Modelado y simulación de flujo en la zona no saturada y transporte de solutos en medios porosos

Abstract

Recently, interest in soil's unsaturated zone has signi cantly increased since it was realized that the subsurface environment can be severely damaged by human activities. For this reason, several models and codes have been developed in recent years in order to study di erent processes of relevance in this topic. A considerable number of those are based on Richard's equation, which describes the evolution of the water content and the pressure head, under capillary and gravitational forces in porous media. In this context, this work considers two case studies of interest in Environmental Engineering: rstly, we study the water movement and solute transport in soils, focusing speci cally in those associated with mallines patag onicos and, secondly, we performed the hydrological characterization of Municipal Solid Waste Land lls (MSWL), considering several designs for the top and basal barriers. First, we introduced the mathematical formulation and the numerical methods to describe ow in unsaturated porous media, as well as those associated with solute transport in soils. During this stage, we developed and implemented several routines which allowed us to solve the resulting di erential problems of interest parametrically while invoking HYDRUS-1D code as the core solver. With this tool, we studied di erent water ow and solute transport regimes associated with the central and peripheral zones of a mall n located in the vicinity of San Carlos de Bariloche. We determined soil's hydraulic properties in steppe wetlands through the use of pedotransfer functions implemented on the Rosetta code. The input data required for this code arises from the textural classes of the soil's horizons, which we determined with the hydrometer method. By simulating a families of periodic regimes, we were able to calibrate the most sensitive parameters of the model. We also studied the transient evolution of the water content based on the daily precipitation database for the Tte. Luis Candelaria airport for the period of 1990-2014. Lastly, we simulated solute transport for two di erent hydrological regimes.The results obtained for the water movement analysis in mallines were adequate for the peripheral zone, when the hydraulic parameters obtained from the Rosetta code were considered. However, this procedure did not yield good results in the central zone. In this case, we parameterized the retention curve in terms of the two most sensitive parameters and analysed the system's response to these parameters. These parameterscontrol the position and height of the retention curve. We found that it is possible to adjust these parameters using the annual average values of the minimum water table and the saturation period of the mall n. Regarding the solute transport simulations, we observed that the hydrological regime signi cantly a ects the solute redistribution. Finally, we used the HELP code to perform the hydrological characterization of top and basal barriers of MSWL. In this case, we studied the theoretical framework related to the water balance of MSWL.We proposed several designs for the top an basal barriers and estimated the percolation, drainage and leak uxes through each layer. The proposed designs were applied to a MSWL sized to provide the nal disposal of MSW for the Municipalities of San Carlos de Bariloche and Dina Huapi during the period of 2021-2030. We evaluated the performance of the proposed systems, estimated the drainage owrates and checked which designs satis ed the maximum limits of leachate losses established by international regulations.