Author(s): Yusukenakatani; Shuzonishida; Masayasu Irie; Azusa Hiraoka; Daiki Nei
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Keywords: Three–dimensionalnumerical model; Hydrodynamics; Water quality; Tidal urban river network; Estuary
Abstract: In this study, field observation was conducted to identify waterquality variation characteristics in a tidal urban river network in Osaka, Japan, and three–dimensional hydrodynamic and water quality simulations were conducted to understand the variability characteristics of current, salinity, water temperature, water quality, and materials transport in the estuarine basin. The observation results showed that water quality variations in the estuary were strongly affected by the seawater intrusion process and the mixingof water masses from various sources. The simulations adeptly reproduced time variability of tidal elevation and water quality distributions although further improvements are necessaryto reproduce the vertical mixing process around the salt-water interface in the downstream area. The simulation results showed that biochemical processes and water–sediment interactions exerted during outflow to the coast had a minor influence on the water–quality variations in this estuary. Tracer experiments indicated thatthe contribution of the Neya River water, which is highly polluted by human sewage and industrial effluent, to the water quality degradationwas almost the same around the mouths of the three downstream rivers.
Year: 2014