Groundwater chemistry characterization using multi-criteria approach: The upper Samalà River basin (SW Guatemala)

Improving understanding on groundwater chemistry is a key priority for water supply from groundwater resources, especially in developing countries. A hydrochemical study was performed in an area of SW Guatemala (Samala River basin), where water supply to population is groundwater-based and no systematic studies on its groundwater resources have been performed so far. Traditional hydrochemical analyses on major ions and some trace elements metals coupled with chemometric approach were performed, including principal component analysis and hierarchical clustering analysis. Results evidence that chemical differentiation is linked to the spatial distribution of sampled waters. The most common hydrochemical facies, bicarbonate calcium and magnesium, is linked to infiltration of meteoric waters in recharge areas represented by highlands surrounding Xela caldera, a wide plateau where most of population is concentrated. This trend undergoes chemical evolution in proximity of active volcanic complexes in the southern area, with enrichment in sulphate, chloride and magnesium. Chemical evolution also occurs towards the centre of Xela caldera due to slow circulation in aquifer and consequent sodium enrichment due to ion exchange with the porous medium. Water quality did not reveal severe concerns, even though some sources of contamination could be identified; in particular, agriculture and urban wastewater could be responsible for observed threshold exceedances in nitrate and lead. This integrated multi-approach to hydrochemical data interpretation yielded to the achievement of important information that poses the basis for future groundwater protection in an area where main water features were almost unknown.