Groundwater Recharge Evaluation in Brazilian Cerrado Biome Site by Saturated Zone Flow Numerical Modeling

ABSTRACT Natural groundwater recharge is a key information to the integrated water resources management (IWRM), but still not well researched in Cerrado Biome – being as an important continental recharge zone, responsible for tzhe base flow in some stretches in major Brazilian rivers. In this context, the purpose of this study was to research and understand key aspects of this process in this important biome: (i) rates; (i) spatial distribution; and (iii) determining factors. The studied area encompasses an experimental basin located in the western portion of the Federal District and the methodology consisted in the application of Numerical Modeling Flow of Saturated Zone. In the method proposed, the spatial distribution of groundwater recharge was previously mapped, and the rates of the recharge zones were estimated by numerical model calibration. In spite of model limitations, simulated rates were close to that provided by literature. The hydraulic properties of the porous media were overriding in the study process, however, land cover/use was considered as an important regulatory factor in the groundwater recharge process in the area. The results obtained were considered valid as a starting point for further implementations studies in Cerrado biome, showing a better porous medium characterization and a better methodology alternative to characterize the spatial variability of recharge zones.

摘要 天然地下水补给是水资源综合管理（Integrated Water Resources Management, IWRM）的核心参考信息，但塞拉多生物群区（Cerrado Biome）的相关研究仍未得到充分开展——该区域作为重要的大陆补给区，为巴西部分主要河流的部分河段提供基流。在此研究背景下，本研究旨在探究并阐明该重要生物群区内地下水补给过程的关键特征：(i) 补给速率；(i) 空间分布特征；(iii) 主控决定因素。研究区域涵盖巴西联邦区西部的一处试验流域，研究方法采用饱和区水流数值模拟（Numerical Modeling Flow of Saturated Zone）。在所提出的方法中，研究人员首先对地下水补给的空间分布进行了制图，并通过数值模型率定估算了各补给区的补给速率。尽管模型存在一定局限性，但模拟得到的补给速率与文献报道值较为接近。本研究中，多孔介质（porous media）的水力特性对研究结果起主导作用，而土地覆盖/利用则被视为该区域地下水补给过程的重要调控因子。本研究所得结果可作为塞拉多生物群区内后续相关研究的有效起点，结果表明，通过更精准的多孔介质表征与更优化的方法，可有效刻画补给区的空间变异性。