Hydrography and circulation of the Chubut River estuary (Argentina)

The hydrography and circulation of the Chubut River were investigated under exceptionally low river discharge. The frontal zone formed by the entrance of the tide in the estuary may be observed as far as 4.5 km from the mouth, showing that the salt intrusion due to tidal effects reaches further inland than during normal river discharge. Based on the classification of Hansen and Rattray (1966), the estuary corresponds to Type 1 with some vertical stratification observed on the seaward side of the frontal zone. A lateral salinity gradient was found, which was not the result of Coriolis force. The general morphology of the estuary and the consequent secondary circulation due to meanders and interchannel bars may explain the lateral variation. Wind effect is a major component of the circulation and mixing of this shallow estuary.