Comparative analysis of different boundary conditions and their influence on numerical hydrogeological modeling of Palmital watershed, southeast Brazil

Abstract

Study region: The study is based on field data of a shallow phreatic aquifer occurring at a small watershed in Viçosa, Minas Gerais, Brazil. Study focus: The present study aims to evaluate numerical hydrological models generated using different boundary conditions as field data did not allowed a proper definition of the most adequate boundary condition to simulate the field characteristics observed within the study area. Data field was used to build a conceptual model and to determine initial and some of the boundary conditions of model mesh. Three numerical hydrogeological models were generated on Visual Modflow®. Once created, the models were calibrated using the WinPEST®. GHB, River and Stream boundary conditions resulted on a calibrated standard Root Mean Square (RMS) varying from 7.3% to 13.02% and showed high correlation coefficients, varying from 94% to 97%. Using another set of hydraulic head field data, these models were later validated. New hydrological insights for the region: Results show that, for all three boundary conditions, the normalized RMS obtained in calibration was similar to that obtained in validation, confirming its validity. The Rivers boundary condition have presented the most representative values for normalized RMS, absolute average error and correlation coefficient, and are the most indicated boundary conditions for areas with similar physical characteristics to the area under study.

Keywords

• Phreatic aquifers
• Visual modflow
• Internal boundary conditions
• Rural areas