M. Cintia Piccolo

Fractal analysis of tidal channels in the Bahı́a Blanca Estuary (Argentina)

The fractal dimension (D) was estimated for nine tidal channels depicted in thematic mapper (TM) Landsat-5 imagery to derive information about the degree of geomorphological control on a tidal channel network characteristic of the Bahia Blanca Estuary (Argentina). Two methods, box counting and contiguity, were used to estimate fractal dimensions for each tidal channel. All channels produced D values close to 1, meaning that they are self-affine fractal features. However, these fractal dimensions do not represent the meandering pattern complexity characteristic of the tidal channels analysed. Although both methods allowed for estimation of D, the contiguity method showed that three of the channels actually are not fractal but have sinusoidal characteristics, a condition that was not detected by the former method.

Evolución de los Recursos Hídricos en el “Bajo de Sarmiento” (Patagonia Extra Andina): Impactos Naturales y Antrópico

La dinamica de los recursos hidricos dentro de una cuenca depende de factores naturales (latitud, topografia, variabilidad climatica) y de los usos consuntivos y no consuntivos que el hombre haga de dichos recursos. La percepcion social que se tenga de la situacion ambiental de la cuenca y los objetivos que se prioricen sobre el uso de los recursos, terminan definiendo su grado de conservacion. Esto es especialmente critico en la Patagonia Argentina, donde las condiciones de aridez se prevalecen desde el Holoceno temprano a la actualidad. En el presente trabajo se estudia la dinamica de los cuerpos de agua (lagos y rios) en el “Bajo de Sarmiento”, el cual se localiza en el centro de la Patagonia extra andina. El objetivo de este trabajo es comprender si la percepcion social en cuanto a la prioridad en el uso del recurso hidrico esta derivando en un manejo que pudiera acrecentar el impacto que naturalmente afecta a los lagos y rios de la zona por la variabilidad climatica de la region. Para ello, se reconstruyo la dinamica hidrogeomorfologica del “Bajo de Sarmiento” derivado del impacto conjunto de la variabilidad climatica y la actividad antropica desde el Holoceno a la actualidad. Se analizo la Hoja Geologica 4569-IV Escalante, el modelo digital de terreno SRTM (30m) e imagenes satelitales Landsat (5-7-8) para comparar el regimen de los cauces permanentes principales descriptos y representados en la bibliografia y en la cartografia historica del “Bajo de Sarmiento” con sus regimenes actuales. Los datos obtenidos se contrastaron con relevamientos en campo. Por otro lado, se realizaron encuestas estructuradas a actores sociales de la cuenca, con el fin de analizar la percepcion social sobre los recursos hidricos. Los resultados permiten observar que si bien la variabilidad climatica (en especial las condiciones de aridez imperantes desde el Holoceno medio) historicamente ha sido el principal factor que afecta a la dinamica de los cuerpos de agua de la zona, el desarrollo de diversas actividades humanas (basada en la percepcion de los recursos que los habitantes de la cuenca tienen) han acrecentado esos efectos en los ultimos 120 anos. De esta manera se ha producido el cambio de regimen exorreico a endorreico de la cuenca y el retroceso de uno de sus lagos hasta casi desaparecer en el ano 2016.

Wind energy potential assessment and techno-economic performance of wind turbines in coastal sites of Buenos Aires province, Argentina

ABSTRACT An assessment of wind energy potential was carried out in five sites (four onshore and one offshore) in South-West (SW) of Buenos Aires province (Argentina). We use high-resolution wind data (2 and 5 min) for the period 2009–2012. The power law was used to estimate the wind speed at 30, 40, and 60 m height from the anemometer position. Turbulence intensity and wind direction were analyzed. Statistical analyses were conducted using two-parameter Weibull distribution. A techno-economic analysis based on a set of commercial wind turbines was performed in those sites. The results derived from this work indicate that the SW of Buenos Aires province represents a promising area for the wind energy extraction, which would encourage the construction of wind farms for electricity generation.

Assessment of surf zone environmental variables in a southwestern Atlantic sandy beach (Monte Hermoso, Argentina).

The aim of this study was to investigate the temporal dynamics (monthly/tidal) of water temperature, salinity, chlorophyll-a (chlo-a), suspended particulate matter (SPM), particulate organic carbon (POC), and dissolved nutrients in the surf zone of Monte Hermoso sandy beach, Argentina. We also aimed to understand the underlying mechanisms responsible for the observed variability. Sampling was carried out approximately monthly (September 2009–November 2010), and all samples were collected in a fixed station during high and low tide. Water temperature showed a clear seasonal variability (July: 9xa0°C–December: 26.5xa0°C) and a thermal amplitude of 17.5xa0°C. Salinity ranged from 33 to 37, without a pronounced seasonality. SPM (10–223xa0mgxa0L−1) and POC concentrations (399–6445xa0mg Cxa0m−3) were high in surf zone waters. Chlo-a (0.05–9.16xa0μgxa0L−1) was low and did not evidence the occurrence of surf diatom accumulations. Dissolved nutrient concentration was quite fluctuating. None of the variables seemed to be affected by tidal stage. The results showed how fluctuating the physico-chemical and biological variables can be in this particular system. The observed variability can be related with local beach conditions but also with regional processes. The study area is highly influenced by a neighbor estuary and as a consequence, could be vulnerable to their seasonal and inter-annual dynamics. All of these characteristics must be considered for further studies and planning of the uses of natural resources and should be taken into account in any environmental monitoring program conducted in a similar beach system.

Algorithm to calculate equal-area grid cells in irregular estuarine cross-sections

Calculation of residual fluxes in estuarine cross-sections requires the definition of a grid scheme which depends on the shape of the profile and the tidal height. Although it has been demonstrated that a full proportional grid provides error-free conditions for this estimation, the computational procedure to define the grid when the cross-section is geomorphologically complex is not trivial. An algorithm programmed in C++ is presented to provide the automatic computation of a grid with equal cell areas. An advantage of the algorithm is the fact that the cell center corresponds to the center of the cell area rather than the geometric center contributing the most adequate weight and reducing further the error in the calculation of the fluxes.

Effect of southern climate modes and variations in river discharge on lake surface area in Patagonia

ABSTRACT Multiple regressions, wavelet spectra, and Fourier spectra were employed to analyze fluctuations in the surface areas of 2 Patagonian lakes during 1998–2015 and relate these to fluctuations in precipitation, evaporation, river discharge, and 2 southern climate modes, the Antarctic Oscillation (AAO) and El Niño Southern Oscillation, expressed in terms of the Southern Oscillation Index (SOI). Multiple regression analysis suggested that discharge was the primary driver of interannual lake area variations. Cross-spectrum analysis demonstrated a maximum significant correlation between river discharge and both AAO and SOI indices at annual and interannual timescales (2–3u2005yr). During 1998–2015, the annual discharge signal was related to both the AAO annual and every 2 year signals. When a strong La Niña (positive SOI) event occurred, however, river discharge was significantly reduced, resulting in a decrease in lake surface area.

Efecto de la Variabilidad Climática Sobre el Estado de la Vegetación y la Cobertura de Agua en una Cuenca de Clima Templado (Argentina)

El area de estudio se encuentra en el sur de la provincia de Buenos Aires (Argentina) y forma parte de la region pampeana Argentina. Se caracteriza por el predominio de un clima templado. El objetivo de este trabajo fue cuantificar los efectos de los eventos climaticos extremos en el estado de la vegetacion y la extension del area cubierta por agua, en una cuenca hidrografica de clima templado (cuenca del arroyo Naposta Chico). El periodo de estudio fue 2000-2013. La metodologia incluyo el analisis de serie de datos del Indice Estandarizado de Precipitacion y Evapotranspiracion (SPEI) a escala 1, 3 y 12 meses, para la deteccion de eventos climaticos extremos. Mediante interpretacion visual de imagenes satelitales, se determinaron las diferentes coberturas de la cuenca y se calculo el Indice de Vegetacion de Diferencia Normalizada (en ingles, NDVI). Ademas, se delinearon los cuerpos de agua del area de estudio mediante procesamiento digital de imagenes satelitales Landsat 5 TM y 7 ETM+ correspondientes a los eventos extremos definidos mediante la aplicacion del SPEI. Los mismos fueron definidos para 2001 y 2004 (eventos humedos), 2008 y 2009 (eventos secos) y 2007 (evento normal). El estado de la vegetacion asi como tambien las extensiones cubiertas por los cuerpos de agua, presentaron variaciones a lo largo de los diferentes eventos climaticos extremos. La vulnerabilidad climatica de la cuenca y el conocimiento de los eventos de precipitacion extremos es fundamental para la gestion de los recursos hidricos y de las actividades agroeconomicas que alli se desarrollan.

3D Numerical Model of the Thermal Interaction Between Sediment–Water–Atmosphere

This paper describes a three-dimensional numerical model of heat flux using finite-difference approximation for the simulation, prediction, and visualization of sediment, water, and air temperature, applied in Villa del Mar saltmarsh, Bahía Blanca Estuary, Argentina. To make this computation, we develop an open-source software tool called Hemera 1.0 which is characterized by having little complexity and low hardware requirements. The model considers three heat transfer processes: diffusion, convection, and radiation, using bulk aerodynamic formulas as boundary conditions between the interfaces. The aforementioned model was applied for the month of January 2009. The model reproduced adequately the physical processes of the heat balance and showed an adequate response to changes in the boundary conditions. In addition, according to the model design, meteorological and oceanographic data and some soil properties are the only data input used for modeling. It is easily adaptable to other environments such us lakes and reservoirs, among others, in order to carry out similar studies.

Suspended Sediment Fluxes in the Middle Reach of the Bahia Blanca Estuary, Argentina

Puerto Galvan (Fig. 1) is one of the five harbors that form the BahIa Blanca Harbor System, the largest and deepest of Argentina. The harbors are all located along the Canal Principal of the BahIa Blanca Estuary, a mesotidal, coastal plain environment (Perillo, 1995) formed by a series of major NW-SE trending channels separating extensive tidal flats, low salt marshes and islands. The geomorphology and physical characteristics of the estuary are described in detail elsewhere (Perillo and Piccolo, 1999) including a recent review of its major environmental features (Perillo et al., 2000).