Simulation of Thermal Stratification in Urban Man-made Lakes

Abstract

Chitgar artificial lake, located in the urban District-22 Municipality of Tehran northwest of Tehran, Iran is by volume l0 Million Cubic Meter (MCM), by depth average 10 meters (m.) and by area 225 hectares (ha) as the Iran’s largest man-made lake. The most important water resources of the district, which can support the lake water, are Kan River, municipal runoff, the middle part watersheds runoff and the treated wastewater of urban regions. In this study the way to take water from each resource individually or some of them together have been discussed and twelve different choices of resources maintain the lake water have been introduced. Thermal stratification is one of the most important parameters that can affect the lake water quality after construction in regard to Tehran climatic conditions. In this research Water Quality for River and Reservoir Systems (WQRRS) model has been run to every 12 aforementioned choices individually to predict the probable thermal stratification in the lake for each one. This simulation has been done during a five-year period, which is assumed to be a typical period of time in this study. The needed input data to run the model are quality factors, meteorological data, and geometrical characteristics of the reservoir, the characteristics of inflow and also the needed coefficients for the model. These data have been collected from hydrometric and meteorological stations of the region and also the results of other researchers. After running the model the simulation results show that the Kan River, as one of the proposed water resources, has the least difficulties in thermal stratification.