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Most of existing dams are often faced two major problems, the first relates to flood mitigation which can leads to dam submerging risks, the second to the loss of storage capacity due to sedimentation. Wanakbori dam was constructed across River Mahi in Gujrat in 1959 with gross storage capacity of 41.9 MCM at FRL. Wanakbori dam was modified in 1993 with 33 nos. of fuse gates to increase gross storage capacity of dam 82 MCM from 41.9 MCM. Most existing free flow spillways have standardized shape (ogee weir). Their discharge capacity is directly proportionally to the crest length. The spillways provide passage for flood and assure control of flood. It is most important to increase the storage capacity as well as overflow capacity of dam without increasing submergence on upstream side of dam. The capacity of existing spillway can be increased by lengthening the crest length or increasing the head on crest. one solution for this problem is the implementation of new shape of non linear type weir, called Piano Key weir (PK weir). PK Weir is the best alternative solution to improve overflow capacity of existing as well as new dam. Currently, no universal design criteria are available for design of PK weir. it is recently developed new shape of weir and required large experimental works. in present research paper the effects of PK weir geometry on weir performance is evaluated. laboratory scale sectional models of PK weir and ogee weir are fabricated and tested for various discharges.
