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.

The pressure drop in 90 deg elbows under the operating conditions of geothermal power plants in Mexico is studied using the computational fluid dynamics model. The elbow resistance coefficient was calculated for a steam flow with high Reynolds numbers (1.66–5.81 × 106) and different curvature ratios (1, 1.5, and 2). The simulations were carried out with the commercial software ANSYScfx, which considered the Reynolds-averaged Navier–Stokes (RANS) compressible equations and the renormalization group (RNG) k–ε turbulence model. First, the methodology was validated by comparing the numerical results (velocity and pressure) with published data of airflow (25 °C, 0.1 MPa) with high Reynolds numbers. Then, scenarios with different diameters (0.3–1.0 m) and conditions of the working fluid (0.8–1.2 MPa) were simulated to obtain velocity, pressure, density, and temperature profiles along the pipeline. The temperature and density gradients combined with the compressible effects achieved in the 90 deg elbows modified the flow separation, pressure drop, and resistance coefficient. Based on the resistance coefficient, factors were generated for a new equation, which was integrated into Geosteam.Net to calculate the pressure drop in a pipeline at the Los Azufres geothermal power plant. The difference with the data measured by a pressure transducer was 7.59%, while the equations developed for water or air showed differences between 11.23% and 45.22%.

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.