Forests and water - case studies
Copper mining and highland water in northern Chile
The Andes in northern Chile are separated from the Pacific ocean by the Atacama desert and the coastal range. At these latitudes, of 18° to about 26° S, the cold Humboldt current accentuates the rain-shadow effect of the western Andean slope to create one of the driest regions on earth. Arica, in the far north, for example, claims a record of 27 consecutive years without measurable precipitation. There are a few, mainly saline, open water bodies located at more than 4 000 m above sea level, but precipitation is slight at the highest altitudes of the puna (highland prairie). An absence of glaciers over 6 000 m above sea level is also remarkable.
Research has indicated that the recharging of lowland Chilean aquifers depends on infiltration from the highlands. Experimental studies suggest that this infiltration is extremely small, and sometimes close to zero. Most underground water is probably fossil, and originated during the early Holocene period. Conditions became much drier about 3 000 years ago. Intensive pastoralism may also have affected the climate. At present, conditions in the transect from the highest mountains to sea level are probably the driest they have been for 20 000 years.
The human population of this area is concentrated in coastal towns. Agriculture is limited to areas around the stable oases along the highland drainage, with some seasonal pasturing on the Altiplano. Traditionally, fishing and trading are the major industries, but mining - especially for copper - has dominated since the nineteenth century. Today, most mines are operated by multi-national corporations. Mining has expanded rapidly over the last 15 years, and now accounts for 29 percent of Chilean gross national product (GNP).
Mining operations require a lot of water; groundwater is the main source of water in arid northern Chile, but there are no precise estimates of underground water resources. The mining companies’ growing demand for water has put pressure on the government to permit the construction of pipelines to tap several of the rare freshwater lakes on the Altiplano. This would seriously damage the way of life of highland pastoralists, because an essential resource for animal grazing would rapidly be spoiled, and landscapes would become less attractive for ecotourism. At the same time, tapping the highland lakes would not be a long-term solution for the thirsty mining industry. Indigenous people and environmental organizations are resisting this exploitation.
Adapted from J. Ives. 2001. Highland-lowland interactive systems.<p>Download the full-text document<br><br></p>