Streamflow Prediction and Flood Forecasting with Time-Lag Informed Deep Learning framework in Large Transboundary Catchments

In facing the challenges of limited observational streamflow data and climate change, accurate streamflow prediction and flood management in large-scale catchments become essential. This study introducing a time-lag informed deep learning framework to enhance streamflow simulation and flood forecasting. Using the Dulong-Irrawaddy River Basin (DIRB), a less-explored transboundary basin shared by Myanmar, China, and India, as a case study, we have identified peak flow lag days and relative flow scale. Integrating these with historical flow data, we developed an optimal model. The framework, informed by data from the upstream Hkamti sub-basin, significantly outperformed standard LSTM, achieving a Kling-Gupta Efficiency (KGE) of 0.891 and a Nash-Sutcliffe efficiency coefficient (NSE) of 0.904. Notably, the H_PFL model provides a valuable 15-day lead time for flood forecasting, enhancing emergency response preparations. The transfer learning model, incorporating meteorological inputs and catchment features, achieved an average NSE of 0.872 for streamflow prediction, surpassing the process-based model MIKE SHE's 0.655. We further analyzed the sensitivities of the deep learning model and process-based model to changes in meteorological inputs using different methods. Deep learning models exhibit complex sensitivities to these inputs, more accurately capturing non-linear relationships among multiple variables than the process-based model. Integrated Gradients (IG) analysis further demonstrates deep learning model's ability to discern spatial heterogeneity in upstream and downstream sub-basins and its adeptness in characterizing different flow regimes. This study underscores the potential of deep learning in enhancing the understanding of hydrological processes in large-scale catchments and highlights its value for water resource management in transboundary basins under data scarcity.