ABSTRACT Sustainable groundwater management implies a good knowledge of recharge processes, especially in areas with water deficit, like the semi-arid region of Banabuiú watershed (Ceará State, Northeast of Brazil). In this zone, phreatic aquifers consist of Precambrian crystalline fractured reservoirs characterised by a high spatial anisotropy, both in terms of hydrodynamics and water quality. This study implemented a multi-tracer approach (18O, 2H, 14C, 3H, CFC, SF6), combined with hydrodynamic data (i.e. groundwater levels) to identify the groundwater recharge origin and the recharge mechanisms, and to estimate the groundwater residence time. At the basin scale, hydrodynamic data and local observations indicated the high reactivity of aquifers to precipitation and suggested that infiltration processes occur mostly through preferential infiltration zones. Stable isotope data showed a major contribution of evaporated surface water in the recharge process from many artificial or natural ponds. Groundwater residence time determination highlighted the spatio-temporal heterogeneity of flow path organisation within aquifers, with variable contributions between fast vertical flow (present-day end-member; 15–85 %) and a slower horizontal flow (old end-member <1960), underlining the vulnerability of aquifers to present-day environmental stress or pollution.

中文翻译：

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结晶裂隙含水层地下水补给机制的同位素特征和年代测定：半干旱巴纳布乌流域（巴西）的例子

摘要 可持续地下水管理意味着对补给过程有很好的了解，特别是在缺水地区，如巴纳布乌流域（巴西东北部塞阿拉州）的半干旱地区。在该区域，潜水含水层由前寒武纪结晶裂缝性储层组成，其特征是在流体动力学和水质方面具有高度的空间各向异性。本研究采用多示踪剂方法（18O、2H、14C、3H、CFC、SF6），结合水动力数据（即地下水位）确定地下水补给来源和补给机制，并估算地下水滞留时间。在盆地尺度上，水动力数据和当地观测表明，含水层对降水的反应性很强，并表明渗透过程主要通过优先渗透区发生。稳定同位素数据表明，蒸发的地表水在许多人工或天然池塘的补给过程中起了主要作用。地下水停留时间的确定突出了含水层内流动路径组织的时空异质性，在快速垂直流动（今天的端部；15-85%）和较慢的水平流（旧端部 <1960）之间有不同的贡献，强调含水层对当今环境压力或污染的脆弱性。