Water supply: an increasing challenge in Chilean mining

Large mining projects, currently being developed in Chile’s northern region, are generally located in the Andes Mountains at altitudes of 3000+ meters above sea level. Possible sources of water supply for mining are the mountain aquifers and sea water. Due to Chile’s geographic configuration, using sea water is always feasible, as the average width of the country in the northern zone is 150km to 350km. However, the great altitude for pumping increases the  capital and operating costs.

Searching for water in the Andean aquifers is an alternative that poses a great hydrogeological challenge as these aquifers form part of complex geological systems. In a modern volcanic environment, periods of sediment deposition alternate between volcanic flows of different origins and poorly consolidated material of varying grain size, and is structurally superimposed by a complex fault system which causes very deep and complex hydrogeological basins. Low rainfall in this high-altitude desert environment and the lack of meteorological stations to provide data on rainfall, snowfall and evaporation, make it difficult to predict recharge to the aquifer systems. On the other hand, some unique biotic ecosystems and water sensitive systems in the Andean valleys limit the ability to exploit these aquifers from an environmental point of view.

SRK has evaluated an aquifer located in Region III of the Andes Mountains at a median altitude of 4300 meters above sea level, which could ensure the water supply for a large mining project. The project, located approximately 125km  from the well field, requires an average flow of 785L/s or 68 thousand m3 of water per day.

The hydrographic basin, where a complex aquifer system has been identified, covers approximately 520km2. Information was obtained from 16 pumping wells and 26 exploration and monitoring wells, as well as from the results of several geophysical, chemical and isotopic works.

The evaluation allowed SRK to define an aquifer system with excellent hydrogeological characteristics to support wells whose performance will surpass 100L/s. To verify that exploiting this aquifer will not cause adverse effects on environmentally sensitive areas, SRK built a numerical model of the aquifer operation, which demonstrated the feasibility of using the well field to supply the needs of the mining project with no measurable effects downstream.

Osamu Suzuki: osuzuki@srk.cl



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