Wei Huang

Agricultural non-point source pollution (ANPSP) presents a critical threat to water security in the upper reaches of the Yangtze River Economic Belt (UYREB). Traditional export coefficient models (ECMs) often fail to capture the spatially heterogeneous processes of pollutant transport and ecological attenuation in complex mountainous terrains. Here, we constructed an improved ANPSP risk assessment framework by integrating ecosystem regulating functions (water yield, soil retention, and habitat quality) into the ECM. By coupling the Patch-generating Land Use Simulation (PLUS) model and Geographically and Temporally Weighted Regression (GTWR), we evaluated the spatiotemporal risk evolution from 2000 to 2020, projected risk configurations for 2030 under three scenarios (Natural Development, ND; Cropland Protection, CP; Ecological Protection, EP), and identified the spatiotemporal non-stationary drivers. The key findings are: (1) Independent validation using observed river water-quality data further demonstrated that the modeled risk index was significantly positively correlated with contemporaneous TN and TP concentrations (Pearson’s r = 0.673, p < 0.05), supporting its ability to identify the spatial distribution of relative ANPSP risk while accounting for regional differences in ecosystem regulation. (2) Historically, the integrated ANPSP risk index exhibited a “rise-then-decline” pattern, peaking in 2010 with extreme risk areas covering 12.1% of the region. Under the 2030 EP scenario, high-risk areas contract by 15.3% compared to 2020, demonstrating superior mitigation compared to ND and CP scenarios. (3) GTWR reveals that cropland proportion is the dominant positive spatial associate (0.800 − 0.852), while GDP shows a negative spatial association in economically developed sub-regions, reflecting potential environmental management co-benefits rather than direct causation. This framework provides an effective relative risk assessment tool for mountainous watersheds, highlighting that land use optimization under ecological regulation may contribute to reducing potential pollutant transport risk.

Focusing on contrasting climate and land use pathways, this analysis explores the changing trajectories of water conservation function over time. An integrated framework combining the PLUS and InVEST models with Spearman’s correlation analysis and geographically weighted regression (GWR) was applied to examine the spatiotemporal heterogeneity and underlying drivers of water conservation function in the Chengdu–Chongqing Economic Zone during the period 2000–2020. Thus, it further predicted the evolution trend under two scenarios, namely SSP1-1.9 (Sustainable Development Pathway) and SSP2-4.5 (Medium Development Pathway), for the period 2030–2050. The findings reveal that: (1) Between 2000 and 2020, the spatial distribution of water conservation function shifted markedly, with low-value areas contracting and high-value zones expanding, alongside a progressive transition toward a predominantly medium-to-high functional structure. (2) In mountainous and hilly transition zones, precipitation (PRE) and forest cover proportion (FCP) exhibited notably positive effects, whereas evapotranspiration (PET) exerted a negative effect. In contrast, in plain and urbanized areas, built-up land proportion (BUP), population density (POP), and gross domestic product density (GDP) demonstrated pronounced negative effects. (3) Future simulations indicate that under the sustainable development pathway (SSP1-1.9), the combined area of high and extreme functional zones will recover by 2050, whereas under the moderate development pathway (SSP2-4.5), such extreme functional zones will be nearly eliminated. These results underscore the substantial impact of development pathways on regional water security and sustainability.

Identifying the evolutionary trends of water conservation functions and their climatic impacts under future scenarios is crucial for enhancing regional ecological security. This study integrates the PLUS and InVEST models with projected land use and meteorological data to analyze water conservation patterns in the Chengdu–Chongqing Economic Zone during 2030–2050 under natural development (ND) and ecological protection (EP) scenarios. Key findings include the following: (1) during 2000–2020, low-value areas decreased from 60% to 40%, while high-value zones expanded from 27.32% to 40.35%; (2) both the ND and EP scenarios project lower water conservation volumes compared to 2020 levels; (3) under the ND scenario, the combined proportion of high and extreme importance zones fluctuates at 0.51% (2030), 0.11% (2040), and 3.97% (2050); (4) spatial heterogeneity shows high-value clusters concentrated in Chengdu’s urban core and northeastern regions, contrasting with midland low-value areas; (5) the SSP1-1.9 climate scenario yields higher water conservation capacity with stronger spatial aggregation compared to SSP2-4.5. This integrated modeling of PLUS and InVEST provides scientific support for regional ecological security and sustainable development strategies.