WATER AND ENERGY BUDGET ANALYSIS OF AN URBAN RIVER UNDER STRONG ANTHROPOGENIC INFLUENCE

Abstract

To reveal the anthropogenic influences on thermal environment in urban rivers, stream temperatures from 1990 to 2010 of the Tama River were investigated. Both the long-term and longitudinal changes of stream temperature, as well as flow rate, effluent temperature and volume, and water and energy budget were revealed. Stream temperature in winter season increased significantly at points where the temperature and discharge volume of effluents from wastewater treatment plants increased over the past 20 years. The different longitudinal variations in upstream temperature between winter and summer seasons were found primarily due to the flow rate decrease. Water and energy budget analysis suggested that the anthropogenic heat inputs from the wastewater were the dominant warming factor both in winter and summer seasons in downstream segments, while other factors such as groundwater recharges, and air-water and water-sediment interactions were contributing to suppress the stream water warming.