Chile is one of the privileged countries in terms of availability of groundwater resources counting with one of the major reserves of these resources in South America. However, water is irregularly distributed on the territory due to its geographic and climatic diversity. To these it is added a high demand of waters, especially in north-central Chile where there is an intense mining activity and an exponential growth of agriculture that contrast with the natural environment of a semi-desert area.
An analysis of water stress by Water & Wastewater International places Chile in the top 33 countries of the world that will faces high water-stress in 2040 (Fig. 1). There is a combination of factors contributing to water-stress in Chile in which the exponential increase of water demands for mining, industry and agriculture is complemented by shifts in climate by increasing the temperature and reduce precipitations which is currently a critical facet of several arid and semi-arid regions worldwide. In these regards the increase aridity in the last decade especially in northern Chile, make the water supply a critical problem for the local communities. Only recently has been considered the exploration of using seawater and sewage water for the large consuming sectors such are industry and mining.
The exponential increase of water demands in northern Chile is mainly caused by the intensification of mining explorations (mainly copper) and extensive agriculture in the watersheds of the main hydrographic basins Elqui, Limari and Choapa. These high users of water cause a fragile balance especially between the rich mining sector and population’s domestic needs that became more sever after the implementation in 1999 of the “free-market” system. As a result of privatization, Chile’s water rates are now the highest in Latin America. The water rights were granted to private companies especially for mining on lands that belongs to indigenous communities. The mining sector is considered the “motor” of national development, at the detriment to the majority of the population’s access to this basic resource. Chile’s water sector has proven to be a windfall for these companies and investors, which make steady annual returns of 25 per cent. These profits are subsidized by the government of Chile, which guaranteed the water companies a return of at least 10 per cent. Meanwhile, the citizens of Chile have seen their water rates rise progressively. One of the regions where the groundwater are highly exploited are located in northern part of Chile where the mining industry and agriculture are flourishing.
Coquimbo in north-central Chile is the IV administrative region of the country out of a total of 15. Coquimbo is bounded on the east by Chile’s Andean Mountains reaching 6900 m above sea level and to the west by the Pacific Ocean (Fig. 2). In this region groundwater is almost exclusively obtained from alluvial aquifers which are confined y semi-confined whit shallow water table (bellow 50 m) and in close contacts with the rivers. The climate is arid in the north and semi-arid in the south of Coquimbo, with scarce rainfall (100-240 mm/yr and decreasing). This makes the aquifers to be mainly recharged mainly by snowmelt from the Andean Mountains and secondarily by surface runoff and precipitation (Arumi & Oyarzun, 2006).
The economy of Coquimbo region is mainly focused on mining (gold, silver, and copper) and agriculture (for national and international markets). In the Choapa River basin, one of the main watersheds in the region besides Limari, there are a number of environmental conflicts between the local communities and mining companies – the main cause being water use. In this region of high water scarcity the water rights are holds especially by private companies, mostly being multinationals which have rights of surface and groundwater. In the case of the Antofagasta area (located in the northern part of Coquimbo region) the mining companies has almost 100% of the groundwater rights, using over one thousand litres per second of surface and groundwater. One of the highest consumer of water in the region are the copper mine Los Pelambres owned by Antofagasta Minerals (owned by the Luksic group) and Andacollo (Teck, Canada). The water used for the mining activity are extracted from aquifers, rivers and the glaciers located in the Andes Precordillera. Since 2008 up to now there were many incidents of toxic spills recorded from Los Pelambres, one of the most devastating ones occurred in 2009, when 13,000 liters of copper concentrate spilled directly into the Choapa river. These toxic spills legally contravene various existing health and environmental regulations in Chile. However, Chilean State ́s actions against pollution in more than 140 kilometers of the Choapa river, (from the mine site to the ocean) has been generally weak and favoring the mining sector. An evaluation of groundwater recourses and quality in the Choapa basin by Direction General de Agua (DGA) shows that they are mainly contaminated with trace metals, cooper and manganese and punctually with arsenic that was actually proved to be natural in the aquifers of the area (DGA, 2009).
Agriculture in Coquimbo region
Mining activity is not the only risk on aquifers in the region. Having a privileged location between the Cordillera de la Cote and Precordillera, Coquimbo has several transverse valleys such is Copiapo, Elqui, Huasco, Limari and Choapa. In the alluvial floodplain there are extended crops of fruits, cereals, vegetables and vineyards crops. In the region of Choapa the first vineyard was planted in 1549 by the conquistador Francisco de Aguirre, the founder of the city of La Serena, that makes this region of Chile the most known for producing famous wines such are Sauvignon, Chardonnay and Pinot Noir. Due to low rainfall in the area having an average of 130 mm/yr excepting the upper part of the basin where rich 240 mm/yr, the irrigation of these crops is ensured by an integrated irrigation system formed by interconnected canals supplied with water from small artificial ponds supplied with water extracted from aquifers via boreholes.
The farmers in Coquimbo region uses large amounts of pesticides, insecticides, herbicides and fertilizers, all of which being hazardous for both surface and groundwater water quality in the Choapa watershed (Fig. 3). Current studies indicates that the surface waters in the Choapa basin has high concentration of zinc, copper and lead, but also organic composites such as polycyclic aromatic hydrocarbons, herbicides, pesticides, and fungicides. A recent study on local farmers directly and indirectly exposed to pesticides causes a lowering in executive function, verbal ﬂuency, and visual and auditory memory (Corral et al., 2017). Currently, the monitoring of aquifers is ensured by DGA and Las Juntas de Vigilancia del Rio Choapa, but the analytic is mainly focused on basic water parameters used for aquifers characterization. Although the content of heavy metals in aquifers are monitored because of the intense mining activity in the area, the contaminants resulted from agriculture are still not considered for groundwater quality assessments.
Agriculture and mining have lived side-by-side for decades in the region of Coquimbo, but now excessive expansion of mining and intense use of the aquifers for irrigation and the application of pesticides and fertilizers, has placed unsustainable pressure on groundwater resources in the area. To this it is summed the climatic changes, Coquimbo as well as any other worldwide arid and semi-arid regions, is predicted to become drier and warmer during the 21st century. The conjunction effects resulted from the reduction of rivers flow that feed the aquifers, enhanced evapo-transpiration and depletion of aquifers for different uses will undoubtedly threaten the groundwater resources in the region, forcing the authorities to look for suitable management of water resource system.
The groundwater fauna of Chile is poorly known, most of the studies being focused on aquifers hydrological processes and physico-chemical characterization of the water (Arumí & Oyarzún, 2006; Arumí et al., 2012) or to determine the groundwater quantity for its potential use in mining industry. The only reports about groundwater biota from the Chilean groundwater are from limnic groundwater and caves (Brehier et al., 2010) and interstitial sediments of rivers, streams and lakes from central and southern part of Chile (Rio-Escalante et al., 2016). In Coquimgo region the aquifers are considered fossils due their very low natural recharge. Considering the high endemicity for several freshwater invertebrates from wetlands, streams and rivers in northern Chile, it is assumed that the groundwater may also host an incredible fauna that need to be explored from two perspectives: on one side to be discovered and protected and on the other, from a more practical view to be used as indicators for groundwater quality. GROUND-BIODIV our project in Coquimbo region aims to evaluate the groundwater biodiversity in aquifers of the Choapa watershed and detect the presence of pesticides, insecticides and fertilizers in groundwater. The study is conducted in collaboration with researchers from CEAZA and University of La Serrena, Chile.
Arumí Ribera, J.L. y Oyarzún Lucero, R.A. 2006. Las aguas subterráneas en Chile. Boletín Geológico y Minero, 117 (1): 37-45.
Arumí, J.L., Rivera, D., Muñoz, E. y Billib, M. (2012). Interacciones entre el agua superficial y subterránea en la región del Bío Bío de Chile. Obras y Proyectos 12, 4-13.
Corral, S.A., V. de Angel, N. Salas, L. Zúñiga-Venegas, P.A. Gaspar, F. Pancetti, 2017. Cognitive impairment in agricultural workers and nearby residents exposed to pesticides in the Coquimbo Region of Chile. Neurotoxicology and Teratology, 63: 13-19.