Abstract
Use of river water for the cooling water of heat pumps in district heating and cooling plants is starting in Japan from the view point of energy conservation. River water after having been used as cooling water is discharged into the river at the higher temperature by about 5℃ than the natural river water. Therefore it is very important to predict the influence of discharged warm water on river environment when we use the river water as the cooling water. The purpose of this study is to predict the influence of discharged warm water on the river environment of the Old Yodo River which flows through Osaka city and is one of the typical urban rivers in Japan. To achieve the purpose, it is essentially important to survey the present conditions of flow pattern and water quality of the Old Yodo River which includes present the Oh River, the Dojima River, the Tosabori River and the Aji River. This report describes the characteristics of flow pattern and water quality of the Old Yodo River based on the data obtained by actual surveys having been carried out in winter and in summer. The following properties became evident through the surveys, 1) The depth of water of the Old Yodo River changes with sea level in the same way over the all water system from the Kema water-gate in the upper stream to Ajigawa great bridge in the lower stream. 2) The stream in Oh River upper than Kawasaki bridge flows always towards the sea but in the region lower than the point where the Oh River and the Neya River join inverse current appears in the period of the rising tide. 3) Salt water wedge reaches the lower stream of Tenjin bridge at high tide. 4) Water temperature and water quality in the Neya River are rather different from those of the Oh River. So it is necessary to know the water temperature, water quality and flow rate of the Neya River to predict the river environment of the water system of the Old Yodo River.
