Data-Driven Evaluation of Structural and Functional Differences in the Karst Water System of Western Hubei, China

Karst groundwater is an important freshwater resource, but its heterogeneous structure and multi-media architecture complicate water-resource management. In western Hubei, China, this study established a regional-scale dynamic karst water database and developed a 43-indicator evaluation framework to characterize karst system structure and function. The indicator system integrates statistical features, time-frequency domain parameters, recession process characteristics, and multifractal metrics. To avoid bias caused by unavailable physicochemical indicators in surface-water records, multivariate analysis was conducted using separated matrices: 32 shared discharge and hydrological-process indicators for surface-water stations and the complete 43-indicator matrix for groundwater systems. Principal Component Analysis (PCA) and Ward's hierarchical clustering were used for functional classification. The results show that recession coefficients, the fitted hydrograph parameter μ, the VESPA index, and the Barnes-derived regulation index IB contributed strongly to the PCA structure of the groundwater-system matrix. Groundwater systems were further classified into eight functional subtypes, including karst-spring, borehole-groundwater, and intermittent karst-system regimes. Karst water systems in Western Hubei exhibit climate-related differentiation in karst development and systematic functional variations across heterogeneous aquifer structures. These findings provide a scientific basis for functional classification of karst systems in Western Hubei and offer a transferable perspective for functional analysis of karst aquifer systems in other regions.