Articles | Volume 15, issue 12
Hydrol. Earth Syst. Sci., 15, 3689–3700, 2011
Hydrol. Earth Syst. Sci., 15, 3689–3700, 2011

Research article 09 Dec 2011

Research article | 09 Dec 2011

Hydro-physical processes at the plunge point: an analysis using satellite and in situ data

A. T. Assireu1,2, E. Alcântara1, E. M. L. M. Novo1, F. Roland3, F. S. Pacheco3, J. L. Stech1, and J. A. Lorenzzetti1 A. T. Assireu et al.
  • 1Remote Sensing Division, National Institute for Space Research, C.P. 515, São José dos Campos, SP 12001-970, Brazil
  • 2Natural Resources Institute. Federal University of Itajubá, UNIFEI, Itajubá, Brazil
  • 3Aquatic Ecology Laboratory, Biological Science Institute, Federal University of Juiz de Fora, MG, Brazil

Abstract. The plunge point is the main mixing point between river and epilimnetic reservoir water. Plunge point monitoring is essential for understanding the behavior of density currents and their implications for reservoir. The use of satellite imagery products from different sensors (Landsat TM band 6 thermal signatures and visible channels) for the characterization of the river-reservoir transition zone is presented in this study. It is demonstrated the feasibility of using Landsat TM band imagery to discern the subsurface river plumes and the plunge point. The spatial variability of the plunge point evident in the hydrologic data illustrates the advantages of synoptic satellite measurements over in situ point measurements alone to detect the river-reservoir transition zone. During the dry season, when the river-reservoir water temperature differences vanish and the river circulation is characterized by interflow-overflow, the river water inserts into the upper layers of the reservoir, affecting water quality. The results indicate a good agreement between hydrologic and satellite data and that the joint use of thermal and visible channel data for the operational monitoring of a plunge point is feasible. The deduced information about the density current from this study could potentially be assimilated into numerical models and hence be of significant interest for environmental and climatological research.