The energy budget under the influence of topography in the Zhujiang River Estuary in China

The Zhujiang River （Pearl River） Estuary （ZRE） is a very complicated and large-scale estuarine system in China. It consists of two parts： the river networks and the estuarine bays. Not only is the network system one of the most complicated in the world, but also each estuarine bay has a very special morphodynamic feature due to the geological settings. Morphological boundary conditions have direct effects on the energy dissipa- tion and balance. On the basis of a three-dimensional （3-D） barotropic model whose domain includes the river networks and the estuarine bays, the energy budget is discussed under the influence of topography in the ZRE. The elevation and discharge of this model are validated by the observations collected in July 1999 and February 2001. The results show that （1） the source of energy in the ZRE is mainly generated by tides and river runoffs, which have an obvious seasonal change, and （2） there are some typical hotspots where the energy dissipation is 1-2 orders higher than those in the immediate upstream and downstream sections in the ZRE. These hotspots are linked with the small-scale dynamic structures （SSDS） and morphological units. On the basis of the characteristics of the morphology and the energy dissipation, the hotspots can be catego- rized into three types： the outlet of the ZRE, the meandering river, the branch and junction.