Nonlinear modeling of stormwater infiltration in municipal solid waste landfills: Integrating geomechanical compaction and biogenic heat flux

Precise prediction of leachate generation is critical for the hydraulic stability and optimal gas production of municipal solid waste (MSW) landfills. Conventional water balance models, such as HELP V 4.0, often utilize static parameters, inadequately capturing the nonlinear interactions between mechanical waste compaction, atmospheric vapor pressure deficits, and internal biogenic heat generation. This study introduces an integrated nonlinear framework to quantify stormwater infiltration (I) dynamically. A comprehensive five-year field investigation (2016–2020) with monthly temporal resolution was conducted across four regional sanitary and semi-sanitary landfills in Bosnia and Herzegovina (Smiljevići, Mošćanica, Desetine, and Gračanica). These sites are highly representative of broader European continental climates. The model integrates the dynamic compaction modulus (E vd ) to define hydraulic conductivity, alongside continuous monitoring of internal temperatures at a 30 cm depth (T 30 ). The nonlinear framework employs the dynamic compaction modulus (E vd ) as a state-variable for hydraulic conductivity, while the internal temperature (T 30 ) acts as a thermodynamic regulator for winter moisture flux. By integrating these transient parameters, the model captures the nonlinear hydrologic response of the waste matrix, moving beyond static water balance approximations. Results demonstrate that continuous biogenic exothermic reactions maintain a positive thermal gradient (T 30 > 0 °C) even under sub-zero ambient conditions, facilitating continuous basal snowmelt and winter infiltration. The proposed model demonstrated robust predictive capability with a Nash-Sutcliffe Efficiency (NSE) of 0.84 and a Coefficient of Determination (R 2 ) of 0.89, significantly outperforming static linear approximations. This framework provides essential technical guidance for the accurate dimensioning of leachate collection systems (e.g., 50 cm drainage layers and 200 mm perforated pipelines) and can be generalized to global regions with similar climatological and geotechnical profiles.