Hydrodynamics, Hydrochemistry, and Stable Isotope Geochemistry to Assess Temporal Behavior of Seawater Intrusion in the La Yarada Aquifer in the Vicinity of Atacama Desert, Tacna, Peru

Abstract

The La Yarada aquifer is the primary water resource for municipal, irrigation, and industrial uses in the semi-arid Tacna, Peru. Presently, over-pumping has caused severe groundwater management problems, including the abandonment of saline water wells. This study presents multivariate analysis and chemical–isotopic trends in water to investigate seawater intrusion and hydrogeological processes affecting water quality. The chemical and isotopic analysis of water samples, collected in two campaigns in the dry (August 2020) and wet (November 2020) seasons, together with the 1988 data, were evaluated with a mixing model, cluster, and factor analysis. The hydrochemical and isotopic mixing model suggested the formation of a wedge with 20% seawater intrusion. The heterogeneity of piezometric map isolines corroborates the wedge formation associated with the groundwater movement. The spatial distributions of factors, FA1 and FA2, suggest two processes of seawater front movement: dispersion (diffusion) of chemical elements and different types of water mixing, respectively. At the edge of the La Yarada aquifer, the water head was relatively low, permitting seawater and freshwater mixing. On the other hand, along the sea-land boundary, the water head of the La Yarada aquifer was relatively high, avoiding seawater and freshwater mixing; however, the chemical species were migrating from the seawater to the groundwater due to the diffusion processes. The cluster 4 samples are in the region corresponding to the isotopic mixing process represented by the FA2, while cluster 4 describes the chemical diffusion process represented by the FA2. Thus, the integrated approach is helpful to assess the seawater intrusion mechanisms in coastal aquifers in a semi-arid region.

Characterization of Southern Peru hydrothermal systems: New perspectives for geothermal exploration along the Andean forearc

“…To ensure consistency of all our data, and supplement some missing data, we resampled some water previously studied by INGEMMET (Peña et al, 2009;Cruz et al, 2010;Cruz, 2018;Cruz & Olascoaga, 2021)) and by Vera et al (2021). New data have been acquired in Ticaco, Chucatamani and Puquio, following the sampling and analytic protocols detailed below.…”

“…The low temperature (Tab.1) and the Na/Cl>1 of the well water (Fig. 4b) could be explained by mixing with surface water, such as seawater from marine intrusion (Vera et al, 2021;Chucuya et al, 2022).…”

Hydrogeochemical Characterization and Identification of Factors Influencing Groundwater Quality in Coastal Aquifers, Case: La Yarada, Tacna, Peru

“…Marine intrusion and salinization of groundwater are common problems that affect many arid and semi-arid coastal areas, such as the aquifer of La Yarada in the Tacna region [ 1 ]. In the absence of surface water resources, farmers in the flatlands of La Yarada use groundwater as their only source of irrigation, reaching levels of overexploitation of the aquifer [ 2 , 3 , 4 ]. This leads to a gradual decrease in the water table and, as a consequence, the quality of the water is affected by marine intrusion and by reducing secondary recharges of good quality, being confined to receiving the main recharge from the Caplina River, that presents neogenic volcanic activity in the source of its basin [ 5 , 6 ].…”

“…Multivariate statistical analysis (cluster analysis and factor analysis) together with ionic relations analysis represent solid tools for detecting and explaining the hydrogeochemical processes that govern the hydrochemical composition of groundwater in the aquifer [ 3 , 9 , 10 , 11 ]. As a result of multivariate analysis applying chemical and isotopic variables [ 3 ], two processes were identified mainly of seawater front movement: dispersion (diffusion) of chemical elements and different types of water mixing.…”

“…Multivariate statistical analysis (cluster analysis and factor analysis) together with ionic relations analysis represent solid tools for detecting and explaining the hydrogeochemical processes that govern the hydrochemical composition of groundwater in the aquifer [ 3 , 9 , 10 , 11 ]. As a result of multivariate analysis applying chemical and isotopic variables [ 3 ], two processes were identified mainly of seawater front movement: dispersion (diffusion) of chemical elements and different types of water mixing. Defining and delimiting the influence of each hydrogeochemical process in La Yarada aquifer by an analysis from three different approaches: (1) main elements, (2) trace elements, and (3) physicochemical and isotopic parameters, is, therefore, an important step for the identification of the “factors that influence water quality.” Management requires the collection and analysis of large water quality data sets that can be difficult to assess and synthesize.…”