Many mines in the Andes rely on snow and glacier melt as components of their water supplies. In the central Chilean case study mine, projected future climate change scenarios predict increased temperature (in the order of 2.5 to 4.5 degrees Celsius, during the period between 2075 and 2100)and decreased precipitation (in the order of 8 to 23 percent)for the catchment, which may significantly affect streamflow volumes and timing, and hence future water availability for the mine. There is, however, relatively extensive local hydrometeorological data available as part of mine operations (rare in such high-altitude Andean catchments), which is useful in evaluating such potential impacts. In this study, a hydrological model was developed and calibrated using a degreeday snowmelt model coupled to a catchment moisture deficit (CMD)soil accounting model and an exponential routing model. While the hydrological model requires refinement before operational use, the results indicate that annual mean streamflow will decrease by (proportionally)more than the projected decrease in precipitation. This is due to increased evapotranspiration and earlier, smaller snowmelt flow peaks. Predicted streamflows under future climate change scenarios were then used to simulate the future water balance of the mine using GoldSim. The modeling indicates that there is a significant risk of water shortage under all modeled future climate scenarios, with production losses possible due to water shortage in some of the more severe climate scenarios. Three adaptation options were then modeled, along with a 'do nothing' option: (i)pumping water from lowland streams, (ii)reclaiming water from the existing lowland tailings dam, or (iii)constructing a new highland reservoir. Option 2 appears to be the most feasible option, balancing reasonably low equivalent annual cost (considering capital, operational, and lost production expenses)as well as being the most robust to uncertainty in future streamflows.
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