Water balance in landfills: Comprehensive review of modeling approaches

Controlling pollution from waste landfills remains a critical environmental challenge, particularly in developing regions and fragile ecosystems. An effective tool to support this process is the hydrological assessment of disposal sites through simulation models. This study provides a comprehensive systematic review of mathematical models used to simulate landfill water balance over the past 15 years. A total of 32 relevant studies were identified from the Scopus, Web of Science, and SciELO databases, classifying them by model type, application scope (real or experimental), and climatic region. Five main models were recognized: HELP, UNSAT-H, VADOSE/W, MODUELO, and EMWMF. Their structural features, simulation capabilities, and applicability are examined. Processes such as evapotranspiration, evaporation, infiltration, runoff, and leachate generation are represented using distinct approaches, ranging from empirical to physically based methods. The findings show that HELP is the most widely applied model, whereas MODUELO and VADOSE/W enable more detailed simulations and/or account for spatial variability. A knowledge gap persists in tropical and low-income regions, where landfill hydrology remains insufficiently investigated. The study emphasizes the need for models adapted to local conditions and data availability to enhance landfill management and reduce risks that may be intensified by climate change. This review offers a foundation to support the selection and application of models in underexplored or resource-limited contexts.