Abstract The Guarani Aquifer System (GAS) covers 1,088,000 km2, 68% of which is in Brazil, 21% in Argentina, 8% in Paraguay, and 3% in Uruguay. It is one of the most important aquifers on the continent and one of the largest transboundary aquifers in the world. More than 15 million people share this resource. Extensive analysis of existing documentation, supported by research questions, resulted in classification of five cooperation phases regarding management of the GAS: (i) 1970–2000, where scattered initiatives tried to grasp the aquifer’s geological and hydrogeological features as well as its regional circulation dynamics; (ii) 2000–2003, time needed for developing the project proposal; (iii) 2003–2010, the period marking the beginning of the official launching of the Environmental Protection and Sustainable Integrated Management of the Guarani Aquifer (GASP), funded by the Global Environmental Facility, the implementation of which lasted until 2009. This period was marked by intense cooperation efforts and concrete partnership achievements, including the Strategic Action Plan and, later, the Guarani Aquifer Agreement (GAA); (iv) 2010–2017, marked by a slowdown in transboundary cooperation, limited to sporadic cross-border projects, and some new local/national projects; and (v) 2017–present the benchmark of which is the ratification of the GAA by the four countries, a bright and formal move forward. Water availability in the region is extensive, and the absence of transboundary conflicts within the GAS has created a sense of abundance that is leading, unfortunately, to a lack of proactivity in terms of agreement implementation. The consequences are clear: data and tools developed by the GASP have not been updated; there has been a disruption of cooperation and administrative networks; there has been a loss of momentum generated by the GASP by societies and stakeholders; and there has been a loss of opportunities for detailed assessments to manage the aquifer’s heterogeneities and dynamics. Absent any coordinated approach, chances to obtain international funds are diminishing. There is no doubt that the GAA is one of the first examples of groundwater-related hydrodiplomacy—a negotiation process that seeks to simultaneously balance national interests and strengthen regional and local cooperative governance in aquifers shared between countries. Thus, the GAA should be considered a model, both for fulfilling requirements of international treaties and for designing an integrated water resource management approach.

中文翻译：

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南美洲瓜拉尼含水层系统的外交进展和挫折

摘要 瓜拉尼含水层系统 (GAS) 覆盖 1,088,000 平方公里，其中 68% 在巴西，21% 在阿根廷，8% 在巴拉圭，3% 在乌拉圭。它是非洲大陆最重要的含水层之一，也是世界上最大的跨界含水层之一。超过 1500 万人共享此资源。在研究问题的支持下，对现有文献的广泛分析得出了关于 GAS 管理的五个合作阶段的分类：(i) 1970-2000 年，分散的举措试图掌握含水层的地质和水文地质特征及其区域循环动态; (ii) 2000-2003 年，制定项目建议书所需的时间；(iii) 2003-2010 年，由全球环境基金资助的瓜拉尼含水层环境保护和可持续综合管理 (GASP) 正式启动的时期，该项目的实施一直持续到 2009 年。伙伴关系成就，包括战略行动计划和后来的瓜拉尼含水层协议 (GAA)；(iv) 2010-2017 年，跨界合作放缓，仅限于零星的跨界项目和一些新的地方/国家项目；(v) 2017 年——现在的基准是四个国家批准 GAA，这是一个光明而正式的进步。该地区的水资源供应广泛，GAS 内不存在跨界冲突，这造成了一种富足感，不幸的是，这导致在协议执行方面缺乏积极性。后果很明显：全球航空安全计划开发的数据和工具没有更新；合作和行政网络中断；社会和利益相关者失去了 GASP 产生的势头；并且已经失去了进行详细评估以管理含水层的异质性和动态的机会。如果没有任何协调的方法，获得国际资金的机会就会减少。毫无疑问，GAA 是与地下水相关的水文外交的首批例子之一，该谈判过程旨在同时平衡国家利益并加强国家间共享含水层的区域和地方合作治理。因此，GAA 应被视为一个模型，既可满足国际条约的要求，又可用于设计综合水资源管理方法。