A Consideration to River-bed Flow Downstream of Dams for Evaluation of Environmental Preservation Discharge

Abstract

Recently, in order to improve the condition of rivers downstream of dams, the preservation discharge from a reservoir has been drained off for conservation of river environment. However, in a watershed basin where sedimentary materials are actively produced from a mountainous area, it is impossible to disregard the seepage flow from river channels, i. e. the river-bed flow, because a thick layer of sediment is formed on the bottom of a valley. The purpose of this research is to consider the hydraulic characteristics of the river-bed flow downstream of dams. Through the theoretical analysis based on the physical principles, the spatial distribution of seepage potential, the seepage rate and its total quantity from the channel have been evaluated. The analytical results have been validated by the numerical simulation combined the river-bed flow with the channel flow.