Monitoring toxic metals to redress the impacts of large-scale mining in the Jequetepeque Basin


Demonstration at Cajamarca, Perú (2008). Source: EScGD


Water treatment plant, Cajamarca, Perú (2008). Source: EScGD

Residents in Porcón, Peru had every reason to think their lives would henceforth improve when in 2004 their community was allowed to draw water from sources nearby. Ten years before, large-scale mining had initiated its activities in the Jequetepeque River basin. With mining, pollution by toxic metals soared. Later on, however, Yanacocha Mining proceeded to drill a 150-metre deep well for its own supply, and water flows in Porcón – as well as in other communities – significantly dropped. Road blocks followed, riot police intervened, and several activists were arrested. Again, in July 2012, public contestation of the new Conga project ended up with five dwellers dead by police-fired bullet shots. The Porcón watershed is the natural sink for toxic metal-rich waste used for leaching gold in the largest open mine in Latin America.

Monitoring toxic metals is the core activity of a team of researchers – led by Cristina Yacoub – that from 2007 to 2013 was characterizing water and sediment pollution in the Jequetepeque River basin. EScGD acts in partnership with local actors to develop innovative tools to redress the problem. Thus, for instance, between 2008 and 2010 we assisted GRUFIDES – a Peruvian rights organization – to monitor the effects of acid mine drainage. Additionally, a SWAT model of the basin was calibrated and used to better understand the dynamics shaping the flow of pollutants downstream. As a result, research was informing the elaboration of an environmental monitoring protocol by a consortium of Peruvian and Spanish universities.


Jequetepeque basin with different concentrations of trace elements and element speciation. Source: Yacoub, C. (2013).


Comparison of measured and simulated daily streamflow from 2006 to 2009. Source: Yacoub, C. et al. (2013).

The analyses of water quality done by EScGD have revealed major peaks of pollution nearby mining areas. Water sources across the Jequetepeque River Basin are polluted by toxic metals. Pollution in surface water is becoming a critical issue, since water is increasingly a source for a nearby population of 390,000 (2005). The basin covers 4,372.5 km2, and comprises mining activities across an area twice the size of Barcelona. During two years, EScGD and GRUFIDES analyzed 249 water samples taken in 30 monitoring sites along the basin. By doing on principal component and hierarchical cluster analysis, they characterized the distribution of trace metals and their sources, as well as the concentrations of pH, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), chloride, weak-acid-dissociable (WAD) cyanide, total cyanide, nitrite and nitrate, ammonium, sulfate, Al, As, Ca, Cd, Cu, Cr, Fe, Mg, Mn, Ni, Pb, and Zn.

EScGD is at the forefront of efforts to unveil the crucial role of the topographical setup in pollution patterns. Cristina Yacoub and Agustí Pérez-Foguet, for instance, have singled out terrain slope as a key driver conforming runoffs in mountain basins. In so doing EScGD became the first research group to consider slope as a variable when calibrating SWAT models describing river basins. This breakthrough has paved the way for the further improvement of SWAT models for simulating mountainous basins dynamics.

Once the basin had been monitored and modeled, a consortium of researchers has undertaken the elaboration of a protocol in order to control environmental quality. The protocol – devised by EScGD, Universidad Nacional de Cajamarca and Universidad de Barcelona – is a comprehensive tool aiming to cover: 1) water quality, 2) sediment quality, and 3) macro-invertebrates and riverside vegetation. The consortium has realized that analyzing sediments is crucial since, in the long run, they are in a better position to detect pollution by trace elements than analyses of water quality. Monitoring protocols such as this one can help local organizations facing environmental threats to benefit from simple and cost-effective answers to assess the quality of local water sources.