Articles | Volume 18, issue 10
Hydrol. Earth Syst. Sci., 18, 4153–4168, 2014
Hydrol. Earth Syst. Sci., 18, 4153–4168, 2014

Research article 17 Oct 2014

Research article | 17 Oct 2014

Analytical approach for predicting fresh water discharge in an estuary based on tidal water level observations

H. Cai1, H. H. G. Savenije1, and C. Jiang2 H. Cai et al.
  • 1Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, P.O. Box 5048, 2600 GA Delft, the Netherlands
  • 2School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou, 225127, China

Abstract. As the tidal wave propagates into an estuary, the tidally averaged water level tends to rise in landward direction due to the density difference between saline and fresh water and the asymmetry of the friction. The effect of friction on the residual slope is even more remarkable when accounting for fresh water discharge. In this study, we investigate the influence of river discharge on tidal wave propagation in the Yangtze estuary with specific attention to residual water level slope. This is done by using a one-dimensional analytical model for tidal hydrodynamics accounting for the residual water level. We demonstrate the importance of the residual slope on tidal dynamics and use it to improve the prediction of the tidal propagation in estuaries (i.e. tidal damping, velocity amplitude, wave celerity and phase lag), especially when the influence of river discharge is significant. Finally, we develop a new inverse analytical approach for estimating fresh water discharge on the basis of tidal water level observations along the estuary, which can be used as a tool to obtain information on the river discharge that is otherwise difficult to measure in the tidal region.