Environmental Studies Center, São Paulo State University (UNESP), Rio Claro, Brazil.
School of Sciences, Technology and Education, São Paulo State University (UNESP), Ourinhos, Brazil.
Isotopes Environ Health Stud. 2024 Aug;60(4):400-416. doi: 10.1080/10256016.2024.2397469. Epub 2024 Sep 3.
Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (H) and oxygen-18 (O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δO in rainwater exhibit higher variability, resulting in -4.49 ± 3.18 ‰ VSMOW, while δO values from the well show minor variations, similar to those of the spring, recording -7.25 ± 0.32 ‰ and -6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model's outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.
露头在地下水补给中起着重要作用。了解地下水的来源、动态及其与不同水源的关系，对于从数量和质量两方面进行有效的水资源管理和规划至关重要。在瓜拉尼含水层系统（GAS）露头区，由于直接补给过程，地下水特别容易受到污染。本研究集中在巴西圣保罗州中部布鲁塔斯市附近的 Alto Jacaré-Pepira 子流域，该地区的地下水对于支持旅游业、农业、城市供水、溪流、河流和湿地至关重要。该地区属于湿润的热带气候，既有强降雨期，也有干旱期，全年河流均为常年性河流。因此，本研究的目的是调查泉水与其潜在补给源（即雨水和地下水）之间的相互关系，以阐明不同水源之间的关系。为此，我们于 2013 年至 2021 年在现场监测了地下水深度、降雨量以及雨水、泉水流量和监测井中的稳定同位素比值（氘（H）和氧-18（O））。结果表明，雨水的氧稳定同位素平均值和标准偏差具有更高的变异性，导致 -4.49 ± 3.18 ‰ VSMOW，而井中的氧值变化较小，与泉水相似，分别记录为 -7.25 ± 0.32 ‰和 -6.94 ± 0.28 ‰ VSMOW。混合模型的结果表明，水源贡献存在季节性变化，表明地下水约占全年泉水流量的 80%。将稳定同位素纳入水文监测为补充流域分析提供了有价值的数据。所得值支持含水层作为主要水源的重要性，从而为该地区溪流动态提供了关键见解。
