Spatiotemporal urban-water interactions in upper Min River settlements within a triaxial framework

Abstract

The upper Min River basin in southwest China serves as a representative region for studying urban-water interactions. Focusing on Songpan, Taoping, Shuimo, and Guanxian, this study establishes an X–Y–Z triaxial framework of temporal evolution, spatial hierarchy, and functional mechanism to reconstruct interaction trajectories, analyze contemporary perceptions, and extract spatiotemporal synergistic mechanisms. The main findings are as follows: (1) Settlements exhibit structural continuity yet differentiated development logic—from headwater frontiers to the outlet plain—driven by the differential coupling of the three axes. (2) Contemporary perceptions vary significantly between social groups, revealing challenges such as cultural dilution, commercial encroachment, and a disconnect from traditional water-culture expressions. (3) Evolutionary pathways are shaped by the shifting influence of natural constraints, trade-transport networks, and institutional-cultural embedding. This study offers a transferable methodological paradigm for the governance and sustainable development of urban-water heritage in mountainous watersheds globally.

Introduction

Globally, the urban-water paradigm is shifting from technical engineering control toward systemic resilience¹, with the watershed increasingly identified as the fundamental scale for understanding regional synergy and governance^2,3, While water has historically functioned as a core driving force for the origin and spatial morphology of human settlements^4,5,6, existing research frequently relies on single-point analysis or static assessments, which fail to capture the long-term evolutionary dynamics across different hydrological gradients. This highlights a critical need for a unified framework that situates historic settlements within their broader regional patterns.

In international scholarship, watershed-scale urban-water interactions are typically situated within the Integrated River Basin Management framework, which emphasizes synergy between hydrological systems, socio-economic activities, and governance^7,8, The European Water Framework Directive has strengthened the concept of the watershed as a fundamental governance unit, while adaptive management focuses on balancing water systems, social demands, and ecological constraints through dynamic regulation⁹. Global practices are categorized into representative analytical traditions, such as navigation and trade-led interactions exemplified by the Rhine River¹⁰, where port nodes are deeply coupled with urban zones¹¹, driven primarily by trans-regional trade networks and governance systems¹². Meanwhile, grid-based water interactions, represented by Amsterdam and Jiangnan, China water towns^13,14, utilize canal networks to guide high-density layouts^15,16,17. Engineering-driven interactions^18,19, typical of the Yodo and Tennessee Rivers, rely on large-scale infrastructure for resource regulation^20,21, in contrast, ecological-adaptive interactions found in high-altitude mountainous basins, such as the upper Min and Mekong Rivers²², emphasize settlement morphology dependent on local hydrological conditions^23,24, Against this global backdrop, the traditional Chinese mountain-water-city paradigm diverges from Western functional water spaces. Regarding formation mechanisms, Western trade rationality contrasts with the Chinese focus on survival needs and topographical adaptation²⁵. In terms of governance, Western systems emphasize rational intervention, whereas the Chinese approach prioritizes following nature through social organization. Furthermore, while Western traditions often view water as an instrumental asset, Chinese paradigms imbue it with ecological worship and humanistic sentiment.

These urban-water interactions are nested within multiple interrelated scales, ranging from regional distributions shaped by fluvial geomorphology^26,27,28, to micro-level embedding in street patterns and daily practices^29,30,31,32, However, contemporary urbanization and landscape consumerism have decoupled many historic settlements from their original hydrological contexts^33,34, leading to fragmented ecosystems and superficial cultural expression^35,36,37, Water bodies are increasingly reduced to mere infrastructure or symbolic landscapes, resulting in pervasive homogenization where commercialization severs the daily connection between residents and the water system^38,39, Consequently, a research gap persists in connecting historical water management with contemporary dynamics through systematic comparisons across upstream watersheds.

The upper Min River, a transition zone between the Qinghai-Tibet Plateau and the Sichuan Basin, features significant topographical variation and multi-ethnic integration, serving as a representative region for the long-term co-evolution of urban-water systems^40,41,42, Unlike Western models, the traditional Chinese mountain-water-city concept emphasizes deep socio-hydrological synergy⁴³. By adapting to natural constraints, trade, and institutional culture, settlements formed living water spaces integrating defense, livelihood, governance, and aesthetics^25,44,45, This study selects Songpan Ancient Town, Taoping Qiang Village, Shuimo Ancient Town, and Guanxian Ancient Town as cases to reveal evolutionary differentiation across hydrological gradients. These settlements span key nodes from the headwaters to the outlet plains, representing headwater frontier defense translation, micro-networks of ethnic defense and communal life, systemic reconstruction under external shocks, and a symbiotic paradigm led by large-scale hydraulic engineering.

Moving beyond the single-settlement perspective, this study situates these cases within a watershed-scale framework of urban-water interactions and develops a triaxial framework integrating temporal evolution, spatial hierarchy, and functional mechanism. The research follows a logical path of trajectory reconstruction, perception analysis, and mechanism extraction to reveal evolutionary patterns and driving mechanisms in the upper Min River. Compared to traditional studies focused on single-point protection or landscape renewal, this research distills local experiences from Western China into theoretical propositions with broader significance. It contributes to addressing important issues in urban-water research, such as scale integration, historical continuity, and regional synergy. Ultimately, this study provides a methodological reference and theoretical support for the sustainable governance of riverine cultural landscapes worldwide.

Methods

Study area and case selection

The upper Min River watershed is a multi-ethnic region inhabited by Tibetan, Qiang, Hui, and Han groups, where the river network provides a stable spatial skeleton. Settlement activities date back to the late Neolithic⁴⁶. Despite influences from the Ancient Tea Horse Road, modern transitions, and seismic disturbances, the evolution of settlements remains clearly defined by hydrological constraints. To analyze differentiated evolution under shared watershed conditions, four settlements with continuous historical development and high spatial legibility were selected (Fig. 1). Selection criteria prioritize the structural role of water systems in spatial organization over administrative status.

Fig. 1: Spatial distribution of the four selected settlements in the upper Min River basin.

This figure illustrates the geographical location and topographical features of the research area across multiple scales. a Location of Sichuan Province within China; b Location of the upper Min River basin within Sichuan Province; c Topographical map and case settlement distribution of the upper Min River basin, where the color gradient represents the elevation (DEM) from high (red, 5888 m) to low (light green, 530 m), and the solid blue line indicates the main stem of the Min River; d Songpan Ancient Town; e Taoping Qiang Village; f Shuimo Ancient Town; g Guanxian Ancient Town.

Songpan Ancient Town (Headwater/Frontier): Situated at 2850 m at a strategic junction, it was historically dominated by military defense and frontier trade. It represents urban-water interactions in plateau frontier environments.

Taoping Qiang Village (Ethnic/Integrated): Located in the Zagunao tributary basin (1500 m), its water system is deeply integrated with defense and daily life. Despite its village scale, the settlement exhibits structural complexities comparable to town systems.

Shuimo Ancient Town (Reconstruction/Transition): Located in the Shouxi tributary basin (920 m), it transitioned from a residential focus to industrialization and post-disaster reconstruction, serving as a model for reshaping interactions under external disturbances.

Guanxian Ancient Town (Hydraulic/Connection): Positioned at the watershed outlet (770 m), its development is led by the Dujiangyan irrigation system, representing a symbiosis between large-scale hydraulic engineering and settlement growth.

Research framework

To systematically reveal the evolutionary logic of urban-water interactions in the upper Min River, this study employs a triaxial framework where the X-axis identifies key historical stages of structural change in urban-water interactions, the Y-axis characterizes the cross-scale spatial embedding features of water systems, and the Z-axis categorizes these interactions based on the dominant functions of water systems during specific historical periods (Table 1).

Table 1 Triaxial framework and indicators for urban-water interactions

The framework operates across three analytical planes. The X–Y plane reveals periodic adjustments in urban-water interactions within individual settlements during historical evolution. The X–Z plane tracks the formation, superposition, and transformation of dominant water system functions across historical stages. The Y–Z plane analyzes spatial variations in the expression of different urban-water interaction types.

By coupling these axes into a 3D coordinate system, individual case evolutions are integrated into a holistic structural logic at the watershed scale (Fig. 2). This approach facilitates both vertical historical tracing and horizontal multi-case comparison, identifying the differentiated evolutionary paths and patterns of urban-water interactions in the upper Min River under its specific geo-cultural context.

Fig. 2: Triaxial research framework for urban-water interactions.

This figure presents a three-dimensional model integrating the core dimensions of the study: the X-axis represents temporal evolution, the Y-axis denotes spatial hierarchy, and the Z-axis illustrates the functional mechanism. The intersecting planes (X–Y, X–Z, and Y–Z) define the systematic coupling between historical stages, spatial levels, and diverse water functions.

Data collection

This study utilizes four primary data categories: (1) Historical archives and maps, including local gazetteers (Songpan, Wenchuan, and Guanxian), Complete Atlas of Sichuan’s Geography and Strategic Sites (Qing Dynasty), and historical maps of Songpan and Guanxian. Architectural maps of Dujiangyan by Ernst Boerschmann (1908) were also integrated, with Google Maps satellite imagery and POI data used for spatial positioning and pattern calibration. (2) Field survey and spatial data, capturing river scales, urban-water spatial relationships, and bridge landscapes. Overlaying these with historical maps verifies historical narratives and enhances structural identification reliability. (3) Social perception corpora sourced from platforms such as Ctrip, Mafengwo, Dianping, TripAdvisor, and Google Maps. By December 31, 2025, records totaled 1619 for Songpan, 2011 for Taoping, 825 for Shuimo, and 2357 for Guanxian. (4) Semi-structured interview data from 24 residents and tourists, used to cross-validate online findings and analyze perceptual variations in urban-water interactions.

Data analysis methods

To systematically examine urban-water interactions, this study employs an integrated methodology that combines triaxial trajectory reconstruction, contemporary perceptual analysis, and mechanism identification. Initially, the research utilizes textual interpretation to identify key transition nodes on the X-axis (temporal evolution), extracting structural characteristics of hydraulic construction, riverbed changes, and urban morphology. For the Y-axis (spatial hierarchy), spatial elements such as topography, river networks, and fortifications are identified by integrating historical archives, satellite imagery, and field measurements. These findings are then consolidated into a spatiotemporal database for each settlement, transforming complex interactions into visualized spatial units. By subsequently determining the dominant functional mechanisms on the Z-axis, the research reveals the long-term evolutionary trajectories of these urban water systems.

Building upon this structural foundation, user-generated content (UGC) is employed as the primary data source to analyze contemporary perceptions of urban water interactions, a method widely validated in studies of urban imagery and cultural heritage perception^47,48,Unlike traditional surveys, UGC captures spontaneous public narratives and intuitive spatial experiences through a specialized processing workflow involving preprocessing, relevance filtering, social semantic network construction, and dimensional induction^49,50, During the initial stage, raw social media corpora are cleaned by removing advertisements, duplicate texts, and vacuous comments. Using key urban water elements identified in the historical analysis as benchmarks, reviews unrelated to water spaces (e.g., dining and accommodation) are filtered to ensure sample representativeness.

Subsequently, social semantic network construction is performed through word segmentation, frequency statistics, and TF-IDF weighting to build a word co-occurrence matrix. Node degree centrality is calculated to identify core perceptual nodes, revealing public cognitive structures. These high-frequency nodes are then clustered into five core perceptual dimensions based on common semantic features: Water System Skeleton (D1), Daily Life Practices (D2), Functional Governance (D3), Waterfront Landscape (D4), and Cultural Symbols (D5). These dimensions represent the contemporary cognitive projection of the Y and Z axes within the triaxial framework. To eliminate disparities in sample sizes across different cases, a normalized Perceptual Weight ($\,{W}_{{pi}}$) index is introduced, calculated as follows:

The Perceptual Weight ($\,{W}_{{pi}}$) for each dimension $\left(i\in \left\{D1,D2,D3,D4,\left.D5\right\}\right.\right)$ is calculated as follows:

$$\,{W}_{{pi}}=\frac{{\sum }_{j=1}^{n}{{\rm{Degree}}}_{i,j}}{{\sum }_{k=1}^{m}{{\rm{Degree}}}_{k}}$$

(1)

Where ${{\rm{Degree}}}_{i,j}$ represents the degree centrality of the$\,j$-th node belonging to dimension $i$, $n$ is the total number of nodes included in dimension $i$, and $\sum {{\rm{Degree}}}_{k}$ is the sum of degree centrality for all nodes in the settlement’s social semantic network. By calculating the proportion of the total degree centrality for nodes within each dimension, a perceptual bubble matrix is generated to visualize the cognitive weight of each dimension.

Finally, the study identifies spatiotemporal evolutionary mechanisms by overlaying historical X–Y–Z trajectories with contemporary perception matrices. This process reveals shifts and deviations between historical physical structures and contemporary social cognition. By integrating semi-structured interviews, the research identifies practical contradictions through cross-temporal, multi-perspective comparison. This logic facilitates the identification of evolutionary divergences among cases and allows for the analysis of patterns and underlying mechanisms of urban-water interactions at the watershed scale, establishing a foundation for formulating optimized development paths.

Results

Songpan Ancient Town: urban-water evolutionary trajectory

The long-term urban-water interaction in Songpan is rooted in a deep history of defense-oriented natural attachment, beginning in 316 BCE when the Qin Dynasty established Jiandi County north of the current town. This strategic importance was solidified in 618 CE with the founding of Songzhou by the Tang Dynasty, subsequently becoming a site of significant military conflict with the Tubo regime in 636 CE. Due to its pivotal geographical location, Songpan evolved as a long-term military stronghold in western Sichuan and a crucial hub for the Tea-Horse Trade, shaping an evolutionary trajectory centered on locational attachment and defensive requirements. During this early stage, water systems were integrated into the settlement primarily in their natural forms; externally, highland valleys and water source nodes functioned as natural barriers and regional corridors for defense and trade, while internally, water remained unsystematically integrated, with natural flows primarily sustaining daily life and frontier security.

This initial stage of natural attachment evolved into a sophisticated defense-trade-oriented structural coupling during the Ming and Qing Dynasties, as the state systematically strengthened Songpan’s military and administrative status. Following its renaming in 1379, continuous fortification and outer-city expansion established a distinctive pentagonal defensive pattern that closely integrated the mountainous terrain with the water systems. This shift toward engineering-led spatial organization meant that urban-water interactions were now consciously incorporated into the urban fabric. Externally, the Min River headwater valley and the Song-Mao Ancient Road maintained a stable regional corridor, consolidating Songpan’s role within multi-ethnic trade networks. Internally, channels were artificially diverted for both defense and fire protection, creating a prominent north-south spatial axis through critical nodes like the Gusong Bridge. Concurrently, water spaces transitioned from purely functional coupling to a deeper structural-cultural composite; traditional landscapes—such as “Moon Reflection in the Dragon Pool”—began to integrate hydraulic infrastructure with cultural imagery, endowing the water system with symbolic and aesthetic significance (Fig. 3).

Fig. 3: Analysis of urban-water interactions in Songpan (Qing Dynasty).

a Water network and urban layout based on the Songpan Jilue (Tongzhi Period, Qing Dynasty); b Map of Songpan Ancient Town from the Complete Atlas of Sichuan’s Geography and Strategic Sites (Qing Dynasty, Collection of Sichuan University Library). The solid blue lines represent the Min River, while solid brown lines indicate the city walls and fortifications.

In the modern era, although Songpan’s defensive functions have significantly weakened and fortifications have deteriorated, the interaction logic has transitioned toward conservation-oriented functional restructuring and memory anchoring. The shift toward historical conservation and tourism in the late 20th century allowed the foundational Ming–Qing urban-water framework to persist as a stable layout. Within this framework, water systems underwent a functional translation, evolving from utilitarian defense and supply infrastructures into core supportive elements for landscape experience and historical cognition. Externally, the upper Min River now serves as a vital landscape and accessibility resource within a regional tourism network connecting Jiuzhaigou and Huanglong Scenic Areas, reinforcing Songpan’s identity as a plateau gateway to Western Sichuan. Internally, the Min River maintains its historical path through the town, where the restored 50-meter-long Gusong Bridge continues to function as a central public node, anchoring the collective memory and daily practices of both tourists and residents within the historic urban-water environment (Fig. 4).

Fig. 4: Analysis of urban-water interactions in Songpan (Contemporary).

a North Gate; b Overlooking from West Hill; c Min River within the town; d Tongyuan Bridge; e Gusong Bridge; f Yingyue Bridge. In the central map, the solid blue line indicates the Min River, solid brown lines represent the existing street network, and dark red lines delineate the historical fortification boundaries. Red circular symbols mark the locations of key landscape nodes and bridge structures shown in (a–f).

Taoping Qiang Village: urban-water evolutionary trajectory

Taoping is located in the Zagunao River valley ethnic corridor within the upper Min River basin. Legend holds that Qiang ancestors established the settlement in this rugged terrain to seek refuge around 111 BCE. Historically, the settlement evolved with defense and survival as its core, resulting in urban-water interactions characterized by a highly cohesive, multi-functional, and integrated morphology. During this long-term period of defense-survival-oriented cohesive growth, the village externally leveraged the Zagunao River and alpine meltwater to form a “mountain-backed and water-facing” natural defense pattern. Here, the water system provided a stable supply while reinforcing external connectivity control through valley barriers and rope bridges. Internally, alpine springs were diverted into the village, utilizing topographical elevation for cascading distribution through four water mills into a comprehensive network. This multi-functional system simultaneously addressed drinking water, fire protection, micro-climate regulation, irrigation, flood resilience, and wartime security, with channels integrated into roads and building gaps in a sophisticated interplay of surface and underground structures⁵¹.

This historical foundation underwent transformation starting in the late 20th century, as Taoping transitioned from defense-oriented survival to ethnic living, with tourism becoming integrated after the 1990s. A pivotal shift occurred following the 2008 earthquake; to facilitate the long-term protection of the traditional stone settlement, a portion of the residents was relocated from the original site. This led to the construction of a New Village by the river at the base of the mountain slope. This strategic differentiation established a “dual-town” structure: the river-aligned New Village now primarily hosts modern residence and tourism services, while the Old Village focuses on heritage conservation and cultural exhibition. Consequently, urban-water interactions evolved into a state of “heterotopic symbiosis,” spatially separating new developments while maintaining the Old Village’s stable historical water system.

Externally, a 1-km tributary serves as a spatial link between the old and new villages, transforming the river into a primary landscape and cultural carrier beyond its original utility. Internally, the Old Village’s water network largely preserves its historical morphology. The underground and open channel systems remain clearly identifiable (Fig. 5). Channels measure approximately 0.6 m in width and 0.9 m in height. Street scales are compact, with widths ranging from 2–3 m and narrowing to 1 m. Most pathways maintain a distance-to-height (D/H) ratio below 1, providing a key index for understanding Qiang spatial organization. Although the wartime defensive role has diminished, the water system remains central to residents’ daily lives. In the contemporary era, it increasingly facilitates exhibition and cognitive functions.

Fig. 5: Analysis of urban-water interactions in Taoping (Contemporary).

a Old Village; b New Village; c Water Mill; d Underground Water Channel; e Water-lifting device; f Open Water Channel. In the central map, the thickest dark blue line represents the Zagunao River, solid brown lines indicate the road network, dark blue lines represent the open water network, and light blue lines represent the underground water network. The water system structure is adapted from ref. ⁵¹.

Shuimo Ancient Town: urban-water evolutionary trajectory

Shuimo’s history dates back to the Shang and Zhou periods, serving as a long-term multi-ethnic settlement for Tibetan, Qiang, Hui, and Han peoples. Locals regard the Shouxi River as a life-nourishing source, earning the region the title “Home of Longevity”. Urban-water interactions were characterized by a low-intervention mode focused on natural dependence. Water systems primarily supported daily domestic needs and the courier station of the Tea-Horse Trade. Externally, the Shouxi River provided a stable natural environment and basic accessibility. Shuimo functioned as a vital node on the ancient trade route, with sites like Feima Village reflecting its role in regional exchange. Internally, the town structure centered on Chanshou Old Street along the riverbank. Ming and Qing architectural remains—such as Wannian Pavilion and Ziku Tower—together with ancient water mills, formed a spatial morphology dominated by agriculture and daily life.

After the mid-20th century, Shuimo shifted toward industrialization. High-energy and high-pollution industries entered the valley, significantly impacting the traditional settlement pattern. Traditional features were largely confined to Chanshou Old Street. Urban-water interactions shifted from life support to discharge hosting. Consequently, the water system retreated from the core of spatial organization, resulting in functional weakening and broken connectivity. Externally, industrial enterprises discharged wastewater directly into the river through private facilities, weakening the link between water and town functions. Internally, river-based characteristics of the traditional living space gradually eroded.

The 2008 earthquake caused structural damage to the town. Post-disaster reconstruction phased out industry in favor of tourism, culture, and education. The Shouxi River–Shouxi Lake system was used to reshape the town into a landscape settlement. Urban-water interactions transitioned from passive hosting to active organization. Water system became the skeleton for spatial structure and cultural expression. Externally, the river and storage bodies were integrated into a framework balancing flood control and landscape. The town now extends 1.8 km along the riverbank. Inspired by the Dujiangyan irrigation system, the plan adopts an “outer river–inner lake” structure: the outer river manages runoff and flood control, while Shouxi Lake serves as an ecological buffer and landscape core^52,53, Internally, the 1300-m Chanshou Old Street and Shuimo Qiang City unfold along the water. Public nodes like Chunfeng Pavilion and Xiqiang Hui Area, combined with pedestrian bridge systems, enhance spatial continuity and water affinity. Notably, the 87-meter-long Chancheng Bridge, a wooden corridor structure, serves as a regional symbolic landmark on the water (Fig. 6).

Fig. 6: Analysis of urban-water interactions in Shuimo (Contemporary).

a Chanshou Old Street; b Chunfeng Pavilion; c Wannian Stage; d Shuimo Qiang Town; e Chancheng Bridge; f Shouxi River. In the central spatial map, the thickest dark blue line indicates the Shouxi River and Shouxi Lake. The solid brown lines represent the current road and street network. Dark red circles and gold circular symbols mark the locations of key architectural nodes, and bridges shown in (a–f).

Guanxian Ancient Town: urban-water evolutionary trajectory

The construction of the Dujiangyan irrigation system during the Qin Dynasty enabled dam-less water diversion through three pivotal structures: Yuzui Weir, Feisha Weir, and Baopingkou. At Yuzui Weir, the Min River bifurcates into the Inner and Outer Rivers, with the former channeled into the Guanxian via Baopingkou. While the town prototype emerged during the Tang and Song Dynasties, the Ming and Qing eras saw the refinement of city walls and gates according to the local topography and water flow. Urban-water interactions were characterized by high synergy driven by hydraulic engineering, with water systems deeply integrated into urban operations and spatial organization. Externally, Guanxian was strategically positioned along the inner bank of the Inner River. The river, combined with the Yulei Mountain barrier to the west, formed a natural defensive perimeter and a visual corridor that facilitated hydraulic management. As the starting point of the Song-Mao Ancient Road, the Min River system and terrestrial routes jointly supported regional trade. Internally, the street layout conformed strictly to the water network. The Yangliu River, which served as a defensive moat in the Tang and Song periods, evolved into a comprehensive irrigation and domestic network by the Ming and Qing Dynasties. Its intersections with streets—marked by the Guang’an, Guanyin, and Jiangjun bridges—transformed the water system into an active axis for daily life and commerce. Furthermore, the Water Conservancy Office in the town center formed a spatial axis with sacrificial sites like Erwang Temple and Fulong Guan. This created a composite system integrating administration, ritual, and production. Finally, the Puji Bridge (South Bridge) across the Inner River became a vital cross-water node, reinforcing the spatial connection between the town and the Min River (Fig. 7).

Fig. 7: Analysis of urban-water interactions in Guanxian (Qing Dynasty).

a Urban-water spatial pattern based on the Guanxian Zhi (Qianlong Period, Qing Dynasty); b Regional spatial pattern surveyed by Ernst Boerschmann (1908); c Detailed analysis of urban-water interactions, showing the distribution of bridges, temples, and the Water Conservancy Office. Thick dark blue lines represent the primary water system of the Dujiangyan irrigation system, and thin blue lines indicate the secondary urban water network. Thick green dashed lines represent the primary spatial axes. Dark red circles mark the locations of key architectural nodes and bridges.

Since the modern era, Guanxian has undergone city wall demolition and functional transformation due to urban expansion and seismic impacts. the Dujiangyan irrigation system remains operational, fostering urban-water interactions characterized by “living heritage”. The water system continues to serve as a vital support for the urban spatial framework and local life. Externally, rooted in the Taoist philosophy of following nature, the region is recognized as a cultural arena where water forms the basis for spatial narratives. The ancient town extends approximately 1.1 km along the riverbank. During normal water levels, the channel is approximately 300 m wide at the Yuzui bifurcation, narrowing to 20 m at the Baopingkou inlet before widening again downstream. This significant variation in hydraulic scale reflects the continuity of the “diversion according to natural flow” engineering concept, providing a spatial clue for visitors to understand hydraulic culture. Internally, the water management system remains embedded in daily life and tourism through accessible water networks and street spaces. The Yangliu River—an Inner River tributary—measures roughly 5 m in width and 400 m in length. Along its core sections, the distance-to-height (D/H) ratio of waterfront streets typically ranges from 1:1 to 1:1.5, a scale that supports pedestrian movement, social lingering, and commercial activities. Cross-water nodes like the South Bridge have been rebuilt several times; the current structure, completed in 1979, is 54 m long and 12 m wide. It serves as a prominent social venue, integrating transit functions with scenic water viewing (Fig. 8).

Fig. 8: Analysis of urban-water interactions in Guanxian (Contemporary).

a Xuanhua Gate; b Yangliu River Street; c South Bridge; d “Blue Tears” water landscape; e View from the bridge. The large-scale spatial map on the left shows the primary hydraulic components. In the central detailed map, Thick dark blue lines represent the primary water system of the Dujiangyan irrigation system, and thin blue lines indicate the secondary urban water network. Solid brown lines represent the contemporary street network. Dark red circles mark the locations of key bridges.

Contemporary perceptions of urban-water interactions

Gephi-generated semantic networks visualize the cognitive structures of urban-water interactions (Fig. 9). Node size denotes Degree Centrality (element importance), while line thickness represents Co-occurrence Frequency (association strength). Generally, tourists prioritize landscape imagery and historical narratives, whereas residents emphasize daily utility and survival. These divergent perceptions directly reflect each settlement’s unique water culture and spatial logic. In Songpan, the semantic network is macro-narrative-driven, with “source,” “frontier fortress,” and “Princess Wencheng” as core nodes. This reflects how frontier defense history guides tourist perception, positioning the Min River as a spatial skeleton for historical memory; residents, however, emphasize its practical role in markets and social interaction. In Taoping, the semantic network displays features of embedded penetration regarding the water system. Nodes such as “underground,” “water network,” “watchtower,” and “natural air conditioning” point to tangible iconic landscapes, framing water as deeply embedded in settlement and defense structures. Residents identify deeper spatial layers where functional attributes remain in active practice. In Shuimo, “post-disaster reconstruction” and the “Shouxia River” form the visual axis for tourists, though association paths are singular and longevity culture has not yet stabilized into daily practice. Residents highlight the river’s role in economic transition while noting environmental pressures from tourism. In Guanxian, tourists clearly perceive the intricate interweaving of the “Dujiangyan,” “Yangliu River” with the town, revealing the long-term symbiotic resilience between large-scale engineering and town space. Here, the engineering worship of tourists and the life reliance of residents converge within the spatial order.

Fig. 9: Semantic network of urban-water interactions across the four settlements.

This figure illustrates the cognitive structures and key thematic clusters associated with urban-water interactions based on semantic analysis. a Songpan Ancient Town; b Taoping Qiang Village; c Shuimo Ancient Town; d Guanxian Ancient Town.

The bubble matrix diagram reveals the distribution of perceptual weights across dimensions, reflecting the effectiveness and deviation of historical mechanisms during the modern transformation (Fig. 10). Guanxian exhibits a relatively balanced perception structure; beyond Cultural Symbols (D5), both Daily Life Practices (D2) and Waterfront Landscape (D4) maintain high weights. This proves that the Dujiangyan water system has transitioned from engineering hydraulics to living landscapes, achieving synergy between practice and aesthetics. Conversely, Songpan, Taoping, and Shuimo show high weights in Cultural Symbols (D5), reflecting an “overlay effect” where macro-narratives dominate public perception. Notably, Taoping’s weight in Functional Governance (D3) far exceeds other cases, revealing its underground water network as living heritage not yet eclipsed by consumption-oriented imagery.

Fig. 10: Comparative perceptual weights of urban-water interactions across the four settlements.

The horizontal axis represents the cognitive dimensions: D1 (Water System Skeleton), D2 (Daily Life Practices), D3 (Functional Governance), D4 (Waterfront Landscape), and D5 (Cultural Symbols). The vertical axis lists the four representative settlements: Songpan, Taoping, Shuimo, and Guanxian. The bubble size indicates the relative weight of each dimension within a specific settlement, while the color gradient on the right represents the perception intensity.

Field observations and interviews indicate that these deviations reveal problems triggered by modern intervention, primarily the tension between traditional water culture and modern consumption logic. In Songpan, the dominance of Cultural Symbols (D5) fails to translate into high-quality spatial experiences; excessive commercial activity at core nodes has replaced the solemnity of frontier history with overcrowding. In Shuimo, the contradiction lies in narrative disembedding, where promoted longevity culture lacks a deep connection with Daily Life Practices (D2), making it difficult to foster community identity. In Guanxian, excessive vendors along the Yangliu River negatively impact the perception of Waterfront Landscape (D4). Furthermore, modern aesthetic interventions—like the “Blue Tears” lighting—activate the night economy but replace the natural imagery of the Min River with standardized technology, risking the dilution of the regional culture. Taoping faces the issue of delayed exhibition, where the transmission of the Water System Skeleton (D1) and its meaning to tourists remains insufficient. Concurrently, as residents relocate, water-related public activities in the Old Village—core to Daily Life Practices (D2)—are at risk of fading.

Comprehensive analysis of regional urban–water interactions under the triaxial framework

Based on the previous analysis of the evolution of urban-water interactions in the four settlements, this study summarizes the triaxial indicator results (Table 2). They show distinct evolutionary pathways, and their spatial organization and dominant mechanisms vary in differentiated combinations across stages.

Table 2 Results of the triaxial analysis of urban-water interactions across the four settlements

In the X–Y plane, the X-axis drives scale transitions in the Y-axis through evolving societal requirements. Changes in social productivity and technological levels have transformed human capacity to utilize the spatial hierarchy of the Y-axis. The staged evolution of the X-axis necessitates the synchronous adaptation of the water system’s scale, depth, and structural status within urban spaces. This process generally evolves from “macro-scale natural dependency” to “micro-scale structural coupling,” culminating in contemporary “multi-scale functional reconstruction”. In early stages, water systems primarily functioned at the regional level, serving as site selection criteria, defensive barriers, and survival safeguards, with rivers defining urban boundaries as natural limits. As history progressed, settlements internalized water systems into internal structural skeletons through artificial diversions, bridge construction, and surface/underground water networks. In the modern era, external forces—such as industrialization, post-disaster reconstruction, and tourism—have triggered multi-dimensional functional translations. The external spatial level transitioned from traditional transport and defense carriers to ecological and landscape experience networks, while the internal level integrated cultural symbols and historical memory into its existing production support functions. The progression of the X-axis continuously reconfigures the intervention depth and structural status of the Y-axis spatial hierarchy.

In the X–Z plane, evolving societal needs along the X-axis drive the reconfiguration and overlay of dominant mechanisms on the Z-axis. Urban-water interactions in the upper Min River have progressed from early single-function dominance (defense and survival) to multi-functional complexity, and finally to contemporary functional translation and imagery reconstruction. This evolution reflects a fundamental transition from survival dependency, where water systems acted as natural barriers, to deep structural coupling that integrates production, trade, and aesthetics into a composite framework. Contemporary dominant mechanisms follow four distinct trajectories: Songpan has shifted from defensive functions toward historical narratives and landscape perception; Taoping maintains an integrated functional grid as a heritage carrier through a “new-old separation” strategy; Shuimo achieved a leapfrog transition from an industrial discharge carrier to ecological wellness; and Guanxian demonstrates stable, synergistic continuity between its Dujiangyan hydraulic heritage and urban life.

In the Y–Z plane, the coupling between Y-axis and Z-axis represents a staged functional adaptation driven by the X-axis. By altering socio-economic constraints, the X-axis dictates that specific mechanisms seek optimal expression at corresponding spatial scales—shifting from macro-boundary security in early defense stages to micro-street aesthetics in the contemporary tourism era. Externally, each case establishes a unique narrative: Songpan frames the mainstream as a historical frontier gateway, while Taoping maintains a tributary terrace-barrier defensive pattern. Shuimo has transitioned into an ecological window via its “outer river and inner lake” design, whereas Guanxian reinforces the macro-hub imagery of its Dujiangyan hydraulic culture. Internally, spatial organization logic diverges based on the depth of mechanism penetration: Songpan utilizes water as a narrative backdrop for historical districts; Taoping achieves absolute functional penetration through the deep integration of water networks and defensive architecture; Shuimo centers on waterfront landscape consumption along its lakefront visual axis; and Guanxian demonstrates high synergy between living and engineering systems as the canal network integrates into the street fabric.

Regional evolutionary characteristics and mechanisms

The evolution of urban-water interactions in the upper Min River is not a sequence of isolated stages but a differentiated expression within a unified hydrological framework. The longitudinal axis formed by the mainstream and tributaries provides more than a natural backdrop; it coordinates a synergistic division of labor through the “source valley—tributary terrace—mountain outlet plain” gradient. This logic maintains structural continuity longitudinally while generating functional differentiation laterally based on geographical, cultural, and transport factors. Songpan, as a source gateway, defines the macro-boundary for defense and trade; Guanxian, as a hub at the mountain outlet, utilizes the Dujiangyan system for watershed-scale water regulation and cultural integration; meanwhile, Taoping and Shuimo exhibit livelihood resilience and catastrophic reconstruction at tributary ends. Consequently, urban-water interactions evolve into a watershed-level synergy based on hydrological gradients and functional complementarity, anchoring the evolutionary logic within the geographical substrate.

The dynamic evolution of these interactions is driven by three coupled mechanisms: natural constraints, trade/transport networks, and institutional/cultural embedding. Natural constraints provide the foundational impetus during the generative stage. High-altitude drops and closed valley topographies establish water systems as structural boundaries of spatial order, locking in the “water-oriented” genetic code of settlements. Trade and transport networks promote watershed-scale connectivity. The Song-Mao Ancient Road along the Min River valley connected Guanxian to Songpan, transforming water from a survival resource into a medium for trade and ethnic exchange. This repositioned each settlement’s hierarchical status within the regional network. During the modern transformation stage, institutional and cultural embedding mechanisms gradually become dominant. Hydraulic engineering systems, community water network governance, and planning regulations integrate water resources into long-term operational structures, while cultural narratives endow water with symbolic and identity significance, facilitating functional translation and value reconstruction. Consequently, the dynamic structure of urban-water interactions exhibits a temporal transition of weights: natural constraints establish the structural foundation, connectivity enhancement reshapes network relationships, and institutional/cultural embedding stabilizes or reconstructs the meaning system. The evolution of the X-axis continuously deconstructs and reconfigures the influence weights among these three drivers.

Within the unified hydrological framework, differentiated interaction paths result from the X-axis acting as a dynamic variable that controls the specific coupling of the Y-axis and Z-axis. This shapes a mountain watershed pattern that maintains global continuity despite internal differentiation. Songpan achieves functional continuity by transitioning from a military barrier to a historical narrative through cultural translation; Taoping maintains morphological resilience via deep micro-water net integration; Shuimo exhibits catastrophic restructuring under external disturbances; and Guanxian represents long-term synergy based on large-scale engineering. In this paradigm, the X-axis is no longer restricted to historical periods but marks key nodes of structural change in interaction logic. The Y-axis and Z-axis serve as generalized dimensions characterizing the spatial scale and functional attributes influenced by water resources.

Discussion

This study takes four historical settlements in the upper Min River basin—Songpan, Taoping, Shuimo, and Guanxian—as empirical objects. Relying on the X–Y–Z triaxial framework (temporal evolution–spatial hierarchy–functional mechanism), the research reconstructs interaction trajectories, maps contemporary perceptual characteristics, and validates spatiotemporal synergistic logic. It systematically reveals the differentiation characteristics, evolutionary mechanisms, and contemporary developmental challenges of urban-water interactions in mountain watersheds while proposing watershed-scale governance paths and extracting a theoretical paradigm with cross-regional transferability. The specific conclusions are as follows:

First, urban-water interactions in the upper Min River exhibit differentiated evolutionary characteristics within a continuous watershed structure. The mainstream and tributaries of the Min River constitute a hydrological skeleton across the region, forming a gradient distribution pattern from upstream valleys and tributary terraces to mountain outlet plains. Although the four settlements possess different locational conditions and developmental trajectories, they have formed a division of nodes and functional complementarity within a unified hydrological framework: Songpan features an imagery continuity transitioning from frontier defense to historical narrative; Taoping adopts a “new-old separation” model to protect the structural resilience of ethnic defense and symbiotic living; Shuimo exhibits catastrophic restructuring under external shocks; and Guanxian demonstrates long-term synergy supported by large-scale hydraulic engineering. Regional differentiation is essentially the result of the differentiated coupling of X–Y–Z variables across various spatial scales and mechanism combinations.

Second, contemporary urban-water interactions are characterized by differences in subjective perception and insufficient expression of water culture. Semantic analysis and interviews show that tourists prioritize landscape and historical narratives, whereas residents place greater importance on daily functional utility. In Songpan, excessive commercial concentration has weakened the heritage experience; in Shuimo, longevity cultural symbols are not closely connected to daily life; in Guanxian, while the “Blue Tears” lighting has popularized night tours, it also risks diluting the natural artistic conception of the Min River; and Taoping lacks in-depth displays of its water culture. These issues collectively reflect an insufficient connection between historical urban-water structures and contemporary perception or utilization.

Third, the core of the evolution of urban-water interactions is the staged reconfiguration of functional mechanisms rather than simple replacement. Urban-water interaction is jointly driven by three mechanisms: natural constraints, trade/transport networks, and institutional/cultural embedding. Natural constraints established the early spatial foundation; trade and transport networks shaped the hierarchical relationships and functional division among settlements; and institutional/cultural embedding stabilized the social value of water through hydraulic engineering and governance systems. The evolutionary differences among the four settlements stem not from different types, but from the temporal weight shifts and divergent action paths of these three drivers during their evolution.

At the theoretical level, the triaxial Framework constructed in this study integrates temporal evolution, spatial hierarchy, and functional mechanism into a unified analytical structure. It explains the regional differentiation and evolutionary logic of urban-water interactions in the upper Min River, providing a transferable analytical tool for the study of mountain watershed systems. This framework features stable core logic and adjustable key parameters, making it capable of identifying long-term evolutionary trajectories and resilience characteristics in combination with the geographical and socio-economic backgrounds of different mountain watersheds. It is applicable to comparative studies of global mountain riverine cultural landscapes. Furthermore, by using mountain watersheds in the ethnic regions of Southwest China as cases, this study reveals a traditional interaction model integrating engineering, governance, and culture. It provides an empirical and theoretical reference with “Oriental” characteristics for the international academic community to understand evolutionary mechanisms under high natural constraints and multi-ethnic symbiosis.

At the practical level, urban-water landscape construction and governance paths should be coordinated under a holistic watershed framework. First, an integrated narrative system for Upper Min River Water Culture should be constructed to create a watershed-scale “Urban-Water Cultural Heritage Corridor”. Relying on the trade and transport network of the Song-Mao Ancient Road, waterfront cultural nodes should be linked to reinforce the symbiotic relationship between the ancient road and the water system. Settlement-specific positioning should be clarified to avoid homogenization: Songpan should strengthen frontier trade culture, highlighting the social attributes of waterfront nodes; Taoping Qiang Village should accentuate the wisdom of defensive settlements and underground water networks; Shuimo should focus on post-disaster reconstruction culture, integrating “Longevity” heritage into daily life through elder-friendly waterfronts and community social programs; and Guanxian should emphasize the contemporary expression of the Dujiangyan water governance spirit. Second, implement layered protection and functional regulation based on differentiated positioning. Strictly protect Water System Skeletons (D1) and core nodes while guiding high-intensity tourism and commerce to peripheral areas. This will resolve practical issues such as commercial clustering in Songpan and symbolic landscape fragmentation in Shuimo, ensuring that the integrity of Taoping’s underground water system is maintained. Third, establish a cross-settlement watershed coordination mechanism. Through unified branding, shared interpretation systems, and upstream-downstream responsibility sharing, the synergy of ecology, hydraulics, and cultural inheritance can be promoted, forming a cooperative network among the settlements.

Although this study has made progress in explaining the characteristics and mechanisms of regional urban-water interaction evolution, several limitations remain. First, the research objects are concentrated in the upper Min River, and the universality of the theoretical propositions has not yet been verified through cross-watershed comparisons. Future comparative studies can be carried out in mountain watersheds with different geomorphic types. Second, the judgment of driver contributions is mainly based on historical literature and structural deduction. Future research could introduce spatial econometrics or network analysis to test hierarchical changes and mechanism impacts quantitatively. Third, limited by the historical material conditions of ethnic mountain areas, there is a lack of archaeological excavation reports and early spatial measurement data, making it difficult to achieve full-period spatial trajectory tracking. Future research can rely on newly discovered archaeological materials and more systematic historical spatial verification to further improve the integrity and precision of evolutionary trajectories.