Caracterizacion hidrografica del estuario del rio Valdivia, centro sur de Chile

Abstract

RESUMEN.La costa sureste del Océano Pacífico entre 37º y 41°S, se caracteriza por la presencia de un gran número de estuarios micromareales (rango mareal menor a 2 m). Uno de los estuarios más importantes dentro de estas latitudes es el estuario del río Valdivia, cuya estructura y dinámica termal y halina es poco conocida. Mediante mediciones hidrográficas de temperatura y salinidad tomadas durante un ciclo estacional anual y el análisis de sus principales forzantes (marea, caudal del río, vientos y radiación solar) se explica la variabilidad así como sus cambios en la estratificación vertical. El análisis de la estructura termohalina de la columna de agua reveló que el estuario varió estacionalmente comportándose como un estuario de cuña salina en invierno y primavera producto del mayor caudal de los ríos afluentes, mientras que en verano y otoño se comportó como parcialmente mezclado, producto del menor caudal de los ríos. En invierno y primavera la columna de agua presentó inversión térmica, la cual fue asociada a pérdida de calor superficial y a la advección subsuperficial de aguas cálidas desde el océano adyacente hacia el interior del estuario que no se mezclaron con las de la superficie debido a la intensa estratificación salina. El cambio en el régimen estuarino de cuña salina a parcialmente mezclado según la estación del año y presencia de la inversión térmica estacional, son características hidrográficas necesarias tanto para la implementación de esfuerzos de conservación de hábitat vulnerables presentes en la zona (áreas de crianza de juveniles de especies explotadas), como para la utilización de este sistema para actividades de acuicultura y manejo de recursos marinos. Palabras clave: hidrografía, boyantes, mezcla, inversión térmica, río Valdivia, Chile. Hydrographic features of Valdivia river estuary south-central ChileABSTRACT. The area between 37º and 41°S of the southeastern Pacific coast, have a great number of microtidal (tidal range less than 2 m) estuaries. One of the most important estuaries in these latitudes is the Valdivia River estuary, whose thermal and haline structure is poorly known. Thus, this work, through hydrographic measurements of temperature and salinity taken during an annual seasonal cycle and the analysis of the main forcings (tide, river flow, wind and solar radiation) explain the variability and its changes in vertical stratification. The analysis of the the thermohaline structure of the water column revealed that the estuary varied seasonally behaving like a salt-wedge estuary in winter and spring due to a higher flow of tributaries. However, in summer and autumn behaved as partially mixed due the lower river flow. In winter and spring the water column showed a temperature inversion which was associated with a large surface heat loss and subsurface advection of warm waters from the adjacent ocean to into the estuary that is not mixed with the surface due to intense stratification by salinity. The change in the estuarine salt-wedge regime to partially mixed according to t...

Flooding in Central Chile: Implications of Tides and Sea Level Increase in the 21st Century

“…In Southern Chile, Rojas and Mardones [20] established that in the microtidal estuary of the Valdivia River (39 • S, Chile), 80% of floods occurred during syzygies. According to Garcés-Vargas et al [58], in winter, this estuary behaved as a salt wedge, with depths of between 7-22 m and a tidal influence reaching 50 km upriver from the mouth. In comparison, in winter, the Andalién River behaved as a highly stratified mixed estuary, with a depth of between 0.5-2.5 m, and a tidal intrusion of 5.9 km.…”

Tidally Forced Saltwater Intrusions might Impact the Quality of Drinking Water, the Valdivia River (40° S), Chile Estuary Case

“…The flow of the Calle-Calle and Cruces Rivers is in synchrony and both represent the most important components of the VRE. The sum of their annual average discharge is~670 m 3 s −1 being maximal in austral winter (~1500 m 3 s −1 in July) and minimal in austral summer (~210 m 3 s −1 in March) [13,19]. Tides exhibit semi-diurnal phases in Corral Bay with a mean tidal height range of 0.8 m but vary from 1.48 m during spring tides to 0.53 m during neap tides [20].…”

“…However, neither stratification of the water column nor saline intrusion were keenly analyzed. More recently, the hydrographic data obtained by [12] corresponding to the middle part of the estuary of the Valdivia River and the mouth of the Corral Bay were examined together with tides, river flow, wind, and solar radiation to delineate the thermal and haline structure of this part of the VRE [13]. This study established that the VRE varied seasonally and behaved like a salt-wedge in austral winter and austral spring due to a large water transport by the rivers.…”

“…Although winds play a less important role in driving saltwater intrusions into the VRE [13], they can become important under certain conditions. Winds could break stratification of the water column when competing with buoyancy, which in turn is controlled mainly by salinity during certain periods.…”

“…In the present investigation, we analyzed the intrusion of saline water in one of the largest estuary systems of the Southeast Pacific coastal zone [11], the Valdivia River estuary (VRE), located in south-central Chile. Although some studies established relationships between saltwater intrusions and river flow [12,13], these relationships have not been quantified and the hydrographic measurements did not consider neap tide periods. In addition, their samples were taken four times a year, with each only for 1~2 days, which only allowed for the evaluation of seasonal changes.…”