56 implications of this choice and extensions to multi-model and multi-scenario configurations will be addressed later. 2.2 Climate-Informed Indicators of Extractable Water HyIR derives indicators of extractable water availability from simulated water storage and flow in surface water bodies, rivers, and aquifers. Extractable water is defined here as the volume that can be withdrawn while remaining physically sustainable under climate-driven variability, rather than total storage or flow. For lakes and reservoirs, extractable water is defined as a fixed fraction of stored volume. At each time step, yearly extractable water is set to 10% of the maximum stored volume of the previous year. This assumption ensures that, in the absence of recharge, a surface water body would persist for at least ten years, including during drought periods. Annual extractable volumes are redistributed across months using latitude-dependent seasonal profiles: strongly seasonal distributions in temperate regions, inverted seasonality between hemispheres, and weak seasonality near the equator. River water availability is derived from daily river discharge and restricted to discharge above long term low-flow thresholds. For each river, a yearly moving minimum low-flow indicator is computed over a 30-day window, from which a long-term multiannual QMNA5 quantile is derived to define the low-flow threshold. Monthly extractable discharge is defined as the portion of discharge exceeding this threshold. Groundwater availability is derived from aquifer storage above a depth threshold determined from a permeability limit of 10⁻¹³ m² using an empirical depth–permeability relationship. Extractable groundwater is defined as a fraction of this accessible storage, representing a conservative 50-year long-term sustainable withdrawal rate assumption. All indicators evolve dynamically in response to climate forcing and are computed at the native spatial resolution of the driving climate model. The resulting indicators represent physically extractable water volumes through time and space, without assumptions about sectoral allocation, infrastructure, or competing demands. They provide a consistent hydrological basis for comparison with externally defined water requirements. 2.3 Quantifying Water Requirements for Copper Production To assess how future water availability constrains mineral production, extractable water indicators are coupled with estimates of water requirements for copper production derived from a process-based modelling approach. Water demand is quantified at the deposit scale and represents direct net water use associated with the production of copper concentrate. The model represents the main water flows associated with the extraction and processing of copper sulfide ore from porphyry deposits. It assumes the sequence of operations typical of
RkJQdWJsaXNoZXIy MTM0Mzk2