Double-Stilling Basin Modelling, Pakistan – Case Study

The Mohmand Dam is a 213m tall concrete-faced rockfill dam (CFRD) under design by a consortium of consultants in Pakistan. The consortium comprises SMEC International (Australia), Nippon Khoe (Japan), National Engineering Services (Pakistan), Associated Consulting Engineers (Pakistan), Engineering General Consultants (Pakistan), and BAK Consulting Engineers (Pakistan). The dam is for construction on the Swat River in Pakistan. A strategic component of the hydraulics studies has been large-scale physical model studies carried out by the Irrigation Research Institute, Pakistan. The paper will discuss in detail the use of, and the hydraulic behavior of a double hydraulic jump stilling basin facility incorporated in a 600m long concrete chute. The upper basin was designed to operate with a maximum head of about 100m, and the lower basin was designed to operate with a maximum head of approximately 120m with respect to tailwater level. The studies considered discharges up to approximately 25,500 m3/s. Detailed pressure transducer measurements of transients as part of the design of the basins, and the chutes incorporated several aerators along the length of the chutes.