955 regions such as Peru, however, limited baseline monitoring -especially for groundwater and headwaters- increases hydrological and financial risk (Quiroz, personal communication, 2025). Water-use efficiency and alternative water sources for mining processes The literature highlights that modern large-scale mining operations already operate with high internal water recirculation rates, often exceeding 70–85% in mineral processing circuits, particularly in copper and iron ore operations (Northey et al., 2019). Information provided in interviews shows that recirculation could be higher (up to 85%-99%), as in large-scale mining (Quiroz, personal communication, 2025). Water recovery from tailings thickening, filtration systems, and closed-loop process designs has substantially reduced the freshwater intensity per tonne of ore processed. These efficiency gains constitute a major technological advance in mining water management over the past two decades. However, despite high recycling rates, mining still requires substantial make-up water to offset evaporation, tailings and concentrate moisture, seepage, and system losses. In arid regions such as northern Chile and southern Peru, large-scale copper mines processing over 100,000 tonnes per day depend on significant external inputs even under high recirculation (Cacciuttolo & Valenzuela, 2022). This structural reliance on make-up water limits the ability of efficiency measures alone to secure long-term water resilience. Recent research shows that internal efficiency gains, while necessary, are insufficient in water - stressed basins. Integrated “One Water” approaches therefore complement recirculation with diversified supply portfolios including desalination, urban wastewater reuse, managed aquifer recharge, and seasonal storage (de Lima et al., 2025). The choice among these options is context-specific, shaped by infrastructure, energy costs, regulatory frameworks, and local demand. The literature increasingly frames these interventions in economic and risk-management terms. Water scarcity, variability, and social opposition create operational uncertainty, making alternative water sources strategic risk-mitigation investments rather than mere environmental expenditures. Interviews confirm that decisions are driven primarily by supply reliability rather than compliance (Torreblanca, personal communication, 2025). In water-intensive mining systems, reliability -not marginal cost minimization- ultimately determines economic viability (Hamilton, 2019; Northey et al., 2019). Thus, high levels of internal recycling represent a necessary foundation of responsible water management in mining, but long-term sustainability requires sustained efficiency improvements combined with basin-scale supply diversification and coordinated water governance mechanisms. Basin-level water supply augmentation and flow regulation In many mining regions, desalination is not viable due to distance from the coast or high conveyance costs, and domestic wastewater reuse may be limited by the absence of large nearby urban centers. The literature therefore highlights the importance of basin-level supply augmentation and flow regulation through multi-purpose infrastructure that increases reliability across users (ICMM–IFC, 2017). Reservoirs, managed aquifer recharge, seasonal storage, and regulated transfers can enhance dryseason availability and reduce interannual variability, generating shared benefits for agriculture, communities, and ecosystems. Even when a mining operation secures its supply through alternative sources, contributing to basin-wide reliability can strengthen legitimacy, reduce conflict risk, and support long-term project viability (ICMM–IFC, 2017; Tapsuwan et al., 2022). Nature-Based Solutions (NbS) complement grey infrastructure by improving hydrological performance through infiltration, seasonal storage, and baseflow enhancement rather than creating new water volumes. High-Andean wetlands (bofedales), terraces, and infiltration systems are often identified as socially accepted, relatively low-CAPEX measures with regulatory benefits (Ross et al., 2023). However, NbS remain limited in scale, partly due to insufficient valuation frameworks that capture their incremental supply
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