Assessment of groundwater sustainability in the Maipo River Basin (Chile)

In Central Chile, precipitation decreases while drinking water and irrigational demand increase. In the Maipo Basin, shortages in surface water are compensated by increased groundwater abstraction for agriculture and drinking water. Also, agricultural land is transformed due to the expansion of Santiago city. Effective groundwater management is required to protect available groundwater resources and ensure equal distribution among users. Therefore, this study aims to analyze the current groundwater management and governance framework at the basin scale. The study assesses the context of groundwater management and the functioning cooperation mechanisms between the stakeholders. Furthermore, the current knowledge gaps and challenges are identified, and approaches to improve water resources management policy are proposed. A literature and legal context analysis in the context of the Maipo Basin is supplemented by interviews and a survey among stakeholders. Groundwater sustainability indicators are applied to enhance sustainable water planning and management, support data sharing, show groundwater users’ current impact, and stimulate stakeholder communication. Lastly, a sustainable yield index is developed and proposed to assess groundwater management and to provide a concrete initial step to sustainable groundwater management in the Maipo Basin, which could be applied in other basins in Chile. The results show that groundwater is seen and treated differently than surface water, and its management and governance are neglected. Moreover, hydrological boundaries are not always respected because groundwater management is organized by administrative regions which are not always clearly based on hydrogeological boundaries, and groundwater management is decentralized. Some difficulties in allocating resources to monitoring groundwater use were found. The groundwater sustainability indicators show the urgent situation of ‘overgranting’ of groundwater rights compared to the recharge. The sustainable yield index demonstrates the unsustainable situation of the region, threatening groundwater-dependent ecosystems. Further recommendations are made towards a more robust groundwater management with the well-defined role of the General Directorate of Water (DGA).