La calidad del recurso hídrico Quebrada El Arenal, es de vital importancia en el municipio de Junín, debido a que es la principal fuente receptora del agua de esta población. El objetivo del presente artículo es diseñar un modelo de simulación de calidad de agua superficial del cuerpo mencionado, que permita determinar la afectación de los vertimientos domésticos en época de estiaje. La metodología utilizada para realizar el artículo se basa en la determinación del índice de calidad de agua, análisis e interpretación ambiental de las cargas contaminantes de los vertimientos domésticos y la determinación de las diferentes variables utilizadas para realizar el modelo en el programa QUAL2K. Los resultados obtenidos permiten evidenciar las condiciones moderadas y buenas del cuerpo hídrico en la época de estudio, así como las bajas cargas contaminantes de los dos vertimientos y por tanto la capacidad de autodepuración del cuerpo hídrico ante las mismas, señalando como principal problema en la Quebrada El Arenal, la presencia de Coliformes Totales y nutrientes (Nitrógeno Total y Fosforo Total). | The water’s quality of the Quebrada El Arenal, it is an issue of big importance in the town of Junin, because it is the main source of water receiving this population. The purpose of this paper is to design a simulation model surface water quality resource mentioned, should determine the allocation of domestic discharges in the dry season. The methodology used for the article is based on the determination of the water quality, environmental analysis and interpretation of pollutant loads from domestic discharges and the determination of the different variables used for the model in the QUAL2K program. The results obtained show moderate and good condition of the water body at the time of study and low pollutant loads of the two discharges, therefore the self-purification capacity of the water body, noting that the main problem in Quebrada El Arenal, is the presence of total coliforms and nutrients (nitrogen and phosphorus).

This article was intended to contribute to the knowledge of the behavior of Dissolved Oxygen in the water column that appeared in the ecuadorian fixed stations in La Libertad and Manta, average monthly values were obtained and the maximum at different depth monitored and shown to be 75 meters in the years when "El Niño" events appeared, the highest concentrations were found monthly in the two fixed stations, allowing behavioral tendencies contribute to a chemical parameter, to warn the start of warm event. | El presente artículo tiene como propósito aportar al conocimiento del comportamiento del Oxígeno Disuelto en la columna de agua que se presentó en las estaciones fijas ecuatorianas ubicadas en La Libertad y Manta, se obtuvieron valores mensuales promedios, así como los máximos y mínimos en las diferentes profundidades monitoreadas y se demostró que a 75 metros en los años en que se manifestaron eventos "El Niño", se encontraron las mayores concentraciones mensuales, en las dos estaciones fijas, lo que permitió aportar con tendencias de comportamiento de un parámetro químico, para advertir el inicio de un evento cálido. | Published

Introduction: Riffle beetles are aquatic organisms frequently associated with well-oxygenated clean running water; however, some genera of Elmidae can also be found in moderately polluted streams proving their tolerance to certain degree of habitat degradation. Objective: In order to determine the contamination sensitivity and tolerance of each genus and the main factors that influence the presence and composition of Elmidae in Colombia, Methods: 60 locations between 450 and 4000 masl were sampled in six localities of Colombia, mainly in the Andean Region. Collection was carried out with D and Surber nets. Physico-chemical, bacteriological and environmental quality information was recorded. With these data, Canonycal Correspondence Analysis and descriptions of occurrence intervals for each genus were made. Results: Twenty-two genera were found in the streams evaluated; which represents 85% of known national richness. The most important factors influencing the presence and composition of Elmidae were oxygen saturation, sediment deposition, suspended solids, epifaunal substrate availability and geographic location. Conclusions: Results are useful for classifying elmids according to their sensibility to changes in environmental conditions and habitat degradation, which is a first step to incorporate Elmidae in water quality biotic indexes. | Introducción: Los élmidos son organismos acuáticos frecuentemente asociados con aguas corrientes, limpias y bien oxigenadas. Sin embargo, algunos géneros de esta familia también se encuentran en aguas moderadamente contaminadas, lo cual puede ser un reflejo de su tolerancia al deterioro del hábitat. Objetivos: Con el fin de determinar los principales factores que influyen en la presencia de Elmidae en microcuencas colombianas, Métodos: se muestrearon 60 localidades en seis ventanas entre 450 y 4000 msnm, principalmente en la región Andina. Se hicieron arrastres con red D y Surber y se determinaron los géneros de Elmidae. Se tomaron datos físico-químicos, bacteriológicos y de calidad del hábitat (ICH). Se calcularon los Índices de Contaminación y Calidad de Agua (ICA-FSN e ICOs), se realizó un Análisis de Correspondencia Canónica entre las variables ambientales y la composición de Elmidae y se definieron intervalos para cada género. Resultados: Se encontraron 22 géneros que representan el 85% de la riqueza nacional conocida. Los principales factores que influyeron en la riqueza y composición de Elmidae fueron: saturación de oxígeno, deposición de sedimentos, cantidad de sólidos en suspensión, disponibilidad de sustratos para colonización y la ubicación geográfica. Conclusión: Con esta información fue posible clasificar los géneros de Elmidae por su sensibilidad y relacionarlos con la calidad del agua y el hábitat en microcuencas de Colombia.

This study describes a low-cost method for sampling individual fractures in open wellbores in crystalline bedrock utilizing naturally occurring flow conditions in the well. The method entails using the dissolved oxygen alteration method (DOAM) to identify transmissive fractures and vertical flow direction. After obtaining information about relative hydraulic gradients, flow direction in the well is modified using a single control pump to isolate fractures of interest for sampling. Additional dissolved oxygen, injected during the DOAM procedure, serves as a tracer to ensure the water quality in the sampling zone is characteristic of the fracture of interest by requiring a tracer-free zone prior to sampling. Sampling procedures are described conceptually for nine bedrock wells with varying flow conditions containing one, two, or three transmissive inflowing fractures. The method was demonstrated in two crystalline bedrock wells containing one and two transmissive inflowing fractures.

Con el propósito de evaluar los impactos generados por el uso de un método de pesca artesanal denominado "boliche" en la laguna costera tropical Ciénaga Grande de Santa Marta, se cuantificaron diferentes aspectos; uno de los cuales fue orientado a analizar algunas alteraciones físico-químicas de la columna de agua, producidas durante la maniobra de pesca. Se determinó la concentración de oxígeno disuelto, la transparencia del agua y la concentración y composición del seston, antes y después de 70 lances de boliche. Los resultados indican que la maniobra de pesca genera algunos cambios momentáneos de poca repercusión en el ecosistema, tales como resuspensión de partículas principalmente inorgánicas, aumento de la concentración de seston y en consecuencia disminución de la transparencia de la columna de agua. La concentración de oxígeno disuelto no presenta alteración apreciable. | With the purpose of assessing the impact generated by the use of an artisanal fishing method populary called "boliche", in the tropical coastal lagoon Ciénaga Grande de Santa Marta, different aspects were quantified; being one of them designed to analyze some physical-chemical alterations of the water column, produced during the fishing operations. The dissolved oxygen concentration, water transparency and seston compositiori and concentration, before and after of 70 boliche's thrusts were determinated. The resultsshow that fishing operations genérate some momentary changes of little repercution to the ecosys'tem, such as particle resuspention principally inorganic an increase in seston concentration and a consequen water column transparency decrease. The dissolved oxygen concentration does not show appreciable alteration. | Published

Goodenough Spring (Texas, USA) is a large spring near the border of the American state of Texas and the Mexican state of Coahuila, discharging into the international Amistad Reservoir on the river Rio Grande (Rio Bravo). Discharge was routinely measured from 1928 until 1968 to partition the flow of the river between the two countries in accordance with water-use treaties. Samples were analyzed for water-quality parameters in 1967–1968 prior to inundation under 45 m of Amistad Reservoir in 1968. Subsequently, discharge has been estimated indirectly by the International Boundary and Water Commission (IBWC). For the first direct measurements of the spring in 37 years, velocity and cross-sectional measurements were made and water samples collected in the summer of 2005 using advanced self-contained underwater breathing apparatus (SCUBA) techniques. Spring discharge was calculated at 2.03 m³ s–¹, approximately one-half of the historical mean of 3.94 m³ s–¹. In situ and laboratory analyses of samples for temperature, pH, dissolved oxygen, specific conductance, alkalinity, nitrate-nitrogen, dissolved solids, chloride, sulfate, fluoride, phosphorus, calcium, sodium, potassium, magnesium, and iron showed the water quality to be very good for human consumption and crop irrigation. Measurement values are relatively unchanged from those reported 37 years prior.

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO 3 – ), iron (Fe2+), manganese (Mn2+), and sulfate (SO 4 2– ). Redox conditions were evaluated also based on methane (CH4), excess nitrogen gas (N2) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.