Comprehensive classification and categorization of Qanat features: an interdisciplinary exploration using landscape infrastructure concept and semi-systematic review

Abstract

Qanats, as traditional and intelligent water infrastructures, have garnered attention across various scientific disciplines. However, a comprehensive, holistic view of Qanats remains elusive. This study aims to identify and present a thorough perspective on Qanat features. To achieve this objective, a semi-systematic review methodology was employed. The semi-systematic or narrative review approach is well-suited for subjects that span multiple disciplines and different periods. The research process commenced with an extensive search for the keyword “Qanat” within the titles and abstracts of articles across the MagIran, ScienceDirect, Taylor and Francis, and Springer databases. Subsequently, a thematic content analysis method was applied to analyze the content of these articles. Thematic content analysis involves the identification and presentation of recurring patterns in the form of distinct themes within the textual data. At this stage, Qanat features were extracted from the articles and categorized thematically. The research findings underscore the functional significance of Qanats as vital water supply systems. Furthermore, within the realm of management, Qanats are recognized as essential water infrastructures. In light of these findings, this study incorporates relevant literature from the infrastructure domain to systematically categorize Qanat features. In the research, the Landscape approach, characterized by its objective-subjective perspective, will serve as an overarching narrative framework to comprehensively classify all Qanat features. The resulting model portrays Qanats as possessing a diverse spectrum of tangible and intangible attributes, spanning environmental, cultural, social, and economic domains. This comprehensive analysis enhances our understanding of the multifaceted nature of Qanats, facilitating their preservation and sustainable management.

Introduction

A Qanat is a traditional water supply system and a valuable cultural heritage. Some scholars believe that the invention of Qanats dates back to around 6000 years ago, while others trace it to the time of the Achaemenids (Sedghi and Jan 2020; Delfani et al. 2021). The Qanat is essentially a horizontal well that extracts water from aquifers and conveys it from hills to the surface of the earth through gravity alone. The Qanat also consists of some interconnected shaft wells that are vital for maintenance as well as ventilation (Labbaf Khaneiki 2019) (See Fig. 1).

Fig. 1

(Source: Authors inspired by Estaji & Raith 2016)

Qanat Diagram

In addition, the Qanat is a multi-layered water distribution system that carries significant environmental, social and cultural value.

For instance, Qanats influence the the organic carbon content by increasing soil moisture. (Bagwan et al. 2003). Or playing a role in sociocultural communication through its unique water management network (Fadakar Davarani 2009; Fadakar Davarani and Samaraam 2018; Labbaf Khaneiki 2019).

Unfortunately, in the modern era, Qanats have been replaced by more contemporary water infrastructure such as deep wells and piped water systems (Alhashemi 2021). Today, discussions about reviving Qanats arise for two reasons: water crises and cultural preservation.

However, the one-dimensional modern perspective that led to the neglect and deterioration of Qanats cannot be employed in their revival. For instance, in the Mehrgerd Qanat revival project in Tehran, a technocratic approach focused solely on restoring the Qanat structure, utilizing it for urban green space irrigation. Similarly, in the Kish Qanat revival project, a one-sided approach emphasized the historical and cultural values of Qanats, turning them into underground museums.

This one-dimensional perspective in Qanat revival projects stems from a one-dimensional view of Qanats in research. Consequently, there is a gap in research literature for a holistic portrayal of Qanats. The primary goal of this article is to answer the question: “What values and characteristics do Qanats possess?”.

This article also aims to provide a comprehensive and holistic overview of Qanat as multi-layered water system, offering a complete picture of these traditional infrastructure.

Since the most significant feature of Qanat is its functional role as a water infrastructure, this research has tried to deal with this phenomenon under the "infrastructure" literature. Therefore, the two main areas of “infrastructure” and “Qanat” have been presented as the background of the research.

Infrastructure

Urban infrastructure networks serve as vital lifelines for modern cities (Yang 2018). The scale and population of contemporary urban areas make life without essential infrastructures like water, energy, and transportation virtually impossible. These components are critical for distributing goods and services, enabling resource flow, powering businesses, and connecting communities. Essentially, infrastructure acts as the backbone sustaining the economic and social fabric of cities (Timilsina et al. 2020).

While the term "infrastructure" is modern, its history extends far back, encompassing the development of infrastructure in historical indigenous settlements such as Qanats and Stepwells.

In traditional contexts, knowledge production was rooted in the interconnectedness of the human, natural, and spiritual realms. This perspective resulted in indigenous knowledge being characterized as holistic due to its relational dynamics (Kinchelo and Semali, 2011).

For example, Indigenous societies, in their approach to water sources, prioritized holistic spiritual and natural connections, valuing nature's needs over human consumption. Water held a sacred role in their existence, viewed spiritually rather than economically, reflecting their profound beliefs and values (Groenfeldt 2003). Roman Roads are another examples of historical infrastructures, which serve a purpose beyond facilitating travel from one point to another. They encapsulate matters of ideology, authority, and self-definition, intertwined closely with the way we shape our perceptions of the world within societal contexts (Forcey et al 1998).

However, modernist science simplifies consciousness to physiological neuroprocesses, overlooking how dissecting the components of a whole weakens our understanding of social, physical, and human phenomena. Cartesian-Newtonian perspectives perceive “wholes” and their relationships as less genuine than distinct parts (Kinchelo and Semali, 2011). Therefore, since the modernization and post-Cartesian era, there has been a fundamental change in infrastructure, similar to other phenomena. During this period, the design of infrastructure was done separately and with a technocratic approach.

Infrastructure is usually divided into two general categories: hard and soft. Hard in infrastructure includes physical networks such as transportation (roads, mass transportation, rail ways, etc.), facilities (water, sewage, electricity, telephone, internet etc.), and other such networks, while soft infrastructure includes institutional systems such as, school, college, hospital, courts, municipality building, bank, post office, cinema, theatre hall, etc. These infrastructures meet the economic, social, and other needs of society (Rouse et al. 2013). From the postmodern era to the present day, this perception and division are common in the field of urban infrastructure.

In the second half of the twentieth century, various events revealed the limited capacity of industrial and technocratic infrastructure to meet the complex challenges of urbanization, such as falling bridges, canal failures, submerged beaches, power outages, water shortages, sewage decay, and so on (Belanger 2009; Rouse et al. 2013). For example, the toxic tragedy of Love Canal in 1987 (Belanger 2009), Francis Dam disaster in 1928 (Hundley et al 2016). Moreover, the advent of ecological branches, and the publication of the book "Design with Nature" by Ian McHarg in 1969, as well as his activities in television programs and academic spaces, a deeper understanding of the long-term effects of industrialization and urbanization on biophysical systems among the community and professionals emerged. This led to a renaissance in urban development approaches. Furthermore, the introduction of the term "green infrastructure" in architectural and urban literature by Benedict and McMahon in the early twenty-first century laid the foundation for modern approaches in urban infrastructure. It ushered in a new phase of the relationship between humans and the natural environment, shifting the focus from dominating nature to conserving it as a predominant approach (Wright 2011).

The ecological approach was subsequently introduced, which considers urban infrastructure systems as an integrated ecological system. In this approach, urban infrastructure is a complex and flexible system whose stability and resilience are associated with complex interactions and changes in the engineering, environmental, and economic infrastructure of a city over time and space (Pandit et al. 2017; Brown 2014). As different urban infrastructures have a multi-layered relationship with each other, designing and planning them separately can lead to an increase in costs and negative environmental consequences. Therefore, in the ecological infrastructure approach, the grey and green infrastructure systems, as well as socio-economic flows (considering the stimuli of decision-making and investment as well as the flow of wealth and welfare in society), are viewed in a unified manner in urban planning.

Another approach, landscape infrastructure, was introduced in response to environmental hazards and the limitations of technocratic infrastructures, as well as the influence of phenomenology in philosophy and cognition. In addition to the physical protection provided by ecological infrastructure, landscape infrastructure deals with the semantic and intrinsic values of a city's infrastructure.

In 2009, Pierre Belanger provided a comprehensive definition and overview of landscape infrastructure, which offered a large-scale perspective on the effects that it can have on a city, such as providing services, diverting resources and energy flows, and facilitating dynamic and flexible changes for a city’s expansion, all of which are important for supporting and developing a city (Belanger 2009).

According to Belanger's definition, landscape infrastructure considers the environmental and social problems of the post-industrial era and their impact on lifestyles, business, and the economy together in an integrated framework called the city landscape (Rouse et al. 2013). Landscape infrastructure studies the possibility and method of combining landscape and grey infrastructure, which can lead to a holistic approach to infrastructure management (Ji and Shao 2016, 2017).

Mansouri and Aleashemi emphasize the importance of integrating nature with social, cultural, and identity issues in landscape infrastructure. They consider it a natural infrastructure within a city, which is linked to the landscape approach in physical and sociocultural aspects, and simultaneously serves functional, aesthetic, and landscape identity goals. Landscape infrastructure is not only a service but also intertwined with urban life and citizens in various aspects. The stability and durability of this infrastructure in the city and its structures are crucial factors in the quality of urban landscapes. They also present the landscape approach as a multidimensional, objective- subjective, and holistic solution to address the rigid and one-dimensional nature of infrastructure that emerged during the industrial era, and to enable the multifaceted presence of infrastructure in the city as a whole (Alehashemi et al 2017; Alehashemi et al. 2015). (See Table 1).

Table 1 different approaches towards infrastructure (source: Alhashemi et al., 2017 and Authors’ significant revision)

As mentioned, approaches in infrastructure have evolved from the beginning of the modern era to the present, aiming to address infrastructure-related issues and enhance the quality of life. These developments have ranged from a technocratic approach to green infrastructure, ecological infrastructure, and landscape infrastructure. This progression, in parallel with the development of the concept of sustainability, has moved away from purely physical and functional perspectives and has also encompassed other environmental, social, cultural, and economic aspects.

The most recent approach) landscape infrastructure(, Because of its objective and subjective dimensions, has a greater potential to address the complex and multifaceted problems of contemporary urban infrastructure (See Figs. 2, 3).

Fig. 2

infrastructure’s transition (Authors)

Fig. 3

Landscape Infrastructure Diagram (Authors)

Qanat

Qanat, an ingenious water management system, holds deep historical and cultural significance as an ancient method of supplying water in arid regions, contributing to sustainable agriculture and settlements. For a thousand years until today, this phenomenon has been the subject of research and study by scientists.

Al-Karji's book is likely the oldest text about Qanat (Iranmanesh et al. 2021).

In around 1010 AD, Al-Karaji compiled the achievements and personal experiences, along with the insights of his predecessors, on the digging of Qanats, in his book “Extraction of Hidden Waters.” Despite its scientific content, this treatise was not widely utilized and was forgotten in its time. In fact, those who could benefit from it (the diggers of Qanats) were rarely able to read. However, this book holds significance for documenting an ancient engineering method and preserving traditional knowledge (Goblot 1979).

Later on, in the 1930s, Goblot, a French scientist was invited by the Iran government to conduct research about Qanat. And he published the result of his research in a book titled “Qanat a technical for Accessing Water,”. In the book he attributed the invention of Qanat to the miners and introduced the technical and cultural features of Qanat. He also proposed the theory that Qanat was originally invented to drain mine tunnels and later was used as a water extraction system (Papoli Yazdi and Vosoghi 2019).

This book holds significance in emphasizing the importance and technical, historical values of Qanats, demonstrating that Qanats are not merely an insignificant traditional water system; rather, they are a valuable and noteworthy phenomenon, capable of being a subject of research for scholars. Since then, various scientific articles have discussed different aspects of Qanat.

In the result section, a detailed discussion will be provided regarding the perspectives on Qanats in various historical periods. Here, to enhance the organization of the text, we will delve into mentioning the different branches through which Qanats have been examined. Hydrology and technical innovation, Built Environment, Water Management and Social Science, Environment & Sustainability, Geography, Biology & Aquatic, Heritage & History, Chemistry, Rehabilitation, Archaeology, Disaster Risk, Tourism, Philosophy (See Table2).

Table 2 Different field of science which have studied Qanat.

Semsar Yazdi and Papoli Yazdi as well as Labbaf Khaneiki, have been among the researchers who have shown the most interest in Qanat, studying its technical, cultural, social, and economic aspects in various articles and books (Semsar Yazdi and Karimian 2018; Semsar Yazdi and Labbaf Khaneiki 2017; Semsar Yazdi and Karimian 2021; Papoli Yazdi and Vosoughi 2019; Labbaf Khaneiki 2015, 2017, 2020, 2022, 2023; Labbaf Khaniki et al. 2019, 2023).

Labbaf Khaneiki's research have focused on Qanat and he has published 48 research over last 18 years. Some of his research presented innovative perspectives on the Qanat phenomenon. For instance, he analyzed the position and function of endowments (Waqf) in the Karizi civilization in a chapter of the book “Hydro Social Cohesion in Iranian communities”. There is a common belief that endowments have their roots in religious beliefs. In addition, regarding the endowment of Qanats, Labaf Khaniki presents the idea that endowments did not solely occur for the satisfaction of God; rather, they were a social mechanism to address and mitigate class disparities. Utilized the method of investigating historical texts and employing logical reasoning to substantiate his theory (Labbaf Khaneiki 2022). Moreover, he studied oral culture and customs related to Qanat in the book “Production and Water Culture” (Labbaf Khaneiki 2020) he and Semsar Yazdi also presented the same concept it the “interview with local participatory” book chapter. (SemsarYazdi and Khaneiki, 2023) These investigations are based on a reviewing historical texts, semi-systematic interview and content analysis.

Furthermore, PapoliYazdi perspective delves into the wider aspects of Qanat equipment and professions. He explores a network of traditional vocations related to the establishment of Qanats, delving into the examination of the Qanat's role in the economic life of communities. Moreover, his works aim to document historical tools by reviewing historical text and observation.

In conclusion, although Qanat has been studied in various fields, there is a vacant space for a comprehensive portrayal of it. While recent articles studying Qanats in the realm of sustainability have approached this comprehensive view, a review article is still necessary to summarize previous studies and present various aspects of Qanats side by side within one article.

Methods

Since the main objective of this paper is to provide a comprehensive perspective on Qanat, the “semi-systematic review” approach was chosen to conduct this research. The semi-systematic or narrative review approach is suitable for topics that have been studied in various disciplines (Wong et al. 2013). Additionally, this research method is suitable for depicting the progress of a subject over time or among different scientific traditions. In general, this type of review research aims to identify all research traditions related to the subject (Snyder 2019). Furthermore, researchers typically use over-arching narratives to synthesize different narratives to provide a general understanding of complex and extensive fields and issues. (Wong et al. 2013).

Therefore, given that Qanats have been studied across various disciplines and the aim of this article is to summarize all aspects of Qanats studied in these articles, the semi-systematic review method is an appropriate approach for this research.

In the upcoming research, the Landscape approach will serve as an over-arching narrative to comprehensively classify all the features of the Qanat. Because landscape approaches highlight the importance of inter- and trans-disciplinary collaboration. This means addressing interconnected challenges by fostering increased involvement across various scientific fields and engaging a wider range of stakeholders from society. So, this approach is able to bridge the gaps between research, policy, and practical implementation.

In the second step we should select a suitable type of analysis. Several methods can be employed to analyze and synthesize findings in a semi-systematic review. A common approach is thematic or content analysis, which involves identifying and presenting patterns in the form of themes within the text. (Braun and Clarke 2006). Since our research is a review article and the material of our study consists of textual content, thematic analysis has been chosen as a suitable method for this research.

In the first step, we searched the Magiran website for Persian papers. For English sources, we searched through Science Direct, Taylor and Francis, and Springer. The MagIran database was chosen for its capability to index almost all reputable Persian scientific articles and journals. The selection of 'Springer,' 'ScienceDirect,' and 'Taylor & Francis' databases was guided by their strong academic reputation, extensive coverage across disciplines, and robust search capabilities. 'Springer' offers a broad range of impactful research, while 'ScienceDirect' provides a diverse array of cross-disciplinary content. 'Taylor & Francis' boasts comprehensive coverage across academic fields. These choices were made to ensure access to high-quality, peer-reviewed articles and enhance the credibility and depth of our study. (See Table 3).

Table 3 The Number of Papers with “Qanat” in the title and in Abstract; based on different publisher and fields. (authors)

Initially, we conducted a search using the keyword “Qanat” specifically within paper titles, ensuring that the articles under consideration were directly focused on the topic of Qanats. During this phase, 74 Persian articles and 49 English books and articles from various disciplines, including “Hydrology and Technical Innovation,” “Built Environment,” “Water Management and Social Sciences,” “Environment and Sustainability,” “Geography,” “Biology and Aquatics,” “Heritage and History,” “Rehabilitation,” “Chemistry,” “Cultural Science,” "Archaeology," “Disaster Risk,” "Tourism," and "Philosophy," were found.

Then all 123 founded articles (all have Qanat key word in their title) were carefully studied. Then, using the Thematic Analysis method, all the passages were analyzed to find the various values and features of Qanat. Thematic Analysis is a common method to identify, analyze, and report patterns in the form of themes of a text (Braun and Clarke 2006). The statements in the text of the articles were analyzed to identify tangible and intangible values of Qanat as desirable themes based on logical reasoning. Every part of the text that refers to a feature of the Qanat forms the statement, and the referred feature, which is a summary of the statement, forms the theme. For example,” Qanat, Traditional Eco-Technology for Irrigation and Water Management” (statement) refers to “ecological” feature of Qanat (theme). We identified 20 features based on 356 statements.

At this stage, the mentioned statements and themes were categorized into sustainable discipline fundamental categories: "environmental," "economic," and "socio-cultural," to organize the research process. Since the concept of sustainability is the dominant paradigm in various filed and sections in today’s world, it was chosen as the basic factor for categorizing the result (Castro 2004).

Next, all statements were summarized, and themes that represented content close to each other were combined. Some topics were divided into several different topics according to the scope of the subject. At the end of this stage, five themes were identified in the environmental category, three in the economic category, and thirteen in the socio-cultural category.

In the third step, 1082 papers were identified by searching for "Qanat" among abstracts and keywords in the four mentioned databases. After scanning abstracts, papers that presented a unique perspective on Qanat were selected for reading the entire texts. And then 17 papers were selected and then analysed exactly the same as papers in previous step. Subsequently the table of themes and statements was completed. In the final step, the various features of the Qanat were classified into a comprehensive framework based on the landscape approach. (See Table. 4 and Figure 4).

Table 4 The Number of papers with Qanat in their title and abstract in four data bases

Fig. 4

flowchart of research steps (source: authors)

Results

Statistical analysis of results

Since the Qanat is a complex invention with diverse territorial and ethnic characteristics, and has spread to different countries and territories, it has been studied in various disciplines. However, the technical aspects of the Qanat as a water infrastructure have been studied more than other features. with a 32% share of studies and a total of 40 studies. These studies include a technical-analytical examination of Qanat in different regions, as well as technical innovations and suggestions for modernizing the Qanat.

After that Built Environment is the discipline with the highest number of papers related to the Qanat, accounting for 11% and a total of 13 studies.

Since 2003, specialists from more fields have shown an increased interest in Qanats.

Water management and social Science, Environment and sustainability, geography, biology, heritage- history, chemistry, rehabilitation, cultural science have paid the most attention to the Qanat, with 11% (13 number), 10% (12 number), 8% (10 number), 8% (10 number), 5% (6 number), 4% (5 number), 3% (4 number) and 2% (3 number), respectively.

During last ten years, scholars from four new fields have studied Qanat. Archaeology, disaster risk, tourism, and philosophy with 2% (3 number), 2% (3 number), 1% (1 number), 1% (1 number), respectively. (See Fig. 5).

Fig. 5

The percentage of published articles on "Qanats" (with the keyword "Qanat" in the title) in various fields

Generally, as science has developed in various fields, research related to the Qanat has also experienced an upward trend. A glance at (Fig. 6) shows that the Qanat has been prominent in the academic sector as an infrastructure with outstanding technical features in different periods.

Fig. 6

The percentage of published articles on "Qanats" (with the keyword "Qanat" in the title) in various fields

However, with the development of other trends, such as sustainable development and ecological, economic, and sociocultural values, the unique cooperative management of Qanat's water infrastructure has been gradually taken into consideration. In recent years, architects, urban planners, and landscape architects have paid more attention to the role of Qanat in the formation of urban and rural structures than in previous years. Based on presented charts, disciplines such as sustainability, sustainable architecture and urban planning, and landscape architecture (in the field of build environment) have attempted to study Qanat with a holistic view. However, the multiplicity of features of the Qanat has caused researchers to only mention its values in headlines or fail to address them fully. In the last ten years, researchers in the fields of geography, biology, reconstruction, archaeology, disaster risk, history, cultural heritage, philosophy, and tourism respectively have published the most articles about the Qanat. This indicates that the features of the Qanat have been studied with a deep, specialized, and practical view in different fields, and it seems that this trend will continue in the coming years.

The features of the Qanat

The statements referring to the characteristics of the Qanat were extracted from the texts of articles in different fields in order to identify the features of the Qanat. This research has identified all the features of the Qanat that have been mentioned directly or indirectly in previous articles and summarized them into three groups: sociocultural, economic, and environmental. (See Fig. 7).

Fig. 7

the number of statements and sources supported ant theme (features)

The following tables present the definition of each feature (See Tables 5, 6, and 7).

Table 5 Cultural and Social Features (source:authors)

Table 6 Ecological features (source: authors)

Table 7 economic features (source: authors)

Discussion

As indicated by the section of statistical findings, Qanat have been extensively studied in various scientific fields, ranging from hydrology to cultural and social aspects, due to their multifaceted values. It seems that one of the most important aims of all these research endeavors is to preserve this phenomenon.

However, having a comprehensive understanding of multi-layered heritages is crucial for their revitalization and restoration with a holistic and all-encompassing approach (Mısırlısoy and Günçe, 2016). One-dimensional perspectives in Qanat planning and management have stripped them of their intangible significance, leading to their gradual decline or alteration over time.

The revival and protection of the Kish Qanat system is a prime example of this one-dimensional perspective on Qanats. In this project, the structure of the Qanat was initially restored, and some of the dry branches of the Qanat were allocated for uses such as cafes, restaurants, and exhibitions, actually its new function is museum (Alemohammad and Gharari 2017). In this project, only the physical structure of the Qanat has been preserved, while other social, cultural, and economic values associated with it have been neglected. Today, the Qanats in the city of Kish bear little resemblance to the life and essence of Qanats in the past. (See Fig. 8).

Fig. 8

kish Qanat rehabilitation project (source, www.tasnimnews.com)

Returning to the main point, the functional performance of Qanats as a water supply system has consistently been their most emphasized value across all disciplines, making it appropriate to classify Qanat values within the context of infrastructure definition.

Another reason for exploring Qanat in the literature on water infrastructure is that they are typically evaluated within this domain, and decisions are made concerning them. For example; In Iran, the management and oversight of Qanats are under the jurisdiction of the Ministry of Energy and the Ministry of Agriculture, Jihad, and Natural Resources. These two ministries have various responsibilities, including the supervision of water resources, irrigation infrastructure, and water distribution, and in Oman the Ministry of Regional Municipalities and Water Resources is officially responsible for Qanats.

In practice, Qanat systems are often viewed solely as water infrastructure and are compared unfavorably to other modern water supply systems, deeming them as outdated and inefficient. While scientific and managerial prudence prevents a demolition verdict, the lack of attention to this phenomenon and the absence of a well-defined preservation plan indirectly leads to their elimination. (Hosseini et al 2010; Abbasnejad 2016, Ahmadi et al 2010; Lightfoot 1996).

While considering the functional, cultural, social, and heritage values of Qanat is crucial, presenting a comprehensive image of Qanat as a multi-layered value-laden water infrastructure requires practical and applied research.

Each Qanat has unique technical specifications, including factors like water yield, well and water channel durability, groundwater volume, and more. These complexities require thorough technical examination and precise testing. For example, in-depth technical studies employ various fields and methodologies, such as Tectonic geomorphology (Taib et al. 2023), to address these specificities.

Furthermore, numerous scientific chemical methods are available for assessing groundwater quality. One such method is Principal Components Analysis, which can be used to enhance our understanding of groundwater hydrochemistry (Kallel et al. 2018).

Moreover, while values, traditions, construction methods, and Qanat management techniques may share some similarities, they each possess distinctive characteristics in their specifics. For instance, by conducting in-depth semi-structured interviews with local community members (Brinkmann 2014), one can uncover the cultural and social values associated with a Qanat. Additionally, by analyzing the content of oral history and local customs (Krippendorff 2018), it is possible to identify the intangible values of a Qanat.

Besides, Qanat's footprint on the various city's structure can be traced by analyzing historical maps and the evolution of urban development.

Given the significance of Qanat in executive systems and the responsible entities for Qanat, the authors of this article believe that Qanat revitalization can only be achieved when they are initially addressed academically within the realm of infrastructure.

As previously mentioned, diverse approaches have been proposed from historical times to the present in the field of urban infrastructure. However, due to the diverse features of Qanat encompassing functional, physical, cultural, social, and economic domains, a comprehensive approach to classification is necessary. Therefore, the landscape infrastructure approach, which offers a holistic, comprehensive, and objective-subjective perspective by deeply connecting infrastructure with various tangible and intangible layers of the cities, while simultaneously considering functional, cultural, and aesthetic objectives for the infrastructure, (Mansoury and Alhashemi 2015; Rouse et al. 2013; Belanger 2009) is the most suitable choice for creating a comprehensive framework of Qanat features.

Consequently, the classification of features was initially conducted under the landscape infrastructure definition, organizing them into two main categories: tangible and intangible, relying on the conventional primary classification (environmental, cultural-social, economic). Subsequently, the triple objectives of landscape infrastructure (functional, identity-based, aesthetic) were incorporated as the third-level organizing factor in the final framework (See Fig. 9).

Fig. 9

Qanat’s Features Classification based on the landscape infrastructure definition. (Authors)

Conclusion

A semi-systematic review of the literature related to Qanat in various scientific disciplines reveals that Qanat possesses a wide spectrum of tangible and intangible features in environmental, cultural, social, and economic domains.

In addition to supplying water to settlements, Qanats are deeply intertwined with cultural and religious beliefs. They play a role in traditions, social ceremonies, naming practices, and even colloquial proverbs. A social network has developed around the construction and operation of Qanat water, shaping social roles and informal rules, strengthening social capital, and contributing to the formation of social classes. Moreover, Qanat water holds significant trade value and plays a crucial role in fostering various businesses and industries related to Qanat construction and operation. In dry and semi-arid regions of Iran, Qanat represent the main, and sometimes only, source of water supply, contributing to the preservation of vegetation cover and wildlife. Wells and underground facilities, along with the distributary network of water, have had a significant impact on shaping the spatial structure of cities. Public land use, water facilities, neighborhood boundaries, green and agricultural patches, all have been influenced by the presence of Qanat in cities reliant on this water system.

Qanat represent a water infrastructure that extends beyond a mere water supply system and fulfills roles in various social, economic, and cultural layers. Therefore, the landscape infrastructure approach seems to be the most suitable option for classifying Qanat features due to its tangible-intangible nature and comprehensive perspective. By considering the functional, identity-based, and aesthetic values of Qanat, the landscape infrastructure approach can offer a comprehensive image of this phenomenon.

This comprehensive image of Qanat, as a general framework, can be utilized in the study and planning of Qanat revitalization. Having an overarching view of this phenomenon allows for the consideration of all tangible and intangible values of Qanat and their interconnectedness as a coherent system. The classification system, guided by the landscape infrastructure approach, helps researchers identify various aspects to explore and ensures that values, especially intangible ones, are not overlooked inadvertently. This comprehensiveness in studying Qanat ensures the preservation of this valuable heritage with a holistic perspective at the implementation level. Without safeguarding the meaningful values, Qanat might become mere sets of empty wells and passages devoid of significance, with little justification for their preservation and maintenance.

Finally, provided model serves as a roadmap for initiating a comprehensive study of case study examples. It assists researchers and decision-makers in understanding the characteristics they need to identify in a Qanat revitalization project.

Consequently, these Qanat features can be revitalized within contemporary cities to the extent possible.

Studying various Qanats using this comprehensive model helps ensure that certain aspects of Qanats are not inadvertently overlooked. A comprehensive understanding of each Qanat's geographical and cultural uniqueness is essential groundwork for their proper and sustainable restoration. Once the different characteristics are identified, practical and executable steps can be taken for their revival. However, without knowledge of these features, planning for their restoration will be virtually impossible.