61 Figure 3 - Mean water stress ratio for South American porphyry copper production (mean monthly demand / mean monthly available water, 2015–2100), TaiESM1, SSP2-4.5. Across South America, 5 grid cells exhibit mean mining water stress ratios greater than 20% which is considered the threshold for moderate to high water scarcity. These cells contain 36 porphyry copper deposits, representing 25% of the total south American porphyry copper resources included in the analysis. The highest mining water stress ratios occur along the northern Chilean coast, where a concentration of large porphyry copper deposits coincides with low extractable water availability. These results are consistent with observed conditions, as major mines in the region, including Escondida, rely on alternative water sources such as desalination to sustain operations. 3.3.3 Time-Dynamic Mining Water Stress under Production Scheduling Figure 4 highlights the temporal evolution of the mining water stress for South American porphyry copper production under the IEA STEPS scenario. Three maps are shown at ten-year intervals between 2030 and 2050. For each year, the mining water stress ratio is calculated as the ratio between water demand associated with scheduled production in that year divided by the mining adjusted extractable water available in the corresponding grid cell for the same year.
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