ObjectiveHydraulic control structures such as weirs, culverts, pump stations, and sluice gates play a crucial role in regulating river flow and mitigating flood risks. However, simulating these structures accurately in 1D river network models faces challenges including diverse structure types, complex flow conditions, and abrupt hydraulic parameter changes near the structures. Existing numerical methods often involve complex iterations or struggle to capture dynamic regulation processes, limiting the reliability of flood simulation results. This study aims to develop a straightforward and efficient simulation algorithm to address these issues, enabling accurate and stable modeling of various hydraulic control structures while ensuring computational efficiency and adaptability to real-world complex river networks.MethodsThe algorithm was developed based on the source term method and integrated into a 1D river network hydrodynamic model solved using the Godunov scheme. The 1D shallow water equations (Saint-Venant equations) were adopted as the control equations, with hydraulic control structures treated as source terms to account for their flow regulation effects. A novel artificial area method was proposed for junction processing, where each junction was modeled as a "reservoir" with a fixed base area calculated using adjacent river reach parameters. This eliminated the need for iterative calculations, simplifying junction water level updates through mass conservation equations. For specific structures: Weirs: Flow was computed using the weir flow formula incorporating discharge coefficient, weir crest width, and head over weir. Culverts: Different formulas were applied for free-flow and submerged flow conditions, considering culvert shape, height, and upstream-downstream head difference. Pump stations: Two processing modes were implemented: boundary adjustment based on pump curves for internal pump stations, and direct flow addition/subtraction for stations connected to external water bodies. Sluice gates: A virtual gate calculation zone was established between closed boundaries. Dynamic regulation was modeled through two control modes: manual operation with predefined opening sequences and automatic regulation based on upstream flow/water level. Flow through gates was determined by orifice flow (when K(t)/h < 0.65) or weir flow (when K(t)/h > 0.65) formulas, considering gate opening height and head difference. Ideal cases were constructed to validate the model against the well-established Storm Water Management Model (SWMM). Field application was conducted in the urban river network of Ganzhou City, Jiangxi Province, using two historical flood events (1998) and a 50-year return period flood for verification. Evaluation indices included the coefficient of determination (R²) and Nash-Sutcliffe Efficiency (NSE).Results and Discussions In ideal case validations, the proposed model showed excellent agreement with SWMM results: For weirs, R² values for flow and water level reached 0.990 and 0.960, respectively, with minor temporal lags attributed to different junction processing methods. For culverts, flow and water level R² values were 0.980 and 0.987, with slight discrepancies due to flow regime transition considerations in the proposed model. For pump stations, the model accurately captured flood diversion processes, achieving R² values of 0.992 (flow) and 0.998 (water level), maintaining stable internal river water levels after pump activation. For sluice gates, the model effectively simulated complex regulation processes (e.g., controlled discharge and free discharge), with a flow R² of 0.994. It successfully captured abrupt flow changes during gate opening/closing and accommodated multi-gate independent control. In the Ganzhou field application: Historical flood simulations yielded NSE values of 0.957 and 0.983, with peak water level differences of 0.08 m and 0.02 m compared to measured data. For the 50-year return period flood, controlled discharge simulations stabilized downstream flow at 3000 m³/s when upstream flow exceeded 2000 m³/s, and switched to free discharge at 4000 m³/s. Constant upstream water level control (102 m) was achieved through dynamic gate adjustments, maintaining stable water levels with continuous model convergence. Overall, the model demonstrated high accuracy (average R² > 0.97 for all structures) and stability. The artificial area method simplified junction calculations without compromising precision, while the source term approach efficiently integrated diverse hydraulic structures without requiring complex boundary redefinition. The gate regulation module, with detailed control rules and flow regime discrimination, outperformed SWMM in capturing real-world operational complexity.ConclusionsThe proposed source term-based algorithm provides a simple and reliable solution for simulating hydraulic control structures in 1D river networks. Key conclusions include: The algorithm accurately models weirs, culverts, pump stations, and sluice gates, with R² values ranging from 0.971 to 0.994 compared to SWMM, exceeding the threshold for strong correlation (R² > 0.7). The artificial area method enables efficient junction processing, eliminating iterative calculations and improving computational efficiency. The sluice gate simulation module effectively captures dynamic regulation processes, with control rules closely aligned to engineering practices. Field validation in Ganzhou confirms the model's applicability to real-world flood simulations, with NSE > 0.95 for historical floods and stable performance in complex regulation scenarios. This study advances river network hydrodynamic modeling by enhancing the accuracy and efficiency of hydraulic structure simulation. The model serves as a valuable tool for flood risk assessment and water resource management, particularly in urban river networks with dense hydraulic infrastructure.
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