he objective was to characterize the water quality in a section of the Grijalva River and in some of its tributaries on the border between the States of Chiapas and Tabasco, in the rainy and dry seasons. Twenty-three physical, chemical and microbiological parameters as well as contaminants were determined. The values obtained were compared with the maximum permissible limits (MPLs) for water use and human consumption set out in O cial Mexican standard NOM-127-SSA1-1994, and with the water quality classi cation scale of the Comisión Nacional del Agua (CONAGUA). The water quality in the studied section of the Grijalva River decreases as it descends to more populated areas of the State of Tabasco. Water turbidity and E. coli coliform levels increase, both in the river channels and in sources destined for human consumption. For the other variables evaluated, there are acceptable water quality characteristics, mainly in the dry season, except for mercury, which occurs at levels higher than those recommended. Further studies on the presence of mercury in the Grijalva River basin are recommended.

En el valle del Yaqui, Sonora, México, la actividad agrícola depende del almacenamiento de agua en el sistema de presas construido en la cuenca del río Yaqui, el cual tiene una capacidad de almacenamiento de 7008.4 hm³. Sin embargo, para el ciclo otoño-invierno 2003-2004 no se autorizó la utilización de esta agua para uso agrícola, debido al bajo nivel de almacenamiento. En respuesta a esto, se extrajeron del acuífero aproximadamente 350 millones de m³ de agua. De acuerdo con estudios recientes, la mayor parte del acuífero contiene un intervalo de 1000 a 5000 mg L-1 de sólidos totales disueltos. El objetivo de esta investigación fue estudiar la composición iónica de 224 muestras de agua y clasificarlas de acuerdo con los criterios más conocidos. Se seleccionaron 164 muestras que cumplieron con un error de balance iónico menor de 5% y se calcularon los parámetros necesarios para clasificar el agua desde el punto de vista agrícola. El valor promedio para las características evaluadas fue: pH, 7.25; conductividad eléctrica, 2.06 dS m-1; cationes en meq L-1: Na+, 8.5; Ca2+, 7.69; Mg2+, 5.08; aniones en meq L-1: SO4(2-), 4.57; CO3(2-), 0.83; HCO3-, 3.3; Cl-, 12.5; relación de adsorción de sodio (RAS), 3.91; RAS corregido, 4.44; RAS ajustado, 8.82; RAS corregido por HCO3-/Ca2+, 4.38; salinidad efectiva, 14.8; salinidad potencial, 14.7; carbonato de sodio residual, 0.57; índice de permeabilidad, 53.3, y porciento de sodio intercambiable (PSI), 5.83. El agua extraída del acuífero del valle del Yaqui muestra limitaciones para la irrigación de especies sensibles a la salinidad, además de que existen pozos que extraen agua, cuya calidad no es recomendable para uso agrícola y cuya utilización podría provocar un incremento en la salinidad del suelo. Por otra parte, la concentración de iones tóxicos como Na+ y Cl-es alta, lo cual se considera una restricción adicional. Con relación al Na+, la mayoría de los pozos extraen agua con un riesgo bajo de sodificar el suelo, en lo cual coinciden la mayoría de los esquemas de clasificación utilizados. | In the Yaqui Valley, Sonora, Mexico, agriculture depends on the reservoir system built in the Yaqui River basin, which has a storage capacity of 7008.4 hm³. For the 2003-2004 autumn-winter crop cycle, water utilization was not authorized for agricultural use due to the low storage level. In response, 350 million cubic meters of water was extracted from the aquifer. According to recent studies, most of the acquifer contains 1000 to 5000 mg L-1 total dissolved solids. The objective of this study was to assess the water quality of 224 samples and classify them according to the best-known criteria. 164 samples were selected that had an ionic balance error of less than 5%, and the necessary parameters were calculated to classify the water for agricultural purposes. The average values for the evaluated characteristics were the following: pH, 7.25; electrical conductivity, 2.06 dS m-1; Na+, 8.5; Ca2+, 7.69; Mg2+, 5.08; SO4(2-), 4.57; CO3(2-), 0.83; HCO3-, 3.3; Cl-, 12.5 meq L-1; sodium adsorption (SAR), 3.91; corrected SAR, 4.44; adjusted SAR, 8.82; adjusted SAR HCO3-/Ca2+, 4.38; effective salinity, 14.8; potential salinity, 14.7; residual sodium carbonate, 0.57; permeability index, 53.3; percentage of exchangeable sodium (PES), 5.83. Water extracted from the Yaqui Valley aquifer shows that its use for irrigation of saline-sensitive species should be limited. Moreover, some wells have water of a quality that is not suitable for agricultural use since it could provoke an increase in soil salinity. In addition, the concentration of toxic ions such as Na+ and Cl- is high and is considered to be an additional restriction. Regarding Na+, most of the water samples extracted indicate a low risk of sodifying the soil, coinciding with most of the classification schemes used.

Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos.

The present had the purpose of expanding the hydrogeochemical knowledge of the aquifer in the area of ​​the sub-basin of the Acahuapa River, in the department of San Vicente. Samples were collected from 10 points in the surface waters of the water network of the sub-basin. The samplings were carried out in the dry and rainy season during the period from February 2011 to August 2012. The parameters analyzed were cation data (Na, K, Ca, Mg, total Fe) and anions (HCO-3 , Cl-, SO-24, CaCO3-2), as well as carbonates in order to determine the mass balance and flow of CO2 gas. In addition, physicochemical parameters of temperature, dissolved oxygen, pH and electrical conductivity. Such analyzes are sufficient for the study of the main chemical processes in most aquifers and their relationships with hydrological systems. In general, it was concluded that the chemical behavior of the aquifer in the Acahuapa river sub-basin in both rainy and dry seasons is similar, and that the predominant water families are bicarbonate magnesium and calcium bicarbonate. The bicarbonated waters are bad for irrigation, due to the fixation of ions in the ground and creation of an alkaline environment. | El presente tuvo la finalidad de ampliar el conocimiento hidrogeoquímico del acuífero en la zona de la subcuenca del río Acahuapa, en el departamento de San Vicente. Se recolectaron muestras de 10 puntos en las aguas superficiales de la red hídrica de la subcuenca.  Los muestreos se llevaron a cabo en la época seca y lluviosa durante el periodo comprendido de febrero de 2011 hasta agosto de 2012.   Los parámetros analizados fueron datos de cationes (Na, K, Ca, Mg, Fe total) y aniones (HCO-3, Cl-, SO-24, CaCO3-2), así como de carbonatos con el fin de determinar el balance de masa y flujo de gas CO2. Además, parámetros fisicoquímicos de temperatura, oxígeno disuelto, pH y conductividad eléctrica. Tales análisis son suficientes para el estudio de los principales procesos químicos en la mayoría de los acuíferos y sus relaciones con los sistemas hidrológicos. De forma general se concluyó que el comportamiento químico del acuífero en la subcuenca del río Acahuapa en ambas épocas lluviosa y seca, es similar, y que las familias de agua predominantes son bicarbonatadas magnésicas y cálcicas bicarbonatadas. Las aguas bicarbonatadas son malas para riego, debido a la fijación de iones en el terreno y creación de un medio alcalino.

En una parcela de 2520 m cuadrados se han instalado 50 extractores de agua del tipo bujía porosa de porcelana, a una profundidad de 0,4 m para analizar la variabilidad espacial de las concentraciones en SO4E2-, NO3-, Cl-; HCO3-, MgE2+, CaE2+, Na+ y K+. Se han encontrado coeficientes de variación que oscilan entre el 37% para el Na+ y el 110% del Cl-. La variabilidad temporal puesta de manifiesto en dos muestreos separados 4 meses es muy baja comparada con la espacial. El análisis de los semivariogramas muestran una distribución espacial aleatoria de todos los iones. El número mínimo de repeticiones para obtener valores representativos de la variabilidad espacial es 40 para esta parcela. Se ha estudiado la incidencia del número de repeticiones en la precisión del valor medio obtenido. Entre las 50 muestras se seleccionan al azar grupos desde 3 hasta 45 y se calcula el valor medio en cada caso. El proceso se repite 2000 veces y se comprueba que la desviación típica de las funciones de distribución decrece logaritmicamente con el número de repeticiones utilizadas en el grupo de partida. Esto nos permite ajustar por mínimos cuadrados la ecuación [CVn=A+b*Ln N] para cada ion. Los valores de A y b así obtenidos, se correlacionan a su vez linealmente (r=0,998) con la variabilidad espacial obteniéndose la expresión final [CVt=CVe+CVn=CVe (1+(0,75-0,916 lnN))]. Esta ecuación permite obtener el coeficiente de variación total que ha de asociarse a un valor medio obtenido con N repeticiones y cuya variabilidad espacial es CVe.

The Agua Negra drainage system (30 12'S, 69 50' W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4200 up to 6300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO₃⁻----Ca²⁺ solution and rock-glaciers a SO₄²⁻----HCO₃⁻----Ca²⁺ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulphide oxidation (i.e. abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source of NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g. Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved rare earth elements (REE) tends to increase with discharge. Through PHREEQC inverse modelling, it is shown that gypsum dissolution (i.e. sulphide oxidation) is the most important geochemical mechanism delivering solutes to the Agua Negra drainage system, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e. gypsum and calcite). Meltwater chemistry in glacierized arid areas appears strongly influenced by sublimation/evaporation, in contrast with its humid counterparts.

It was studied the distribution patterns of the native European white-clawed crayfish (Austropotamobius pallipes) and the introduced signal crayfish (Pacifastacus leniusculus), and looked at the water chemistry in several streams in the north of the Iberian Peninsula (Cantabrian watershed). Fifty fluvial reaches which were currently or previously inhabited by crayfish and had physical attributes similar to the known habitat requirements of crayfish were sampled. P. leniusculus was the most common species encountered (54 percent of the samples), A. pallipes was found in 19 percent and neither species was recorded in the remaining reaches. In this paper it was determined the relationship between crayfish presence and water chemistry. As neither species inhabits waters with the highest NO2- concentrations found, it seems both species are sensitive to NO2-. Mg+2 and S04-2 concentrations are the factors separating sites with and without crayfish (crayfish inhabit water with higher concentrations of both cations). The main differences between reaches inhabited by native and signal crayfish lies in SO4-2 concentration: higher concentrations favour signal crayfish. Applications to management based on the river water chemistry are proposed

En una parcela de 2520 m cuadrados se han instalado 50 extractores de agua del tipo bujia porosa de porcelana, a una profundidad de 0,4 m para analizar la variabilidad espacial de las concentraciones en SO4E2-, NO3-, Cl-; HCO3-, MgE2+, CaE2+, Na+ y K+. Se han encontrado coeficientes de variacion que oscilan entre el 37% para el Na+ y el 110% del Cl-. La variabilidad temporal puesta de manifiesto en dos muestreos separados 4 meses es muy baja comparada con la espacial. El analisis de los semivariogramas muestran una distribucion espacial aleatoria de todos los iones. El numero minimo de repeticiones para obtener valores representativos de la variabilidad espacial es 40 para esta parcela. Se ha estudiado la incidencia del numero de repeticiones en la precision del valor medio obtenido. Entre las 50 muestras se seleccionan al azar grupos desde 3 hasta 45 y se calcula el valor medio en cada caso. El proceso se repite 2000 veces y se comprueba que la desviacion tipica de las funciones de distribucion decrece logaritmicamente con el numero de repeticiones utilizadas en el grupo de partida. Esto nos permite ajustar por minimos cuadrados la ecuacion [CVn=A+b*Ln N] para cada ion. Los valores de A y b asi obtenidos, se correlacionan a su vez linealmente (r=0,998) con la variabilidad espacial obteniendose la expresion final [CVt=CVe+CVn=CVe (1+(0,75-0,916 lnN))]. Esta ecuacion permite obtener el coeficiente de variacion total que ha de asociarse a un valor medio obtenido con N repeticiones y cuya variabilidad espacial es CVe.

In coastal-zone fields with a high groundwater level and sufficient rainfall, freshwater lenses are formed on top of saline or brackish groundwater. The fresh and the saline water meet at shallow depth, where a transition zone is found. This study investigates the mixing zone that is characterized by this salinity change, as well as by cation exchange processes, and which is forced by seepage and by rainfall which varies as a function of time. The processes are first investigated for a one-dimensional (1D) stream tube perpendicular to the interface concerning salt and major cation composition changes. The complex sequence of changes is explained with basic cation exchange theory. It is also possible to show that the sequence of changes is maintained when a two-dimensional field is considered where the upward saline seepage flows to drains. This illustrates that for cation exchange, the horizontal component (dominant for flow of water) has a small impact on the chemical changes in the vertical direction. The flow’s horizontal orientation, parallel to the interface, leads to changes in concentration that are insignificant compared with those that are found perpendicular to the interface, and are accounted for in the 1D flow tube. Near the drains, differences with the 1D considerations are visible, especially in the longer term, exceeding 100 years. The simulations are compared with field data from the Netherlands which reveal similar patterns.

Correct understanding of groundwater/surface-water (GW–SW) interaction in karst systems is of greatest importance for managing the water resources. A typical karst region, Fangshan in northern China, was selected as a case study. Groundwater levels and hydrochemistry analyses, together with isotope data based on hydrogeological field investigations, were used to assess the GW–SW interaction. Chemistry data reveal that water type and the concentration of cations in the groundwater are consistent with those of the surface water. Stable isotope ratios of all samples are close to the local meteoric water line, and the ³H concentrations of surface water and groundwater samples are close to that of rainfall, so isotopes also confirm that karst groundwater is recharged by rainfall. Cross-correlation analysis reveals that rainfall leads to a rise in groundwater level with a lag time of 2 months and groundwater exploitation leads to a fall within 1 month. Spectral analysis also reveals that groundwater level, groundwater exploitation and rainfall have significantly similar response periods, indicating their possible inter-relationship. Furthermore, a multiple nonlinear regression model indicates that groundwater level can be negatively correlated with groundwater exploitation, and positively correlated with rainfall. The overall results revealed that groundwater level has a close correlation with groundwater exploitation and rainfall, and they are indicative of a close hydraulic connection and interaction between surface water and groundwater in this karst system.