This study focuses on the river discharge and the tidal propagation in upstream and downstream of the Pearl River Delta, China. From the results, it is concluded that the discharge division at the apex of the Pearl River Delta shows a pronounce seasonal variation, and that lateral sources of river discharges affect tidal wave propagation and the phase difference between velocities and water levels of the incoming tidal waves.
River discharge and tidal propagation in upstream and downstream parts of the Pearl River Delta, China
The purpose of this research is to provide insight into the hydrodynamic processes that control the subtidal (i.e. tidal-averaged) discharges to the Pearl River Delta (PRD) region. In the upstream part of the delta the channels that connect to the apex are studied, where two rivers are interconnected by a small channel. In the downstream part of the delta, the focus is on the two largest bays. Both bays are funnel shaped, and are characterized by lateral sources of river discharge, issues by multiple distributaries. The lateral river discharges are larges in the West Bay. The discharge division at the apex system of channels is analyzed with daily measured discharges between 1999 and 2004, at stations located in each of the two rivers and with results from a delta-wide, steady-state hydrodynamic model simulating typical dry season and wet season conditions of river discharge. The tidal wave propagation is analyzed with hourly measured water levels and discharges for approximately two weeks in the wet season of 1999, at stations located along the East and West Bay, and using the model results. A wavelet analysis and a harmonic analysis are performed to determine the tidal damping coefficient and the characteristics of tidal propagation. At the apex, three alternative modes of discharge division occur. In one of these modes, during the transition from the wet to the dry season, a reversed, landward discharge occurs in one of the distributaries. Data from the West Bay reveal the lateral sources of river discharge affect the tidal wave propagation, showing larger phase differences between velocities and water levels than in the East Bay. The model shows similar results, despite doubts about the reference level of the bathymetry in the model. It is concluded that the discharge division in the PRD shows a pronounce seasonal variation, and that high river discharges affect tidal wave propagation and the phase difference between velocities and water levels of the incoming tidal waves. The river discharge, however, does not affect the damping coefficients of the incoming tidal waves.