A Digital Twin Framework Integrating Multiscale Signal Decomposition and Hybrid Deep Learning for Intelligent Water Storage Control on Remote Islands

Precipitation on remote offshore islands is characterized by non-stationarity and strong stochasticity. However, rainwater harvesting systems require accurate precipitation forecasts to ensure effective water storage and discharge and a stable freshwater supply. Here, we propose an intelligent framework integrating precipitation signal decomposition, a hybrid neural network for predicting daily precipitation over the next 30 days, and digital twin technology to optimize water storage and discharge strategies for rainwater collection pools. For signal preprocessing, variational mode decomposition decomposes the original daily precipitation series into multiple intrinsic mode functions, a chaotic sparrow search optimization algorithm performs global parameter optimization, and singular spectrum analysis is applied twice to denoise high-frequency mode components. The hybrid prediction model combines a convolutional neural network to extract local temporal features, bidirectional long short-term memory to capture bidirectional long-term dependencies, and a multilayer perceptron for nonlinear mapping and regression output. Finally, this model is integrated into a digital-twin-enabled decision framework to automatically implement water storage control through water balance calculations and threshold comparisons. The proposed method achieves a test mean absolute error of 2.49 mm, a root mean square error of 5.72 mm, and an R2 of 0.83; digital twin control significantly reduces overflow losses and, during typical typhoon months, maintains the water level in the rainwater collection pool below the warning threshold. In summary, we present a simulation-based pathway for optimizing small-scale intelligent rainwater harvesting systems, which offers a practical pathway to enhance the sustainability of freshwater resources on remote offshore islands by improving the efficiency of rainwater utilization and reducing dependence on external water supplies.