Original Article
Pressurized Irrigation Systems
Mustafa Goodarzi; Saber Zolfaghari
Abstract
Extended AbstractIntroductionPressurized irrigation systems are increasingly used to improve water management and reduce water losses in agricultural production, particularly in regions facing water scarcity. However, the expected benefits of these systems cannot be achieved solely through appropriate ...
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Extended AbstractIntroductionPressurized irrigation systems are increasingly used to improve water management and reduce water losses in agricultural production, particularly in regions facing water scarcity. However, the expected benefits of these systems cannot be achieved solely through appropriate design and installation. Their long-term performance also depends on proper operation, preventive maintenance, timely technical support, and continuous monitoring during the service life of the system. Inadequate operation and maintenance may gradually alter hydraulic conditions, reduce the effectiveness of water application, and lead to deterioration in the overall condition of irrigation systems. In addition, farmers and system operators need adequate technical knowledge and continued access to professional support to maintain the systems under field conditions. The objective of this study was to evaluate changes in selected technical indicators of pressurized irrigation systems following the implementation of an operation and maintenance monitoring program and to assess farmers’ perceptions of the factors contributing to successful long-term operation and maintenance of these systems.MethodologyThe study was conducted in Arak and Shazand counties of Markazi Province, Iran. A total of 30 pressurized irrigation systems were selected for field evaluation, including 20 systems in Arak and 10 systems in Shazand. The systems were evaluated repeatedly at four measurement stages consisting of the initial technical supervision stage and three subsequent follow-up stages during the cropping season. Two field-based technical indicators were used to assess the condition of the irrigation systems: operating pressure and soil water content. Operating pressure was measured using a pressure gauge and expressed as meters of water head. These two indicators were selected because operating pressure provides an important indication of the hydraulic operating condition of pressurized irrigation systems, while soil water content provides information about the resulting moisture condition of the root-zone soil following irrigation. In addition to the field measurements, a structured questionnaire was administered to the operators of the evaluated irrigation systems. The questionnaire consisted of 24 items and was designed to assess farmers’ perceptions of factors affecting the successful operation and maintenance of pressurized irrigation systems. Responses were recorded using a five-point Likert scale. The content of the questionnaire was reviewed by experts in irrigation and operation and maintenance of pressurized irrigation systems. Field data were analyzed using descriptive statistics and repeated-measures analysis of variance. Measurement stage was considered the within-system factor, whereas county was considered the between-system factor. Where appropriate, pairwise comparisons were conducted using Bonferroni adjustment to control the probability of Type I error associated with multiple comparisons.Results and Discussion The results showed that the mean operating pressure of the evaluated irrigation systems was 42.33 m of water head at the initial technical supervision stage. The corresponding values at the first, second, and third follow-up stages were 39.73, 40.30, and 39.97 m, respectively. Thus, operating pressure showed an overall decline after the initial supervision stage, although the values remained relatively stable across the three subsequent follow-up stages. Repeated-measures analysis indicated a statistically significant effect of measurement stage on operating pressure, demonstrating that operating pressure changed over the monitoring period. However, the overall difference between Arak and Shazand counties was not statistically significant. Bonferroni-adjusted pairwise comparisons showed that the pressure at the initial supervision stage was significantly higher than the pressure recorded at the second and third follow-up stages. In contrast, the difference between the initial supervision stage and the first follow-up stage was not statistically significant. Furthermore, none of the differences among the three follow-up stages was statistically significant. These results suggest that although some reduction in operating pressure occurred following the initial supervision, the pressure conditions were comparatively stable during the subsequent monitoring stages.Soil water content also showed an overall declining tendency. The mean soil water content decreased from 27.51% at the initial supervision stage to 26.47%, 26.83%, and 25.72% at the first, second, and third follow-up stages, respectively. The repeated-measures analysis showed no statistically significant overall difference between Arak and Shazand counties. The results therefore indicate that the general temporal pattern of soil water content was similar in the two counties. Bonferroni-adjusted pairwise comparisons indicated that the significant difference was primarily observed between the initial supervision stage and the first follow-up stage, whereas the subsequent pairwise differences were not statistically significant. An important finding was the increase in variability in soil water content toward the third follow-up stage. This increase may indicate greater heterogeneity among irrigation systems or differences in management conditions among operators. However, because spatial variability, irrigation discharge, application uniformity, and detailed soil characteristics were not independently evaluated, the underlying causes of this variability cannot be determined from the present data.The questionnaire results provided complementary information concerning farmers’ perceptions of operation and maintenance. The highest percentage score was obtained for operation management (83.33%), followed by technical recommendations (70.33%). The scores for operator training, increased productivity, and water saving were 56.67%, 46.67%, and 41.33%, respectively. These results indicate relatively high perceived performance in operation management and technical recommendations, while training, productivity, and water saving received comparatively lower scores.ConclusionsThe findings indicate that the operation and maintenance monitoring program was associated with relatively stable hydraulic and soil-moisture conditions during the follow-up period, although both operating pressure and soil water content showed an overall declining tendency after the initial supervision stage. The results support the importance of moving from a one-time supervision approach toward a continuous operation and maintenance support system. Periodic technical inspections, follow-up visits, preventive maintenance, operator training, and routine monitoring of key indicators such as operating pressure and soil water content can help identify potential changes in system condition at an early stage. Nevertheless, because the study did not include an independent control group and did not directly measure indicators such as discharge, distribution uniformity, application efficiency, or water productivity, the findings should be interpreted as evidence of changes in selected technical indicators rather than direct proof of improvements in overall irrigation efficiency. Future studies should incorporate a broader range of hydraulic, agronomic, and economic indicators and, where possible, include control systems to provide stronger evidence regarding the causal effectiveness of continuous monitoring and technical supervision programs. Conflict of InterestThe authors declared no potential conflicts of interest concerning the research, authorship, and publication of this article. FundingThe authors received no financial support for the research, authorship, and publication of this article. Data Availability StatementsAll relevant data and results supporting the findings of this study are presented within the article. The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. Author ContributionAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors. All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.AcknowledgementThe authors sincerely appreciate the cooperation and assistance of the farmers and irrigation-system operators who participated in this study, the technical experts and supervisors of the pressurized irrigation systems, and the management and technical staff of Arak and Shazand agricultural jihad centers for their valuable support during the fieldwork and data collection.
Original Article
Pressurized Irrigation Systems
Zahra Mahdian; Abdolmajid Liaghat; Farhad Mirzaei; Armin Hasanzadeh
Abstract
Extended AbstractIntroductionWater scarcity in arid and semi-arid regions has increased the need for irrigation technologies that improve water-use efficiency while minimizing water losses. Subsurface irrigation delivers water directly to the root zone through buried emitters, thereby reducing surface ...
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Extended AbstractIntroductionWater scarcity in arid and semi-arid regions has increased the need for irrigation technologies that improve water-use efficiency while minimizing water losses. Subsurface irrigation delivers water directly to the root zone through buried emitters, thereby reducing surface evaporation and runoff. PVC cylinder–based subsurface irrigation systems have attracted attention because of their simple design, low cost, and adaptability. However, the medium surrounding the cylinder can strongly influence water transfer into the soil and, consequently, the geometry and temporal development of the wetting bulb. Differences in porosity, hydraulic conductivity, pore structure, and water-retention capacity among surrounding media may alter water-flow pathways and wetting patterns. Therefore, this study investigated the effects of eight surrounding media on wetting-bulb depth, width, area, and volume at 1, 3, and 7 days after irrigation.MethodologyThe experiment was conducted at the research station of the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, using a silty clay loam soil (30% clay, 56% silt, and 14% sand), with a bulk density of 1.13 g cm⁻³ and total porosity of 47%. The antecedent soil water content was 0.07 cm³ cm⁻³ for all treatments. Perforated PVC cylinders (6 cm internal diameter and 55 cm length) were installed vertically to a depth of 50 cm, leaving 5 cm above the soil surface for connection to a bubbler emitter. Each cylinder had eight outlet perforations distributed at four depths (10, 20, 30, and 40 cm), with perforation diameters determined using an orifice-flow relationship to achieve uniform discharge. Eight surrounding media—aeolian sand, agricultural pumice, local soil (control), perlite, pea gravel, non-woven geotextile, vermicompost, and cocopeat—were evaluated, with one PVC cylinder used for each treatment. Each treatment received a single 100-L irrigation application at an inlet pressure of 0.1 bar. Wetting-bulb development was monitored using the trench method. The same trench was progressively extended at 1, 3, and 7 days after irrigation to expose the advancing wetting front while avoiding repeated backfilling and re-excavation that could disturb soil structure and preferential flow pathways. To minimize evaporative losses from the exposed soil surface, the trench was covered with a plastic sheet between successive observations. Wetted-zone boundaries were traced and digitized in AutoCAD, and two-dimensional and three-dimensional reconstructions were used to determine wetting-bulb depth, width, area, and volume.Results and DiscussionBecause one PVC cylinder was used for each treatment, the results represent observed differences rather than statistically tested treatment effects. Vermicompost and non-woven geotextile progressively restricted outlet flow, causing an inflow–outflow mismatch and water overflow; consequently, both were excluded from further analysis. Among the remaining six media, perlite produced the most balanced wetting pattern and the greatest wetted area and volume. By day 7, its wetted area and volume reached 5,227 cm² and 348,877 cm³, representing increases of approximately 50% and 80%, respectively, relative to day 1. This performance may be associated with its high porosity, low bulk density, and favorable hydraulic properties, which could facilitate lateral and vertical water redistribution. Agricultural pumice produced the greatest wetting depth, suggesting that its coarse and heterogeneous pore structure may have promoted greater vertical redistribution. Thus, pore-size distribution and pore continuity, in addition to hydraulic conductivity, may influence dominant flow pathways. Aeolian sand and pea gravel exhibited relatively rapid initial wetting but limited subsequent expansion. By day 7, wetted area and volume had increased by approximately 24% and 29% for sand and 32% and 50% for gravel, respectively. The local-soil control produced a more restricted wetting bulb than most amended media. Cocopeat showed the most limited initial wetting but the greatest relative expansion over time, with wetted area and volume increasing by approximately 153% and 205%, respectively, by day 7. This behavior may be related to its fibrous structure and high water-retention capacity, which can support gradual redistribution of stored water.ConclusionsThe surrounding medium strongly influences the hydraulic performance and geometric and temporal development of wetting bulbs in PVC cylinder–based subsurface irrigation. Vermicompost and non-woven geotextile may be unsuitable for direct placement around concentrated outlets because they restricted discharge and caused overflow. Among the functional media, perlite produced the greatest wetted area and volume and the most balanced wetting pattern, whereas agricultural pumice resulted in the greatest wetting depth. Cocopeat, despite limited initial wetting, exhibited the greatest relative expansion over time, indicating potential for gradual water redistribution. Therefore, surrounding-medium selection should consider the intended hydraulic function—maximizing wetted volume and spatial coverage or promoting gradual redistribution—rather than relying on a single hydraulic property such as saturated hydraulic conductivity. These findings are limited to the tested soil texture, irrigation volume, discharge conditions, seven-day observation period, and single-cylinder design. Further studies using multiple replicates, different soil textures, and non-destructive moisture monitoring are recommended. AcknowledgmentsThe authors would like to express their sincere appreciation to the Editor-in-Chief and the anonymous reviewers for their valuable time, thorough evaluation, and insightful comments and suggestions. Their constructive feedback substantially contributed to improving the scientific quality, methodological rigor, structural organization, and overall clarity of this manuscript.Conflict of InterestThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.FundingThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.Data Availability StatementsThe datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. Authors’ ContributionsAll authors contributed equally to the conceptualization of the research problem and to the preparation of both the original draft and the final version of the manuscript. Z.M. was responsible for the methodology, literature review, execution of the research, data collection, data analysis, and preparation of the preliminary draft of the results section. A.H. contributed to the implementation of the experimental work, including laboratory and field experiments, as well as data collection. A.L. and F.M.A.S. jointly supervised the research, validated the findings, provided the facilities and resources required for the study, and critically reviewed and edited the manuscript. All four authors contributed to the conceptualization of the research problem, participated in preparing the original and subsequent drafts of the manuscript, and have read and approved the final published version.
Original Article
Irrigation network management
Tahmine Dehghani; Fatemeh Khayat; Bijan Nazari; Abdolmajid Liaghat
Abstract
Extended Abstract
Introduction
Given Iran’s location in an arid and semi-arid region and a decline of 211 ± 34 billion cubic meters in total water storage between 2003 and 2019, reforming agricultural water management and distribution practices has ...
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Extended Abstract
Introduction
Given Iran’s location in an arid and semi-arid region and a decline of 211 ± 34 billion cubic meters in total water storage between 2003 and 2019, reforming agricultural water management and distribution practices has become essential. In this context, volumetric agricultural water delivery can contribute to more accurate water accounting, improved transparency, and more efficient water management. This study aimed to assess the policy, technical, social, and implementation dimensions of volumetric agricultural water delivery in Iran and to identify the major barriers, prerequisites, innovations, and success factors from the perspectives of 69 experts and stakeholders, including researchers (30.4%), consultants (18.8%), Ministry of Energy specialists (18.8%), Ministry of Agriculture Jihad specialists (17.4%), and farmers or water users’ association representatives (14.5%), selected through purposive snowball sampling.
Methodology
Data were collected using a researcher-developed questionnaire consisting of 16 items covering four dimensions—policy, technical, social, and implementation—and six priority-oriented questions. The questionnaire items were measured using a five-point Likert scale. The collected data were analyzed using the Friedman test, Wilcoxon signed-rank test, Kruskal–Wallis test, Spearman's rank correlation coefficient, and Chi-square test. A significance level of 0.05 was considered for statistical inference.
Main Findings
The findings revealed that the most frequently identified challenge facing volumetric agricultural water delivery in Iran is management and institutional weakness, rather than a lack of technical equipment. The highest mean score was related to water users' association participation (4.43), while the lowest was related to coordination among responsible organizations (1.95). Increasing water productivity (38%) was identified as the primary objective, management weakness (58 %) as the most important barrier, water users' association participation (29%) as the most critical prerequisite, a national smart water monitoring system (48%) as the most frequently selected proposed innovation, and monitoring and effective enforcement of laws (23%) as the most important success factor. Additionally, 84% of respondents assessed the future of volumetric agricultural water delivery as unchanged, concerning, or very concerning.
Conclusion
Respondents’ assessments indicate that the main challenge of volumetric agricultural water delivery in Iran is institutional and managerial weakness, not merely technical limitations. Success requires a holistic governance approach that simultaneously strengthens inter-organizational coordination, empowers water users' associations, develops smart monitoring systems, and ensures legal enforcement. The unchanged-to-very-concerning outlook reported by approximately 84% of respondents indicates that without fundamental institutional reforms and implementation improvements, the sustainable implementation of volumetric agricultural water delivery—and its goals of enhanced productivity and equitable water distribution—will face serious obstacles. A gradual, participatory, and evidence-based implementation strategy is therefore recommended.
Conflict of Interest
The authors declare that they have no conflict of interest. All authors have read and approved the final manuscript.
Funding
This research was conducted without receiving financial support from any specific organization or institution.
Data Availability
All relevant information and results are presented in the article.
Author Contribution
D. : Study design, data collection and analysis, interpretation of results, and initial drafting of the manuscript. F. Kh. : Contribution to study design, methodological review, and scientific editing of the manuscript. B. N. : Contribution to study design and research supervision, interpretation of findings, and scientific review of the manuscript. A. L. : Scientific supervision of the research, contribution to study design, interpretation of results, and final review of the manuscript.
Acknowledgement
The Institute of Environmental Water and Soil Research at the University of Tehran sincerely thanks all research participants for their valuable cooperation and for providing their views, which greatly contributed to the completion of this study.
Review paper
Water Government
Mohammad Javad Monem; Ensiyeh Mehrabi
Abstract
Extended AbstractIntroductionThe limitations of water resources, and low productivity of agricultural water use, have long sounded the alarm of a water and food crisis. Sustainability of water resources and adaptation to water scarcity require increasing productivity and reducing water losses through ...
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Extended AbstractIntroductionThe limitations of water resources, and low productivity of agricultural water use, have long sounded the alarm of a water and food crisis. Sustainability of water resources and adaptation to water scarcity require increasing productivity and reducing water losses through improving water delivery in irrigation networks. Improving water delivery methods and their flexibility has long been the focus of researchers. A wide range of issues related to delivery methods and their technical aspects have been studied. However, the issue of volumetric and hectare-based water delivery has not been mentioned directly. This is because the generally accepted mechanisms for water delivery and payment of water fees are well respected internationally. Given good monitoring and reasonable water fee, there is less scope for water waste, which has resulted in volumetric delivery in practice. In Iran where the importance of the issue of volumetric delivery has been emphasized, engineering research has focused on technical aspects of water delivery methods. Even though the importance of institutional, social, and legal aspects of volumetric water delivery is not less than that, for technical aspects, these issues are less considered. The conventional method of delivering water per hectare, and corresponding fee collection, has led to a mismatch between irrigation requirements, low productivity, and high water losses. Volumetric water delivery proportional to the actual irrigation needs while increasing productivity reduces water losses, and its replacement has been emphasized for years. Although important steps have been taken to implement volumetric delivery, it still faces many challenges. It is necessary to examine the legal, technical, and administrative records and the measures taken to implement volumetric water delivery. The challenges should be identified, and suggestions should be made to overcome them.Results and DiscussionReview of the volumetric water delivery laws and regulationsIn order to increase agricultural water productivity, the legal and executive determination to transition from hectare-based to volumetric water delivery has been seriously considered for at least 35 years. Significant time gaps exist between the enactment of laws and regulations, and several deadlines are determined for their execution. Reasons for this shortcoming include the slowness and inertia of the existing administrative system, unavailability of the prerequisites, and unrealistic deadlines. Due to the lack of attention to the drawbacks from time to time, the relevant laws and regulations have been re-examined. This has led to further complications and ambiguity in responsibilities. It highlights the need for reform of decision-making processes. Given the interagency nature of the issue, despite the formation of the required structure, the weakness of interagency coordination has delayed the implementation of the regulations. Reviewing the regulations and rules without a comprehensive pathology and identifying the main bottlenecks will not solve the existing problems.Introducing the Guideline and Instruction for volumetric water delivery in irrigation networksThe Ministry of Energy prepares the guideline for volumetric water delivery in irrigation networks. The purpose of preparing the guideline is to provide the necessary conditions for delivering water in a volumetric manner for higher productivity and lower water losses. The three stages of the process are managing water distribution for volumetric delivery, providing the necessary equipment for volumetric delivery, and using an appropriate information system. The guideline explains the volumetric water delivery process under normal and drought conditions, and for paddy fields. The required training for managers and officials, water suppliers, and consumers is also described. The details of operational steps for the transition from hectare-based delivery to volumetric delivery are discussed. Oversimplification is done in evaluation of existing networks to establish volumetric delivery.The instructions for volumetric water delivery were prepared by working group on adaptation to water scarcity. The purpose of the document is to create uniformity and improvement on volumetric water delivery process, and to increase water productivity. In this instruction, while providing the necessary definitions, the required executive structure at the national and provincial levels is proposed, and the duties and responsibilities of the relevant institutions are determined. The schedule for the implementation of the instruction and the prioritization of irrigation networks has also been determined.The weakness of the guideline and the instruction are insufficient attention to the required pre-requisites, administrative, and financial consequences. It is necessary to revise and update the guideline and instruction according to the mentioned deficiencies.ConclusionsIt can be stated that for the full implementation of volumetric water delivery, it is necessary to reform the decision-making processes and continue the implementation of laws and regulations despite management changes. It is necessary to provide legal, credit, compensation, and motivation support to the relevant stakeholders. A comprehensive pathology analysis to remove obstacles facing volumetric water delivery should be done. Key words: Guideline, Instruction, Irrigation Networks, Laws, Regulations, Volumetric Delivery. Conflict of InterestThe authors declare that they have no conflict of interest. All authors have read and approved the final manuscript.FundingThis research was conducted without receiving financial support from any specific organization or institution.Data Availability StatementAll data presented in the article are available from the corresponding author.Author ContributionsMrs. Mehrabi has provided the required documents, information, and references, and the corresponding author was responsible for other roles in preparing the article.AcknowledgementThe authors thank Ministry of Energy, Beurea of Technical & Operation Systems Development, and National Working Group of Adaptation to Water Shortage for their contribution to the volumetric water delivery.
