Hourly scale real-time flood forecasting in the Three Gorges Reservoir basin based on the VIC model
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Abstract:
The existing basin real-time flood forecasting system is based on the lumped model. With the increasing demand for spatial and temporal refinement of flood forecasting in large-scale basin flood control, the lumped model cannot adequately consider the unevenness of rainfall and spatial and temporal distribution of subsurface, and it is difficult to apply it to the current large-scale basin real-time flood forecasting. With the wide application of remote sensing and geographic information technology in the field of hydrology, the source of rainfall and subsurface data acquisition and data accuracy has been greatly improved, so the distributed hydrological model has gradually developed into a research hotspot in the field of hydrological modeling. However, due to the limitation of the accuracy of rainfall, runoff, and subsurface data, the application of distributed hydrological models in the field of real-time flood forecasting, especially in hourly scale forecasting, is still relatively small, and the forecast accuracy needs to be improved. With the abundant and accumulated information from satellite telemetry and ground observation sites in the basin, the hydrological and subsurface information can meet the demand for hourly flood forecast modeling by distributed hydrological models.Taken the Three Gorges Reservoir basin as an example, the process of real-time flood forecasting by the VIC model is carried out. The process of real-time rolling flood forecasting by the VIC model is divided into three parts: data access, model operation, and result output. To address the problem the original unit line routing method of the VIC model has a daily time scale and can not be used for hourly scale real-time flood forecasting. The slope routing is carried out using the slope unit line based on Gamma distribution, the river network routing is carried out using the IRF-UH method, and the hourly-scale VIC distributed flood forecasting model is established. The real-time rolling flood forecasting scheme is constructed, and the VIC distributed flood forecasting model is deployed, and applied to the reservoir area in 2022 for real-time flood forecasting.The results show that the average passing rate of flood volume and flood peak in the four sub-basins of the Three Gorges Reservoir area during the regular and validation periods is above 80%, and the average value of the coefficient of certainty is above 0.70. The VIC model shows good applicability in hourly-scale flood forecasting. It achieves good results in the real-time flood forecasting of four typical floods in the Three Gorges Reservoir area in 2022 and 2023, and can accurately grasp the flood volume and incoming water process in the key flow-producing areas of the reservoir area. The VIC hourly scale model is therefore a useful tool in the Three Gorges Reservoir area.Therefore, the VIC hourly scale model shows good performance in real-time flood forecasting in the Three Gorges Reservoir area and has great potential to be applied in real-time flood forecasting in large-scale basins. Since there are many small and medium-sized reservoirs in the Three Gorges Reservoir area, the model structure can be further improved and enriched at a later stage to further enhance the accuracy of the real-time flood forecasting system by considering the influence of human activities.