Este trabalho analisa a turbidez e a circulação da agua no canal San Blas durante um ciclo de maré teórico através de imagens satelitais. Foram utilizadas 8 imagens Landsat TM e ETM adquiridas em condições de céu claro e ao longo de diferentes momentos da maré. As imagens foram proporcionadas pela Comisión Nacional de Actividades Espaciales (CONAE) y pelo Serviço Geológico dos Estados Unidos (USGS). As correções geométricas e radiométricas foram realizadas nas bandas do espectro visível e do infravermelho próximo, utilizando técnicas padrões de processamento digital. Foi aplicada a correção atmosférica COST (CHAVEZ, 1996). Foi realizada uma classificação ISODATA não supervisionada para identificar diferentes níveis de turbidez al longo do canal e zonas adjacentes. Os resultados sugerem que o transporte de sedimento em suspensão para a boca do canal se da ao longo de ambos flancos, pela ação das correntes de refluxo. Estas correntes geram um delta de refluxo com uma tendência de rotação para a direção sul. As correntes de fluxo provocam turbidez principalmente sobre a costa sul do canal, gerando um delta de fluxo com bancos alargados na direção das correntes de maré. As plumas de turbidez permitiram identificar padrões gerais de circulação da maré.

This paper deals with the application of satellite images to study turbidity and water circulation patterns in San Blas channel during a theoretical tidal cycle. Eight Landsat TM and ETM images acquired under clear-sky conditions and representing different tidal stages were selected from a pool of Landsat images provided by the argentinean National Commission of Space Activities (CONAE) and the US Geological Survey. Standard digital image processing techniques were used to perform geometric and radiometric corrections on the visible and near-infrared bands. An image-based atmospheric correction (COST method by CHAVEZ, 1996) was applied. An ISODATA unsupervised classification was performed in order to identify different turbidity levels throughout the channel and adjacent areas. The results suggest that suspended sediment transport towards the channel mouth by ebb currents occurs along both flanks. These currents carry suspended sediment into the open sea, generating an ebb tidal delta which tends to rotate in a clockwise direction. Flood currents trigger turbidity mostly over the southern flank of the channel, generating a flood tidal delta with elongated banks extending in the direction of the tidal currents. From the elongated shape of the turbidity plumes, general tidal circulation patterns were identified.

The town of Las Grutas, in a semiarid region on the north west coast of San Matías Gulf (Argentina), is intersected by two drainage basins that are activated immediately after intense rainfall events. These events generate flows capable of producing local flooding, such as the flood of April 2004. The purpose of this study is to establish the hydrologic behavior of these geoforms and the manner in which the land use interacts with them. The lack of hydrometric records necessitates the explanation and prediction of hydrologic responses through empirical approaches such as fluvial morphometry and the USDA Soil Conservation Service curve number (1972), supported by Geographical Information System technology. The study area has characteristics that favor the concentration of runoff into streams during extreme events. First-order segments play an important role in the hydrologic response, showing great potential to receive surface runoff. The effect of urbanization produces an additional runoff of 17.3% and 2.1% in the respective basins. A potential increase in the number of these extreme events in the future due to climate change may lead to more disturbances in the urbanized area. The results of the present study will contribute to the implementation of measures to mitigate the consequences of floods.

La localidad de Las Grutas está emplazada en una región semiárida, en la costa Noroccidental del Golfo San Matías (Argentina) y es intersectada por dos cuencas de drenaje que responden ante eventos de precipitaciones intensas. Estos eventos generan flujos capaces de producir riesgos de inundación local, tal como la inundación de abril de 2004. El objetivo de este trabajo es establecer el comportamiento hidrográfico de dichas geoformas y la manera en el cual los usos de la tierra interactúan con ellas. La falta de registros hidrométricos conduce a explicar y predecir respuestas a través de aproximaciones empíricas como el análisis morfométrico fluvial y el número de curva del Servicio de Conservación del Suelo de los Estados Unidos (1972), apoyados en sistemas de información geográfica. El área en estudio presenta características que favorecen la concentración del escurrimiento en cauces durante eventos extremos. Los segmentos de primer orden juegan un rol importante en la respuesta hidrológica. El efecto de la urbanización produce un efecto adicional del 17.3 y 2.1% de escurrimiento en cada cuenca. El incremento potencial del número de eventos extremos en el futuro debido al cambio climático, podría conducir a mayores perturbaciones en el área urbanizada. Los resultados contribuirán a implementar medidas que mitiguen posibles consecuencias de los peligros de inundación.

Two mysids species were present in the Bahia Blanca estuary: Arthromysis magellanica (Cunningham) and Neomysis americana (Smith). They were present in the estuary from August to March. The abundance of A. magellanica was highest, 31.92 ind.m-3 in spring and N. americana abundance reached a maximum of 10.91 ind.m-3 during midsummer. These high abundance values were coincident with the increment of the water temperature. The mean temperature value registered during the sampled period was 15.7°C. Both species were present from 10°C to 23.3°C and were absent from 6.6°C to 22°C. In agreement with the spatial distribution of both species, a relationship in the abundance of A. magellanica for the three sampling stations was not detected (ANOVA, n=8, P> 0.80) but there was a relationship in the abundance of N. americana for the three sampling stations (ANOVA, n=10, P<0.05) since the highest density of this species was recorded in the inner zone of the estuary. Significant differences in salinity were found between the three sampling stations for those dates when N. americana was present (ANOVA, n=10, P<0.05) but it could not be demonstrated that this variable is related with the spatial distribution of this species in the estuary (covariable, P>0.15)

Dos especies de misidáceos estuvieron presentes en el estuario de Bahía Blanca: Arthromysis magellanica (Cunningham) y Neomysis americana (Smith). Durante el periodo de estudio ambas especies fueron detectadas desde agosto hasta marzo. A. magellanica fue más abundante durante la primavera, con un valor de 31,92 ind.m-3 mientras que N. americana lo fue durante el verano, con un valor de 10,91 ind.m-3. Estos altos valores de abundancia fueron coincidentes con el aumento de la temperatura del agua. La temperatura media registrada durante el período de muestreo fue de 15,7°C. El rango de temperatura de presencia para ambas especies fue de 10°C a 23,3°C. El rango de temperatura en el cual ambas especies estuvieron ausentes fue de 6,6°C a 22°C. En cuanto a la distribución espacial, no se detectó una relación en la abundancia de A. magellanica para las tres estaciones de muestreo (ANOVA, n=8, P>0,80). Sí existió una relación en cuanto a la abundancia de N. americana (ANOVA, n=10, P<0,05), ya que de esta especie se capturó un mayor número de individuos en la zona más interna del estuario. Se hallaron diferencias significativas en relación con la salinidad entre las tres estaciones de muestreo para aquellas fechas en la que N. americana estuvo presente (ANOVA, n=10, P<0,05), pero no se pudo demostrar que esta variable estuviera relacionada con la distribución espacial de esta especie en el estuario (covariable, P>0,15)