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Estimation of seepage losses in an ephemeral multibranched stream by simultaneously solving for seepage and unsteady flow
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Rasol Ghobadian *   |
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Abstract: (11147 Views) |
| Due to transmission losses and
absence of initial flow prior to flood occurrence, it is impossible to estimate
seepage losses and flow routing for an ephemeral stream with several branches
and complex connections by using common routing methods, and it is necessary to
develop a routing method for such streams. To this end present research
prepared a computer for irregular stream
cross section, in which partial
differential equation for non-uniform unsteady flow(saint- Venant equation) are
solved by using finite difference method and alternative technique(staggered
method) after being linearized. Water
flow elevation at fluvial connection is determined at any time step completely
implicitly by using influence line method. Model accuracy was examined in terms
of programming, its ability to simulate uniform flow, and to satisfy continuity
relationship by using a loop stream consisted of 8 open channels. The results
of verification showed 0.7 and 0.0209 percent as maximum calculation error for
discharge and flow depth, respectively. With very high accuracy, therefore,
present model estimates discharge and water surface profiles at each branch.
Employing Lane hydrograph and characteristics of Hughes Wash River, prediction
of flow behavior and transmission losses showed that compared to other
experiment relationship, Muskat’s estimates seepage losses and peak flood
better. Under seepage condition, a highly complex system of open channel with
24 branches and low slopes was employed, in which the flow of any branches is
sensitive to small changes in flow depth. Also, in this network, the model is
able to detect flow direction at any branches. For steady flow, the results
showed a 1.127% decrease in system output discharge due to seepage losses. For
unsteady flow, with the present seepage, system output hydrograph volume is 6.37%
less than that of input hydrograph volume. |
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| Keywords: transmission losses, ephemeral stream, flood routing, Saint-Venant equation |
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Full-Text [PDF 658 kb]
(2880 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2015/03/2 | Accepted: 2015/03/2 | Published: 2015/03/2
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