Globally, the agriculture is one of the largest consumers of groundwater (GW) resources, that has a wide range of impacts on subterranean ecosystems. The pressure on groundwater from agricultural watersheds is remarkably higher in arid and drought-prone regions, where the aquifers depletions due to water abstraction for irrigation and water degradation resulted from nutrients load, exerts major alterations of water quality, groundwater recharge and the natural renewal rate. Groundwater biodiversity assessment is essential in understanding the impact produced by agriculture activities on groundwater as a resource and as ecosystem, a nexus that become more and more widely recognized.

Coquimbo
Figure 1. Coquimbo region, the IV out of 15 administrative divisions of Chile, located at about 400 km north from Santiago de Chile

The aquifers in the arid zone from northern Chile are confined y semi-confined whit shallow water table (bellow 50 m) located in fluvial valleys and their recharge are mainly ensured by precipitations, surface runoff and snowmelt. The mining industry is the main cause of water deficits in northern Chile where one of the largest mining exploitation are present. Los Pelambres located in north-central Chile (Coquimbo region, Fig. 2) is one of the largest copper reserves in the world, having estimated reserves of 4.9 billion tons of ore (Fig. 2).

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Figure 2. Los Pelambres cooper mine, Coquimbo region (north-central Chile)

But mining activity is not the only risk upon aquifers in the region. Having a privileged location between the Cordillera de la Cote and Precordillera, the Coquimbo region has three transverse valleys with extended crops of fruits, vegetables and vineyards that contrast with the natural environment of a semi-desert area (Fig. 3). The first vineyard was planted in 1549 by the conquistador Francisco de Aguirre, the founder of the city of La Serena, making this region of Chile the most known for producing famous wine such are Sauvignon, Chardonnay and Pinot Noir.

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Figure 3. Field crops in Coquimbo region (Chile)

The rainfall in the area is very low having an average of 130 mm per year and hence the crops irrigation is ensured by an integrated  irrigation system of interconnected of dams and canals supplied with water extracted from aquifers via irrigation groundwater boreholes. Current studies indicates that the surface waters besides a high content of zinc, copper and lead, contain also organic composites such as polycyclic aromatic hydrocarbons, herbicides, pesticides, and fungicides. But the aquifers are so far known to be mainly contaminated with trace metals. There is a program monitoring of groundwater in distinct regions throughout the country by Direction General de Agua (DGA) focused on general aquifers water characterization, but the contaminants resulted from agriculture are still not considered.

Our investigations in the semi-arid region of Coquimbo aims to assess the environmental alterations of groundwater ecosystems from agricultural watersheds in the Choapa valley, by evaluating the groundwater fauna biodiversity and the effects of contaminants proceeding from agriculture on biotic communities and of ecosystem services they provide. The study is conducted in collaboration with Nicolas Gouin and Angeline Bertin from the CEAZA and the University of La Serrena.

 

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