Hydrodynamics and mixing at the confluence of rivers: Influence of density and tide contrasts
Metadatos
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Universidad de Granada
Director
Rueda Valdivia, FranciscoDepartamento
Universidad de Granada. Departamento de Ingeniería CivilMateria
Hidrología Ríos Hidrodinámica Dinámica de fluidos Análisis por sedimentación Ecología de ríos Fauna de ríos
Materia UDC
556 2500
Fecha
2016Fecha lectura
2016-03-10Referencia bibliográfica
Ramón Casañas, C.L. Hydrodynamics and mixing at the confluence of rivers: Influence of density and tide contrasts. Granada: Universidad de Granada, 2016. [http://hdl.handle.net/10481/43718
Patrocinador
Tesis Univ. Granada. Programa Oficial de Doctorado en: Ciencias de la Tierra; Work on the confluence between the Ebro and Segre rivers was funded through a collaborative agreement between the University of Barcelona and the University of Granada to work jointly in the project “Gestión hidráulica y técnicas de detección remota aplicada al control de poblaciones mejillón cebra: el caso del embalse de Ribarroja y el tramo inferior del río Ebro”, funded by the Spanish Ministry of the Environment. Work on the Sacramento River was funded through the project “North Delta Salmon Out-migration Study”, funded by the United States Department of Interior ― Bureau of Reclamation (USBR), solicitation No. 09SS200013. The PhD student was supported by a PhD grant (Programa Estatal de Promoción del Talento y su Empleabilidad, subprograma de Formación de Profesorado Universitario) from the Spanish Government.Resumen
River confluences are critical points in river networks where strong physical and
chemical gradients develop, resulting in a wide range of distinctive environmental
conditions (habitats) for biological growth. Large variations in water temperatures,
organic matter, nutrients, for example, and in general, in water chemistry have been
reported to occur at these sites. As a consequence of their high spatial and temporal
heterogeneity of habitats and resources, river confluences behave as biological hotspots,
where the number of species appears to increase very significantly in comparison with
other river reaches. The effects of river confluences persist downstream, therefore,
affecting biological communities and ecological processes at scales of river reaches and
channel networks. The spatial extent of the reaches downstream of river junctions where
heterogeneous habitat conditions persist, largely depends on the rate at which mixing
between the mainstream and tributary waters occurs. The literature on mixing in river
confluences is extensive, but still, our understanding of flow and mixing dynamics in
these sites is far from complete. In particular, the effect of density contrast between the
confluent streams on mixing has traditionally been neglected, which has been justified by
differences in the inertia of the confluent flows being much higher than density
differences. However, as the scale of the confluent channels increases, the probability of
draining different geological terrains also increases which results in an increasing
potential for significant differences in density.
In this work, we present results of a series of field experiments carried out in a
confluence in Northern Spain where the presence of density contrast is important for both
the spatial arrangement of the rivers once at the confluence and river mixing.