ABSTRACT In the eastern region of central Costa Rica, land use in the sub-basins of the Maravilla-Chiz and Quebrada Honda rivers (47 km2) is dominated by agricultural and livestock production, while groundwater resources constitute the main drinking water supply. This study aimed to (a) evaluate the location of groundwater recharge areas and groundwater flow paths, and (b) provide a characterization of the hydrochemistry and possible anthropic impacts. Groundwater was collected from 20 sites during the dry and rainy seasons and analysed for major ions, water stable isotopes and 222Rn. Approximated recharge areas were estimated through a local altitudinal line based on isotopic compositions in springs. The hydrochemical and isotopic characterization of groundwater showed that the main recharge areas occur in the upper part of the basin, except for springs in the middle part of the basin probably due to a certain hydraulic disconnection from the upper part that facilitates local recharge processes. In the lower basin, groundwater exhibited greater transit times and longer flow paths. Low nitrate, chloride and sulphate concentrations found in groundwater indicate low leaching of fertilizers or urban wastewaters. Our results are focused to improve water resources and agricultural management plans in a dynamic tropical landscape.

中文翻译：

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水文地球化学和同位素表征在哥斯达黎加中部东部地区火山含水层补给评估中的应用

摘要 在哥斯达黎加中部东部地区，Maravilla-Chiz 和 Quebrada Honda 河流（47 平方公里）子流域的土地利用以农业和畜牧业生产为主，而地下水资源构成了主要的饮用水供应。本研究旨在 (a) 评估地下水补给区和地下水流动路径的位置，以及 (b) 提供水化学和可能的人为影响的特征。在旱季和雨季从 20 个地点收集地下水，并分析了主要离子、水稳定同位素和 222Rn。近似补给区是通过基于泉中同位素组成的局部海拔线估算的。地下水水化学和同位素特征表明，主要补给区位于盆地上部，除了盆地中部的弹簧，可能是由于与上部有一定的液压断开，这有利于局部补给过程。在下流域，地下水表现出更长的传输时间和更长的流动路径。在地下水中发现的低硝酸盐、氯化物和硫酸盐浓度表明肥料或城市废水的浸出率低。我们的结果侧重于改善动态热带景观中的水资源和农业管理计划。在地下水中发现的氯化物和硫酸盐浓度表明化肥或城市废水的浸出率很低。我们的结果侧重于改善动态热带景观中的水资源和农业管理计划。在地下水中发现的氯化物和硫酸盐浓度表明化肥或城市废水的浸出率很低。我们的结果侧重于改善动态热带景观中的水资源和农业管理计划。