Hydrologic characteristics and estuarine dynamic process during the dry season in Modaomen Estuary of the Pearl River

Based on the data from the tidal-gauge stations and synchronously surveyed data during Dec.9-15,2003,the present paper provides a brief analysis of the characteristics of tide,the residual currents,the suspended sediment content and salinity during the dry season at the Modaomen Estuary of the Pearl River. The preliminary research are made on the estuarine dynamic process,including the mixing of fresh water and salt water and the estuarine jet.During the dry season,the tidal current becomes dominant due to the weakened runoff.The surface residual current at each station basically goes downstream along the river course due to the effect of the runoff and wind,while the residual current near the mouth,below the middle layer,goes stably upstream. In the dry season,the suspended sediment content in the Modaomen is very small(<1 kg/m³)and the salinity changes both along the longitudinal and the vertical direction at the Modaomen Estuary. The fresh water and salt water mixes with the N parameter between 0.01 and 1 at all stations. The surveyed velocity configuration shows that the gravitational circulation exists near the mouth caused by the density difference. In light of the densimetric Froude number calculated through the actual surveyed data,the estuarine jet in the dry season in the Modaomen Estuary is buoyant.