Interactions between several parameters to estimate leachate and biogas production are very complex especially in irregular disposal areas without operational control and with few climate information. Nevertheless, the modeling challenges can be overcome using a System Dynamics (SD) approach that allows measure long term dynamics of a complex system. The proposed model is based upon a computer simulation to understand circular causality among soil water balance model and modified first-order decay methane generation aided by MSW landfilled volume calculation from Digital Terrain Model. The leachate accumulated is considered as targets for the calibration and validation. A model test run demonstrated that measured and calculated values of the leachate flow rate, applied in Volta Redonda’s uncontrolled landfill (Brazil) with a spatial resolution of 4,3 cm, were similar (RMSE = 0.10013 and SD = 0.0994). The SD model fitted with higher accuracy with the real data, indicating differences less than 8% for leachate production. After landfill methane generation parameters translating among first-order decay model it was found k = 0.28 1/yr and the L<sub>0</sub> = 62,18 (m<sup>3</sup> CH<sub>4</sub>/ton waste). The obtained result were compared to the LandGEM modified model results and shows that the proposed method was capable of predicting the final productivity without overestimating the methane yield and was also able to capture the system behavior.