Estimation of Seepage Losses in Ephemeral Network and Branching Streams

Abstract

Flood routing of seasonal waterways with no base flow involves considerable uncertainties due to transmission losses. This case would be more complex when water flows into network and branching rivers. A finite-difference scheme is developed in this study to solve Saint-Venant equations for unsteady flow through irregular branching streams. An alternative technique (staggered method) was employed for solving linearized equations. Water elevation at fluvial connections is determined at any time step implicitly using the influence line method. The accuracy of the model and its ability to simulate flow and losses is examined for steady and unsteady flow estates. This is done for simple and complex systems of channels (in situ and artificial systems) with and without consideration of seepage losses. Due to uncertainties involved in practice, results of the model verification showed an acceptable range of error when estimating seepage losses in complex systems. The results of this study reveal the considerable effect of seepage loss on estimation of discharge and flow direction in river branches. Using Lane’s hydrograph and characteristics of Hughes Wash River, Muskat’s equation predicted peak flood and transmission losses more accurately than other seepage equations.