5OFF. Furthermore, the study evaluates the horizontal distribution of water within the soil profile under intermittent water flow conditions associated with the SDI system.

Effects of ON:OFF ratio and water use efficiency PRP 25cm

As illustrated in Figure 9, the investigation into soil water retention across varying depths offers profound insights influenced by diverse water application practices. At a depth of 10 cm, the analysis revealed no statistically significant differences in soil water retention, regardless of the varying cycles of water application, which spanned from one to five, nor in the tested ON:OFF ratios. This finding suggests that the uppermost layer of soil remains largely unaffected by the irrigation strategies implemented, indicating the limited impact of these practices at such shallow depths. In contrast, at a depth of 20 cm, we observed marked improvements in water retention. The two-cycle water addition strategy, deployed using a 1ON:5OFF ratio, exhibited a statistically significant retention improvement rate of 57% relative to the initial water content. Furthermore, when assessing treatments WF3C, WF4C, and WF5C under a 1ON:3OFF ratio, maximum retention rates of 48, 51, and 52% were recorded, respectively. This suggests that the 1ON:3OFF configuration may be particularly effective in sustaining elevated water levels in the upper-middle soil layers, fostering a more favorable moisture environment. Extending the analysis to a depth of 30 cm reinforced these observations, affirming the effectiveness of both the two-cycle and five-cycle water application patterns. Notably, the WF2C treatment, which utilized a 1ON:5OFF configuration, demonstrated exceptional water retention, achieving an impressive 87% relative to initial conditions. Among the alternate treatments (WF3C, WF4C, and WF5C), the 1ON:3OFF ratio yielded substantial retention rates of 70, 76, and 78%, respectively. These compelling results underscore the critical role that tailored water application strategies play in enhancing soil water retention deeper within the soil profile. At a depth of 40 cm, the findings indicated that continuous water application had similar effects regardless of the varying periods of operation and cessation. However, when the number of water application cycles increased to five, there was no significant effect on retention unless the durations of application aligned closely with those of the stoppage times. This observation highlights a critical threshold beyond which additional cycles fail to enhance water retention, suggesting a diminishing return in effectiveness. In stark contrast, at a depth of 50 cm, neither the number of water application cycles nor the variations in ON:OFF ratios produced discernible impacts on water retention. This lack of measurable effect implies that deeper soil layers may possess inherent properties that contribute to enhanced water retention, making specific application techniques less effective in modifying water dynamics at this depth. In summary, these findings collectively illustrate the complex interactions between water application practices and soil depth, emphasizing the importance of strategic water management to optimize soil water content retention, especially in the upper layers of soil where water availability is crucial for plant growth and agricultural productivity.

Effects of ON:OFF ratio and water use efficiency PRP 35cm

The analysis presented in Figure 10 examines the effects of various water application treatments on soil water retention at multiple depths, specifically evaluating the 10 cm, 20 cm, 30 cm, 40 cm, and 50 cm layers. The data reveal that at the shallower depths of 10 cm and 20 cm, there were no significant differences in water retention among the diverse application strategies and their respective cycle counts (ranging from one to five) or ON:OFF ratios. Under the two-cycle water addition with a 1ON:5OFF ratio, a retention rate of 51% of the initial water content was successfully achieved, indicating some efficacy of this approach, albeit modest compared to deeper layers. In contrast, deeper evaluations at 30 cm and 40 cm highlight more pronounced variations in retention based on specific strategies. Notably, at a depth of 30 cm, the continuous water application with a single cycle (referred to as WF1C) exhibited a significant initial surge in soil water content. This enhancement in saturation was evident across both 1ON:1OFF and 1ON:3OFF ratios, although it diminished rapidly over time. Comparatively, the WF5C method also contributed to increased soil water retention, yet the retention rates showed a similar swift decline under a 1ON:5OFF ratio. The WF2C application stood out, demonstrating an extended retention period at 30 cm depth, achieving a more sustained increase in soil water content as it resisted the rapid decline noted in other methods. At 40 cm, the data reflected trends consistent with the findings at 30 cm, reinforcing the conclusion that continuous water application maximizes short-term retention increments. The exceptional retention rate observed for WF2C, achieving 87% of initial water content under the 1ON:5OFF condition, further substantiates its effectiveness, especially in comparison to the retention capabilities of WF3C, WF4C, and WF5C at a 1ON:3OFF ratio, resulting in 71, 76, and 78% retention rates, respectively. However, at a depth of 50 cm, the investigation unveiled a distinct threshold for water retention capacity, with neither the number of water application cycles nor the ON:OFF ratios causing significant changes in soil water content. This finding suggests a limited impact of the application strategies at this depth, prompting the conclusion that effective water retention may require adjustments according to various soil depths.

The integration of (PRP 35cm) further enhanced water retention, indicating its potential as a useful technology for improving agricultural practices through optimized water application efficiency. This implementation may offer a valuable mechanism for sustaining crop growth under diverse climatic circumstances. Moreover, the research highlights that water application strategies must be tailored to depth-specific requirements to optimize retention capabilities effectively. As observed, increasing the number of cycles to five yielded negligible differences unless the durations of application and stoppage were equal, underscoring the importance of synchronization in cycle durations. Overall, this comprehensive study contributes vital insights into the intricate dynamics of soil-water interactions, revealing that refined water application techniques can significantly bolster agricultural productivity. The critical role of treatment-specific responses illustrates the necessity for nuanced hydrological management that considers both depth and application strategies to maximize efficiency and sustainability in soil water retention. The findings advocate for a more sophisticated understanding of water management in agricultural practices, promoting sustainable approaches tailored to varying environmental conditions.

Comparing soil water retention (SDI25cm, SDI35cm) for (WF1C: WF5C) under ON:OFF times ratio (1ON:5OFF)

The outcomes of the previously conducted experiments during the simulation process provide significant insights into the relationship between water application cycles, on–off periods, and soil water content retention across varying soil depths. As demonstrated in Figure 11, no substantial effects were detected at a depth of 10 cm regarding the different water application cycles or on–off durations. In contrast, at a depth of 50 cm, soil water content retention showed minimal sensitivity to the aforementioned variables, with noteworthy exceptions observed when a permeable reservoir pipe (PRP) was positioned at a depth of 35 cm under equal on–off ratios. When analyzing water application rates, configurations employing three-to-one and five-to-one ratios within a continuous irrigation system exhibited enhanced soil water retention. Particularly at critical depths vital for optimal root system growth—20 cm, 30 cm, and 40 cm—placing the PRP at a depth of 25 cm resulted in superior water retention compared to its placement at 35 cm.

An increase in the frequency of water application cycles was found to have a positive correlation with soil water retention, specifically under one-to-one and three-to-one on–off rates. Conversely, a distinct anomaly emerged with the five-to-one on–off ratio; here, the treatment featuring two water application cycles achieved the highest water retention rate, surpassing all other treatment configurations, including continuous application and those with three to five cycles. This two-cycle treatment resulted in an exceptional water content retention rate of 145.5%. The configurations evaluated in this study suggest that deliberate modifications to water application parameters can significantly enhance water utilization efficiency, thereby improving agricultural productivity. These results furnish a robust foundation for further inquiries into customized water application methodologies aimed at maximizing water efficiency in agricultural practices.

The investigation also meticulously examined water movement within the soil profile, exploring various scenarios to ascertain the most effective subsurface water application strategy employing PRP. The findings indicated that optimal water addition occurs with PRP installed at a depth of 25 cm beneath the soil surface. This study concentrated on an intermittent water application method characterized by two distinct cycles, with the timing and frequency of water application correspondingly set to a ratio of five times the duration of non-water application periods. This structured approach significantly enhances water retention and distribution within the soil, thereby facilitating improved accessibility of soil water for plant uptake. To further clarify the dynamics of water movement, the horizontal distribution of water content was systematically monitored at distances of 10 cm and 20 cm from the dripper. Measurements were taken at multiple time intervals—immediately after the initiation of water application (30 min), followed by assessments at 60, 120, 180, and 360 min. Analyzing these temporal data points allowed for a comprehensive understanding of the progression of water distribution within the soil matrix.

Horizontal water distribution under SDI intermittent water flow

The results illustrated in Figure 12 provide a detailed depiction of the intricate patterns of water distribution resulting from various water application cycles. The data reveals a noteworthy relationship between the horizontal distance from the dripper and the corresponding soil moisture content. As one moves further away from the point of water application, there is a pronounced decline in the water retention within the soil matrix. This trend suggests that the effectiveness of water distribution diminishes significantly as distance increases from the dripper, potentially leading to areas of insufficient moisture for optimal plant growth. In a contrasting vertical assessment, the analysis indicates that different water flow cycles exert a substantial influence on the distribution of moisture throughout the soil profile. The variability in water penetration can likely be attributed to the inherent properties of the soil, specifically its loamy sand texture, as well as the type of irrigation system employed, such as the use of porous piping. These critical findings emphasize the necessity of understanding the complexities of water infiltration and its movement through the soil. They point to the importance of strategic dripper placement and water application design, which can greatly enhance the availability of soil moisture for crops. Ultimately, such optimization not only supports better moisture retention but also has the potential to significantly uplift agricultural productivity.

The simulation outcomes directly address the study’s core objectives: enhancing water use efficiency, minimizing deep percolation losses, and optimizing soil moisture retention in loamy sand soils under arid conditions. The superior performance of the two-cycle intermittent flow (WF2C) with a 1ON:5OFF ratio and 25 cm emitter depth confirms the hypothesis that strategic emitter placement combined with pulse irrigation significantly improves moisture retention within the active root zone (20–40 cm). These findings validate the HYDRUS model’s reliability in simulating subsurface water dynamics and underscore the potential of porous rubber pipes (PRP) in delivering efficient, sustainable irrigation. The observed retention patterns and redistribution behavior provide actionable insights for designing site-specific irrigation schedules that align with crop water requirements while conserving resources—thereby fulfilling the study’s aim of informing sustainable agricultural practices tailored to arid and semi-arid environments.

Yield performance and gemination rate

At the conclusion of both growing seasons, plant productivity and germination rates were evaluated to assess the effects of pipe installation depth and irrigation frequency on plant performance. As illustrated in Figure 13 Data on yield and germination were systematically collected across all experimental treatments, revealing distinct treatment-specific trends. Significantly, shallow pipe installations (PRP 25cm) demonstrated superior germination rates, achieving 61% in the first season and rising to 70% in the second. In contrast, deeper installations at 35 cm (PRP 35cm) exhibited lower rates, starting at 50% and increasing to 60%. These results indicate that shallow emitter depth is beneficial for seedling emergence by promoting favorable soil moisture conditions. As illustrated in Figure 14, further analysis of potato yield in relation to irrigation strategies indicated that PRP 25cm consistently outperformed PRP 35cm, with yields of 105 kg and 123 kg in the first season, increasing to 118.7 kg and 134.4 kg in the second. Additionally, irrigation frequency had a marked impact on productivity; higher frequency (WF5C) yielded superior results compared to lower frequency (WF1C). For example, in Group A, PRP 35cm, WF5C yielded an improvement from 27.9 kg to 31.1 kg, while WF1C produced only 11.9 kg and 15.4 kg. Overall, employing shallower emitter depths combined with pulsed irrigation enhanced yields by 40–49% compared to continuous irrigation, underscoring the agronomic advantages of integrating optimized irrigation techniques in arid conditions. As showed in Table 6: Group A (PRP 35cm) displayed the lowest performance, while Group B (PRP 25cm) excelled, achieving significant second-season improvements with 46 ± 6.5 plants, 26.9 ± 5.9 kg weight, 134.3 kg yield, and 69.7% germination.

Statistical analysis indicators

Significant variations in agricultural output across four important parameters were found by the Analysis of Variance (ANOVA). With a p -value of 0.034, Treatment in particular showed significant variations between replicates. Depth had a significant effect, with p = 0.021, highlighting the efficiency of 25 cm compared to 35 cm.

By comparing observed and expected values as shown in Table 7, this analytical table assesses how well a statistical model captures agricultural reality. High accuracy is demonstrated by the Coefficient of Determination (R 2) values of 0.94 for yield and 0.91 for germination, which show that more than 90% of the variance is explained. There is little difference between the actual and expected results, as indicated by the Root Mean Square Error (RMSE) values of 4.12 and 3.87. Model Efficiency (ME) scores of 0.93 and 0.89 indicate great predictive efficiency, approaching unity, while Mean Absolute Percentage Error (MAPE) values of 6.3 and 5.9% demonstrate the model’s practical accuracy.

This study presents a significant and timely advancement in irrigation science, offering original insights that extend and refine previous findings (Zhu et al., 2024; Rasheed, 2020; Vyrlas and Sakellariou-Makrantonaki, 2005; Zhang et al., 2024; Douh and Boujelben, 2011; Mei et al., 2012; El-Abedin, 2006) through a rigorous integration of field experimentation and HYDRUS/2D simulation. With a newly developed subsurface irrigation system fabricated from recycled tire waste—an environmentally conscious innovation that addresses both water conservation and circular economy goals. By systematically evaluating intermittent (pulsed) water application in loamy sand soils—characterized by rapid infiltration—the research demonstrates that increasing pulse frequency and optimizing emitter depth (20–35 cm) markedly improves lateral water distribution, minimizes deep percolation losses, and enhances moisture retention within the active root zone (20–40 cm). These results not only corroborate earlier observations of improved water spread at 0–15 and 15–30 cm depths (Rasheed, 2020; Vyrlas and Sakellariou-Makrantonaki, 2005; Zhang et al., 2024; Douh and Boujelben, 2011; Mei et al., 2012; El-Abedin, 2006), but also reveal that a (1ON:5OFF) dual-cycle strategy significantly prolongs water availability, offering a practical framework for subsurface drip irrigation design. The study’s contribution is particularly relevant to agricultural stakeholders operating in arid and semi-arid environments, as it provides actionable, field-validated recommendations that support water conservation, optimize irrigation scheduling, and promote sustainable crop productivity. By bridging simulation with empirical data, this work empowers irrigation engineers, agronomists, and policymakers to adopt precision irrigation strategies that align with both environmental stewardship and agronomic efficiency, thereby reinforcing the role of scientific innovation in safeguarding water resources and enhancing agricultural resilience.

This study successfully applied the HYDRUS (2D/3D) simulation model to investigate the effects of continuous and intermittent subsurface water flow on vertical and horizontal water distribution in loamy sand soil, with the goal of enhancing water use efficiency (WUE) in arid agricultural systems. Through a series of precisely structured simulations, the research evaluated five irrigation cycles (WF1C–WF5C) under three ON:OFF time ratios (1ON:1OFF, 1ON:3OFF, and 1ON:5OFF) at two emitter depths (25 cm and 35 cm). The model accurately captured soil moisture behavior at different depths (10–50 cm), providing a clear picture of how intermittent water application modifies wetting dynamics and retention over time. Methodologically, this research provides a robust and reproducible modeling framework using HYDRUS (2D/3D) integrated with Rosetta-estimated hydraulic parameters to predict soil–water interactions under varied pulse schedules. Through rigorous calibration and validation against field-measured data, the model achieved a high degree of accuracy (R > 0.9; ME > 0.9; RMSE < 3%), confirming its suitability for predictive and design purposes in irrigation management. The study contributes significantly to the field by identifying optimal ON:OFF ratios and emitter depths, validating the efficacy of porous rubber pipes (PRP) in intermittent irrigation, and addressing a critical research gap in understanding pulse irrigation compatibility with subsurface systems. These insights not only enhance the scientific understanding of soil moisture redistribution under intermittent flow but also offer practical design guidance for sustainable irrigation scheduling in water-scarce environments. The results revealed that intermittent (pulsed) irrigation markedly improves soil water retention compared to continuous flow. Results indicated that at a 10 cm depth, water application treatments did not significantly impact water content, regardless of the cycle number or ON:OFF ratio, suggesting minimal influence in the upper soil layer. In contrast, at 20 cm depth, a two-cycle treatment with a 1ON:5OFF ratio achieved a maximum retention rate of 57% relative to the initial water content, demonstrating the effectiveness of intermittent watering in this zone. At 30 cm depth, the same two-cycle pattern with a 1ON:5OFF ratio maintained high soil water content levels, reaching 87%, while treatments with a 1ON:3OFF ratio yielded retention rates ranging from 70 to 78%. The three- to five-cycle treatments under a 1:3 ratio also displayed substantial retention, with rates varying between 44 and 78%, depending on the depth. Notably, at 40 cm, two-cycle and five-cycle treatments using a 1:5 ratio achieved retention rates of approximately 51 and 87%, respectively, indicating that specific cycling patterns significantly enhance water retention. Conversely, at 50 cm depth, no significant differences were observed across treatments, implying a soil-inherent capacity for soil water content retention at this level. In contrast, continuous irrigation showed rapid saturation but poor long-term retention. Moreover, the 25 cm emitter depth consistently outperformed 35 cm, confirming its suitability for sandy soils where capillary rise is limited. The study also found that horizontal water movement remained relatively constant, emphasizing the predominance of vertical infiltration under subsurface irrigation. The present study extends findings by quantifying vertical retention dynamics using a comprehensive simulation approach. While previous work mainly focused on surface or limited-depth observations, this research provides a multi-depth, time-dependent analysis supported by advanced numerical modeling. Furthermore, studies like Rasheed (2021) highlighted the sensitivity of soil moisture to emitter depth and irrigation frequency; this study builds upon those conclusions by determining specific combinations that optimize water conservation without compromising root-zone availability. In summary, this study establishes a scientifically validated foundation for intermittent subsurface irrigation design, demonstrating that controlled pulsed water delivery—particularly two-cycle applications with a 1ON:5OFF ratio at 25 cm depth—can achieve superior water retention, minimize wastage, and enhance irrigation efficiency. The outcomes contribute both theoretically and practically to modern precision irrigation strategies, guiding future integration of simulation tools and field validation to develop adaptive, resource-efficient agricultural water management systems.