A Novel Integrated Vector-Raster Model for Multi-Process Hydrological Simulation in Heterogeneous Landscapes

Traditional raster-based distributed hydrological models often face challenges in representing the geometric complexity of landscape features, leading to fragmented boundaries and oversimplified topological relationships. To address these limitations, this study proposes a novel Integrated Vector-Raster Hydrological Model (VeRHyM). By employing a flexible spatial discretization scheme, the VeRHyM utilizes vector polygons to represent irregular land features (e.g., glaciers, reservoirs, agricultural fields) and vector polylines for river networks, while maintaining raster data for continuous field variables (e.g., precipitation, topography) and describing internal heterogeneity within individual land features.

Enabled by its hybrid data structure, the proposed model offers several key advantages over conventional grid-based approaches: (1) Geometric Integrity: It preserves the precise boundaries of land features, preventing the fragmentation of physical objects into disjointed pixels; (2) Topological Accuracy: It provides a more rigorous description of river networks, water conveyance structures, and the spatial connectivity between different land features; and (3) Multi-scale Coupling: It facilitates the seamless coupling of hydrological processes across varying spatial scales, from individual glaciers to the entire watershed. This also enables precise coupling between distinct physical models (e.g., glacier runoff and crop water stress) at their native spatial scales.

We applied the VeRHyM to the Urumqi River Basin in Tianshan, China, a typical complex watershed characterized by diverse landscapes ranging from high-altitude glaciers and alpine vegetation to arid piedmont zones containing oases, cropland, and urban settlements. The model performance was rigorously validated using multi-source data: River discharge was calibrated against observations from the Tianshan No. 1 Glacier station and the mountain outlet hydrological station; simulated evapotranspiration was compared with remote sensing products; and human water consumption estimates were verified against regional statistical records. Results demonstrate that the VeRHyM captures the spatiotemporal variability of the water cycle effectively in this complex terrain. The successful application suggests that the vector-raster integration strategy significantly improves the representation of heterogeneous landscapes and provides a robust tool for integrated water resources management in arid regions.