Abstract
The objective of the paper is to compare the hydrologic and hydraulic reservoir routing methods in term of assumptions, equations, numerical computation procedures, necessary data and advantages-disadvantages of their use. To test the results provided by the two methods, a set of two reservoirs from Romania was chosen: one long and narrow and the other one roundly shaped. Corresponding inflow hydrographs were chosen, and similar conditions were imposed for the outflow dam control structures, namely the initial water level in the reservoir to be at the Spillway Crest Level (SCL) and no outflow control. For the hydrologic method the Puls procedure was used and a program was written in Scilab to solve the continuity equation in finite differences. For the hydraulic method HEC-RAS software was used to solve the 1D Saint-Venant equations. Outflow and stage hydrographs at the dam were compared together with the stage hydrograph at the reservoir tail for the hydraulic method. Results show that the hydraulic method should be used for the long and narrow reservoirs, as it considers the backwater effect, whereas the hydrologic method can be efficiently used for all other reservoirs where this effect is negligible.
Highlights
Flood attenuation is one of the roles of storage, flood control or multipurpose reservoirs created by dam impoundment, as a key component of hydropower development schemes
The objective of this paper is to prove this by analysing comparatively the two methods of reservoir routing for two differently-shaped reservoirs from Romania: one long and narrow and one roundly shaped
For the Izvorul Muntelui reservoir, 36 cross-section topobathymetric profiles surveyed along the reservoir were linearly interpolated at a maximum distance of 100 m in order to create the hydraulic model geometry
Summary
Flood attenuation is one of the roles of storage, flood control or multipurpose reservoirs created by dam impoundment, as a key component of hydropower development schemes. Attenuation has a major protective impact upon downstream areas by decreasing the peak discharge and delaying the time of its arrival, diminishing depth and extent of downstream flooding, protecting river banks of erosion and the floodplain of scour, at the same time limiting the transport and deposition of large quantities of sediments [1]. Reservoir (or storage) routing is a mathematical procedure for computing changes over time in magnitude and shape of a flood wave transition through a water retention facility. The wave travels from the reservoir’s tail to the outflow structures of the dam. Computations are made considering the elevationstorage and elevation-discharge characteristics of the reservoir and of its outflow structures, respectively. Applications are in the flood forecasting, regulation and protection, design of reservoir and its outflow structures and reservoir operation, since the flow downstream the reservoir is usually limited to a predetermined maximum value [2]
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