The Guaraní Aquifer System (SAG) is the largest transboundary aquifer in Latin America, extending beneath parts of Brazil, Paraguay, Argentina, and Uruguay. This paper presents the results of recent hydrogeological studies in the southern portion of the SAG. Locally, the abundance of surface water bodies precluded the use of conventional hydrological tools to characterize groundwater flows. Geological, hydrochemical and environmental isotope investigations were integrated to postulate a revised hydrogeological conceptual model. The revised geological model has provided a better definition of the geometry of the aquifer units and outlined the relevance of regional faults in controlling flow patterns. The new potentiometric map is consistent with groundwater flow from the SAG outcrops to the centre of the Corrientes Province, where upwards flows were identified. Hydrochemical and isotope data confirmed the widespread occurrence of mixing. Noble gas isotopes dissolved in groundwater (⁴He and ⁸¹Kr/Kr) provided residence times ranging from recent recharge up to 770 ± 130 ka. Groundwater age modelling confirmed the role of the geological structures in controlling groundwater flow. The southern sector of the SAG is a multilayer aquifer system with vertical flows and deep regional discharge near the Esteros del Iberá wetland area and along the Paraná and Uruguay rivers.

Nature-based solutions (NBS) are increasingly being promoted because they can solve different pursued aims together with providing an additional array of multiple ecosystem services or co-benefits. Nevertheless, their implementation is still being curbed by several barriers, for example, a lack of examples, a lack of finance, and a lack of business cases. Therefore, there is an urgent need to facilitate the construction of business models and business cases that identify the elements required to capture value. These are necessary to catalyze investments for the implementation of NBS. This article presents a tool called a Natural Assurance Schemes (NAS) canvas and explains how it can be applied to identify business models for NBS strategies providing climate adaptation services, showing an eye-shot summary of critical information to attract funding. The framework is applied in three case studies covering different contexts, scales, and climate-related risks (floods and droughts). Finally, a reflective analysis is done, comparing the tool with other similar approaches while highlighting the differential characteristics that define the usefulness, replicability, and flexibility of the tool for the target users, namely policymakers, developers, scientists, or entrepreneurs aiming to promote and implement NAS and NBS projects.