The intensity of heavy rainfall, driven by climate change, has significant effects worldwide, including flash flood, droughts, water degradation, landslides and crop damages. To ameliorate these impacts, accurate forecasting is crucial to address the dynamic nature of rainfall for sustainable utilization. But the non-linearity inherited within the rainfall significantly influence the model precision. Artificial Intelligence (AI) models have shown promising results in detecting complex rainfall patterns. This paper proposed a hybrid model using overcomplete rational dilation discrete wavelet transform (ORDWT) integrated with autoregressive integrated moving average (ARIMA) and long-short-term memory (LSTM), constructing ORDWT-ARIMA-LSTM to forecast one-month ahead rainfall. The ORDWT provides multi-scale decomposition and better shift-invariance, while ARIMA with LSTM captures complementary dynamics across ORDWT coefficients, lowering errors. Aiming to extract more representative features, the ORDWT coefficients are investigated, and then sent to the ARIMA-LSTM for prediction. The ORDWT–ARIMA–LSTM achieved highest performance for Melbourne Airport: Root Mean Square Error (RMSE) = 2.9, Mean Absolute Error (MAE) = 1.93, RSE = 0.215, Willmott's Index (WI) = 0.990, Nash–Sutcliffe Index (ENI) = 0.970; Melbourne Botanical Gardens: RMSE = 3.84 MAE = 2.65, RSE = 0.287, WI = 0.710, ENI = 0.962; and Preston Reservoir: RMSE = 3.94 MAE = 2.87 RSE = 0.310, WI = 0.973, ENI = 0.971. The ORDWT–ARIMA–LSTM reduced RMSE by 4.5 % and MAE by 5.3 % on average across stations against comparing models. Results confirmed the efficiency of ORDWT–ARIMA–LSTM in rainfall forecasts, providing valuable support in weather, water management, droughts and floods.

Developing accurate soft computing methods for groundwater level (GWL) forecasting is essential for enhancing the planning and management of water resources. Over the past two decades, significant progress has been made in GWL prediction using machine learning (ML) models. Several review articles have been published, reporting the advances in this field up to 2018. However, the existing review articles do not cover several aspects of GWL simulations using ML, which are significant for scientists and practitioners working in hydrology and water resource management. The current review article aims to provide a clear understanding of the state-of-the-art ML models implemented for GWL modeling and the milestones achieved in this domain. The review includes all of the types of ML models employed for GWL modeling from 2008 to 2020 (138 articles) and summarizes the details of the reviewed papers, including the types of models, data span, time scale, input and output parameters, performance criteria used, and the best models identified. Furthermore, recommendations for possible future research directions to improve the accuracy of GWL prediction models and enhance the related knowledge are outlined.