The coastal aquifer La Yarada has anthropogenic and geogenic contamination that adversely affect the quality of groundwater for population and agricultural use. In this scenario, multivariate statistical methods were applied in 20 physicochemical and isotopic parameters of 53 groundwater pumping wells in October 2020, with the aim of characterizing the hydrogeochemical processes that dominate the groundwater of the coastal aquifer and the factors that cause them to optimize the effective management of water resources, delimiting areas affected by more than one salinization process. The samples were grouped into three clusters (C1, C2, and C3) with cluster analysis, the spatial distribution of C2 and C3 (reclassified in stiff diagrams), evidenced hydrogeochemical facies associated with the flow and recharge directions governed by the structural lineaments (NE-SO), favoring some areas more than others, arising different facies and hydrogeochemical processes. Factor analysis was applied from three different approaches: (1) main elements, (2) trace elements, and (3) physicochemical and isotopic parameters; exposing 6 distinguishable hydrogeochemical processes in the aquifer and factors that cause them: (i) salinization—marine intrusion, (ii) fertilizer leaching and dissolution of (Ca²⁺, Mg²⁺), (iii) wastewater mixture (NO³⁻), (iv) reducing conditions (Fe, Mn, Al), (v) contributions of (B, Sr), (vi) conservative mixtures and dissolution (As, F). It was validated with water quality indices (WQI) according to the national limits, delimiting 67 km² parallel to the coast with “bad” to “very bad” quality for human consumption and unsuitable for irrigation according to the Wilcox diagram thus pre-treatment in this area is indispensable.

Global projections of climate change indicate negative impacts on hydrological systems, with significant changes in precipitation and temperature in many parts of the world. As a result, floods and droughts are expected. This article discusses the potential effects of climate change and variability on the maximum precipitation, temperature, and hydrological regime in Devil’s Creek, Tacna, Peru. The outputs of precipitation and daily temperature of fifteen regional climate models were used for the RCP4.5 and RCP8.5 emission scenarios. The methodology used includes the bias correction and downscaling of meteorological variables using the quintiles mapping technique, hydrological modeling, the evaluation of two emission scenarios, and its effect on the maximum flows of the stream. The results of the multi-model ensemble show that the maximum annual precipitation will probably increase by more than 30% for the RCP4.5 and RCP8.5 scenarios for the 2021–2050 period relative to the 1981–2005 period. Likewise, as expected, the maximum flows could increase by 220% and 154% for the RCP4.5 scenarios for the 2021–2050 and 2051–2080 terms, respectively, and 234% and 484% for the RCP8.5 scenarios and for the 2021–2050 and 2051–2080 terms, respectively, concerning the recorded historical value, increasing the probability of flood events and damage in populations located downstream.

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.

A heuristic weighting methodology is formulated to classify the susceptibility to chemical weathering in the Caplina basin from two approaches: hydrogeochemical and geological morphometric. The main objective was to study the hydrological recharge of an arid basin with differential chemical weathering of geological formations in contact due to the salinization of water flow. The parameters in the morphometric approach were analyzed in two proposed indices: (1) historical reload, from the parameters of shape and hypsometric curve; (2) runoff speed with low slopes (3-12 %), drainage density < 0.8 km-1. According to their morphometry, the Caplina and Magollo sub-basins are more susceptible to chemical weathering in the Caplina basin. For the validation of the methodology, the inventory of hydrochemical samples of the Peruvian Geological Service (Ingemmet) was used. The resulting classification of weights determined about 80 % of underground and surface sources in the basin are predominantly salinized in hydrogeological units of high and medium susceptibility to weathering. The final map generated at a scale of 1:500 000 identifies two hydrogeological units with high susceptibility to weathering: (1) fissured aquifers with hydrothermal alteration, in the Chachacumane, Chulluncane, Huilacollo, Volcánico Barroso formations, contributing calcium sulfate trends in 41.2 % of the total samples; (2) intrusive aquitards, in the Yarabamba and Challaviento formations, which influence the oxidation of sulfides in the hydrochemistry of 17.6 % of the samples. Likewise, aquitards of the volcanic origin of medium susceptibility to weathering are identified, with a considerable sodium contribution in 20.6 % of the study samples. Se formula una metodología de ponderación heurística para clasificar la susceptibilidad a la meteorización química en la cuenca del Caplina desde dos enfoques: hidrogeoquímico y geológico morfométrico. El objetivo principal fue estudiar la recarga hidrológica de una cuenca árida con meteorización química diferencial de formaciones geológicas en contacto debido a la salinización del flujo de agua. Los parámetros en el enfoque morfométrico se analizaron en dos índices propuestos: (1) recarga histórica, a partir de los parámetros de forma y curva hipsométrica; (2) velocidad de escurrimiento en pendientes bajas (3-12 %), con densidad de drenaje < 0.8 km-1. Según su morfometría, las subcuencas Caplina y Magollo son más susceptibles a la meteorización química en la cuenca Caplina. Se interrelacionó la geoquímica (litología, minerales alterables y presencia de alteración hidrotermal) e hidrogeología (porosidad y permeabilidad). Para la validación de la metodología se utilizó el inventario de muestras hidroquímicas del Servicio Geológico Peruano (Ingemmet) y la clasificación resultante de ponderaciones determinó 80 % de fuentes subterráneas y superficiales en la cuenca están salinizadas predominantemente en unidades hidrogeológicas de alta y media susceptibilidad a la meteorización. El mapa final generado a escala 1:500 000 identifica dichas unidades hidrogeológicas: (1) acuíferos fisurados con alteración hidrotermal en las formaciones Chachacumane, Chulluncane, Huilacollo, Volcánico Barroso, aportando tendencias cálcicas sulfatadas en el 41.2 % del total de muestras; (2) acuitardos intrusivos en las formaciones Yarabamba y Challaviento, que influyen en oxidación de sulfuros en la hidroquímica del 17.6 % de muestras. Asimismo, se identifican los acuitardos de origen volcánico de susceptibilidad media a la meteorización, con un considerable aporte sódico en el 20.6 % de muestras del estudio.