Abstract
Taunsa barrage has been rehabilitated by constructing a subsidiary weir at 800 ft distance from the barrage
crest. The stilling basin floor was strengthened by replacing 2 ft top layer with 3 ft thick, high strength structural
concrete, whereas the impact and friction blocks were replaced by chute blocks and end sill, respectively. While
designing rehabilitation project at Jinnah barrage the Detail Design Consultants proposed a similar structure, the
subsidiary weir to be constructed at 600 ft form the barrage crest. The replenishment of loose stone in gabion is
recommended whereas the stilling basin floor was considered adequate.
Arguments have emerged regarding hydraulic justification of subsidiary weir being proposed at the Jinnah
barrage. It looks imperative that the energy dissipation systems of both the barrages are to be reviewed.
Furthermore, suitability of the constructed subsidiary weir at Taunsa barrage is to be studied to establish its role in
the barrage operation.
This research indicated that both the barrages have distinct energy dissipation mechanism; therefore the
provision of subsidiary weirs may independently be justified. The study revealed that the energy dissipation system at
Taunsa Barrage is jump type, whereas it is impact/jump type at Jinnah barrage. Tail water levels at Taunsa barrage
are adequate indicating that the subsidiary weir was not required. The proposed subsidiary weir at Jinnah barrage
would change energy dissipation concept and will have serious hydraulic consequences. Furthermore, the subsidiary
weir adversely affects hydraulic functioning of these barrages and reduces their discharging capacity.
Zulfiqar Ali Chaudhry. (2010) Performance Assessment of Taunsa Barrage Subsidiary Weir for Long Term Rehabilitation Planning, Pakistan Journal of Engineering and Applied Sciences, Volume 7, Issue 1.
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