993 requirements (Mm³/year) and water intensity (m³/t Cu). Figure 1 illustrates the alignment of South American porphyry production capacity with projected demand from 2024 to 2027, after which a deficit emerges as resources are insufficient to meet demand. This deficit primarily reflects the assumption that South America maintains a constant 46% share of global production, for comparison, at the global scale, a deficit emerges later, around 2040. Annual water requirements broadly follow the trajectory of production, increasing with rising demand and slowing after 2036 as production declines. Water intensity per ton of copper increases continuously over time, reflecting the progressive activation of lower-grade deposits. These results reflect the grade-based scheduling and linear interpolation of IEA demand; alternative scheduling strategies or demand trajectories could alter the timing and magnitude of deficits. For comparison, the deficit begins earlier under the NZE scenario (2033) and later under APS (2039), reflecting higher copper intensity of decarbonization and electrification pathways. 3.3 Results: Spatial and Temporal Assessment of Mining Water Stress 3.3.1 Spatial Distribution of Extractable Water Climate-informed extractable water availability in South America is derived from HyIR for the TaiESM1 general circulation model under SSP2-4.5, which is chosen as it is broadly consistent with the IEA STEPS scenario. Figure 2 presents the spatial distribution of extractable water computed at the native resolution of the climate forcing (1.25° × 0.9°). Figure 2 - Extractable water availability in South America from (a) lakes and reservoirs, (b) rivers, and (c) aquifers, derived from TaiESM1 under SSP2-4.5 (mean 2015–2100). 3.3.2 Mining Water Stress Ratio for Porphyry Copper Production The mean mining water stress ratio for porphyry copper production in South America is calculated as the ratio of mean monthly water demand associated with copper production to 10% of mean monthly extractable water availability over the period 2015–2100. Results are shown at the climate model grid resolution, and only grid cells containing at least one porphyry copper deposit are displayed; all other grid cells are masked (see Figure 3).
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