Abstract

INIGUEZ-COVARRUBIAS, Mauro; OJEDA-BUSTAMANTE, Waldo  and  DIAZ-DELGADO, Carlos. Improvements in the Hydraulic Efficiency of Weirs with Free Outfalls in Dams. Tecnol. cienc. agua [online]. 2015, vol.6, n.1, pp.69-79. ISSN 2007-2422.

Hydraulic infrastructure in Mexico is aging and in many cases there is an urgent need for rehabilitation. This task requires the application of new hydraulic as well as hydrological design methods that are consistent with current technological developments, to the extent possible. Free weirs are hydraulic infrastructures used in reservoirs and are generally located in very wide channels or those with high hydraulic loads, characteristics which are vitally important to determine the height of a dam wall. A proposal is presented for an alternative design and to improve hydraulic efficiency by substituting the free weir with a labyrinth weir. This proposal is based on the duckbill weir design. A case study was conducted in the "El Ejidatario" dam located in Sombrerete, Zacatecas, Mexico. The results show that with the installation of a labyrinth weir the length increased to 5.67 times that of the free weir. In addition, with a change in load from 80 to 30 cm the weir load decreased 62.5% and the capacity of the reservoir increased 12°% with the same mean elevation. The hydraulic efficiency of the duckbill weir was compared to that of the piano key weir for the same weir length and installation conditions, resulting in a 208% improvement. It is recommended to install the new weir in the same site as the free weir, only adapting the entrance to the stilling basin while using the same outlet to the discharge channel. A labyrinth weir is recommended when physical or study conditions require it, since in this case by increasing the hydraulic efficiency of the weir the capacity of the reservoir will increase and, thus, the service life.

Keywords : Labyrinth weir; duckbill weir; free outflow weirs; dam safety.